4.7 Solar Energy: the Pros and Cons; Geology and Alternative Energy Sources

4.7 Solar Energy: the Pros and Cons; Geology and Alternative Energy Sources

The term solar energy generally refers to the direct use of the sun’s rays to supply energy for the needs of people. The simplest and perhaps most widely used passive solar collectors are south-facing windows. As sunlight passes through the glass, its energy is absorbed by objects in the room. These objects in turn radiate heat that warms the air. In the United States we often use south-facing windows, along with better insulated and more airtight construction, to reduce heating costs substantially.




More elaborate systems used for home heating involve an active solar collector. These roof-mounted devices are usually large, blackened boxes that are covered with glass. The heat that they collect can be transferred to where it is needed by circulating air or fluids through piping. Solar collectors are also used successfully to heat water for domestic and commercial needs. For example, solar collectors provide hot water for more than 80% of Israel’s homes.

Although solar energy is free, the necessary equipment and its installation are not. The initial cost of setting up a system can be substantial, including a supplemental heating unit for times when solar energy is diminished or unavailable, such as cloudy days, winter, or night time. Nevertheless, over the long-term, solar energy is economical in many parts of the United States and will become even more cost-effective as the price of other fuels increases.

Research is currently underway to improve the technologies for concentrating sunlight. One method being examined uses mirrors to track the Sun and keep its rays focused on a receiving tower. A solar collection facility with 2000 mirrors has been constructed near Barstow, California. Solar energy focused on a central tower heats water in pressurized panels to more than 500 degrees Celsius. The superheated water is then transferred to turbines, which turn electrical generators.

Another type of collector uses photovoltaic cells that convert the sun’s energy directly into electricity. Today, even with many government subsidy programs and tax incentives, solar energy accounts for less than 1% of U.S. energy consumption. Small rooftop photovoltaic systems are now being used in rural households of some third world countries, including the Dominican Republic, Sri Lanka, and Zimbabwe. These units are about the size of an open briefcase and use a battery to store electricity that is generated during the daylight hours. In the tropics, these small photovoltaic systems are capable of running a television or radio, plus a few light bulbs, for 3 to 4 hours. Although much cheaper than building conventional electric generators, these units are still too expensive for poor families. Consequently an estimated 2 billion people in developing countries still lack electricity.

While solar energy is advertised as clean and free, it is actually neither. The manufacturing process for huge solar panels and banks of storage batteries necessary to generate enough electricity to fully power a home uses a great deal of non-renewable mineral resources and fossil fuel energy just to mine, refine and manufacture the equipment. The great hope was that technology improvements over time would decrease these wastes and costs. Certainly, 20+ years of technological advancements have greatly improved the efficiency of solar panels and batteries, but the initial investment costs are still quite prohibitive for most homeowners. Furthermore, after 20 years of hoping, future promises of better technologies are wearing thin.

The same problems can be attributed to electric cars. Are electric vehicles better for the environment? Yes, but probably not as much as you think. This is because much of the electricity that electric powered vehicles use comes from power plants that use non-renewable fossil fuels. Yes, the pollutants are not coming directly from the car. Rather they are coming from the power plant that generates electricity for the car. The manufacture of the car itself is still in a factory powered by fossil fuels. Nonetheless, modern (and very expensive) electric powered vehicles are engineered to be more fuel efficient than traditional gasoline-powered vehicles, so they generate fewer pollutants per mile.