Energy Resources and Consumption, Part 2
Question 1: Discuss the methods, benefits, and costs of hydroelectric power.
Answer 1: Hydropower can be harnessed by dams, waterwheels, small generators that don't block the course of a river, and devices along coastlines that use the energy in tides and waves. Since it does not use up any of the water, hydropower is a renewable form of energy. It generates about a quarter of the world's electricity. Most hydropower presently comes from turbines in dams, but dams create some problems: Land flooded to create reservoirs can displace many people (as many as a million, in the case of the Three Gorges Dam in China). The area behind the dam collects silt, eventually making it unusable or uneconomical.Silt is prevented from flowing to agricultural lands along the course of rivers.Fish can't travel along the river, unless good fish ladders or other systems are installed, which interferes with their reproduction (salmon) and limits fishers' catch.Some dams help control flooding, but a dam break can cause massive flooding.
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Question 2: Give examples of how energy conservation will help make energy use more sustainable.
Answer 2: Energy efficiency is a measure of the amount of energy going into a process that does useful work (rather than being lost as useless heat). Energy Star and other higher-efficiency machines waste less energy, as do compact fluorescent light bulbs. Industries and electricity-generating plants can adjust their processes to waste less. Hybrid electric vehicles capture the waste energy from burning gasoline and use it to charge batteries, which are then tapped to propel the vehicle for additional miles.Higher-mile-per-gallon gasoline vehicles have been the trend since the Energy Policy Conservation Act established the idea of Corporate Average Fuel Economy (CAFE) standards in 1975. They are related to the fuel economy ratings available with car sales information. Personal vehicles can be made that use even less gasoline per mile.Buildings can be made or retrofitted to prevent the loss of useful heat, through insulation and super-insulating windows.
Question 3: Give some examples of using renewable energy provided by the Sun—directly, through photosynthesis, or through the water cycle.
Answer 3: Renewable energy can be used without being used up. Most of it comes from the Sun and its effects on Earth. Examples: Solar power - Active and passive solar heating of water and building materials uses the Sun's energy directly. Solar energy also can be captured and concentrated to make steam to run electricity-generating turbines or for use in solar cookers. Photovoltaic (solar) cells can convert sunlight to electricity. Biomass - The Sun's energy is stored in trees and other plants and in plant and animal wastes that we can burn or process to make biofuels, such as biodiesel. Hydropower - The water cycle is powered by the Sun. The kinetic energy in water moving through the cycle can be converted to electricity with dams and by small-scale hydroelectric machinery in flowing rivers. There are also devices to harvest the movement of tides and waves.
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