Overlooked but not forgotten, solar thermal deserves a second look

By Pierre Bull. Posted December 4, 2013.  When Kevin Virkler’s daughter Megan takes a shower—the kind of long, hot shower that only an adolescent can take—he doesn’t worry anymore about how much warming up all that hot water is going to cost. The reason? Solar hot water heating. Solar hot water and heating, sometimes called solar thermal or, also, solar heating and cooling (because some cooling technologies are activated by heat), is a technology that’s more than 100 years old, invented first in Baltimore in the 1890s. Passed over in many of our attentions by its sexier cousin - solar photovoltaics, solar thermal has much to offer. In fact, a recent report by the Solar Energy Industries Association estimates that solar heating and cooling (SHC) in the U.S. could, by 2050:

• Generate almost 8 percent of the nation’s heating and cooling.
• Create more than 50,000 good paying jobs.
• Save $61 billion annually on energy.
• Cut carbon dioxide emissions by 226 million tons every year(the equivalent of taking 64 coal-fired power plants offline for good).

How it works: solar hot water heating, and SHC in general, are based on a simple principle, one we know well from parking our cars in the hot sun. “Something left out in the sun is going to get hot. And if you put glazing over it, that’s going to trap the sun’s heat,” explains Tim Merrigan, a solar thermal expert from the National Renewable Energy Laboratory.   Residential solar thermal collectors, the most common type of solar thermal technology in use today, are pretty simple devices, usually just 4’ x 8’ black, metal boxes with glass covers that are mounted on roofs. Water or another liquid is piped through the box, to pick up the trapped heat. The hot water can be stored in a water tank; other liquids can be used to transfer that heat, or can power radiant heating systems or heat air to heat buildings or use as process heating in industry.

See rest of original article