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Heat is a form of energy. We use it for a lot of things like warming our homes and cooking our food.Heat energy moves in three ways:
- Conduction
- Convection
- Radiation
Conduction is when energy is passed directly from one item to another. If you stirred a pan of soup on the stove with a metal spoon, the spoon will heat up. The heat is being conducted from the hot area of the soup to the colder area of spoon.
Metals are excellent conductors of heat energy. Other things like wood or plastics are not good conductors of heat energy. These "bad" conductors are called insulators. That's why a pan is usually made of metal and the handle is made of a strong plastic.
Convection is the movement of gases or liquids from a cooler spot to a warmer spot. If the soup pan above was made of glass, we could see the movement of convection currents in the pan. The warmer soup moves up from the heated area at the bottom of the pan to the top where it is cooler. The cooler soup then moves to take the warmer soup's place. The movement is in a circular pattern within the pan.
Wind is often caused by convection currents. During the daytime, cool air from over water moves to replace the warm air over land that rises. During the nighttime, the directions changes and the water is warmer and the land is cooler.
Radiation is the final form of movement of heat energy. The sun's light and heat cannot reach us by conduction or convention because space is almost completely empty. There is nothing to transfer the energy from the sun to the earth. The sun's rays travel in straight lines called heat rays. When it moves like that, it is called radiation.
When the sun light hits the earth, its radiation is absorbed or reflected. Darker surfaces absorb more of the radiation and lighter surfaces reflect the radiation. So, if you wear light or white clothes outside during the summer, you be cooler.
Geothermal energy is heat from the earth that is used directly as hot water or steam, or used to produce electricity. While high-temperature geothermal sites suitable for electricity production are not widespread, low-temperature sites almost everywhere in the world can provide heating and cooling for buildings.Geothermal power makes use of heat from the interior of the Earth. This is the same energy which rises naturally to the Earth's surface in the form of hot springs, geysers, and volcanoes. Geothermal systems are located in areas where the Earth's crust is relatively thin. By drilling into the ground and inserting pipes, hot water or steam can be brought to the surface. In some applications, this heat is used directly to heat homes or provide process heat for businesses. In other areas, the steam is used to drive a turbine to generate electricity.
Reference to On-Line Renewable Energy Education Module
Other links for Geothermal Energy
Introduction to Geothermal
An overview and theories of Geothermal. Applications and case studies on GeothermalGeothermal Energy
Net Positive Environmental Impact, reserves, flexibility, and reliability of Geothermal Energy
