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Publisher Summary This chapter discusses the use of solar energy in heating and cooling. Solar energy for heating and cooling has the advantages of a large resource base and widespread distribution. Its disadvantages are that it is spread rather thinly and thus must be collected over relatively large areas, and is erratic, fluctuating day to night and with weather conditions. Solar energy is a “free” fuel, but since it requires such a large collection area it often requires a large capital investment to make use of it. Solar energy is the only large resource among the renewable fuels and will steadily become more important as the technology of collection, storage, and use advances, and as other sources of heat become more scarce and expensive. There is no pollution to discharge. In a heavily solar-dependent urban area there may develop problems over solar access, shading, etc., as well as aesthetic consequences. The major environmental impact is apt to be indirect. A lot of conventional energy with its associated environmental impact will be required if a nation were to undertake the manufacture of a large number of active solar systems.

Publisher Summary This chapter discusses geothermal energy as a source of energy. Geothermal energy is primarily the product of a few elements in the Earth's core which release energy as they radioactively decay. This energy is then converted to heat energy that keeps the core molten. In certain places geological forces thrust large pools of this molten rock relatively near the Earth's crust and these form the so-called geothermal “hot spots.” These hot spots occur most frequently near the junctures of the continental plates, where they are colliding or drifting apart. It is being increasingly developed in both direct heating and electricity generation around the world. Because steam and hot water cannot be piped very far without excessive energy loss, geothermal heat will have to be used locally. This restriction to local use and its limited distribution gives geothermal minor roles in the worldwide energy mix.

Publisher Summary This chapter discusses conventional nuclear reactors. Nuclear energy is released by rearranging the neutrons and protons which make up the nucleus, the tiny dense core of the atom. The energy density in the nucleus, the energy per atom which can be released, depends on the strength of the nuclear force. Fission is induced by a neutron, an uncharged particle, which together with the proton constitute the building blocks of the nucleus. When a neutron strikes a U-235 nucleus, energy is released causing the nucleus to become unstable and finally to break into two pieces with the release of much more energy. The purpose of a nuclear converter reactor is to control the chain reaction and extract energy from it. When fission occurs, the released energy appears as kinetic energy of the particles. This kinetic energy is quickly transformed to heat energy via the collision process. Thus the nuclear reactor is a source of very high temperature heat energy.

Publisher Summary This chapter discusses use of wind power as a source of energy. Wind power differs from most other “alternative energy technologies” in that it is an old and proven source. . It is a technology which could be quickly brought to a large-scale use given determination and support on the part of the private and public sectors. The laws of physics tell that kinetic energy varies as the square of the wind speed. Since the amount of air which passes through the diameter of a windmill per unit time depends on the first power of the velocity of the air, the power available depends on the third power or cube of the wind velocity. Thus, if the wind speed doubles, the power available increases eight-fold. It is thus important for wind machines to operate at as high a wind speed as possible. Since the energy comes from the cylindrical volume of air which passes through the blades, the power available varies as the square of the windmill's diameter. Thus if the diameter is doubled, the power output is quadrupled.