Encyclopedia of Global Resources part 120 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. . | 1118 Solar energy Global Resources construction and included in the price of a home these systems will become a cost-effective alternative to utility-provided energy. Two additional advantages of individual PV systems are that they are simple and modular. They are simple because they contain no moving parts and require little maintenance over a thirty-year expected lifetime. Modularity means they can be sized appropriately to a given application by installing only the number of units required. If a panel needs to be ser viced it can be removed while the remaining panels continue to provide energy. Solar cells have both advantages and disadvantages. On the positive side they create no pollution they are quiet and they are fairly efficient at converting sunlight into electricity. Furthermore PV modules can be assembled rapidly and consume few natural resources because their main ingredient is silicon. On the negative side solar cells produce electricity only when the Sun shines and the current they produce is direct DC not alternating AC . Although direct current can operate heating elements and incandescent light bulbs electronic devices such as computers and televisions require alternating current. This is not a major disadvantage however because synchronous inverters may be used to convert direct current from the PV cells into AC for household use. Impact and Economics of Solar Energy The rate at which the world consumes energy is a function of its population and the average energy consumed per person. Both of these are increasing the world population is predicted to reach 10 billion by the middle of the twenty-first centur y while the world s two largest countries by population China and India are expected to increase their per capita energy use by three to five times during the same time. The world is in the process of transitioning to an alternative energy future with solar power as one of the major components. Estimates indicate that the solar industry will .
