Solar energy conversion can be small-scale and low-tech

The interesting feature article “Solar Energy Conversion” by George Crabtree and Nathan Lewis (Physics Today, March 2007, page 37 ) devoted only two sentences to the simplest and cheapest form of solar conversion, the use of un-concentrated sunlight to “heat space and water in residential and commercial applications.” Instead, the article focused on expensive high-tech applications not presently available, at least to the general public.

The immediate answer to the energy crisis is low-tech. Before President Harry Truman left office in 1953, he started a program to develop solar energy, but Dwight Eisenhower scuttled it. I remember attending an energy symposium in the early 1970s where the claim was made that solar energy would never be feasible because it would exhaust our water supply. President Jimmy Carter made a serious attempt to revive solar energy during the 1970s energy crisis, but he was ridiculed. He installed solar collectors on the White House roof, but Ronald Reagan had them ripped out.

Even some members of the technical community have tried to discredit solar energy by making claims that, among other things, solar installations are visually polluting. See, for example, the letters and comments in the October–November 2002 issue of The Industrial Physicist (page 12).

Six years ago, for about $1200, I built and retrofitted from secondhand components a solar space-heating system for our residence, which was built in 1916. In those days, circulating hot-water heating systems were common. They are uniquely suited to conversion to solar heat because the interior heat-transfer arrangement is already in place. All that is needed is to connect solar collectors to the existing system.

A neat feature of the conversion is that the solar heating supplements rather than supplants the gas heating system. On very cold days, we fire up the natural gas and have gas and solar systems working together, with the benefit that free solar heat tempers the cost of the metered gas heat. If the weather is really bad and the sun isn’t shining, we leave the circulating pump from the collectors turned off and rely exclusively on gas heat. Our heating bill has been cut in half.

Our system is sort of a hybrid, like the hybrid autos that when outfitted with plug-in capability will go a long way toward solving that aspect of the energy problem. But that’s another story.