Principles of Solar Energy

Solar Radiation

• Solar Radiation is created in the sun through fusion. The intense gravitational forces inside the sun compress hydrogen atoms together forming a helium atom. The temperature at the sun's core is about 27 million degrees Fahrenheit. The intense heat causes the atoms to emit photons which are converted to electromagnetic radiation. The electromagnetic energy is then emitted from the sun's surface and passes through space.

Insolation

• Solar insolation is the amount of electromagnetic energy from the sun that strikes the earth. This energy can be measured. Scientists start with a square meter and then measure the Kilowatt-hours of energy that strike that square meter in an average day. So the unit of measurement is kilowatt hours divided by meters squared per day. Different areas on earth receive different amounts of solar insolation depending on the location, season and the angle the sun is hitting the earth.

Using Solar Energy

• Solar energy can be used in a variety of ways to power our homes. It can be used directly through passive solar radiation. This might be simply sunlight shining through glass and striking a brick or stone wall and being absorbed and then radiated later when the sun is gone. In a slightly more complex system, solar energy can be absorbed in a system designed to heat water. The water is circulated through a series of tubes that have absorbed the solar energy. Heat is then transferred to the water.

Photovoltaics- Solar Electricity

• The most complex use of solar energy is to produce solar electricity. Back in 1839 Edmund Becquerel discovered that certain materials would give off a spark of electricity when struck by sunlight. Using semiconductors, this principle has been used to get electrons to flow from photovoltaic panels. Semiconductors consist of two layers of different materials. One layer develops a positive charge while the other layer develops a negative charge. Sunlight knocks electrons free from both layers. Electrons want to flow from one layer to the other to balance out the difference in their charges but can't. They flow through the attached circuit instead, generating electricity.