Solar energy

The sun has produced energy for billions of years. Solar energy is the solar radiation that reaches the earth. Solar energy can be converted directly or indirectly into other forms of energy, such as heat and electricity. There are two major drawbacks with solar energy. First, the amount of solar energy an area receives varies. Second, a large area is required to collect it at a useful rate.

Solar energy is used for heating water for domestic use, space heating of buildings, drying agricultural products, and generating electrical energy.

This parabolic trough is used in the largest solar power facility in the world located in California within the Mojave Desert. (Copyright 2008 Jupiterimages Corporation)

In the 1830s, the British astronomer John Herschel used a solar collector box to cook food during an expedition to Africa. Now, people are trying to use the sun's energy for lots of things. Electric utilities are working to convert solar energy directly to electricity. Electricity can be produced directly from solar energy using solar panels that are called photovoltaic cells, or indirectly from steam generators using solar thermal collectors to heat fluid. Individual homes are also sometimes fitted with solar energy panels that collect enough energy to heat the home.¹

The most advanced way to collect solar energy is a system called a parabolic trough. The troughs are made of huge mirrors that reflect solar energy, which is then used to heat liquid to produce steam. The steam is used to propel a generator. The huge system is set up so that the troughs rotate in order to collect energy all day as the sun moves from east to west.

Biodiesel

There are many experimental forms of renewable fuel. One interesting renewable energy source that is being worked with is biodiesel. Biodiesel is made from animal fat or vegetable oil, but it is not safe to eat. It is, however, biodegradable, which means it is not very harmful to the environment if it gets spilled. Biodiesel can be used as diesel fuel or mixed with regular diesel fuel. Ordinary diesel engines can run on biodiesel. Practically any type of vegetable oil or animal fat can be used to make biodiesel, including soybean and rapeseed oil. Soybean and rapeseed oil are less expensive than most other types of vegetable oil, but are more expensive than regular diesel fuel. Most types of vegetable oils and animal fat are really too expensive for this use, but used oil from restaurants has been tried for biodiesel. So, the next time you eat an order of French fries, maybe you will be adding to the supply of oil to create biodiesel!

Footnotes

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