8. Other Renewable Energy Sources
8.1 Water Power
We've all seen destruction caused by floods, erosion, and the energy of water in the sea waves, and swift rivers and streams. Water power also has a great capacity for useful work. Water power is essentially a form of solar energy, because the sun begins the hydrologic cycle by evaporating water from lakes and oceans and then heating the air. The hot air then rises over the water, carrying moisture with it to the land. The cycle continues when the water falls as precipitation onto the land, then it starts over again.
Water is relatively easy to control and produces a high efficiency, because from 80% to 90% of water energy can usually be converted to work, compared with 25-45% efficiency for solar, chemical, and thermal energy systems. For this reason many rivers have been dammed so that waterwheels and water turbines could capture the energy of water.
Individuals and communities can harness this energy to produce power in small hydroplants. The dam increases the reliability and power available from the stream, and is a means for regulating the water flow and depth. People should be aware that a dam changes the local ecosystem, though, and should only do so conscientiously.
Water turbines can produce either direct current (D.C.) or alternating current (A.C.) electricity. The power available will not always supply the total amount desired, so it is useful to think of an integrated power systems approach from the beginning, and combine this with another renewable power source.
8.2 Wind Power
Wind is another form of energy created by, the sun—the heating of our atmosphere during the day and its absence cooling the night sky—like the earth is breathing. Wind is the reaction of our atmosphere to the incoming energy from the sun—heat causes low-pressure areas and the lack of heat results in high-pressure areas, causing the wind.
The wind is probably the oldest and most constant energy source, probably one of the first sources harnessed by man, and now it's being rediscovered as "new."
Wind energy is not as constant and predictable as the sun and water, but there are also solutions to this problem. Usually a storage system is installed that is designed to have the energy available when it is needed. The selection of the site for wind power is very important—for example, it shouldn't be placed near trees that are growing taller, etc. Other factors should be considered on a basis of frequency and intensity: rain, freezing temperatures, icing, sleet, hail, sandstorms, or lightning.
Windmills have been known for centuries. Even Persia had a primitive horizontal windmill in the tenth century that was used to grind corn. Mills were commonly used in China for irrigation. Modern wind generators not only use the wind for mechanical energy, but also convert the energy into electricity. Wind water pumpers are also available. Most generators consist of the tower, devices to regulate the generator or voltage, the propeller and hub system, the tail vane, a storage system to store power during windless days, and an inverter that converts the stored D.C. into regulated A.C. if it is required. There is often an optional backup system (such as a gas or diesel generator) to provide power through extremely long calm periods. Even better, of course, would be a solar backup system.
Biofuels are renewable energy sources from living things. Fossil fuels are also of biological origin, but they are nonrenewable. All biofuels are derived from plants, which capture the sun's energy, convert it to chemical energy by photosynthesis, and in the process of-being eaten or decayed, they pass this energy onto the rest of the living world. In this sense, all forms of life, and their byproducts and wastes are storehouses of solar energy.
Every day, over 200 times more energy from the sun falls on our planet than is used by the U.S. in a year. About half this energy is reflected back into space, and what does penetrate the atmosphere charges all our energy systems.
All plant matter is called biomass. Microbes, plants, trees, animals, vegetable oils, animal fats, manure garbage, and fossil fuels are all forms of biomass energy that can be produced, cultivated, or converted in different ways for our needs. All we need to do is use it. Each year the U.S. produces over 870 million dry tons, of discarded organic matter.
Agriculture is the means by which solar energy becomes our food energy, and organic farming techniques and a realization that planting fruit trees is a priority in attaining higher quality of life for humans are the goals we should be pursuing. Please refer to the lessons on organic gardening and tree crop agriculture for more information.
When organic material decays it yields useful byproducts, depending on the conditions under which decay takes place—it can be aerobic (with oxygen) or anaerobic (without oxygen). Any kind of organic matter can be broken down either way, the end products of each will be different. If we imitate the natural anaerobic process and put manure and vegetable matter into insulated, air-tight containers called digesters, biogas or methane can be produced.
Another source of energy is alcohol in its pure form, which can be used for heating, cooking, lighting, and motor fuel. It is high energy and clean burning. There are two types of alcohol: ethyl alcohol (ethanol or grain alcohol) and methyl alcohol (methanol or wood alcohol). Ethanol can be produced from carbohydrates (starches, sugars, cellulose) found in various farm products such as sugar beets, sugar cane, molasses, fruits, starch crops, grains, etc. Methanol can be produced from wood, sawdust, farm wastes, and urban refuse.
Wood is a renewable energy source that should be used with a conscientious replanting plan, and can be used to supplement other renewable energy systems. (A word of caution: even though wood fires are considered "natural" or "romantic," they put carcinogenic agents into the air. In fact, efficient, slow-burning stoves pose a bigger hazard than roaring flames, since they produce more polycyclic organic compounds (POMs, linked to lung cancer).
We need to learn how to integrate the heat from solar energy, the mechanical power from wind and water energy, and the chemical energy from biofuels, in order to get as much continuous energy as possible from the diverse energy sources.
Home > Lesson 53 - Solar Energy And Your Health
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