In the end, we went with 1st Light Energy, the only company whose sales rep could quote inverter specs from memory and spent hours with us at our dining table going over the numbers. Unfortunately, he knew rather less about organizing work crews and screwed up the installation. It took his replacement months to put things right. In retrospect, we dream of how nice it would have been to have customer ratings and unheroic financial analyses.

Finally, someone has developed a website to provide just that. Launched last month, EnergySage aspires to be the Expedia of solar and eventually of other green technologies such as solar thermal and ground-source heat pumps. A similar service, Solar Choice, operates in Australia, but I believe this is the first in the U.S.

On the site, you set up a profile with your address and either type in your electric bill or upload the PDF. EnergySage automatically emails installers in your area to work up an estimate; a homeowner might expect three or so responses within a few weeks. They come to you—no phone tag required. The service is free to customers; installers pay a commission if they get the job. The site presents the quotes in a standardized format, looks up the government subsidies available in your area, and calculates the payback period rather than accept the installers’ analyses.

Already have an array? Then enter it in the site as a case study for others to learn from. I added mine and was gratified to learn that it has an investment return of 17.8%. You can also rate and review installers and equipment suppliers. EnergySage’s CEO, Vikram Aggarwal, says the company plans to add other features such as bank loans, discussion forums, independent equipment tests, automatic retrieval of electric bills directly from utilities, and estimates of prevailing market prices—doing for renewable energy what the Blue Book does for used cars.

Not only is this great for homeowners, it hastens the day when solar power will reach parity with fossil fuels. The panels have been getting cheaper and streamlined installation systems are cutting labor costs, so the sales and marketing costs loom ever larger. They now account for a tenth of the total, on average—10 times more than in Germany. By providing a central clearinghouse for referrals, EnergySage should help to reduce these soft costs and fire up installers’ competitive spirits. A little less drama in the purchase of a solar array would mean fewer stories to regale your friends with, but more photons knocking electrons into our power grid.

Screen shot courtesy of EnergySage

Years ago, stewing over previous blackouts—they call this the Garden State, not the Reliable Infrastructure State—I investigated backup generators, but the expense put me off. I decided just to set up a transfer switch and battery backup for my steam boiler to ensure we don’t freeze. But the extended post-Sandy outage and likelihood of a recurrence got me thinking about backups again. Last month, I chatted with Harvey Wilkinson and Phil Undercuffler of Outback Power, based just north of Seattle. Their bidirectional inverters can convert DC to AC (so the array can power the house or feed into the grid) or AC to DC (so the grid can charge a bank of batteries). “If there’s a power outage, the system can drop the grid and continue powering the house,” Undercuffler said.

Not only do a bidirectional inverter and battery bank light up the darkness, they give solar homeowners the flexibility of choosing when to buy power from or sell power to the grid, so you can take advantage of tiered rates. In some areas, such as Hawaii, the utility doesn’t allow you to sell power back to the grid at all, because too many people are already trying to do that and the system can’t handle them all. A battery system at least lets you buy when it’s most advantageous to do so. In fact, this is the future we all face, because all grids have only a limited capacity to absorb electricity from panels on people’s roofs and wind turbines in their yards. Not only does solar and wind output fluctuate, distributed power generation can make the network prone to cascading failures. For instance, if the grid frequency wavers, inverters might take themselves offline, which reduces the total generating capacity, which worsens the frequency deviations, which causes other inverters to trip, and so on.

“As you get greater saturation of intermittent renewable supplies, you’ll see less and less grid stability,” Wilkinson said. Undercuffler predicted this would become a major headache when solar and wind produce a fifth of the total power, a goal that New Jersey has set for 2020. Germany has already passed this point and experienced grid imbalances. But if distributed generation creates a problem, it also offers a solution. Batteries in people’s basements would even out the power swings. In addition, as I’ve blogged about before, household inverters could help to stabilize the grid by tweaking their AC waveform, compensating for devices such as electric motors that muck things up by momentarily storing energy in their magnetic fields.

I had a vision of a gigantic pile of batteries, looking like a nest of alien eggs, but Wilkinson and Undercuffler said the company’s basic unit is the size of a minifridge (see photo above). It holds up to 12 lead-acid batteries, for a maximum of 600 amp-hours of charge, providing about 24 kilowatt-hours of energy. That’s the punch of the battery pack in a Nissan Leaf, with the crucial difference that the household batteries don’t go through nearly as many charge-discharge cycles. Their battery life is determined mostly by the ambient temperature and, in a typical basement, should be about a decade.

The issue, as always, is cost. The inverter is $6,000 (twice as much as the inverter I have), the empty battery rack runs $2,000, and each battery is $600. Blackouts are a pain, but are they a $10,000 kind of pain? If you really think so, a natural-gas standby generator would probably be cheaper. That said, I suppose tax credits might offset some of the higher cost. Also, the price tag might be justified if you’re stuck with a utility that won’t buy your power, or indeed no utility at all. Outback’s systems are found in remote African wildlife reserves, Arctic and Antarctic research stations, and other places that are even more infrastructure-challenged than New Jersey.

I’d love to hear what other battery solutions people have tried for their grid-tied systems.

A couple of years ago, I reported on the experiences of a solar homeowner in England, and I was curious how the situation in Britain has evolved since then.

I set up my solar panel company in the U.K. after researching the alternative energy market for some time and coming to the conclusion that photovoltaic energy solutions can help homeowners have a far cheaper (and cleaner) source of energy. The thought that the U.K. government was also encouraging early adopter of solar technology through a system of generous tariffs also made entering this new industry an attractive prospect.

Over the years I have tried to keep up-to-date with how other nations’ governments encourage the solar industry in their countries. There are certainly some telling similarities and differences in approaches to solar—not least between the U.K. and the U.S. I always try and read Ernst & Young’s quarterly reports about the state-of-play in the world’s renewable energy markets and noted that the February 2012 edition pointed out that the solar industry in the U.S. faces a considerable challenge. Despite 2011 being a bumper year for solar, the Solar Renewable Energy Credit system (whereby clean energy production certificates are sold, traded, or bartered) has reached saturation point and looks set to depress prices in the short-term.

Here in the U.K., there are also challenges that need to be overcome if progress with encouraging homes and businesses to invest in solar panels is to continue. We don’t have a Solar Renewable Energy Credit System (SREC) in the U.K., but we do have the feed-in-tariff (FiT) model—a form of subsidising the solar industry that is currently a source of tension between the solar industry and the government.

The FiT system is designed to ensure that householders who have solar panels installed get paid for the electricity they produce through the green technology; regardless of whether they use the energy in their home or export it back to the national grid. This system was introduced when Gordon Brown was Prime Minister and was seen as a way of rewarding Brits who became early-adopters of solar panels. The rate was set at 41.3p (about 65 American cents) for every kilowatt-hour of clean energy produced and resulted in a large number of solar panels springing up on U.K. roofs. The scheme was so popular that the solar industry thrived—giving companies the capacity to reduce costs.

With the solar industry growing stronger, the UK government was keen that solar companies should absorb more of the costs of encouraging green homeowners. A consultation between the government and the solar industry was set up to discuss the idea of reducing the feed-in-tariff—an idea which solar companies acknowledged had to happen. And this is when the trouble really began.

Eleven days before the consultation was due to end, the government, without warning, announced that the FiT would be halved from December 2012. The solar industry was given just one month’s notice of the change and struggled to cope with a ‘gold rush’ of customers who looked to cash in on the old FiT rates before the new, lower ones were applied.

After the gold rush, there was, inevitably, a sharp falling-off in solar panel orders. Two solar power companies teamed up with environmental group Friends of the Earth and went to the High Courts to successfully challenge the government’s right to slash the tariffs before the end of the consultation period. The government appealed the verdict and in the confusion solar companies were unable to advise prospective new customers which tariff they would benefit from.

With the U.K. government launching a second appeal, confusion still reigns. If the U.S. and other countries have anything to learn from the U.K. example it is this: solar industries and customers need plenty of warning and clarity regarding decisions to change solar power grants and subsidies.

Despite this, the Ernst & Young report shows that in 2011 the U.K. overtook Italy to become the fifth highest-ranked nation in terms of attractiveness for investment in renewable energy. We have some way to go before we can catch up with the U.S. (in second place) or China (first place), but no one expects to see the UK shooting up the global solar charts until the current legal dispute is settled.

Image courtesy of Alex Hole

Over the summer, data-lovers suffered a blow when Google pulled the plug on its Powermeter website, which provided a convenient way to track your home’s electricity use. But shortly after I bemoaned its demise, I learned about several other sites that are in some ways even better. They not only display your power consumption but also analyze it for patterns that could help you save money.

To collect the data, I have a unit called The Energy Detective, which consists of a pair of sensors that you clamp around the main power cables in your circuit breaker panel. Other systems, such as those by Blue Line and WattVision, attach to your utility electric meter. All take power readings and keep a running tally you can view through a web interface or mobile app. Lots of other devices are other there—energy blogger Chris Kaiser keeps a comprehensive list—but not all can upload the data to external analysis websites.

Those sites crunch the data and give you a breakdown of where the juice went. They rely on the fact that each appliance has a telltale pattern of power demand. A fridge, for example, regularly cycles on and off—you can easily see it on a graph of your total household power consumption. In principle, the analysis algorithms could go a-huntin’ for power hogs such as broken appliances and family members who crank up the a/c when you turn your back.

Unfortunately the TED monitor can work with only one external website at a time. PlotWatt had the cleanest interface, so I decided to give it a go first. You type in some general information about your house, such as how many of which types of electric appliances you have, so the algorithm knows what to look for. The site said it would take a week before it had enough data to perform an analysis. A week went by, then two, then three. Emails to tech support went unanswered and, out of frustration, I tracked down the email addresses of the site developers, who apologized and said they’d been swamped by people migrating from Powermeter and another soon-to-be-defunct site, Microsoft Hohm. After a month, I finally got some results.

The level of detail was somewhat disappointing—I was hoping for a finer-grained breakdown, revealing patterns I wouldn’t have expected. Still, PlotWatt correctly inferred that window a/c units were our biggest energy sink. On the chart, you can see demand ramp up because of the midsummer heat wave. Our solar panels covered only about half my total demand over this period. Previous summers haven’t been so extreme and we usually don’t even put in the a/c until August. You can also see flatlines where the TED stopped sending data and had to be rebooted.

After putting PlotWatt through its paces, I reconfigured my TED to upload data to another site, EnerSave, and began to wait again. This time, it took two full months—I got my first results only two days ago. And they disagreed with PlotWatt’s. For the one load that should be fairly constant—the fridge—they differed by a factor of three.

One reason may be that, unlike PlotWatt, EnerSave does its analysis on net consumption—it doesn’t add in the solar power generation to get our total consumption. When I signed up, I asked the developers about this and they claimed that net consumption would be enough to detect patterns. Later, though, they backtracked. They said they are still tinkering with their algorithm, so I’ll let it run a bit longer before I switch to a third service, MyEragy, and try it out.

