- Solar thermal plants concentrate and carry heat.Frank Chmura/Photodisc/Getty Images
Solar thermal plants are designed to harness the heat of the sun and use it directly. Electrical power plants use photovoltaic cells to convert the sun's energy directly into electricity. Thermal plants catch the heat of the sun and then move it away from the plant, either storing it for later use or using it to turn water into steam, which powers turbines. There are many different structure models for thermal plants, but the primary difference lies in what media they use to transfer the heat. - Water is an easy medium to use in a solar thermal plant, for several reasons. It can absorb energy from sunlight easily, and can be turned directly into steam to power turbines without further manipulation. It is also cost-effective, and leaks or spills cause relatively little damage to the plant. However, water can also increase the rate of corrosion for the plant, and does not hold heat as long as other substances.
- Solar thermal plants sometimes use a thermal oil for heat transfer. Oil is useful because it can absorb and hold heat for long periods. Plants that use oil can pipe it to tanks and store it for later use after it has been circulated through the heating dish of the plant. This versatility is offset by oil's higher costs, and the potentially greater damage in the event of leaks or spills.
- Molten salt is a useful heat transfer substance. Once it reaches its melting point it stays there easily, storing the heat passed to it by the plant, which concentrates the sun's energy until it reaches high temperatures. Molten salt can be stored in tanks even longer than oil, until the heat is passed out into water to create steam and turn turbines.
- Hybrid plants use a combination of media. Many use oil to take the heat from the plant, but create storage tanks of molten salt that the oil passes the heat onto for longer periods of storage. This allows the plant to become more efficient.
Water
Oil
Molten Salt
Hybrids
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