Renewable energy

Energy is a topic of concern to us all. We increasing desire a secure, affordable, and unlimited energy supply, but the environmental side effects of fossil fuels and nuclear power have become major concerns. Renewable energy may be the key to meeting our energy needs in an ecologically sustainable way. What do we mean by renewable energy? Is any “natural” form of energy renewable? The answer is no. Nature created the fossil fuels that we burn to supply most of our energy needs today, but it took millions of years to build up these reserves of coal, oil, and natural gas that civilization will deplete in only one or two centuries. Renewable energy includes forms of energy that we do not destroy, deplete, or disrupt faster than nature can restore or replenish them. Read the text aloud
Photovoltaic cells arranged in solar arraysSolar energy derives power from the radiant energy in sunlight. Sunlight can be used to heat water for household use; it can be used to create steam, which then powers a turbine; and it can directly generate electric current when absorbed by a photovoltaic cell. Read the text aloud
Inside hydroelectric power generationHydroelectric energy refers to the mechanical energy of water flowing from higher places to lower ones. For centuries, this energy has crushed grain and spun lathes in mills built alongside rivers and waterfalls; today it is used mainly to generate electricity. Read the text aloud Show Energy content of power sources
Wind energy “farm”Wind energy has long been used to pump water or grind grain. Wind energy is today increasingly being tapped to generate electricity. Ultimately, wind derives its power from sunlight and, to a lesser extent, from Earth’s rotation. Read the text aloud
Geothermal power generationGeothermal energy is thermal energy and pressure contained within underground bodies of water heated by magma—molten rock that rises from deep within the Earth. Hot springs and geysers are two natural geothermal phenomena. Read the text aloud
Power generation from ocean tidesTidal energy ultimately comes from the gravitational interaction among the Earth, the Moon, and the Sun. This interaction causes ocean water to flow back and forth twice daily. Tides involve tremendous amounts of mechanical energy—energy that is hardly tapped today. Read the text aloud
Nuclear fusionNuclear fusion derives energy through nuclear reactions that combine lighter elements into heavier elements. Nuclear fusion is the energy source for the Sun and stars. A practical fusion reactor, however, has yet to be developed. (The opposite process, nuclear fission, powers today’s nuclear plants.) Read the text aloud Show Is nuclear fusion energy renewable?
Which of the above-listed forms of renewable energy is fundamentally a form of mechanical energy? (There may be more than one right answer.) Show

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