Harnessing Energy from the Sun
HAVE you ever gotten into an automobile that has been closed up and sitting for a long time in the hot sun? The heat can be almost unbearable! No question about it, the sun is certainly a tremendous potential source of energy.
Just think of it, the sun’s energy could be used to heat our homes, operate our home appliances, light our cities, drive our vehicles or fill any other power needs we may have. In fact, so much solar energy falls on the earth that if man could harness its flow for just fifteen minutes he would have enough power to supply world’s present needs for a full year!
There are skeptics, however. They believe that sunshine is too diffused to be a practical energy source. Yet, according to J. T. Kane, editor of Professional Engineer: “Something on the order of six to ten times the amount of energy required to heat the average building in the U.S. radiates down on the building from the sun each year.”
But is harnessing energy from the sun really practical? Can homes today economically utilize this fabulous flow of energy?
A Practical Energy Source?
You may be surprised at the strides that have already been made in harnessing solar energy. The distinguished geologist Dr. M. King Hubbert noted: “Solar energy is not just a theory. We’re talking about things that already exist, things we already can do.”
What are some of these things? For instance, can the sun be harnessed to supply a home with electricity? In a letter to the editor of the New York Times, United States Senator James Abourezk explained: “The technology for converting solar energy into substantial quantities of electricity is available.” The senator therefore urged: “The major effort should center on converting solar energy into usable electrical energy.”
As yet, though, there is no economical way of doing this. True, there is little question that the sun could be harnessed to provide all the electrical needs of one’s home. Orbiting spacecraft use the sun’s energy to power electrical equipment on board. But producing electricity from sunshine is still too expensive to be practical.
Most authorities believe that the first step in utilizing the sun’s energy is not in producing electricity, but in heating water and in heating and cooling buildings. Some solar experts say that it is practical for many homeowners to do this even now. The idea is to capture the sun’s heat, store it, and circulate the heat to warm the house, or to use the heat to run an air-conditioner.
D. Elliot Wilbur, marketing and business director of Arthur D. Little, a firm involved in solar research, notes: “All the materials to install solar heating in buildings are available on the market right now. All that’s needed is a company that’s willing to put the entire package together and offer it to the general public.”
Will companies begin doing this soon? Peter E. Glaser, a vice-president of the Little firm, is optimistic. “Within three to five years,” he claims, “you should be able to buy a solar heating system from a Sears catalogue.”
Is there sound basis for such optimism? Is a massive solar-heating industry about to develop?
There is no question about the increased interest in solar energy. Last May thousands of persons attended a solar-energy seminar organized by the Solar Energy Industries Association in Washington, D.C. And when the Environmental Information Center of Winter Park, Florida, announced a free booklet, “How to Build a Solar Water Heater,” the first 5,000 printing was exhausted in ten days.
Newspapers and magazines carry a flood of stories about solar energy being used to heat swimming pools, homes, schools and other buildings. To mention just a few reports:
◆ A Colorado developer is installing a solar-heating system in a new condominium complex.
◆ The city of Santa Clara, California, plans to heat and cool a new community center with energy from the sun.
◆ Solar heating is being installed in an Atlanta, Georgia, school; already schools near Washington, D.C., Baltimore and Boston are heated by solar energy.
◆ In Vermont, sunshine heating is planned for a new colony of vacation and ski homes.
◆ Western ranchers are seeking to replace propane driers with solar-heat collectors to dry their grain.
What has prompted this interest in the use of solar energy? Principally, the realization that a change in the present system of generating power is inevitable. It must come. Why? Because the main sources of our energy—oil, natural gas and coal—are limited, with some experts claiming that reserves will run out soon. Already fuel prices have skyrocketed. Furthermore, the use of fossil fuels is beginning to pollute the environment to an objectionable extent.
Future for Solar Energy Brightens
There is much to be said for solar energy. It is abundant and available to all, it does not pollute the environment, and it is free, the only cost being to harness it. It is claimed that, if solar-heating systems were mass produced, they would be more economical than conventional heating systems.
Knowing the merits of solar energy, many scientists are urging its use on a large scale. Dr. Harold I. Zeliger, a New York chemist, went so far as to tell an international environmental conference recently: “It seems obvious that the only long-term solution to the world’s energy-pollution problem is the use of solar energy.’’
This source of energy is also gaining political credibility. For many years the United States government spent only about $100,000 annually on solar projects. But in 1973 this jumped to $4 million, then to an estimated $25 million in 1975, and for 1976 a congressional source foresees more than $100 million going into solar research and development.
In some countries the sun already is harnessed to provide much of the hot-water needs. In Japan, for example, about 160,000 solar hot-water units were sold in 1974. Israel was said to have some 150,000 of such solar installations, providing sun-heated hot water for about one of every five families. And an estimated 10,000 Australian homes use solar water heaters.
