Researchers at Colorado State University developed a solar energy system that integrated air conditioning, space heating, and water heating for use in residential buildings.
Architects and engineers have long recognized the value of the Sun as a source of both heat and light. The ancient Greeks and Romans both incorporated passive solar designs that took advantage of the Sun’s warmth in the winter while blocking it in the summer. From the adobe dwellings of the Native Americans of the American Southwest to the cities of northern Europe, people constructed buildings designed to maximize the Sun’s benefits. The builders often tried to use the Sun for heating water and for cooking, although many of these early attempts at utilizing solar energy were quite crude. By the twentieth century, however, inventors had devised many sophisticated solar-powered devices, including water heaters, stoves, and motors.
Not surprisingly, devices utilizing solar energy were especially popular in areas that enjoyed abundant sunlight, such as California and Florida, although inventors in more northern climates also experimented with solar power. The famous Swedish engineer and inventor John Ericsson experimented with solar motors in the 1870’s. Ericsson, who is perhaps best remembered for his contributions to naval engineering (he designed the ironclad battleship Monitor for the Union forces during the American Civil War), hoped to develop a solar motor that would replace coal-fired engines on steamships. He tried first to harness the Sun’s energy to heat water for a steam engine and then experimented with a hot-air motor. Inspired by the prospect of a cheap fuel source in the form of free sunlight, Ericsson built several working models before abandoning the idea. Sunlight might be free, but the materials needed to build the reflectors required to concentrate its energy were not.
Ericsson’s realization that sunlight, while abundant, was not necessarily cheaply obtained paralleled the experiences of many other solar pioneers. Edward S. Morse, for example, developed plans for solar heating in houses in even northern climates, but was unable to interest many architects and builders. Morse designed a solar air-heating system in 1882 that was installed in a room at the Peabody Museum in Boston. The design was widely admired but seldom copied, possibly because it proved inadequate for the size of the room. In a time when other energy sources such as coal were in abundant supply, the use of solar energy was viewed more as a curiosity than as a serious alternative to more conventional heating systems.
The one use of solar energy that did attract customers at the beginning of the twentieth century was that of heating water.
Kemp’s Climax water heaters were inexpensive, easy to install, and could be purchased for use in both single-family homes and apartment buildings. The Climax water heater utilized what is often referred to as an open system. Water heated in solar collectors on a building’s roof was drawn off and replaced by cold water. This made the Climax unsuitable for installation in climates where temperatures could drop below freezing for long periods of time. Bailey’s Night and Day water heater, in contrast, employed a closed system. A solution of water and antifreeze circulated through solar collectors and then through coils in an insulated water tank. The insulation held the water at a high temperature for many hours following sunset, hence the name Night and Day. Bailey’s heaters proved popular in Southern California, with sales topping one thousand annually in 1920.
The discovery of plentiful supplies of natural gas
Such a crisis occurred in 1973,
Between 1973 and 1981, beginning with the administration of President Richard M. Nixon
Inventors had been refining many of the individual technologies for years. For example, the fact that sunlight could be used to produce electricity had been widely known for more than one hundred years, although it was not until the 1950’s and the onset of the space age that photovoltaics were seen as more than an interesting curiosity. Similarly, solar water heating had been in widespread use for almost a century, and while its use had dwindled in the United States, interest had remained high in other countries, such as Japan and Israel. What made the Colorado State University research particularly exciting was the attempt to put all the various solar technologies together in one package. The result was an integrated solar energy system that would provide residential heating, hot water, and even air conditioning.
The researchers at Colorado State University were not alone in their attempts to develop an integrated solar energy system for residential buildings. Engineers working both in the United States and elsewhere had been trying to develop similar systems for some time. Professional journals such as Solar Energy published numerous articles in which scientists and engineers described their progress toward efficient solar heating and cooling systems. Even amateur inventors had been swept up in the quest for efficient solar energy systems. The May, 1977, issue of Popular Science, for example, as part of its regular monthly feature “Adventures in Alternative Energy,” included a description of a home heating system invented by a New Jersey home owner. O. W. Wood claimed that his system, which was built primarily from salvaged materials, including an old cast-iron radiator, had reduced his family’s consumption of fuel oil by 30 percent.
The integrated system at Colorado State University’s Solar Energy Applications Laboratory was, however, apparently the first project on record to combine all three systems successfully in one house. Many researchers combined solar water heating and solar home heating. Few had considered the feasibility of solar-powered air conditioning, even though the same climates best suited for solar energy applications are also the climates that frequently require air conditioning for at least part of the year.
