SOLAR WATER HEATING

Besides using design features to maximize their use of the sun, some buildings have systems that actively gather and store solar energy. Solar collectors, for example, sit on the rooftops of buildings to collect solar energy for space heating, water heating, and space cooling. Most are large, flat boxes painted black on the inside and covered with glass. In the most common design, pipes in the box carry liquids that transfer the heat from the box into the building. This heated liquid—usually a water-alcohol mixture to prevent freezing—is used to heat water in a tank or is passed through radiators that heat the air.Oddly enough, solar heat can also power a cooling system. In desiccant evaporators, heat from a solar collector is used to pull moisture out of the air. When the air becomes drier, it also becomes cooler. The hot moist air is separated from the cooler air and vented to the outside. Another approach is an absorption chiller. Solar energy is used to heat a refrigerant under pressure; when the pressure is released, it expands, cooling the air around it. This is how conventional refrigerators and air conditioners work, and it's a particularly efficient approach for home or office cooling since buildings need cooling during the hottest part of the day. These systems are currently at work in humid southeastern climates such as Florida.Solar collectors were quite popular in the early 1980s, in the aftermath of the energy crisis. Federal tax credits for residential solar collectors also helped. In 1984, for example, 16 million square feet of collectors were sold in the United States, but when fossil fuel prices dropped and tax credits expired in the mid-1980s, demand for solar collectors plummeted. By 1987, sales were down to only four million square feet. Most of the more than one million solar collectors sold in the 1980s were used for heating hot tubs and swimming pools.Today, about 1.5 million U.S. homes and businesses use solar water heaters—still less than one percent nationwide In other countries, solar collectors are much more common; Israel requires all new homes and apartments to use solar water heating, and 92 percent of the existing homes in Cyprus already have solar water heaters.But the number of Americans choosing solar hot water could rise dramatically in the next few years. With natural gas prices at historically high levels, solar water and space heaters have become much more economic .According to the U.S. Department of Energy, water heating accounts for about 15 percent of the average household's energy use.[4] As natural gas and electricity prices continue to rise, the costs of maintaining a constant hot water supply will increase as well. Homes and businesses that heat their water through solar collectors could end up saving as much as $250 to $500 per year depending on the type of system being replaced. Solar water heating (SWH) technologies are a simple, reliable, and cost-effective method of harnessing the sun's energy to provide for the energy needs of homes and businesses. Simply stated, SWH systems collect the energy from the sun to heat air or a fluid. The air or fluid then transfers solar heat directly or indirectly to your water supply.Though these systems have been in use for centuries, with today's technological advances, SWH technologies can be operated efficiently and affordably in any climate. Systems are specifically designed for various climatic and geographical areas of the country. Regions with temperatures that fall below freezing require the use of an indirect or drain-back system, while warmer, sunnier climates can use a direct system, which directly heats the water to be used.SWH systems also provide an important opportunity to reduce our nation's growing demand for energy from fossil fuels. By installing a SWH system, a typical household can meet 50 to 80 percent of their hot water needs. In warm and sunny climates like Hawaii, a SWH unit can meet 100 percent of a household's hot water needs. Reduced demand for fossil fuels will improve the environment by reducing air and water pollution as well as the heat-trapping gases that cause global warming. And though they cost a little bit more up front to install, a SWH system will save consumers money in the long run as the fuel source (the sun's energy) will always be free.Currently there are more than 300,000 SWH units installed across the United States (excluding swimming pool applications). While the number of installations continues to grow by the thousands every year, there still exists an enormous untapped market with great potential for reducing a significant portion of our nation's energy use. Continue reading below to learn more about solar water heating systems and another clean energy technology for heating your home or business, the geothermal heat pump. Links to additional and more detailed information about these technologies can also be found below.