Encyclopedia of Global Resources part 19 provides a wide variety of perspectives on both traditional and more recent views of Earth's resources. It serves as a bridge connecting the domains of resource exploitation, environmentalism, geology, and biology, and it explains their interrelationships in terms that students and other nonspecialists can understand. The articles in this set are extremely diverse, with articles covering soil, fisheries, forests, aluminum, the Industrial Revolution, the . Department of the Interior, the hydrologic cycle, glass, and placer mineral deposits. . | 150 Buildings and appliances energy-efficient Global Resources This solar-powered building in Athens Greece opened in 2007 and is expected to generate enough energy not only to power the building but also to sell the government its surplus. AP Wide World Photos Solar panels or modules are one of the most promising sources of inexpensive and environmentally safe energy. Although earlier efforts to harness solar energy utilized steam from solar-heated water modern solar panels are photovoltaic They produce electricity from sunlight. The phenomenon was discovered in the eighteenth centur y and studied by Albert Einstein in the 1920 s. After the widespread adoption of silicon for circuitr y in the twentieth cen-tur y photovoltaic cells became less expensive to produce and more efficient in power output. The most common forms of silicon used for the cells are crystalline which became available in the 1950 s and amorphous silicon which is more frequently used now. Typically the cells are joined together in panels which may also be connected together in an array. The units are produced in a great variety of forms. In home applications they may be placed on rooftops or in independent structures at some distance from the dwelling. Some units are also designed so that they are able to move over time to capture the most sunlight like the solar arrays on the International Space Station. For homes and other buildings they may also be disguised visually as shingles or other kinds of roofing material so that they are more seamlessly integrated with the design. The most desirable locations are unshaded or thinly-shaded areas. On roof installations in the Northern Hemisphere southern exposures are preferred. Solar panels may be connected to a grid or self-contained depending on their function. Owners may earn credit by giving energy to the grid during times when their consumption is lower than their own unit s production. The energy may also be stored in batteries. Solar power is a
