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We have been harnessing the wind's energy for hundreds of years. From old Holland to farms in the United States, windmills have been used for pumping water or grinding grain. Today, the windmill's modern equivalent - a wind turbine - can use the wind's energy to generate electricity.

Wind turbines, like windmills, are mounted on a tower to capture the most energy. At 100 feet (30 meters) or more aboveground, they can take advantage of the faster and less turbulent wind. Turbines catch the wind's energy with their propeller-like blades. Usually, two or three blades are mounted on a shaft to form a rotor.

A blade acts much like an airplane wing. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is actually much stronger than the wind's force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity.

It is believed that the first geothermal energy use in industry was during the late 18th century near Pisa, Italy. This history of geothermal shows energy been used to extract boric acid from the Larderello Fields through the use of steam

Most Geothermal Resources Are Near Plate Boundaries The most active geothermal resources are usually found along major plate boundaries where earthquakes and volcanoes are concentrated. Most of the geothermal activity in the world occurs in an area called the Ring of Fire. This area encircles the Pacific Ocean.

The ring of fire goes around the edges of the Pacific. The map shows that volcanic activity occurs around the Pacific rim.Source: National Energy Education Development Project (Public Domain) Naturally occurring large areas of hydrothermal resources are called

They may also reduce the amount of electricity generated from fossil fuels and therefore reduce the amount of air pollution, carbon dioxide emissions, and water use of fossil fuel power plants.

Modern wind turbines are very large machines, and some people do not like their visual impact on the landscape. A few wind turbines have caught on fire, and some have leaked lubricating fluids, though this is relatively rare. Some people do not like the sound that wind turbine blades make. Some types of wind turbines and wind projects cause bird and bat deaths. These deaths may contribute to declines in species that are also being affected by other human-related impacts. Many birds are killed from collisions with vehicles and buildings, by house cats and hunters, and by pesticides. Their natural habitats may be altered or destroyed by human development and by the changes in the climate that most scientists believe are caused by greenhouse gases emissions from human activities (which wind energy use can help reduce).

Making the metals and other materials in wind turbines and the concrete for their foundations requires the use of energy, which may be from fossil fuels.

As a renewable energy, offshore wind and wave energy can provide a constant energy supply that solar and onshore wind lack, he said.

First of all, harnessing geothermal energy does not have the devastating impact on climate change like burning of the fossil fuels does. It is true that fluids drawn from the earth's core include greenhouse gases such as carbon dioxide and methane, but the amount of released greenhouse gas emissions is negligible compared to those from fossil fuel fired power plants.

One of the reasons for this is the fact that geothermal power plants are equipped with emission-control systems that reduce the exhaust.

geothermal power plants are connected with minimal freshwater and land requirements. This means that geothermal energy commonly has minimal impact on nearby ecosystems.

It depends what you mean by "solar energy." Humans have always used solar energy in some sense: to warm themselves, to grow food, etc. However, I'm assuming that's not really what you mean (although it is important to realize that all energy on earth, with the exception of nuclear fission and geothermal, is ultimately driven by the sun's energy -- even fossil fuels, which after all were plants that grew with sunlight millions of years ago). Solar power has been used directly in various forms for over 100 years.

Geothermal electricity generation does involve a small amount of geothermal pollution in that the steam coming up from below ground carries some toxic gases, but in most plants these gases, as well as the steam, are condensed and reinjected into the ground so the effect on the environment is negligible. There are no CO2 emissions from geothermal energy so it is a much better source of electricity than coal or natural gas or nuclear (or even large-scale hydro generation which requires the flooding of large areas of land).

Geothermal electricity generation does involve a small amount of geothermal pollution in that the steam coming up from below ground carries some toxic gases, but in most plants these gases, as well as the steam, are condensed and reinjected into the ground so the effect on the environment is negligible. There are no CO2 emissions from geothermal energy so it is a much better source of electricity than coal or natural gas or nuclear (or even large-scale hydro generation which requires the flooding of large areas of land).

Geothermal electricity generation does involve a small amount of geothermal pollution in that the steam coming up from below ground carries some toxic gases, but in most plants these gases, as well as the steam, are condensed and reinjected into the ground so the effect on the environment is negligible. There are no CO2 emissions from geothermal energy so it is a much better source of electricity than coal or natural gas or nuclear (or even large-scale hydro generation which requires

Solar Energy systems are virtually maintenance free and will last for decades.

Tidal energy is a form of hydropower that converts the energy of the tides into electricity or other useful forms of power. The tide is created by the gravitational effect of the sun and the moon on the earth. Tidal energy is therefore a predictable form of renewable energy, which can be harnessed in two forms:

idal power is taken from the Earth's oceanic tides; tidal forces are periodic variations in gravitational attraction exerted by celestial bodies. These forces create corresponding motions or currents in the world's oceans

Because the Earth's tides are ultimately due to gravitational interaction with the Moon and Sun and the Earth's rotation, tidal power is practically inexhaustible and classified as a renewable energy resource

Because the Earth's tides are ultimately due to gravitational interaction with the Moon and Sun and the Earth's rotation, tidal power is practically inexhaustible and classified as a renewable energy resource

Sea waves have associated a form of renewable energy which can be captured by using a hydro mechanical device that in turn drives an electrical generator to produce electrical energy.

The World Energy Council has estimated that approximately 2 terawatts (2 million megawatts), about double current world electricity production, could be produced from the oceans via wave power.

Wave energy is generally considered to be the most concentrated and least variable form of renewable energy. It is the high power density of wave energy that suggests it has the capacity to become the lowest cost renewable energy source.

Wave energy is a renewable, zero emission source of power