The EnerSave user interface has the distinct advantage of showing you exactly when the algorithm thinks certain appliances cycled on and off. This is revealing not so much of our power habits, but of the limitations of the algorithm. For instance, the graph shows that on August 27th, the room a/c ran almost continuously. That makes sense: we were starting to get water in our basement from Hurricane Irene and the dehumidifier (which registers as a/c) ran all the time. But the graph also suggests that the dehumidifier cycled on and off over the subsequent week, whereas in actuality it ran almost continuously until our basement dried out.

Clearly, these are works in progress. A more reliable way to get detailed data about your power consumption is to attach a hardware sensor to each appliance. Some energy monitors, such as EcoDog and eMonitor, do just that. But they are much more expensive and I personally can’t justify the extra cost. Love of data has its limits.

Screen shots by George Musser

The first thing a smart shopper wants to know is: what’s the catch? In this case, it’s simple. Installing panels is so financially advantageous that SunRun can split the benefits with you and still turn a tidy profit. That profit would be all yours if you paid for the array yourself, as I did. The SunRun representative, Kelcy Pegler, Jr., of Roof Diagnostics (a local installer that SunRun contracts with), was very upfront about this: “Your return will always be better off buying it.” But then you’d need to float the cost and take the risks. The question becomes: do you want to?

Pegler started off by walking around the exterior of the house to inspect the roof exposure and tree shading, confirming an earlier analysis he had done using aerial images. SunRun won’t even offer you a free array unless your roof faces approximately south and has minimal shading. They run the numbers for your site and see whether they can recoup their costs—it’s all very hardheaded. As it happens, my brother and his wife’s house qualified. For fun, we asked Pegler what would happen if they wanted to put the panels on the northwest side of the house rather than the southeast. Then SunRun would have politely declined.

We went inside, had some lemonade, and Pegler looked over the household electric bills. Government subsidies will only pay for an array that covers a family’s annual electric usage—if you want to become a net producer, you’ll have to fork out for that yourself. In my brother and sister-in-law’s case, it didn’t matter: the array size was limited by their roof area, anyway. A system of that size would cost about $30,000, before subsidies.

When Pegler explained the zero-dollar option, we Mussers looked at one another in surprise. It sounded like a real letdown. In return for letting SunRun install and maintain the array, my brother and sister-in-law would save 10% on their electric bill. Ten percent? That’s it? To be more precise, they’d commit to buying all the expected array production at a rate of 16.5 cents per kilowatt-hour, versus the utility rate of about 18.5 cents. As my brother later confessed to me, “It’s not really that exciting.”

This is the tradeoff of a free system. Basically, you get to have only one zero. You can pay zero, or you can zero out your electric bill, but not both.

But as Pegler continued his pitch, the deal started to sound sweeter. SunRun limits its annual rate increases to 2.9%. By comparison, our utility rate has gone up about 40% since 2005, an average of 6% per year. The way it’s going, it’ll top 60 cents in 20 years, versus 30 cents for SunRun. So the 10% savings would grow steadily to 50% or even more if the government introduced carbon pricing.

The same logic applies to a self-financed system, but you need to factor in the maintenance costs. When SunRun pays, it has every incentive to watch the panels like a hawk. I talked to SunRun co-founder and president Lynn Jurich about this in April, after I wrote a post about problems with the quality of solar installations. She said SunRun contracts with Burnham Energy, a solar consultancy, to conduct quality-control checks. SunRun also monitors the output of each array for signs of trouble. Inverters tend to conk out after 10 years, and the company budgets for that. Jurich estimated that diligent monitoring can squeeze 30% more energy out of a system over its lifetime. Once, she recalled, the company noticed that all the arrays in one area were producing less power than expected. It turned out that ash from a forest fire had coated them, and the company sent out cleanup crews.

Pegler said the SunRun contract runs for 20 years, at the end of which my brother and sister-in-law would have the option of buying the system at its depreciated value. If they sell their house before then, the contract gets transferred to the buyers, unless they for some reason would rather not have cheap electricity, in which case the company would unbolt the panels from the roof and truck them away. SunRun sets up an escrow account to pay for continued maintenance in the case the company ever goes bankrupt.

So it really comes down to personal preference. On balance, I’m happy I bought my system. (Besides, SunRun didn’t operate in N.J. at the time I got my array.) But dealing with all the bureaucracy and upfront costs was really a hassle, and I suspect that most people would rather put their time and money elsewhere. I’d love to hear about your experiences. Please comment below or email me directly.

P.S. Whenever I mention government subsidies for solar power, people write in to complain about wasting taxpayer and ratepayer money. Living in a state (N.J.) that consistently subsidizes the rest of the country by paying more in taxes than we receive in Federal spending, I have some sympathy for this grievance. So, yes, let’s eliminate subsidies—starting with those that make electricity from oil, gas, and coal artificially cheap. But until the playing field is level, it’s inconsistent to complain about solar subsidies. Besides, the solar industry is already weaning itself. State rebates are much less favorable than they used to be. Jurich she said she looks forward to the day when solar can stand on its own: “The best thing we can do is to get off subsidies.” So please, don’t hijack the thread to complain about solar subsidies.

Photos by Bret Musser

Right now, an AC light bulb turns on and off 50 to 60 times a second, or even faster for a modern ballasted bulb. If you could stretch out the off intervals, you’d save electricity. And if you could do it cleverly, taking the response of the human eye into account, the flickering would not only be imperceptible, but the quality of light might actually improve. “We’re taking advantage of the dynamics of the visual system,” Macknik says.

So far, most efforts to create greener bulbs have focused on the spectrum of light. Incandescent bulbs have long spectral tails, so even at their best, only about a tenth of their energy goes into useful illumination; most gets squandered as infrared radiation. (You can use this handy online calculator to see how much energy a glowing filament emits over different wavelength ranges.) The three main alternatives—fluorescents, LEDs, and a new technology called electron-stimulated luminescence—all emit light by causing a phosphor to glow at certain wavelengths, lopping off the tail. The downside is that spectral engineering takes a toll on color quality. It took me a long process of trial and error to find a good mix of bulbs for our house; I have a big box in my basement with all the CFLs and LEDs I’ve screwed in and back out again. New York Times columnist Bob Tedeschi recently offered his tips on how to match bulb to room.

Macknik and his colleague Susana Martinez-Conde, who work at the Barrow Neurological Institute in Phoenix and write a column for Scientific American Mind magazine, propose to explore not the spectral but the temporal dimension. The two of them have made a name for themselves coming up with visual illusions, and they think bulbs could exploit these tricks to shed more light with less power.

They start with the famous illusion that two identical gray dots or squares look different when you put them on different backgrounds. They find they can accentuate the difference by flickering the illumination at a certain rate. “You can make something brighter or dimmer if you change the temporal dynamics appropriately,” Macknik says. This result seems simple enough, but he says visual studies are prone to a lot of subtle biases; volunteers’ perception of light and dark can be skewed by the order in which the experimenters present their test scenes. It took years to come up with a controlled experiment that could tease out the optimal flicker rate.

This illusion can work even if you don’t realize the light is flickering. When a light turns off and back on within 20 milliseconds, it looks as if it never went off; retinal cells detect the change, but the stimuli get blurred as the brain processes them—an effect known as flicker fusion. Yet the gray patches still look brighter or dimmer.

To achieve the highest contrast, Macknik says a bulb would turn on for 70 milliseconds, off for 10, and repeat—an 87.5-percent duty cycle. Straight away, this would use 12.5 percent less electricity. You can wring out another 10 percent or so because the enhanced contrast would let you get away with a lower-wattage bulb.

The 12.5-hertz power cycle that Macknik proposes flouts conventional wisdom, which holds that such a low frequency would cause an unbearable amount of flickering. No one wants their bedside lamp to become a dance-club strobe light, which is one reason why power companies chose an AC frequency of 50 or 60 hertz to begin with. (If you still have a CRT computer monitor, try changing the refresh rate to see how low a rate you can stomach.)

Ah, but the AC current is a sine wave. Macknik’s claim is that a different waveform eliminates visible flickering even at very low frequencies. Such a waveform could be readily programmed into LED bulbs, which convert AC power to DC and could modulate the DC output as desired.

A 20-percent savings isn’t all that much, compared to the factor of four you get when changing from an incandescent to a CFL or LED. For me, the bigger lesson is that engineers can draw on the findings of neuroscience and behavior science to fine-tune technology to our needs.

Optical illusion courtesy of Edward H. Adelson

Demonstration of how flickering makes a gray circle look brighter or lighter. (c) Stephen L. Macknik & Susana Martinez-Conde, All Rights Reserved 1998, 2011

If someone in a utility control room can read your meter remotely, shut off power to your house, and modulate individual appliances to shed load during peak hours, then so could hackers. As the number of smart meters grows, so does the incentive for criminals and terrorists to misuse them. Concern has been mounting for several years. In early 2009, IOActive, a security firm, demonstrated how little it takes is to break into smart-meter networks. Last year, computer security expert Nate Lawson of Root Labs hacked a smart meter radio module he’d bought on eBay for $30. Many people who’ve gotten the meters complain about incorrect readings, often with good cause. After all this, I begin to wish I had my old spinning wheel back.

I spoke yesterday with Ben Jun, vice-president of the security firm Cryptography Research, about the risks. The good news is that homeowners don’t need to worry too much about hackers taking over our lights. “I don’t think I’d be too scared about switching over to a smart meter,” he said. At least, not yet. If utilities bungle the transition, Jun says some of the scare stories could come true.

One concern is that homeowners could jimmy their meters. Power theft already saps a percent or two of U.S. electricity production, and much more in other countries; there are pages all over the web showing how to fool a mechanical meter. But at least physical tampering is easy to spot. An unsecured smart meter could be reprogrammed without any visible trace.

Another problem is privacy. By monitoring your power use, utilities get to know rather more about your household routines than you’d like them to. It never ceases to amaze me how much you can learn from simple wattage measurements. Each appliance in your house causes a telltale fluctuation in power, and websites such as PlotWatt and EnerSave can analyze the output of a home power monitor to see how often you run what appliance—useful self-knowledge for those of us looking for ways to conserve energy. Imagine what marketers (let alone burglars) would pay for that information.

Then there are the systemic threats. As electrical engineer David Nicol warns in our July issue, the “smart grid”—the networking of control systems of generators and substations—is a veritable playground for mischief-makers. A government cyberwar exercise in 2007, shown vividly in footage obtained by CNN, caused a generator to self-destruct. In effect the generator was forced to fight the raw mechanical power of the rest of the grid, and lost.

Nicol’s article didn’t mention smart meters, but they, too, are part of the smart grid and pose similar risks. One goal of the meters is to let utilities vary electricity rates by time of day to encourage conservation; you could program electron-guzzlers such as air-conditioners and electric car chargers to take advantage of off-peak rates. But if hackers could manipulate the rates, they might cause vast number of appliances to turn on or off at inopportune moments and bring the whole grid crashing down.

