September 22, 2010 | 28
Editor’s Note: Scientific American‘s George Musser has been chronicling his experiences installing solar panels in Solar at Home (formerly 60-Second Solar). Read his introduction here and see all posts here.
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