When most of us think of solar power, we think about sunlight being converted to electricity, which is then used to power various applications. However, for thousands of years, the power of the sun was understood quite differently. Everybody knows from the example of the sun and magnifying glass that the oldest way the sun has given us power has been through heat, not electricity. Solar thermal systems are applications that use this same approach and convert sunlight to heat instead of electricity. In most cases, this results in a far more direct application of the sun’s power into our everyday lives.
The use of solar thermal systems isn’t as varied as that of solar power, but it nonetheless has a lot of purposes. Solar thermal systems create varying amounts of heat depending on their usage, and they are designed differently depending on the temperature they are trying to attain. Models that generate a low level of heat are normally designed as flat plates, and these are used to heat things like swimming pools. Systems that create medium temperature levels are usually used for houses to boil water or even heat a stove or oven. The solar thermal systems that generate the most heat usually involve mirrors or lenses that magnify or focus the sun’s light to make the most heat possible.
Ironically, the most powerful solar thermal systems are most often used to convert that heat back to electricity. While this may seem like a convoluted way to convert sunlight into electricity, it is actually the norm for most energy sources. Consider gasoline in an automobile – the gasoline is not made into power; it is fed into the engine, where small amounts of it explode. These explosions generate massive amounts of heat, which ultimately is what the engine uses as its power source. This is the principle applied to most energy sources.
Solar energy is unique in that it cannot be stored in the way gasoline can; we must convert it into heat or electricity while it is available. The idea of converting sunlight into heat instead of electricity seems convoluted at first glance; after all, why involve the middle step? But it’s actual efficiency depends on what the power is being used for. Converting sunlight into electricity is far more efficient if that power is going to be used right away. However, not all power is used right away, which is why we store fuels.
Electricity itself is very hard and expensive to store, which is one of the reasons why solar power is hard to utilize as an energy source. Because sunlight itself can’t be stored, and electricity is expensive to store, this greatly limits either the usability or the profitability of solar energy. However, heat is not nearly as hard to store. It is relatively inexpensive to keep heat sustained, at least compared to electricity. So while it doesn’t make sense to convert sunlight’s power to heat energy for direct use, it carries definite potential for the long-term use of solar power as an energy alternative.
Solar power represents a very small percentage of the world’s energy supply – less than 0.02%. Part of this is because of our lack of ability to store solar energy as electrical power. Solar thermal systems, however, can partially eliminate this problem, which is why their continued development bears watching. Of course, the technology of solar power is constantly in development, which means that solar thermal systems may no longer be necessary in the future, especially since research into them doesn’t get a huge amount of money or attention. But as things stand, they are a very effective supply of energy storage that hasn’t been tapped as much as it should.