So what can be done? Jun said utilities have traditionally focused on resilience against random threats such as lightning strikes; unlike, say, banks, they didn’t have to worry much about systematic attacks. They need to learn, and quick. The main thing, Jun said, is to take the same basic countermeasures other industries do, beginning with hardening meters to thwart code-crackers. Lawson got into his module through the USB-like port provided for reprogramming and testing. The module did have some built-in cryptographic security, but it hadn’t been enabled.

Although utilities have plenty of incentive already to secure their systems and many are doing so, others are in the habit of doing the minimum it takes to comply with regulation. So regulators may need to lean on them. A smart meter installed today will probably still be there in 20 years, so the time to act is now. “We may only have one chance to do it right,” Jun said.

Smart meter, photo by George Musser

I downloaded and tried out 20 solar-related iOS apps—all I could find as of July 15th, apart from those that were restricted to customers of certain utilities, were geared toward professional solar installers, or were merely reference books without any ability to calculate. I don’t have an Android or WM7 phone and would love to hear by Twitter or email from users who have tried out solar apps for those devices.

The coolest apps make use of the iPhone’s GPS, compass, and tiltometer. You climb up to your roof and position the iPhone where you want your solar panel to be and these apps calculate how much power it’ll generate. None uses the iPhone’s camera or ambient light sensor to measure the intensity of sunlight directly; rather, they calculate it from your latitude, panel geometry, and, in a couple of cases, time of day.

For my panels, the tilt measurements ranged from 10 to 18 degrees and the azimuths from 144 to 186 degrees. For comparison, the N.J. state inspector who certified our array estimated a tilt of 10 degrees and an azimuth of 202 degrees—so the apps are close enough. By and large, they accurately predicted how much energy my array generates in a year.

Two of the best apps, Solar Checker and Photovoltaic, recalculate the annual energy output in real time as you move the phone, making it easy to experiment with different possible configurations. Their readings suggested that the optimal tilt for my location would be 33 degrees, which is close to the 38 degrees estimated by the industry-standard Solar Pathfinder software and the 34 degrees estimated by MACS Labs, a California-based energy consultancy.

Some of the apps include a rudimentary financial calculator. You enter the cost of your system and your utility’s electricity rate in order to calculate how long it’ll take to break even. I found that these estimates varied hugely. None of the apps can handle all the data that would go into a proper financial analysis. By the way, if you play with this feature, the electricity rate you enter should be the actual rate plus the value of any government incentive. For instance, those of us in N.J. get credits worth about $0.60 per kilowatt-hour.

For reasons known only to the developers, some of the apps work only in Europe. Because the sun doesn’t shine elsewhere, I guess. Try to use them in the U.S. and you get an error message. How hard could it be to make an app that works anywhere? The mathematical formulas are universal and free online databases provide solar yield for anyplace in the world.

Let me start with the apps that measure your solar array parameters for you, listed from my favorite to least favorite:

Solar Checker, by inverter manufacturer SMA Solar Technology, was the best of the bunch. It estimates your annual and lifetime energy production and takes a stab at the rate of return on your investment. But it can be awkward to use. For instance, it makes you enter the total array area in square feet rather than the number of panels.

Solar Meter ($3) is good, too, although it lacks the ability to recalculate the annual energy output as you move the phone around. The app lets you specify your array size in terms of the number of modules and peak power output per module. A nice feature is a graph of the seasonal variation in energy production. A financial screen estimates the cost and payback period, and the values were broadly consistently with other analyses I’ve done for my system. The app’s main deficiency is that it doesn’t fill in data for the U.S.—the closest it could get was Kingston, Ontario.

Solar Friend, by panel manufacturer Bosch Solar Energy, forces you to select among three Bosch-branded modules—how tacky. It also assumes that all American utilities charge the same rate for electricity; there is no place to enter local information. It calculates the total lifetime energy output rather than the annual production, which makes it inconvenient to compare directly to your electric bill.

Photovoltaic, by French manufacturer and wholesaler Axus Technologie Solaire, displays a spiffy graph of predicted energy generation by month. Although it denominates your financial savings in euros, the currency is irrelevant; if you enter your electricity rate in dollars, you can interpret the output values as dollars. The app’s main failing is that, outside Europe, you need to enter the sun data for your location manually. The relevant preference is confusingly labeled "Solar Indicator (kWh/kWc)." It took me a while to figure out what this meant: kilowatt-hours of annual AC energy production per kilowatts of rated DC power output. For my location, this value is about 1,100. It equals the effective number of hours of full-on sunlight—for me, just over four hours per day times 365 days a year—times the AC-to-DC conversion efficiency, typically about 75%.

Solar Panel Advisor ($1), by San Diego-based engineering firm Microtrend, has a clunky interface, but provides a variety of data that other apps don’t—notably, the instantaneous power output at your location, given the time of day. It’s a handy way to see whether your solar array is working as advertised.

Evasol, by a French solar installer of the same name, insisted that I live in the French region of Ardèche and wouldn’t let me override or enter my own electricity rate. Its measurements were imprecise: the best it could do was narrow my tilt to the range of 15 to 35 degrees.

iSolBuddy, by researchers at an engineering school in Lyon, and Solar Total, by the eponymous British solar installer, measured the tilt and azimuth, but failed to return location-specific data or let me enter it manually.

Vario Solar Calculator, by a German renewables installer, measured the tilt of my array, and that was all: no azimuth, no local data. Enel Solar Power, by an Italian solar installer, measured the GPS coordinates, but not the tilt or azimuth.

For completeness, let me mention several other apps that provide more limited functionality, again in rough order from my favorite to least favorite:

PV Test (free version), by Italian solar installer Aniketos, doesn’t measure your tilt or azimuth—you enter it manually—but, like Solar Panel Advisor, calculates what your instantaneous power output should be, given the time of day.

Solar Panel Installer ($5), by New Jersey Solar Consulting, has a beautiful, step-by-step interface to collect your geometry and budget data. It calculates how many panels you’ll need to produce a certain amount of energy annually. There’s a button on the last screen labeled “Financial Payback,” but, lamely, it doesn’t calculate anything. It just puts up some legalese informing you that your payback will depend on many factors blah blah.

PV Performance Calculator ($3), by a British solar wholesaler, lets you enter your system parameters and a variety of financial data, and it estimates your payback period. I found that the app greatly underestimated my system’s power output.

PV Solar Calculator ($3) let you enter your system size in terms of one parameter—either DC or AC power output, annual energy production, system cost, or surface area—and calculates the other parameters for you. I find the app significantly overestimated the power output of my array, which I attribute to various reasons: its database predicted too much sunlight at my location, it defaults to an AC/DC derating factor of 85% rather than a more realistic 75%, and it didn’t adjust for suboptimal panel orientation or tilt. The interface also leaves something to be desired. It forces you to enter the system cost even if the power output is all you want, and it doesn’t save your entries, so you lose them as soon as you return to the main screen.

Solar PV Payback calculates how long an array will take to pay itself off based on its size, installation cost, government rebates, and your electricity rate. The app makes you enter the number of hours of sunlight manually—no automatic lookup.

PVm3 calculates how many modules you’ll need to produce a given amount of power, given your location.

Solabacus ($1) asks for your location but doesn’t seem to do anything with it. You can enter your electric bill for a 12-month period, but the app doesn’t appear to do anything with this data, either. Its most useful feature is a catalog of solar module specifications.

ElecCalc provides 10 simple utilities of use to electricians, including how many modules you’ll need to generate a certain amount of power. But it lacks even the rudimentary data lookup of other apps. You might as well just use the iPhone’s built-in calculator app.

PV Master (free version) began by querying a database for location data. And that’s as far as it ever got: the app was never able to reach the database. Based on this performance, I didn’t feel inclined to shell out $12 for the full version.

Photovoltaique (free version) started, promisingly, by looking up my location—and ended, disappointingly, by telling me the app wouldn’t work outside France.

Clearly, there’s an opportunity here for a developer to come in and do a solar app right.

iPhone screen shots by George Musser

To see what might be done to turn things around, I talked to Paul Cole, vice-president of Tendril, in April and again yesterday. Cole is a psychologist by training and has been conducting some pilot projects to see what might get people to save energy. "We have gotten it wrong so far," he says. "It’s less a question of user motivation than that we energy technologists haven’t gotten the right products to the consumers."

Cole has scathing words about thermostats in particular. A study released in April by Lawrence Berkeley labs found that most people who had programmable thermostats didn’t use them. My first reaction was, "Geez, that’s pitiful." Are they really that hard? But I have to admit that I grew up keying hexadecimal machine code into a homebuilt computer, so I might not be the average customer. And even I occasionally find myself in a freezing house because I neglected to reprogram the thermostat for a change in season or schedule.

It’s not just a matter of making thermostat settings easier to punch in, but to make sure the devices provide useful information. If you lower the temperature and force your family members to put on thicker sweaters, will you really save any money? How much? If you go through all the trouble of weatherstripping your windows, will it pay off in your heating bill? A thermostat should be able to calculate all that for you.

Cole’s group did a pilot study of 100 homes on Cape Cod starting in June 2009. Folks got smart thermostats and energy monitors that gave them direct feedback about their power bills—not only their real-time usage, but also how their usage compared to their past usage, to the usage of other survey participants, and to the predicted consumption for a house of similar size. An online forum let people share ideas, brag about their energy savings, and ask an energy expert for advice. It also offered a list of 25 steps to take (see below).

In the first six months, homeowners reduced their electric bills by an average of 10 percent. Most started off with simple measures like swapping out light bulbs and gradually turned to more elaborate ones such as replacing appliances. "Over time, we saw more equipment-based changes," Cole says. More significantly, perhaps, he says they have kept their consumption low since then—no dieter’s regress. People log in to the site once or twice a month on average. They used to pose their questions to the expert, but, over time, increasingly turned to one another.

Other studies have likewise found that social feedback encourages energy savings. Another psychologist, Robert Cialdini, has also co-founded a company (now part of Opower) to let people know how their energy usage compared with their neighbors’, and early reports suggest the peer pressure works.

Tendril incorporated its lessons into its Energize web-based and Android/iOS apps, which started to ship this week. (Unfortunately, "ship" means "ship to electric utilities"; it will be a while yet before consumers will get to use the system, although Cole demo’ed it for me.) The system lets you set energy goals, check your progress, see where you stand and post tips. What I liked about it is that it works even if you aren’t lucky enough to have a smart thermostat or power monitor. Your monthly bill (which Tendril downloads from the utility for you) is enough to get going.

If you do have a smart thermostat, you can program it through the app, and a slider shows you much the new settings will save (or cost). The company has also been working on a whole new paradigm for thermostat programming. Instead of having to enter numbers for each setback period, you’ll be able to choose a profile that matches your lifetyle: for example, whether everyone works or goes to school during the day, or the house is always occupied. Those of us who like to punch in numbers can still fine-tune the settings.

One problem is that you’ll have to wait for your utility to offer Energize, which it may never do. Also, the system will work with some but not all third-party equipment such as energy monitors. This isn’t Tendril’s fault per se—they have an open API—but device manufacturers need to make the effort to interface with the system (an issue shared by DIY efforts such as Pachube). Finally, the system is electric-only. Cole says they have plans to incorporate gas (which accounts for the bulk of my energy bill) but haven’t set a date yet.

