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Solar radiation describes the visible and near-visible (ultraviolet and near-infrared) radiation emitted from the sun. The different regions are described by their wavelength range within the broad band range of 0.20 to 4.0 µm (microns). Terrestrial radiation is a term used to describe infrared radiation emitted from the atmosphere. The following is a list of the components of solar and terrestrial radiation and their approximate wavelength ranges:

• Ultraviolet: 0.20 – 0.39 µm
   

• Visible: 0.39 – 0.78 µm
   

• Near-Infrared: 0.78 – 4.00 µm
   

• Infrared: 4.00 – 100.00 µm

Approximately 99% of solar, or short-wave, radiation at the earth’s surface is contained in the region from 0.3 to 3.0 µm while most of terrestrial, or long-wave, radiation is contained in the region from 3.5 to 50 µm.

Outside the earth’s atmosphere, solar radiation has an intensity of approximately 1370 watts/meter2. This is the value at mean earth-sun distance at the top of the atmosphere and is referred to as the Solar Constant. On the surface of the earth on a clear day, at noon, the direct beam radiation will be approximately 1000 watts/meter2 for many locations.

The availability of energy is affected by location (including latitude and elevation), season, and time of day. All of which can be readily determined. However, the biggest factors affecting the available energy are cloud cover and other meteorological conditions which vary with location and time.

Historically, solar measurements have been taken with horizontal instruments over the complete day. In the Northern US, this results in early summer values 4-6 times greater than early winter values. In the South, differences would be 2-3 times greater. This is due, in part, to the weather and, to a larger degree, the sun angle and the length of daylight.

source EPLAB

Pick your vehicle—stock car, motorcycle, pickup truck, riding lawn mower—and competitors in the United States race them. So, too, the solar-powered car.

Robert Becho is a member of the solar-powered car racing team at the University of Missouri, Rolla. His crew’s sleek, low-slung vehicle is covered with cells that convert sunlight to electricity and power the vehicle. (The world’s fastest solar racer, the Netherlands-based Nuna 2, has topped out at 105 miles an hour/170 kilometers an hour.)

Competitions take place on public roads. As a result, "we become a rolling science project," said Becho, a computer and engineering student. He notes that red lights often spur impromptu question-and-answer sessions with drivers of regular cars.

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• The origin of the word "Geothermal" is Greek.  It comes from "geo" which means "earth" and "therme" which is translated "heat".
• Geothermal energy ultimately comes from radioactive decay in the core of the Earth, which heats the Earth from the inside out, and from the sun, which heats the surface.
• Volcanoes and geysers are examples of geothermal energy.
• The ancient Romans used geothermal energy to heat water in their bathhouses for centuries. They also used the water to treat illnesses and heat homes.
• The first geothermal power plant was started in 1904 in Larderello, Italy. It is still in operation today.
• Geothermal energy comes from the center of the earth. Its interior heat continual flows  outwards towards the surface
• In 1864, a hotel in Oregon heated rooms using geothermal energy from underground hot springs.
• The first geothermal power plant opened in California in 1921.
• A professor at Ohio State University invented the first geothermal heating system in 1948.
• Geothermal electricity is clean – no fossil fuels are burned.

A solar car is a light weight, low power vehicle designed and built with a single purpose in mind – racing (or "raycing", a combination of "race" and "ray" from the sun). Similar to an Indy or Formula One race cars, solar cars do not represent a practical means of transportation. They have limited seating (usually one, sometimes two people), they have very little cargo capacity, and they can only be driven during the day. They do, however, offer an excellent opportunity to develop future technologies that can be applied to practical applications.