by Wm. Robert Johnston
last updated 10 January 2005
The industrialization of our society was accomplished using hydrocarbon fuels (also called fossil fuels). Hydrocarbon fuels (coal, petroleum, and natural gas) continue to provide most energy consumed by both the U.S. and the world as a whole. This is supplemented by cleaner forms of energy, hydroelectric and nuclear power. Hydrocarbon fuel burning has several drawbacks: it produces pollution, draws on the world's finite resources of such fuel, and generally means some degree of dependence on foreign sources of energy. It also produces carbon dioxide, which may or may not be a drawback.
Solar power is often proposed as an alternate solution to the problems of meeting national or world energy needs. The Sun radiates visible light and other electromagnetic energy which is intercepted by the Earth. Plants utilize sunlight in photosynthesis and store energy in sugars. (In fact, the fossilization of plants with this stored energy is presumed to be the source of hydrocarbon fuels.)
Different man-made methods exist for utilizing this solar energy. Two categories of solar energy are involved: direct and indirect. Direct methods include directly allowing sunlight to light or heat buildings. (If you read a book in sunlight from a window, you are using direct solar energy.) Indirect methods convert or store energy from sunlight for use, often for electrical power. Photoelectric cells are a well-known example: these cells are designed so incident light induces an electric current, which can then be transmitted to run electrical devices elsewhere or stored in batteries. Another indirect method uses large reflectors to concentrate sunlight on a small area, heating fluid in pipes. This heat is used to create steam which turns turbines and generates electricity, much as in a conventional power plant.
Currently, environmentalists are promoting solar power as an alternative energy source. They oppose hydrocarbon fuel consumption and nuclear power and argue that solar power can be developed to meet much of these needs.
Solar energy has important applications, but can it replace other forms of energy such as hydrocarbon fuels or nuclear power? The following exercises will shed light on this question!
What follows is a series of questions: calculate an answer to each , then click for the next page to check your answer and go to the next question.
Energy from the Sun reaches the Earth at a rate of 1,368 W/m2 (watts per square meter). This energy per unit area is called flux. How many MW/km2 (megawatts per square kilometer) is this?
Click here to check your answer and continue...
© 2001-2002, 2005 by Wm. Robert Johnston.
Last modified 10 January 2005.
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