Crude oil and natural gas are called hydrocarbons because they are composed of compounds made up almost entirely of carbon and hydrogen, along with some minor impurities sulfur, nitrogen, and oxygen.
Petroleum is crude oil, a naturally occurring liquid that can be distilled or refined to make fuels, lubricating oils, asphalt, and other valuable products. The word petroleum comes from the Latin petra, meaning "rock," and oleum, meaning "oil." Used in a broad sense, petroleum also refers to natural gas and solid asphalt, or tar.
Crude oil is a valuable raw material that is used in making a great variety of products. About 70 percent of the energy consumed in the western world comes from crude oil and natural gas. Crude oil is refined into fuels, including gasoline, kerosene, jet fuel, diesel fuel, furnace oil, and fuel oil. It is also the source of greases, waxes, and coke. Crude oil and natural gas are used to make feedstocks chemicals that are the basis of hundreds of petrochemical products, including paints, plastics, synthetic rubbers and fibers, fertilizers, drugs, and explosives.
GAS.
Natural gas is a mixture of flammable gases, mainly the hydrocarbons methane and ethane, that occurs beneath the surface of the Earth. Helium is also found in relatively high concentrations in natural gas. Manufactured gas is derived principally from coal and petroleum. Natural gas usually occurs in association with petroleum because geological conditions favorable for it generally are favorable for natural-gas occurrence as well. Although many natural gases can be used directly from the well without treatment, some must be processed to remove such undesirable constituents as carbon dioxide, hydrogen sulfide, and other sulfur componants.
Nuclear Power.
Energy is locked in the nuclei of atoms. The nuclei of atoms contain two kinds of particles protons and neutrons. The nuclear particles can store energy. Some nuclei spontaneously rearrange, or lose some particles, and emit energy. This process is called radioactivity. For example, a radium nucleus can spontaneously eject a cluster of two neutrons and two protons (called an alpha particle) and a gamma ray (electromagnetic radiation). These carry away energy from the nucleus, which changes into a smaller, more stable form.
There are two ways which nuclear energy is released by human intervention. The first makes use of elements with very heavy atoms, such as uranium. More energy is required to hold together the uranium nucleus than to hold together two nuclei that are half the size of a uranium nucleus.
In atom bombs and in fission reactors, free neutrons bombard uranium atoms. When a neutron hits a nucleus, the nucleus splits into two smaller nuclei, releasing a great deal of energy. In the reaction, some of the neutrons of the uranium nucleus fly off and hit other nuclei, causing them to split in two and release more energy and more neutrons. The process can continue explosively unless metal rods are inserted in the middle of the uranium to capture some of the neutrons and slow down the reaction. This sort of reaction is called a fission reaction because in it nuclei are broken apart.
The second kind of nuclear reaction is harder to produce and control. It makes use of the fact that very small nuclei, such as hydrogen and its isotopes, require slightly more energy per proton and neutron to exist than do somewhat heavier nuclei. (The situation is exactly opposite to that of the uranium nucleus, where the lighter nuclei require less energy.) If two hydrogen nuclei can be combined to form one heavier nucleus, energy is released. This type of reaction goes on in the sun.
Renewable Energy Resources
WIND POWER. Wind is a clean and inexhaustible source of energy that has been used for many centuries to grind grain, pump water, propel sailing ships, and perform other work. The amount of wind power available, however, varies depending upon the weather. Thus the windmills used to pump water have been largely replaced by electrically powered pumps.
Today wind power is used primarily in remote areas, but recent interest in fuel conservation has spurred development of modern wind machines for generating electricity. A renewed interest in the use of wind power to generate electricity followed the energy crisis of the 1970s. A program of the United States Department of Energy encouraged the development of new machines, the construction of wind farms, and an evaluation of the economic effect of a large-scale use of wind power.
HYDRO-ELECTRIC
By building a dam across a river, the natural upstream water level is elevated and a difference in levels is created that can be used to drive turbines and generate electricity. A large upstream reservoir may balance seasonal water flow; rain or melted snow can be stored in the reservoir during the wet season to provide electricity during dry seasons. Small "run-of-river" reservoirs or ponds are not large enough to provide seasonal balance. They can, however, provide extra power during daily peak hours.
TIDAL POWER.
At any location the surface of the ocean changesbetween high and low points, called tides, about every 12 1/2 hours. In certain large bays, this tidal action can be made bigger. It can also create waves that move at speeds of up to 60 feet (18 meters) per second. In order to tap the potential energy of tides, a barrage with a gate is built across the mouth of an estuary. As the tide rises, water flows in through the open gate; when the tide begins to recede, the gate is closed. The trapped water is then channeled through a turbine. Normally such plants can generate electricity for about five hours, with seven hours of standstill and refilling. A two-way system that extracts energy from the tide as it flows both in and out of the barrage may also be used.
SOLAR ENERGY. All life on Earth depends on energy from the sun. Solar energy is the source of energy for photosynthesis . It provides the warmth necessary for plants and animals to survive. The heat from the sun causes water on the Earth's surface to evaporate and form clouds that eventually provide fresh rainwater. Solar energy is used to heat houses, and in many countries specially designed solar ovens are used for cooking. The sun also supplies energy to electric generators that provide power for weather and communications satellites and for radio and television equipment.
The potential for solar energy is enormous. Each day the Earth receives in the form of solar energy about 200,000 times the total world electrical-generating capacity. Although the energy itself is free, the high cost of collection, conversion, and storage has limited the development of solar energy. Nevertheless, researchers are experimenting with solar power in a variety of contexts.
