Solar thermal energy increasing in popularity
Efficiency is an important element in any energy application.
For example, if we burn natural gas in a boiler at home, since heat is what we want, and heat is the primary product of combustion, 91 percent of the BTUs in the incoming gas can be distributed through the rooms.
On the other hand, when gas is burned to generate electric energy, the power plant wants to use the violent expansion that occurs when a liquid changes to a gas. That mechanical energy uses about 30 percent of the energy stored in the gas. The remaining 70 percent is just heat, and in this application, there is no use for it. The efficiency of this application is only 30 percent, and the resultant electricity contains only about one-third as much energy as the gas that was burned.
With renewable energy, efficiency is equally important, even though the fuel is free. Here, return on investment takes center stage, as in the case of solar thermal energy.
On a clear day, the sun delivers about 300 BTUs per square foot to anything on the earth’s surface that is facing it directly. Note that this makes square footage of exposure a very important factor in the use of the sun. Also, the term “right angle” is important, because the sun, that’s angle over the earth is constantly changing, is rarely right over any particular point.
Subject to these limitations, solar thermal can be an efficient energy source.
The fuel is free; it is easy to collect without high-tech equipment; and it can be stored in floors and interior walls, or in water.