Before talking to Cole, I was worried that social-networking efforts had failed for lack of willingness—because people would sooner not know how much energy they squander. But it seems people are quite willing to take real steps, if only developers can make it easy and fun.

Image credit: iPhone screenshot courtesy of Tendril

1. Use power strips on home entertainment system
2. Use power strips on home computer system
3. Reduce wattage in multiple bulb fixtures
4. Power off external computer speakers
5. Use CFLs in indoor fixtures
6. Clean your dryer lint filter
7. Run your dishwasher with a full load
8. Set your dryer timer to the minimum time required
9. Use lighting controls or timers
10. Install ENERGY STAR indoor light fixtures
11. Scrub your dryer lint filter periodically
12. Turn off outdoor lights during the day
13. Use your dishwasher’s economy mode
14. Close your refrigerator door
15. Unplug chargers when not in use
16. Activate the high-spin setting on your washing machine
17. Air dry dishes
18. Use fluorescent tube lights
19. Air dry clothes
20. Turn off your desktop computer at night
21. Check the temperature of your refrigerator or freezer
22. Install a programmable thermostat
23. Install CFLs in your outdoor light fixtures
24. Unplug your TV when not in use
25. Check your refrigerator door seals

Heat pumps, of whatever variety, give you the giddy feeling of breaking the laws of physics. The gas boiler in my basement is 80 percent efficient; burning gas unavoidably heats the exhaust gases as well as the water for the radiators. An electric heater is almost 100 percent efficient. But a heat pump can be more than 100 percent efficient. A 1000-watt electric heater emits 3400 BTU of heat in an hour, but the same amount of electricity, used to run a heat pump, might transfer 15000 BTU of heat into the house.

The trick is that a heat pump moves heat rather than generating it. It’s basically just an air-conditioner or refrigerator. During summer, it cools the house; during winter, it runs in reverse, warming the house by refrigerating the outdoors. The outdoors barely notices (unless you’re in an urban area thick with heat pumps)—it’s like spitting in the sea, which scarcely affects the sea, but does affect the spitter. No matter how cold it gets out there, there’s always some heat to harvest, although the task gets harder the colder it gets. By avoiding the production of new heat, the pump evades the naive efficiency limit. It still takes energy to run, but the energy is used mechanically (to circulate and compress a refrigerant) rather than thermally.

Most heat pumps scavenge heat from the outside air. A geothermal one gets it from the ground. In fact, the word "geothermal" is deceptive. These devices don’t tap into geysers or volcanic hotspots. At the depths we’re talking about, the ground is heated not by Earth’s interior but by the sun. "This energy is just solar energy—it’s just another form of it," explains Patrick Ryan of Ryan Energy Technologies in Union, N.J. A better term is "ground-source" heat pump, but "geothermal" has stuck because it sounds so much sexier.

As sunlight warms the surface, heat diffuses downward—a slow process that mutes the daily and seasonal temperature variations. In dry soil, the annual temperature swings are halved with every three feet of depth, so the subsurface temperature quickly approaches the average surface temperature, around 55 degrees Fahrenheit here in New Jersey. That’s already pretty close to a typical thermostat setting, so a ground-source heat pump has less work to do than an air-source pump does and therefore consumes a half or third as much energy.

Two weekends ago, Ryan showed me one of his projects in Whitehouse Station, in the rural western part of N.J. (Yes, there is a rural western part of New Jersey.) The system consists of a horizontal lacework of pipes buried eight feet under a large meadow where the owners are now planting an apple orchard. Water circulates through them and reaches a temperature of 45 degrees. It doesn’t get all the way up to the ground temperature of 55 degrees, because it is flowing too quickly to come to equilibrium with the ground.

Flowing into the basement, the water enters a heat exchanger, where the water pipe wraps around a refrigerant line. The water heats up the refrigerant, cools off to 40 degrees, and flows back outside to warm up again. The pump mechanism then compresses the refrigerant, raising its temperature without adding any heat. Finally, a fan blows air through the refrigerant coil and into the ducts of the house. Another coil preheats domestic hot water, saving money on that, too. In the summer, it is the air that warms the refrigerant that warms the water, sucking heat out of the house and pushing it into the ground. To watch Ryan explaining the system, see the camera-phone video I’ve posted to YouTube.

Unfortunately, the economics aren’t quite as wondrous as the technology. In 2009 Ryan gave me an estimate for my house. Our property is too small for a horizontal loop, so it would have taken three 400-foot wells down into the Triassic-era sandstone under our house. Another complication was that we’d have had to replace our steam heating with forced air. Heat pumps don’t do steam: the temperature difference is too large. The total cost was so outlandish that I use it to this day as a party joke: $70,000, plus the costs of acquiring the permits and repaving our driveway after the drillers had dug it up. A state rebate would have covered $10,000, and a Federal tax credit a third of the remainder, but no bake sale was going to cover this one.

What’s more, it was hard to know how much I’d save. Although heat pumps use less energy, they use electrical energy, which, BTU for BTU, is several times more expensive than natural gas. A rough estimate for my net savings was a third, in which case the payback period would have been longer than my life expectancy. The heat-pump maker ClimateMaster has another savings-calculator here.

Others confirm that retrofitting an old house for geothermal heat makes sense only under limited circumstances. Tom Mandel in Teaneck, N.J., one of the first homeowners in the state to give it a go, estimates he paid $55,000 and saves $400 a month. So he doubts he’ll ever recoup the expense. He adds that his house takes longer to heat up than before and requires an extra boost from an electric heater when the outside temperature drops below 20 degrees.

Geothermal can make sense for new construction, especially in areas where there’s no gas hookup. Alan Sexstone, who responded to a Twitter request I put out for geothermal users, says he decided on a geothermal heat pump when he and his wife built a house south of Morgantown, W.Va., 11 years ago. The system comprises three 100-foot wells and cost about $10,000 to install—about twice as much as propane or electric heat, but low enough that the system will almost certainly pay for itself. Like Mandel, Sexstone says the system works well down to about 20 degrees, below which he needs to supplement it with a wood stove.

Another homeowner I heard from through Twitter built a house two years ago near Boulder. He paid $50,000 (before tax credits) for his geothermal system and estimates he saves $1000 a year. In his case, the savings partly reflect the lower effective electricity rate he gets because of his solar array.

There is irony here, because geothermal should actually make more sense for old construction than for new. New houses tend to be better insulated, which reduces their heating costs and hence the potential for savings. But this fact has to be set against the extra costs of retrofitting and the larger size of the average new house.

Even If I had the money, I’d probably be better using it to button up my whole house as tight as that docking module. After all, the ultimate way to heat your house is not to heat it. Some superinsulated houses stay warm by the body heat of their inhabitants. That’s hard to pull off with an old house like ours, but in an upcoming post I’ll tell the story of a nearby homeowner who has nearly done it.

I also plan to revisit the topic of geothermal heat pumps (and of space shuttles—I’m going down to the Endeavour launch next week), so please let me know your experiences here or on Twitter.

Geothermal installer Patrick Ryan. Photo by George Musser.

That’s what social networks could be good for. People’s competitive instincts might well be the country’s biggest energy source. Also, there’s so much confusing and conflicting information out there that it would help to be able to share our experiences of what works and what doesn’t. In the past couple of years, a number of sites sprouted up to meet this demand.

And now they’re withering away one by one, reports energy blogger Chris Kaiser at Map-A-Watt. He should know. Kaiser started to build a platform to share energy statistics; I tried out a beta version last summer. Then he had to pull the plug. Wattzy turned out the lights in October, and Hug Energy blew a financial fuse in January. The latest victim is Microsoft Hohm—an awkward Microsoftian name for a promising approach that I will miss.

Only a few sites remain:

• Google Powermeter automatically downloads your energy usage from a home energy monitor or, depending on where you live, your utility. You can share the info with friends, if they care, which frankly they probably don’t. The main use, for me, has been the ability to monitor my solar generation from work. You can hack Powermeter to show gas-meter readings, if you have the right kind of meter.
• Read Your Meter has the distinct advantage of recording gas as well as electric usage. Despite what the name might suggest, though, it doesn’t do the reading—you do. You have to type in the data from your utility bills manually. Energy Guy is much the same thing without the social-networking component.
• Welectricity also requires you to type in your data manually. I’ve found it quite buggy; I kept encountering broken links. Only 227 people in the whole country have signed up for it so far. (If you do, friend me; my userid is gmusser.)
• OPower and Tendril (through its acquisition of GroundedPower) provide social-networking software to utilities for them to turn around and provide to their customers. At least, I think they do—their Web sites are incomprehensibly thick with bizspeak. I’m hoping to talk with Paul Cole at Tendril next week and will post my findings.

I’m not quite sure what is going wrong, but my hunch is that people would sooner divulge their salaries than their energy stats. Or maybe they just don’t know their stats. If you fall into this category, get yourself a real-time energy monitor. Point being, the technology is out there—what lacks, for reasons good or bad, is the willingness to use it. As always, let me know your thoughts and experiences in the comment fields below or on Twitter.

Power-tower photo © Copyright Eric Jones and licensed for reuse under this Creative Commons Licence

My life in the past several years has been a living lightbulb joke. I’ve changed, re-changed and re-re-changed the bulbs in my house trying to find replacements that save money but don’t make our skin look like zombie flesh. Compact fluorescents and LED lamps save energy, last longer, and emit less heat than incandescent bulbs. But their light is ickier, versions advertised as "dimmable" often dim only over a limited range, and CFLs take maddeningly long to come to full brightness. No single type works everywhere. LEDs are great for desk lamps, but their narrow beams fail to fill larger spaces. In darkly painted rooms, I went with cold-cathode fluorescents with a low brightness temperature. I’ve filled a big box in the basement with all the bulbs I’ve tried and rejected. So much for saving money.

The color quality has to do with how these bulbs work. The white(ish) light you see is given off by a phosphor coating. In a CFL, the phosphor glows when backlit by ultraviolet light from mercury vapor; in an LED bulb, it soaks up light from a pure-blue LED. (The mercury is why you can’t just throw a CFL in the trash when it dies.) On the left is a graph showing the spectra of incandescent, CFL, and LED bulbs; the x-axis is the wavelength in nanometers. Although this particular graph was provided to me by vu1, which has a certain self-interest in showing its competitors in their worst light, it matches information from other sources such as the lighting control company Lutron and the RPI Lighting Research Center. The CFL spectrum is a series of spikes, reflecting the combination of phosphors used to approximate white light; CFLs therefore accent certain colors and fail to render others.

LED bulbs, which use a different type of phosphor, have a smoother spectrum, but the blue LED that drives the phosphor creates a sharp peak in the blue, short-wavelength range of the spectrum, which might pose a "blue light hazard." Ignacio Provencio of the University of Virginia will have an article in our May issue about how our eyes have a special class of photoreceptor that doesn’t form images; instead it absorbs blue light to synchronize our body clock with the day/night cycle. Too much blue light could disrupt your sleep cycle. I’ve also seen claims that excessive blue light might fry your retina and increase your chances of developing macular degeneration. The French counterpart to OSHA issued a report last November warning that children are at particular risk, although Physics World quoted other experts who thought the claims overblown.

