Copyright Goodheart-Willcox Co., Inc. Chapter 12 Radiant Heating Systems 243 12.2.4 Solar Thermal Storage A renewable energy alternative to conventional fossil fuels is the use of solar thermal storage for hot water generation. Our sun provides an abundant level of thermal energy every day. It is estimated that two weeks of the sun’s energy radiating onto the Earth is equivalent to all of the known amounts of oil, gas, and coal available. The challenge has been to harness this energy and transfer it into hot water to heat our homes and buildings. Solar thermal storage is achieved by first using solar collectors to capture the sun’s energy, Figure 12-10. These collectors, or solar panels, are typically flat plate or vacuum tube collectors filled with water or glycol and mounted in the path of the sun’s rays. As water in the collector is heated, it is circulated through a storage tank and then pumped into radiant heating circuits, Figure 12-11. Solar thermal stor- age systems have the capability of generating supply water temperatures in excess of 150°F, depending on their size and efficiency. They are ideal as a supplement to fossil fuel or geo- thermal heating systems and can increase system and fuel efficiencies dramatically. Chapter 19, Solar Thermal Storage covers these systems in greater detail. GREEN TIP Clean and Efficient Geothermal Energy Geothermal heat pumps are one of the most sustainable sources of renewable energy available. They can provide a lower operating cost than any conventional type of residential or commercial heating system available. A geothermal system differs from a conventional furnace or boiler because of its ability to transfer heat via the refrigeration cycle versus the standard method of producing heat by burning fossil fuels. Super-efficient geothermal heat pumps provide quiet, clean heating while re- ducing energy bills by up to 70%. Compared to solar or wind energy, geothermal systems can perform even if the sun does not shine or the wind does not blow. 3-way mixing valve Radiant panel circuits Check valve Air separator Heating source Buffer tank Goodheart-Willcox Publisher Figure 12-9. A buffer tank should be used when incorporating a heat pump for hot water generation. Ivan Smuk/Shutterstock.com Figure 12-10. An example of a vacuum tube solar collector.