Home photovoltaic systems for physicists

© 2008 American Institute of Physics, S-0031-9228-0807-030-0 Physicists seldom allow students in their courses to escape without understanding and being able to perform calculations pertaining to energy. Outside of science circles, however, “energy” generally refers not to an overall conserved quantity but rather to the large-scale conversion of stored energy into electricity, locomotion, or manufacture. Physicists have much less contact with the conversion aspect of energy, though it is tremendously important to society. Two hundred years ago, the ability to harness energy helped stimulate an industrial revolution that was accompanied by an explosion of agricultural productivity, human population, and economic growth. But human society has never before experienced energy availability at today’s scales—each year some 4 × 1020 J is converted for human activity. About 85% of that energy derives from the use of fossil fuels. At some point in the near future, humankind must necessarily see a declining annual availability of fossil-fuel resources, given their finite nature and geological limitations to the rate of their extraction. That decline will be most sharply felt for petroleum, but it is also relevant for natural gas, less so for coal. The disappearance of global resources that are so important to our way of life is unprecedented. We have little choice but to adapt by reducing demand, migrating to alternative energy resources, or, very likely, employing a combination of both strategies. It was with those concerns in mind that I decided to explore the practical side of photovoltaic energy: In 2007 I built a PV system to power my living room. Though reasonably well informed on the semiconductor physics of PV junctions, I felt unsuitably prepared to evaluate the practical realities of owning and operating a personal solar PV system. Because I believe physicists can play a role in our energy future that extends beyond the confines of advanced research, I want to share my experiences in the hope that others might develop home PV projects. What better way to motivate innovation in the alternative-energy sector than to get a talented pool of physicists engaged on a personal level?