The July 2008 isue of Physics Today has a special focus: "Energy Today and Tomorrow". It features three articles of interest to chemists and physicists, "Grand Challenges in Basic Energy Sciences" by Graham R. Fleming and Mark A. Ratner, "Energy Efficiency and the Built Environment" by Leon Glicksman, and this one by Thomas Murphy Jr. There is a lot of very glib talk about how how future will be full of photovoltaic electricity and not a lot of "nuts and bolts" about what is required to make it happen. Thomas Murphy does an outstanding job of describing two small photovoltaic systems that he has designed and built himself, using off-the-shelf components. It is a cautionary tale; this is a project that is modestly demanding in its technical difficulty. More sobering is the fact that the systems he built produce less than 200 watts at maximum solar intensity, for about five effective hours per day in San Diego. How long would it take to recover the cost, when a KWH of electricity sells for $.15 in San Diego? Of course, the point is not to make a practical energy generator, but to investigate what it takes to make one work.
Thomas W. Murphy Jr.