The new ESL bulbs use a phosphor, too, but one that does not absorb light at all—instead, it absorbs electrons. Roughly speaking, ESLs are cathode-ray tubes repurposed as lamps. The electrons stream off a metal cathode plate and are pulled by an electric field toward an anode, a thin layer of metal on the backside of the phosphor. Charles Hunt of University of California at Davis, who helped to develop the phosphor, explained to me that ESLs differ from the CRTs used in old TV sets by virtue of their lower electron densities and energies.

Because they use a different phosphor, ESLs provide a somewhat more natural light; see the spectrum at left. The company claims all sorts of other advantages, too: the bulb turns on faster, shines omnidirectionally rather than in a narrow beam, dims over a wider range, and contains no mercury. I’ve been trying out a demo, an R30 spotlight for a recessed fixture in my kitchen. When you flip the switch, it comes to full brightnesss in a second or two. My wife judges the light to be yellower and milder than a CFL’s. Measured with a Kill-a-Watt, the bulb draws 16 watts, about as much power as a CFL of the same brightness, roughly equivalent to a 60-watt incandescent. I’m able to dim it down to, or up from, 20 percent of maximum brightness. The main downside is that the bulb is much heavier than any other I’ve ever tried—nearly a pound.

Since vu1 first announced the bulbs last year, people on Internet discussion groups have worried about x-ray emission, since the technology is similar to that of an x-ray tube. Hunt said ESLs do produce some x-rays, but at levels below the ambient background dose. The company says that UL-certification included x-ray safety testing.

The R30 begins shipping this week, for $20. The company says it’ll introduce an A19 standard bulb shape in the summer, followed by decorative and vanity lighting.

Image and graphs courtesy of vu1

Both devices came out about a year ago and provide more detail about where you’re using electricity than a whole-house monitor such as The Energy Detective (TED) does. You or your electrician install it by opening your electrical service panel, clamping a little magnetic coil around each circuit wire, and attaching the coils to an interface box. eMonitor has two crucial differences from both EcoDog and TED. First, the interface box plugs directly into the home computer network—it doesn’t have an intermediate step of sending data over your electrical wiring, which, in my experience, can be flaky.

Second, the eMonitor interface sends the data to an outside server rather than to your own PC. That server does all the calculations and record-keeping, and you visit a web page to view the data. Thus the system works on Windows, Macs, Linux boxes, iPhones, whatever. The interface buffers 24 hours of data (soon to be 14 days, in a coming update) in case your Internet connection or the company’s web server goes down. The company has a demo page you can visit to see a sample data display. The server does entail a monthly fee, but the system itself is a bit cheaper than EcoDog’s, so the total price works out to be comparable.

The same question that I had for the EcoDog comes up: Is the system really worth it for most people? Tim Durant, the company’s vice-president of business development, says they did a customer survey last November and half the respondents reported saving up to 20 percent on their electric bill. An eighth reported saving more than 20 percent. For those people, the system might indeed pay for itself. Obviously, it also depends on how high your electric bill is, although I suspect that people who have high bills are paying mostly for air-conditioning or heating, and an energy monitor isn’t going to help much with that.

Some savings come simply from being conscious of how much power you’re using and resolving to cut back. A little blinking box can be a useful ally in the eternal battle to get the family to turn off unused lights. Some savings come from detecting suspicious deviations from standard operating procedure. Both EcoDog and eMonitor can alert you if they sense something awry. For instance, Durant recalls how he recently got a warning that his freezer was using an abnormal amount of juice. He went to check on it and found that someone had left the door ajar. Last year, Durant says, one of the company’s founders got a message that the kitchen stove had been left on by accident.

If an electric hot water heater begins to use more power, it might be a sign of sediment build-up. If a freezer seems peculiarly thirsty, something might be wrong with the defrost cycle. The system can also watch for safety hazards (and code violations) such as a circuit that routinely draws more than 80 percent of its rated current.

The potential of monitoring devices, as yet untapped, is to let you compare your power usage to other people’s, so you can keep up with the eco-Jonses. "There’s plenty of opportunity to tie this into social networking," says one of eMonitor’s first users, Arnold de Leon. He lives with his wife and daughter in Cupertino and has provided feedback to the company to debug the device and software.

At the same time, energy monitors will probably save countless marriages by revealing that something you thought was a power hog isn’t. De Leon says his oven draws a lot of power when it’s on, but doesn’t even rank in the top-10 loads over the course of a day. He has also found that you might as well leave LED holiday lights on all the time; a timer would use more power than it saved.

Ironically, De Leon says he’d already done so much to conserve energy that the new monitor hasn’t really helped him cut his usage. This is the paradox faced by early adopters: We’re the ones willing to buy these systems, but get the least benefit from them. For my part, I doubt EcoDog or eMonitor would justify its cost. Gas is by far the bigger fraction of my energy bill. So I got excited about when Durant told me the company plans to release a gas-monitoring system later this year. He says it’ll be able to correlate gas and electricity usage to look for patterns. Now that might pay for itself.

Screen shot courtesy of Powerhouse Dynamics

I brought up workmanship last week in the context of municipal codes, permits and inspections. Installers complain about the costly and seemingly arbitrary requirements that many cities, towns and counties impose. But the other side of the story is that local officials have the important responsibility of watching over installers. A couple of people slammed me in the comments field for letting bureaucrats off too easily and giving ammunition to solar’s detractors, but they neglected to address the reality of sloppy installations. A bad fire or lethal electrocution could zap public enthusiasm for photovoltaic power and jack up insurance premiums for all solar homeowners, even those whose installers did everything by the book.

Asbill is an electrical engineer, certified installer and member of a Department of Energy “Tiger Team” that goes around the country offering solar expertise. He tells me about a talk he gave in November 2009 to a meeting of installers and inspectors in Sonoma County, Calif. “It was a really nerve-racking talk, to be honest,” he says. His team had spent several days scrutinizing a sample of 15 nearby solar arrays and finding safety hazards in every one. “I was standing before this crowd and pointing out their mistakes,” he recalls. “I was nervous.”

In an electrician’s version of Where’s Waldo, he put up photos of incorrectly installed equipment and asked the audience to spot what’s wrong. In the photo at the top of this post, for example, the red wires should be white. As code violations go, this one is fairly minor. A skilled electrician never trusts the color-coding, but lots of DIYers are not so savvy and might be led to assume a wire is hot, or not, based on its color.

This double circuit breaker should have a warning label on it, indicating that the electricity is flowing into the service panel (from the solar array) rather than out (to an appliance or lamp). Again, a skilled electrician takes the right precautions regardless of what labels do or don’t say, but not everyone is so diligent.

Here, the installer used a nonstandard part. Asbill speculates that the installers got out to the site only to realize they didn’t bring the right part, so they scrounged around in their toolbox for a substitute. The system works, for now, but will probably wear out prematurely.

This one is more serious. The terminal at the upper right should have a ground wire in it. Grounding protects you if one of the live wires ever becomes frayed and makes contact with the metal box. Without it, someone touching the box could be electrocuted.

Look at these. The installer used grounding connectors meant for indoor use and they’re already corroded.

It doesn’t take an experienced inspector to see that a dangling conductor can’t be good, either.

Now this is a real doozy. The installer never put in AC emergency cutoff switches! So there’s no easy way to shut off the equipment if someone needs to work on it.

Despite Asbill’s initial nervousness, he says the audience took his critiques to heart. Sue Kateley, the executive director of the California Solar Energy Industries Association, raves about his presentation to this day. She has her own litany of complaints, such as a cracked electrical conduit that lets water in or is overstuffed with wires, causing mechanical wear. Greg Sellers, president of Burnham Energy, adds that many installers fail to check whether the general household wiring is up to snuff.

Asbill says he understands why installers cut corners and inspectors miss them. Both are overworked and undertrained. The solar industry is expanding so rapidly that education hasn’t kept up. Some states don’t even require electricians or roofers to get specialized training before they enter the solar trade.

Most installers guarantee their work for 10 years, but they don’t do regular check-ups. So I see a huge potential for after-sales service companies to step into the breach. Just as I get my boiler cleaned and checked each fall, I should get my panels examined annually to make sure everything is tight and nothing is hot. Such companies might also offer to upgrade panels when the technology improves enough to warrant it. Solar arrays may be rated for 25 years or longer, they won’t make it that long without some TLC.

Photos courtesy of Corey Asbill

I had a love-hate relationship with the mounds of paperwork I had to fill out to install my solar panels. On the one hand, who likes paperwork? On the other, I was grateful for such consumer protections as my town, state, and utility were able to provide. That’s the side of the story the Times article failed to capture.

My ambivalence is a microcosm of what is happening with solar energy right now. As the other costs of installing solar panels come down and the industry scales up, regulatory costs loom larger. Those costs, according to the industry study cited by Times, account for $2,500 of the cost of an average residential or small-scale commercial solar installation, or $0.50 per watt of power-generating capacity. Streamlining and standardizing the procedure would, the study estimated, reduce that to $600. These figures are broadly consistent with data collected by the Vote Solar Initiative. In my own case, the installer had to pay $371 for the building permit, $350 for a structural analysis, and some unspecified but not insubstantial amount to hire people to fill out the forms, drive to town hall to file them (which has to be done in person), confer with inspectors, and spend an evening at a town planning meeting.

For some homeowners, these costs tip the economic balance. "Permitting, especially for small projects, adds a significant cost to a project on the borderline of being affordable," says Sky Stanfield, an attorney at Keyes & Fox in Oakland, a firm that specializes in renewable energy. She adds that people are put off by the time commitment: "As we move past early-adopters, it’ll be harder to ask the average homeowner to sit through the meetings."

Perhaps worse, each town, city, and country in the nation sets its own requirements, and they vary enormously. Confusion reigns. Some officials issue a permit after a fairly minimal check; others require elaborate diagrams and engineering studies. Anecdotes abound of the insolence of office. Architect Rob Strong tells of one local building department that insisted on a full property survey, at a cost of $1,500, even though it was completely irrelevant to the panels’ installation and operation. Engineer Corey Asbill of New Mexico State University recalls a building department that required an I-beam to support the panels, even though the roof was plenty strong already. Greg Sellers, president of Burnham Energy, which consults for solar companies and agencies on permitting and inspection procedures, says some municipalities don’t even state their requirements explicitly, forcing installers to play a guessing game of submitting a permit application over and over until they get it right.

These tales of woe are beginning to resonate. Earlier this week, the California Energy Commission announced a new program to help local officials expedite permitting. Many municipalities in the state have already revamped their process and gotten high marks from the California Solar Energy Industries Association (CALSEIA). Last year, Phoenix—which charged three times more than the Arizona average for a permit—took heed and lowered its fee.

