I'd put my money on the sun and solar energy. What a source of power! I hope we don't have to wait until oil and coal run out before we tackle that.
- Thomas Alva Edison, 1931
The oil embargo of the 1970s prompted a national surge of interest in solar energy. A solar water heater was installed in the White House, and photovoltaic panels first came into play, notably in California. While previously solar power as a direct source of electricity had been limited to esoteric functions, such as in spacecraft, companies began to form with the idea of using solar as a regular source of power for ordinary homes.
Theoretically, solar might seem an ideal energy source, as it is free and virtually limitless. According to Greenpeace, "The solar radiation reaching the earth's surface in one year provides more than 10,000 times the world's yearly energy needs" (4). Furthermore, "harnessing just one-quarter of the solar energy that falls on the world's paved areas could meet all current global energy needs comfortably" (Flavin). Yet the technological barriers to harvesting this energy are great regarding collection, distribution, and storage.
Through the end of the 20th century, solar remained a power source for the eccentric few, accounting for well under 1% of energy generation. As the energy crisis waned, it quickly became apparent that solar was not competitive with conventional energy sources, such as coal. One commentator well captures the frustration: "For years, supporters of solar power have heralded every new technical breakthrough as a revolution in the making. Yet time and again it has failed to materialise, largely because the technology was too expensive and inefficient. It simply cost too much, and solar panels settled in as a small niche market" (Daviss).
In the 1990s, as climate change moved in the public consciousness from an esoteric theory to a scientific fact, interest in solar returned, notably in Europe and to a lesser extent in the United States. In the 21st century, growing worries about an energy shortage on a planet voracious for power have added to the demands for solar energy. As Greenpeace points out, "The market has grown by more than 40% a year for almost a decade and the industry is investing large sums to increase production facilities" (3).
The above summary is a bit simplistic, as, technically, humans have used solar power throughout history, notably as a source of light and, in the long run, as a source of pretty much everything, including our very planet. Situating and constructing buildings to best use the light that nature gives us every day is called passive solar. Buildings have long been positioned to take advantage of light and heat, for instance by having large south facing windows to allow plenty of sunlight. For further discussion, see the Discovery Guide Green Buildings: Conserving the Human Habitat (section 4) (http://www.csa.com/discoveryguides/green/review4.php).
This Discovery Guide is not about passive solar, but about more "active" uses of solar as a direct means of replacing energy currently generated mainly by fossil fuels, such as coal, oil, and natural gas.
These more "active" solar energy uses can in turn be divided into two main groups. The first is Solar Thermal, which traditionally has been used to heat water and is increasingly being used, in a more centralized fashion, in large energy plants. The second is solar cells, which can in turn be divided into bulk or wafer based, usually employing silicon, and thin film, which employs a variety of metals and is easily manufactured and installed, but currently requires more square footage to do the work of wafer based cells.
This points to a crucial factor: the efficiency, or percentage of solar energy that can be captured and converted into electricity. In the past this has been too low to allow the technology to replace a substantial portion of fossil fuels; "the efficiency with which a cell can convert light into electricity has been the technology's Achilles' heel" (Daviss). Almost as important are energy storage and delivery, how to get the energy when and where it is needed.
Go To Photovoltaic Cells
List of Visuals
- President Carter inspecting a solar heating panel installed on the roof of the White House.
Photo: Jimmy Carter Library.
- This Bethesda, MD home has photovoltaic panels in front and solar collectors in the rear for heating the family's water.
Photos by author.