The Solar Energy Applications Laboratory facility, a residential-type building known as the Colorado State University-National Science Foundation Solar House I, combined the subsystems for heating, cooling, and service hot water in a typical single-family house while meeting all building safety codes and remaining cost-efficient. Solar heat storage, for example, took place in a nonpressurized tank. A pressurized tank, which would have stored water at higher temperatures, would have both cost more and violated safety codes for occupied buildings. Use of a nonpressurized tank also made it possible to dump excess heat easily from the storage tank when heating requirements were lower.
Ease in venting excess heat, in fact, met one of the primary goals of the research project. The design team recognized that the amount of solar energy available often does not coincide with the highest demand periods for either heating or cooling. Heating demands, of course, peak in midwinter when the number of hours of sunlight is the lowest. Any solar energy system must balance the needs of the user, the amount of sunlight available, and the use of auxiliary energy sources in the event that available sunlight is not sufficient to meet heating or cooling demands. In addition, the system must do so as economically as possible. Although many, if not most, home owners would prefer to use heating and cooling systems that are environmentally friendly (that is, systems that are generally nonpolluting and use a minimum of nonrenewable resources as fuel), economic realities may force a consumer to choose a conventional heating system over a solar one.
Researchers hoped that data obtained from Solar House I would lead to solutions to many of the problems that plagued solar energy systems. By combining the three residential systems that consumed the most energy—heating, cooling, and hot water—an increase in overall efficiency was expected. Preliminary data indicated that this was indeed the case. The integrated system showed significant reductions in the reliance on auxiliary energy sources.
In the decades following the 1970’s, much of the sense of urgency that motivated research into solar energy dissipated. As shortages of fossil fuels eased, so did the demand for alternative energy sources. Research funding, once abundant, dried up. Nevertheless, solar energy remains an important resource in many parts of the world. Information gathered from projects such as Colorado State University’s Solar House I has been used to build more efficient and more economical residential heating and cooling systems throughout the United States. Research funded by the National Science Foundation and the Department of Energy led to significant improvements in the solar energy technology available to the average consumer. Solar heat collectors, once bulky and awkward, have been streamlined. Heat exchangers for both furnaces and water heaters are more efficient, less costly, and more reliable (less prone to leaking) than they were in the 1970’s. Manufacturers of water heaters and residential furnaces moved back into the solar energy business. Companies such as Lennox began marketing solar heat collectors meant to be retrofitted as part of the existing hot water system in the home.
Thus, although Solar House I provided no startling technological breakthroughs in solar energy, the research done at Colorado State University and elsewhere remains significant. It serves as an example of how much technological progress actually occurs by using existing technological knowledge in new combinations to achieve incremental improvements. In addition, Solar House I provided immediate, dramatic data that illustrated to the general public the cost-effectiveness of solar energy systems. Using information provided by projects such as Solar House I, housing contractors and home owners could make informed choices regarding energy-efficient and environmentally sound heating and cooling systems.
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Butti, Ken, and John Perlin. A Golden Thread: Twenty-five Hundred Years of Solar Architecture and Technology. Palo Alto, Calif.: Cheshire Books, 1980. Excellent overview of the utilization of solar energy over the centuries. Numerous line drawings and photographs complement the text. -
Chiras, Daniel D. The Solar House: Passive Heating and Cooling. White River Junction, Vt.: Chelsea Green, 2002. An up-to-date, user-friendly guide to passive solar architecture. -
Herda, D. J., and Margaret L. Madden. Energy Resources: Towards a Renewable Future. New York: Franklin Watts, 1991. A useful overview of the history and applications of various energy sources. -
Papadakis, Andreas. Earth-Sheltered Housing Designs. New York: VNR, 1990. Provides detailed information for both home owners and architects on combining earth-sheltered and passive solar designs for energy-efficient and attractive housing in various climate zones. Illustrated. -
Strong, Steven J. The Solar Electric House. 3d rev. ed. Still River, Mass.: Sustainability Press, 1993. A practical guide to the domestic uses of solar power. -
Wade, Alex, and Neal Ewenstein. Thirty Energy-Efficient Houses. Emmaus, Pa.: Rodale Press, 1977. Describes the underlying principles of passive solar and other energy-saving designs appropriate for climates ranging from New England to the desert Southwest.
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