At times, though, methinks installers doth protest too much. When their dealings with officialdom don’t go smoothly, there is plenty of blame to go around, as even many veteran industry insiders accept. "The solar companies aren’t always prepared," says CALSEIA executive director Sue Kateley. "They tend to fuss a lot, but if they can cool their tempers down and talk to the building inspectors, they find, ‘Oh, that’s why they do it that way.’"

For one thing, requirements vary because places vary. Towns have different building vintages, climate conditions, and seismic and flooding hazards. Streamlining and standardizing can only go so far. An area with strong winds, say, may require extra-large screws to mount the panels.

For another thing, installers have been known to mess up paperwork and cut corners on the job. Asbill goes around the country doing spot checks of systems and has assembled a grim catalog of poor workmanship. Some problems are relatively minor (if still potentially dangerous), such as missing safety labels; others are ticking time bombs, such as using indoor-rated screws outside; and some make you scared ever to go near a solar panel again, such as blank spots on the wall where emergency shutoff switches should be. "We’ve seen systems that are so powerful that if you touch the wrong conductor at the wrong time, you’ll be vaporized," he says. "I’ve seen too many people not give them the proper respect."

Indeed, if I have any complaint about my own local officials, it’s not that the permitting process was costly or slow, but that the inspections were perfunctory. At least our building inspector took the trouble to go up onto the roof; many don’t bother to do even that. Who has the time to provide any real oversight anymore? Budget cuts and staff layoffs mean each inspector has to cover more territory. "He has no time at all," Asbill says. "He’s just going going going."

Training is also a factor. Ours was one of the first two solar projects in town, and the inspectors had never seen its like before. They could look for generic electrical screw-ups, but were less attuned to a photovoltaic system’s likeliest failure points. "If PV installers and inspectors were better trained, there would be fewer problems," says Asbill’s colleague John Wiles, who helped write the relevant section of the National Electrical Code.

So there’s work to be done all around. Towns need to hire and train people, adopt standardized regulations, and automate their systems—and if that means they have to charge more for permits, then so be it. "We think a smooth process is more key than saving a hundred dollars on a permit," Sellers says.

Manufacturers can ease installation. "Solar as an appliance" is the buzzword. A meeting organized last June by the Rocky Mountain Institute, which developed a plan to make solar power as cheap as fossil fuels, recommended that equipment be standardized and pre-certified, like a stove or clothes washer.

And installers should get their own house in order. "There’s no reason for there to be inefficiency here," says Adam Browning, executive director of Vote Solar. "It can and should be worked out—remove that sand and replace it with Teflon."

"I was bleeding energy out," fellow solar homeowner Paul Proctor told me. "I needed to find out how, and why, and where." I can relate. Even though I’ve worked hard to seal up my house and drive a stake through electricity vampires, I still can’t bear to open my monthly utility bill. So I continue to seek out energy forensics tools to ferret out where energy is going and what I can do to stop it from going there. Proctor has been trying out the FIDO Home Energy Monitoring System from EcoDog and he related his experiences to me last week.

In past posts, I’ve raved about the Kill-a-Watt, a module you plug into a wall outlet to display the power draw of the appliance using that outlet, and The Energy Detective (TED), a coil of wire that clamps around the power cables coming into your house to record your total consumption. Both devices have spawned imitators, and fellow energy blogger Chris Kaiser keeps a excellent list. A study in northern Ontario in 2006 found that TED-like monitors encouraged families to reduce their electricity consumption by an average of 6.5 percent.

But the TED tells you only how much and when, not where the energy is going. It’s a pain to go around the house plugging and unplugging the Kill-a-Watt to track down the culprits. I’ve longed for something that combines the automatic data-gathering of a whole-house monitor with the appliance-level detail of a plug-in module. So I was intrigued last year when two products came out that promised to do exactly that: the EcoDog device and the eMonitor from Powerhouse Dynamics.

Proctor, who lives with his wife and daughter in San Diego, was one of EcoDog’s first customers. He said he became aware he had a serious energy problem when he got to talking with his neighbors about their electric bills. (I guess in San Diego, you can’t make small talk complaining about the weather.) Most were $100 a month or so. His was twice that. (In general, I think we could all learn a lot by sharing our energy experiences, both offline and on. Microsoft Hohm is one way you can do this.)

FIDO works much like TED. Its main innovation is that you clamp a coil of wire around each circuit in your breaker box rather than just the main cables (see photo at left). This coil, known as a current transformer, magnetically registers the current flowing through the circuit. It is attached to a monitoring device that takes readings at regular intervals and transmits them to a USB computer interface. Like TED, the EcoDog device uses the household electric wiring for its transmissions. Proctor said the transmission has been completely reliable, but I suspect that someone running electronic devices that also transmit over the power line, such as home automation equipment, would run into trouble and might need to install noise filters, as I had to do with TED.

The computer app (Windows-only, alas, though a Mac version is planned for later this year) shows a floor plan of the house with all the data arrayed around it. The way Proctor described it, it’s an energy geek’s dream. You can study your patterns of electricity use and find places to cut back. Proctor’s biggest power sink turned out to be a water pump for a decorative pond in his backyard—it accounted for fully half his total electric bill. "I certainly shocked my family when I showed them how much energy was being burned," he told me.

Another use, EcoDog’s president Ron Pitt told me, is to watch for changes in appliances’ power draw as an early warning sign they need fixing. A third application, as my colleague Larry Greenemeier wrote about yesterday, will be to monitor electric-car charging. Proctor has ordered a Nissan Leaf, and FIDO will let him break out the charging costs from the rest of his household power consumption.

On the downside, the EcoDog system, unlike TED, doesn’t interface with Google Powermeter, so you can’t watch your household consumption remotely—say, from your office. The biggest shock, however, is the price tag. Proctor said he paid $1,800 for 16 circuits. You can get the system for $1,300, but that doesn’t include installation if you don’t feel up to it yourself (and you shouldn’t, if you don’t have experience with electrical service panels). The eMonitor is nearly the same price ($1,200) for a roughly comparable system. Depending on the state of your household wiring, you might incur other costs. In an old house like mine, there’s very little logic to how the outlets, lamps, and appliances are grouped together. If I wanted to break down my usage room by room or appliance by appliance, I’d need to shift some outlets from one circuit to another.

Few homeowners can justify these systems based solely on the expected savings, unless, like Proctor, they can slay a serious hog. For now, these monitors are in the realm of fun gadget.

A basic issue is that lamps and most appliances use a piddling amount of energy compared to heating and cooling, at least for those of us who live in climates less blessed than San Diego’s. What would really justify spending money on is an energy monitor for heating and cooling. Surprisingly, none yet exists. It would take a sensor to monitor gas or electric use, a few strategically placed thermometers, and a computerized thermal model of the house. Such a system would conduct an ongoing energy audit of your home. For instance, you might find that some areas are systematically colder, suggesting a need for better insulation. Temperature differences between rooms might signal problems with the air ducts or radiator venting. Temperature differences between upstairs and downstairs might indicate that the house suffers from a chimney effect and would benefit from air sealing in the basement and attic.

I bet a $1,000 thermal-monitoring system could pay for itself within a single season. With that data, you could also see whether super-expensive steps such as deep energy retrofits or geothermal heat pumps would justify themselves. Until someone develops such a system, though, I think you’d still benefit from one of the cheaper power monitors.

Photos courtesy of EcoDog

One of the hardest thing about installing solar panels is getting good information, so I’m happy to report that a new book by fellow solar bloggers Stephen and Rebekah Hren, A Solar Buyer’s Guide, is coming out in a couple of weeks. I invited them to write a guest blog on where they think home solar technology stands.

Many people feel inclined to wait on the sidelines until some breakthrough makes solar energy "work" or until it becomes "affordable." Some of those people are apparently the Obamas, who have refused to allow free installation of solar panels on their roof! But even though solar installations are generally not free, they are still a good deal.

We are quite capable of designing buildings and lives in a sustainable way powered by the sun, and much of the basic technology goes back millennia. Yet historically it has taken a crisis of energy supply or ecological devastation to encourage widespread use of solar energy. After they had burned all there accessible forests, ancient Romans developed the heliocaminus, or "sun furnace," a south-facing room that heated their homes in winter. Similarly, once the British had eliminated their woodlands during the late Middle Ages, they also discovered the joys of solar heating. Access to the sun became a fundamental right in Britain for any building, eventually codified in the Law of Ancient Lights. Today, the impetus comes from global climate disruption and the peaking of per-capita fossil energy supplies.

Why solar has been regarded as a technology of last resort is a mystery to us, because it can be extremely cost-effective. We can harvest the sun’s energy in multiple ways. Instead of just using solar energy to heat our homes in winter, we can heat our water, cook our food, and of course convert solar energy into electricity. You can make your home carbon-free, as we have done with our 1932 bungalow (see photo above), or you can put up a solar water heater or smaller photovoltaic (PV) system that offsets only some of your home’s or office’s fossil energy use.

Cost-effectiveness depends not only on a wide array of varying federal, state, and local incentives, but also on the efficiency of the system. Turning solar energy into heat is simpler and typically more efficient than converting it to electricity, so paybacks on solar water heaters are often quicker than for PV systems, but check out your local situation before making any assumptions. Some areas have spectacular incentives for PV at the moment. While a system of patchwork incentives is obviously less than ideal, until the mammoth subsidies and tax breaks for the fossil fuel industries are removed and a carbon cap or tax is established to account for their detrimental effects, such breaks for solar energy allow it to be on a more level playing field. They help create economies of scale and drive technological progress that should help reduce prices in the future.

Technology is advancing all the time. One very cool gadget that is now being incorporated into solar electric panels is the microinverter, a topic of past Solar at Home blog posts (here and here). These sophisticated gizmos are capable of converting the DC juice being pumped out by each individual PV module directly into AC power right there at the module.

One huge advantage of the microinverter is that it mitigates shading problems on the PV array. When installed on the roof, an array will often suffer from partial shading some time during the day due to trees, another building, chimneys, and so on. Conventionally, the output from an array of PV modules is sent to one main inverter, and even small amounts of shade can have disproportionately large effects on the electricity output due to the way the modules and arrays are wired. Without microinverters, the shading of just one PV module could possibly disrupt production for the whole array. But with microinverters, the production from the shaded modules can be isolated, allowing the solar juice to keep flowing from the rest of the array.

Using microinverters, PV array wiring is faster and more straightforward, and the power is easier to shut off in an emergency. Microinverters also allow web-based production monitoring of individual PV modules, providing entertainment when the office gets slow. Maybe no one explained these nifty things to the White House.

As the novelist William Gibson quipped, the future is here now; it’s just not widely distributed yet. The technology to harvest solar energy effectively is already available, but it’s up to us to make its implementation a priority, despite what our First Family does. From high-tech gadgetry like the new microinverters to the more prosaic technologies that can heat our buildings and hot water, solar energy is varied in what it can accomplish. There’s no need to wait for some theoretical time in the future, because solar power is here and ready now.

The Hren’s home, courtesy of them

Editor’s Note: Scientific American’s George Musser will be chronicling his experiences installing solar panels in Solar at Home (formerly 60-Second Solar). Read his introduction here and see all posts here.