Sunshine could also soon be a significant energy source in the United States. It may surprise you, but well over 80 percent of the average homeowner’s energy bill is for hot water and for heating and cooling. And more than a quarter of all the energy consumed in the country goes for these three uses! So if sunshine is harnessed for just these purposes, millions of barrels of oil will be saved daily.
One study last year showed that in the U.S. nearly two hundred solar-heated homes were either completed, under construction or planned. To equip these homes, a solar-hardware industry has emerged; in fact, there are reportedly dozens of solar-equipment makers. But what, you may wonder, is involved in a modern solar-heating system?
How the Sun’s Energy Is Harnessed
Since the industry is in its infancy, there is little standardization. But the basic system consists of a solar-energy collector, a storage tank to hold the heat, and a distribution system.
The collector is usually placed on the roof, and is angled to catch the maximum amount of sunlight. The basic principle of the collector is that of a greenhouse. Black absorber panels are covered by glass or plastic. These panels may consist of aluminum sheets painted with a special heat-absorbent black coating. A fluid, commonly water, is piped through the black paneling. In one system, the paneling is corrugated and the corrugations are ribbed with radiator-like pipes.
Sunlight penetrates the glass or plastic, and the black paneling absorbs the trapped heat. Water flowing through the pipes in the paneling may be heated to 200 degrees Fahrenheit and more. This hot water flows to the storage tank, usually in the basement. In a simple hot-water system, however, the tank is often placed on the roof along with the collectors. About a 140-gallon tank will provide a family of four with hot water.
But to fill also heating and cooling needs, a several-thousand-gallon storage tank is required for an average-size U.S. house. One system heats the house in this way: The hot water is siphoned from the tank to heating coils in a duct. Air is then blown through the coils, heating the air, and the hot air is circulated to warm the house.
In order to cool the house, the hot water is routed through an air-conditioner that has been modified to use hot water as a heat source, instead of a gas burner. There is much to be said for solar air-conditioning, because when the sun shines hotter and more air-conditioning is required, the energy is available to operate the system.
But can an efficient solar-heating system now be mass produced? Many scientists think so. Two professors at upstate New York’s Syracuse University wrote: “Technology is far enough along to begin applying it on a large scale. Some researchers, engineers and architects, including members of the Syracuse University’s Energy Research Council, feel at this time that it is possible to build homes, even in our latitude, that depend entirely on solar energy for heating.”
As noted earlier, some solar experts feel that in three to five years such a solar-heating system will be on the market. But Chicago University professor Roland Winston, who also has spent years in solar research, warns: “It’s a long way from a handful of solar homes to buying a solar heating plant at Sears.”
It will be interesting to observe developments. But, at the same time, what about the prospects for solar-produced electricity?
Solar Energy for Electricity
There are two often-discussed ways to produce electricity from the sun. First, sunlight may be used to heat a liquid that produces steam, which, in turn, drives a turbine engine. It is estimated that a solar-collecting area of five to seven square miles would fuel a steam plant capable of matching the energy output of the largest nuclear power plants. The construction of such a solar electrical plant has been urged by some.
“It appears possible,” notes Dr. R. C. Jordan, head of the University of Minnesota’s School of Mechanical and Aeronautical Engineering, “that, using today’s materials and processes, we can convert 20% of solar energy falling on the Earth at a given point to thermal power and then to usable electric power. This would mean enough power to serve the requirements of this nation for many years to come, and do it at a cost we can afford, making use of unused portions of our land such as deserts without causing pollution.”
This type of electrical power plant, however, is considered the wrong approach by some. Dr. Erich A. Farbet, head of one of the world’s largest solar-energy research efforts, says: “You don’t build a large power plant in Arizona and send the energy to Florida. Solar energy falls on your roof, your yard, on the walls of your house. It can be economically developed right where you are. You don’t need large solar-energy power stations.”
It is true, sunlight can be converted to electricity right at home. This can be done by solar cells. These are thin, waferlike chips of silicon that produce an electric current when sunlight strikes their surface. These photovoltaic cells now produce electricity on orbiting spacecraft. And a thousand square feet of these long-life cells attached to the roof could furnish the electricity needs of a modern home. However, solar cells are much too expensive for such use. Yet they need not always be, claims United States Senator James Abourezk.
“There are,” he says, “numerous laboratories around the country currently producing photovoltaic cells, which, if produced on a mass basis, could (in the opinion of solar cell engineers) become competitive with other forms of electrical generation. . . . And converting solar energy to electricity will have a far greater impact on many more people than attempting to install solar heating and cooling devices in every home in the United States.”
What Future for Solar Energy?
Truly in the sun we have a bountiful, pollution-free source of energy that can be harnessed to serve human needs. How will this be done? When? These are good questions.
Admittedly, there are obstacles. Machine Design observes: “That solar energy has been largely ignored can probably be blamed on economics, vested interests, and government bureaucracies that are founded on fossil-fuel systems.”
Will such obstacles be overcome? Will there be a real commitment to develop this non-polluting energy source, thus conserving earth’s fast-disappearing reserves of oil, natural gas and coal? It will be interesting to watch.