Solar homeowners’ favorite topic of conversation is the performance of their arrays. As part of the sales pitch, the installer estimates how much power you’ll generate, and most systems come with a meter (separate from the utility meter) to monitor the power output continuously. But how can you tell whether your array is really living up to expectations? That simple question set me off onto a mathematical hunt that other solar homeowners might enjoy — and which would make a good term-paper project for a high-school science class.

There are lots of tools out there to estimate the performance of a solar array. NOAA provides an applet and Excel spreadsheet to determine the sun angle at any time of year based on the astronomical geometry, with corrections for atmospheric refraction and the offset between clock and solar time. The PV Watts website combines solar geometry with historical weather data to calculate the expected performance for a panel at a given location with a given orientation. PV Performance also factors in the properties of the solar cells and the inverter that converts their DC output to household AC power. For site-specific issues such as shading, you need to make more detailed measurements. The New Jersey state inspector who signed off on my system used a nifty 360-degrees light meter called the Solar Pathfinder.

So much for the predictive tools. To measure the actual output minute-by-minute, I have two independent energy monitors that are installed in my electrical service panel: the TED5000 and the Locus. They display the total array electrical output through a web interface.

Useful though they are, these devices don’t separate out the myriad factors affecting power output: solar geometry, weather, diffuse vs. direct illumination, shading, reflection off the glass surface of the panels, temperature dependence of solar cell output, solar cell and inverter efficiency, and so forth. These effects work in concert. For instance, if the temperature gets so hot that it cuts the output of the solar cells, the total array output can drop low enough that the inverter chokes.

To weigh some of these effects quantitatively, I put together my own spreadsheet to calculate the expected power output for June 30th — a nice, mild cloud-free day when the air temperature at our site stayed fairly constant, reducing the confounding effects of weather. Those who want to choose a similarly opportune day can look up their local weather records at Weather Underground.

Over the course of a day, the intensity of sunlight varies sinusoidally with time. The amplitude and phase of this sinusoid changes with the seasonal cycle, but in retrospect I didn’t really need to worry about that. I could just have drawn a cosine curve and stretched and shifted it to match the midday peak power. Between 9 a.m. and 3 p.m., the array output followed a sinusoid almost perfectly (see the blue curve in the above plot).

In the early morning and mid- to late-afternoon, however, the output fell off more rapidly than the illumination conditions alone would explain. So I went down the list of other factors.

First, I took a bit more care with the geometry of my roof. Usually, panels in the Northern Hemisphere are assumed to point in the general direction of south, tilted upward. My roof, however, also slopes toward the west, so my panels are tilted along both their long and short axes. It took some linear algebra to account for this orientation. The effect was to give the sinusoid a slight skew.

Second, sunlight passes through a greater mass of air in the early morning and late afternoon, attenuating it. Bradley Hibberd, director of engineering at Borrego Solar Systems, pointed me toward a model adopted by the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE). (For those who care about the technical details, the model uses the Beer–Lambert law, whereby the solar intensity is reduced by the exponential of the secant of the angle between the sun and the zenith.) This helped to explain why the power fell off so dramatically outside the peak hours.

Third, I considered losses due to sunlight glinting off the panel glass. A paper by Sandia Labs has a graph showing how reflection becomes a serious issue when the incidence angle of the sun’s rays is greater than 55 degrees, which in my case meant before 9 a.m. and after 4 p.m. The drop-off goes roughly as the cube of the angle. Incorporating this into my spreadsheet further reduced the off-peak power.

Finally, I took into account the efficiency of my inverter. Below a certain power level, the inverter isn’t able to convert the DC to AC very effectively, giving you the double-whammy of less sunlight and less power per unit sunlight. I approximated this fall-off using as a power law.

Between inverter, reflectance, and atmospheric attenuation, I was able to account for the diminished array output during the morning hours (see red curve). That left the abrupt decrease in the mid-afternoon to explain. I suspect it might be shading. A tree and chimney are located just west of the array, and although they’re not very tall, even partial shading would cause a sharp loss of power. The panels are wired in electrical series, so that whatever affects one of them affects all of them. The Solar Pathfinder measurements showed somewhat more shading in the west than in the east, which should cut into the power output beginning about 3 p.m. One of these days when I find myself at home in the mid-afternnoon, I’ll go up to the roof to see what’s going on.

My analysis was really just the first step and I’m not sure that I’ve really isolated the important effects among all the possible ones. I’d love to hear how other people have sought to explain the performance of their systems!

Graph courtesy of George Musser

Editor’s Note: Scientific American’s George Musser will be chronicling his experiences installing solar panels in Solar at Home (formerly 60-Second Solar). Read his introduction here and see all posts here.

As if the news coming out of Washington about a climate bill weren’t bad enough, state budget crises are also sucking the blood out of many local renewable-energy programs, which are the only concerted action the country is taking on climate right now. In my own state of New Jersey, the rebate for buying a solar array was temporarily suspended in May as the state went scrounging for loose change to plug a general budget gap. It has since been reinstated — partly. Now it provides homeowners only half the money it used to.

The state has also pick-pocketed the funds that ratepayers put into the regional carbon-trading exchange. This money comes from a surcharge on fossil fuel power, which amounts to an average of 41 cents on a $110 monthly electric bill. Conservatives have sought to repeal the surcharge altogether, which is odd, because a true free-marketer would actually want to increase the surcharge until it captured the full external costs of using fossil energy.

Similar dramas have played out in Arizona, Massachusetts, Pennsylvania, Florida, and California as solar incentives have been suspended for varying reasons.

In many cases, though, the subsidies have suffered not from budgetary shenanigans but their own sheer popularity. Evidently the word is getting out that solar is a great deal. It remains so. In New Jersey and elsewhere, the diminished subsidies are partly offset by the higher market value of the tradable credits we receive for the solar power we generate. Also, array prices have fallen by a third over the past couple of years.

So the scaling-back of subsidies, tawdry though it has been, can be seen as a tribute to solar’s success. In fact, solar advocates have always spoken of the government incentives as a way to kick-start to industry — needed only for a limited time. If only we could say the same of subsidies for fossil fuels.

Photo courtesy of George Musser

Editor’s Note: Scientific American’s George Musser will be chronicling his experiences installing solar panels in Solar at Home (formerly 60-Second Solar). Read his introduction here and see all posts here.

A few posts ago, I talked about the tragic conflict between preserving historic homes and reducing their carbon footprint. I thought our solar array had managed to evade the controversy. Our panels were mounted on the rear of our mid-19th-century house, away from the street; the town’s building department, after some delay, approved the project; and the town’s inspectors signed off on the work when it was done. But two months ago I received an alarming notice from the town’s building code enforcer: our array violated the historic district standards.

As readers of this blog may recall, we had a lot of trouble with our installer, 1st Light Energy, and the person who ran our project was fired last year. His replacement is responsive and really knows his stuff. After he mopped up the problems created by his predecessor, I was inclined to feel that all’s well that ends well — until we got that letter.

The problem was that because of the tilt of the panels, the top edge of one of them was visible from across the street (see photo). The installer quickly accepted blame, although I think the building department bore some responsibility, too. After all, our permit application mentioned the array tilt and mounting location, and the department was supposed to have informed us of potential historic issues before they issued the permit.

Our town prides itself on working things out in a non-lawyerly way, so I didn’t want to respond by saying, "You approved it, so go away." Nor did I want to invoke a recently passed New Jersey law that relaxes local planning strictures for renewable energy projects. I’m committed to our historic district. That said, I couldn’t help feeling the victim of a double standard. Elsewhere in town, people have built questionable house additions, contractors have torn down old homes, and a developer built a mini-mall that required a huge number of variances. Here we were, faced with the threat of removing our array because of one errant panel that you wouldn’t notice unless you were actively looking for it.

My wife and our contact at 1st Light went before the town’s Historic Preservation Commission to plead our case. In the end, what defused the crisis was that there was extra space on the roof, so the installer could relocate the errant panel. The utility’s lawyer said the modification would be fine (it wouldn’t trigger a full reassessment of the array), and indeed it doesn’t seem to have reduced the system’s power output.

Nonetheless, this incident shows that towns are still climbing up the learning curve when it comes to solar permitting. For many houses in our town, the historic district rules out solar panels, period. And that’s a problem. We don’t have the luxury to choose between environmental conservation and architectural conservation. We need both.

The errant solar panel, before relocation; photo courtesy of George Musser

In the first installment of this post, Arnold Mckinley of Xslent Energy Technologies described how "reactive power" — that is, power stored momentarily by electrical appliances and then released — destabilizes the electrical grid. Here he explains how home solar arrays can help.

Electricity has traditionally been distributed using a wheel and spoke grid: power travels from a large central generator to loads distributed around it. In some cases, energy travels very long distances, perhaps 500 to 1,000 miles, before being used. That model is changing. Since solar and wind inject energy at numerous local points, the grid is coming to look more like a network than like a wheel — making it even harder than it already is to keep power flowing smoothly. Two recent developments promise to help. The first is a new generation of microinverters, and the second is the growth of the interconnected smart grid.

A solar panel generates DC power, which gets converted to AC power by a device known as an inverter. Most inverters require a certain minimum threshold voltage to work. Therefore the panels must be wired together in electrical series to raise the voltage high enough. Experience has shown that this setup is less than optimally efficient, as an earlier Solar at Home post talked about. A cloud shading a single panel reduces the efficiency of the entire string. Moreover, each panel has slightly different electrical characteristics, creating a mismatch that reduces the power generated. Finally, if the voltage from the string is too low, the inverter never turns on; so on rainy or foggy days, the system generates no power at all. The solution to all three problems is to fit each panel with its own low-voltage inverter, or microinverter. It turns on as soon as light falls on the panel and automatically compensates for the panels’ electrical differences.

But if microinverters were also able to produce reactive power, they could ship the excess over the local load consumption back into the grid, as they do with active power now, and help out the utilities.

The figure at left gives an example of a basic setup where household appliances draw 1000 watts of active power and 600 volt-amps of reactive power. If a solar array can generate 1200 W of DC power, then it is capable of producing 1200 W of active AC power and 1200 VA of reactive AC power. That is enough not only to power the house but also to feed some active and reactive power into the grid. All it requires is the right microinverter.

When the ordinary inverters and microinverters were first developed, the designers paid no attention to reactive power generation. Because consumers pay only for active power, the goal was to produce as much of that as possible. Today it is clear that reactive-producing solar can help stabilize the grid, and microinverters are being designed to produce both. In fact, physics is helping us out here. Since no energy is required to produce reactive power, an inverter can produce it without sacrificing active power or requiring more solar panels.

When I first learned that reactive power can be produced without affecting the active component, I was surprised. To see that this is reality and not fantasy, the figure at the right shows two days of power production at a typical solar facility. On the first day, the microinverter was set to produce both active power (green line) and reactive power (red line); on the second, it was set to produce only active power. The switch did not affect the active power production at all. My company’s website has more details on this issue.

In the past, the big problem preventing microinverters from producing reactive power was the need for weighty capacitors to store the energy temporarily. But new designs pull off the trick simply by changing the shape of the AC wave. This significantly reduces the cost and the size of the devices.

What is more, microinverters are also evolving to communicate with other grid devices, much as smart meters are already doing. Networked microinverters can report data for display on internet browsers, but some also have two-way communication, allowing operators to control their active/reactive power generation mix. Eventually, on-board intelligence will adjust the mix on the fly, providing the best economic benefit to consumers based on their rate structures (which will eventually include reactive power pricing). Such intelligence will allow these distributed networks to separate from the main continental grid and form localized microgrids, so that all the electricity we need is generated where we need it.

Photo and Diagram courtesy of Arnold Mckinley

Solar arrays can do more than feed energy into the power grid. They might also be able to help the grid cope with a problem many people aren’t aware of: the fact that electrical appliances not only consume energy, but also momentarily store and release it. The worst culprits are motors and transformers, whose internal magnetic fields represent a significant cache of energy, giving these devices a type of electrical inertia that causes them to get out of sync with the grid. To describe the problem and a possible solution, I’ve invited a two-part guest blog from Arnold Mckinley of Xslent Energy Technologies. Here’s part one.

We all know that solar power curtails carbon emissions, decentralizes the electrical system, and reduces the nation’s reliance on foreign oil resources, but did you know that solar can now help to stabilize the grid? The grid is highly temperamental. It requires careful monitoring to maintain frequency and voltage within very limited ranges to ensure that motors don’t burn out, that power surges don’t zap computers, and so on. In the U.S. we take quality electricity for granted, but our good fortune comes with a huge infrastructure behind it to make sure it stays that way.

When the grid does get destabilized, the results can be nasty. Blackouts on the West Coast in 1982 and 1996 forced six million people to eat by candlelight. The infamous 1977 New York blackout left deep scars on the city. The 2003 U.S.-Canadian blackout affected 60 million people. In 2004 a joint U.S.-Canadian Task Force compared these events and found that the principal factor common to all was that the demand for reactive power exceeded the supply.

Few people have even heard of "reactive power." So what is it, who needs it, why wasn’t it such a problem before, and how might solar help prevent future blackouts?

We homeowners pay our utility bills based on "active power." It is also known as "real" power, partly because of a mathematical technicality and partly because it carries the kilowatt-hour energy that does the work of lighting our homes, compressing the fluids in our air-conditioners, and pumping water into our swimming pools.

But simultaneously, alongside the active power, flows reactive power. It performs an ancillary service that ensures fluorescent lights actually do light, that computer power supplies actually do work, and compressor and pump motors actually do turn. Modern electronic wizardry, from LCD TVs to electric cars, worsens the reactive-power demand on the transmission lines — so much so that the European Union and the U.S. government are beginning to force manufacturers to reduce significantly the reactive power draw of these devices.

Reactive power flows whenever the load on the grid cause the voltage and current, which oscillate at a very constant 60 hertz, to get out of sync. In the graph at left, the current lags the voltage slightly.

Multiplying the voltage and the current together gives you the power. It is the sum of two components: the active power, which averages to a positive number and therefore represents the energy delivered to the load, and the reactive power, which averages to zero over a full cycle and represents energy that moves back and forth between the grid and the load. That is, the reactive energy flows in one direction toward the load, then turns around and flows in the other direction toward the generator, repeating every cycle.

The total power is measured in kilo-volt-amps (kVA), the active power in kilowatts (kW), and the reactive power in kilo-volt-amps-reactive (kVAr). The ratio of kW to kVA is called the power factor (pf). If pf equals 1, all of the kVA power is active power; if it equals 0, all of the kVA power is reactive power. Home energy monitors such as the TED 5000 display this quantity.

Reactive power causes instabilities for two reasons:

1. It impedes the flow of the useful traffic on the transmission lines. In essence, the fluctuating energy takes up room on the transmission lines that could be used for active power.
2. Excessive reactive power can cause sharp drops in voltage. If, for example, drawing a certain amount of active power causes the voltage to drop from 118 volts to 117 volts, drawing the same amount of reactive power will cause it to drop from 118 volts to 108 volts. That is, by definition, a brownout.

In the next article, I will explain how a new solar technology, called microinverters, can help control the reactive power on the grid and help stabilize our electrical system.

Photo and diagrams courtesy of Arnold Mckinley

Solar power involves wondrous quantum physics and materials science, but its fate may hinge on whether contractors can learn to bolt on the panels without losing too many screws. The panels themselves account for only about half the cost of a solar array; the rest is the installation and back-end equipment. As panel makers slash their prices, the nuts and bolts loom ever larger. Fortunately, a quiet revolution is now underway in installation. Brendan Neagle, the chief operations officer of Borrego Solar, a major U.S. installer, says they’ve sped up installation by 40 percent over the past two years. Zep Solar has invented a new roof mounting system, already supported by the module maker Canadian Solar, that speeds things up by another factor of two. And Nat Kreamer, president of Acro Energy, another large installer, says they’ve streamlined the preparation work and can get a system up on your roof within 30 days of your first phone call — quite an improvement on the eight or so months it took me.

In fact, historically, most of the cost savings for solar power have come on the low-tech side. According to a Lawrence Berkeley Lab study last year, arrays in 1998 cost about $11 per watt of generating capacity: $5 for the modules themselves, $6 for the installation and equipment. By 2008 the modules have fallen by $1 per watt, the installation by $2. Prices have come down as installers have climbed up the learning curve. And there’s clearly room for them to do even better. The study reported that arrays in Germany are $2 per watt cheaper than in the U.S. "Anything that is inefficient needs to be attacked," says Mike Miskovsky, the general manager of Canadian Solar.

Zep Solar CEO Jack West says he began to rethink mounting systems 12 years ago. The roof-mounted rack for a typical 5 kW array consists of 429 metal rails, screws, washers, and other parts that must be hauled up to the roof, kept organized so they don’t go missing, and bolted together using a power drill and a set of nut drivers. The electrician must then run grounding wires to all the metal pieces for safety. Often the parts are a mix of copper, aluminum, and steel, creating dissimilar metal junctions that slowly corrode. In a few years, we may see a wave of grounding failures that create a risk of electrocution for anyone who touches an array.

The system he and his colleagues developed has 91 parts (see the comparison photo above, although it shows a 2 kW rather than 5 kW system) and requires just the drill and one specialized hand tool. The system has a minimalist elegance. A small, adjustable mounting bracket anchors each panel to the roof, and a lateral Erector-set-like piece connects adjacent panels, providing both mechanical support and a grounding connection. In the company’s demonstration video, a pair of workers installed an array in 15 minutes, versus one hour for the standard array (not counting the set-up time on the ground). ZepSolar vice-president Daniel Flanigan claims that the system reduces labor and parts costs by about 50 cents per watt. It also makes it easier to remove and replace a panel should the need arise.

I should point out that I haven’t verified these claims firsthand, although I can attest to the difficulty of assembling a conventional mounting frame. Neagle agrees that most mounting systems are baroque and says he likes the Zep approach, although he’s waiting to see how it proves itself in practice.

Neagle told me about the myriad other ways Borrego has cut installation costs. They preassemble panels into units of four before arriving on the site, standardize practices such as which side of the array to run the wires on, and, adhering to the "measure twice, cut once" adage, thoroughly plan out the installation before anyone gets near a ladder. The company has a team of people who do Frederick Taylor-like controlled experiments of new techniques, using a stopwatch and timekeeping logs. They both collect ideas from workers and train and retrain them. Kreamer offered similar lessons and also says that cost-cutting generally means consolidating smaller firms into a larger company to spread out the overhead costs.

One challenge, says David Kaltsas, vice-president of SunWize, a large distributor of wholesale solar equipment as well as a residential installer on the West Coast, is a shortage of experienced and talented workers. And that’s also a reason that solar arrays are, for the most part, not quite a DIY project yet. Putting them up take expertise and, if anything, the amount of expertise they take has been increasing. Over time, the efforts to simply the process for the professionals may filter down to us weekend warriors. For now, though, I think homeowners would be grateful simply for lower prices.

Photo courtesy of Zep Solar

Earlier this week I posed the question of whether old houses will ever be able to reduce their energy needs by the factor of five or so needed to combat climate change. My discussion was inspired, in part, by a provocative essay written last year by preservationist Sally Zimmerman of Historic New England. Yesterday she wrote to say that my post and the comments that people left have been widely circulated among preservationists. She offered some more thoughts that I think frame the issue beautifully:

Here in New England, where we depend heavily on oil heat and where old houses constitute a large component of our housing stock, we have to deal head-on with the seeming contradictions of conserving energy and preserving historic architecture. But does this mean these two goals are in conflict? Maybe not, if preservationists and conservationists can find a way to meet each other halfway. From the preservation perspective, here are some thoughts on where we are coming from.

1. Old houses are not the problem: We can’t solve the energy crisis on the backs of our "old" houses. According to the U.S. Census Bureau, just over 8% of the nation’s existing housing units were built before 1920. Perhaps making the nation’s "new" houses more energy efficient should be called the "92 percent solution."
2. Early adopters of new technologies pay a higher price: Innovative gadgets usually need some shelf time to bring the cost down and work the bugs out. We should bear this in mind with cutting-edge green technologies and materials and keep them out of our old houses until we know they are safe and effective. "Really old" houses (such as houses built more than 150 years ago) really aren’t the place to experiment with the newest technologies: they’re just too rare and important to be subjected to an onslaught of the most innovative energy strategies. Considering the age and significance of a house will help balance historic preservation and energy efficiency goals.
3. Go ahead and pick the low-hanging fruit: By all means, do everything you can to make your old house less energy consumptive with retrofits that are easily achieved and don’t damage or destroy historic fabric: blower door tests; air sealing; insulating attic floors, basement ceilings, pipes and ducts; weather-stripping and adding storm windows and doors; and keeping heating and cooling equipment serviced. New England preservation and energy groups have already teamed on a new guide outlining prudent strategies. And Historic New England, with 36 house museums, plans to retrofit the 1793 Lyman Estate for a 50 percent reduction in energy use with comprehensive, but reversible, interventions.
4. Keep it simple: Sophisticated "deep energy retrofits" that include super-insulation of exterior walls, roofs, and foundations yield dramatic reductions in energy consumption but may have too many "moving parts" for an old house whose "parts" have very likely moved, shifted, settled, sagged, and generally been mucked-around with a lot already. The USGBC and the American Society of Interior Designers offer good information on the scope of the deep energy retrofit but preservationists will argue that this solution is better suited to newer houses (see the "92 percent solution," above).
5. Get with the program: Energy interventions are a critical part of the solution to a global threat. Recently, the Advisory Council on Historic Preservation issued a prototype programmatic agreement with the Department of Energy providing guidance for preservation regulators around the country to approve energy retrofits that don’t damage significant fabric or publicly visible aspects of historic properties. Old houses have adapted to new technologies before and they can do it again as long as those of us who love old houses and our green planet approach energy interventions with common sense and an open mind.

Energy audit at Lyman Estate. Courtesy of Historic New England