How Does Renewable Energy Work?

• Wind
• Solar
• Biomass
• Biogas
• Geothermal
• Wave

How Does Renewable Energy Work?

Wind

The process behind wind energy is pretty simple. It starts, of course, with the wind, which is actually a form of solar energy. Wind is caused by the sun’s heating of the atmosphere, the irregularities of the earth's surface and its rotation.

The wind turbine captures that energy through propeller-like blades attached to a rotor, usually atop towers to access faster, less turbulent wind. Turbines can operate at variable or fixed speeds. Most new projects use variable speed as it more efficiently converts wind to electricity.

For more, see How Does Renewable Energy Get to My House or Business?

For more information about the state of wind energy in our region and worldwide, watch an interesting interview between PGE Vice President Jim Lobdell and Vestas Wind Systems CEO Ditlev Engel at a 2008 Portland Business Alliance event.

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Solar

The sun is actually the basis for almost every form of energy we use from wind to hydropower. But by “solar power” we typically mean use of the sun’s rays to generate electricity through photovoltaic cells.

PV cells consist of positively charged and negatively charged slices of silicon placed under a thin piece of glass. As sunlight hits these panels it is absorbed by the silicon. During that process the electrons are “knocked” free and caught by small wires on the silicon.

Most PV systems consist of cells averaging about four inches on a side. Each cell generates less than two watts, so they are often grouped into modules and larger arrays. Residential systems tend to rely on roof-mounted PV modules.

By integrating these systems with the local power grid, you can actually sell surplus electricity through the grid. Learn more at Net Metering .

For more, visit How Does Renewable Energy Get to My House or Business?

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Biomass

Growing plants absorb and store atmospheric CO ₂ . As these plants die and decompose, they release this carbon back into the atmosphere in the form of CO ₂ and methane. Because they are releasing the CO ₂ that they already absorbed, there is no net release of CO ₂.

Biomass technologies use this process to generate carbon-neutral electricity. As things like food, yard clippings, wood and other organic matter decompose the gases they give off are collected and burned to create steam, which can then be used to generate electricity.

These gases can also be converted into other fuels like ethanol or biodiesel for later use.

Unlike wind and solar resources, biomass can be stored and used as needed. This enables it to provide “baseload” power on demand 24 hours a day. And because it contains much less sulfur and nitrogen than coal, when it’s co-fired with coal, emissions are lower than when coal is burned alone.

For more on biomass, check out the Renewable Energy Q&A .

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Biogas

Biogas refers to the gas made from the conversion of agricultural and animal waste in a digester. The gas, a mixture of methane and CO₂, is released during combustion, and can be used for a number of applications, including electricity generation.

Biogas digesters have the added benefit of producing a high-nutrient fertilizer and encouraging better sanitation on farms.

PGE operates a biogas facility on the Cal-Gon dairy farm in Salem, Ore. that converts more than 20 tons of cow manure into energy each day.

Manure enters a 28-foot high digester where it releases methane gas, which then fires a generator on the farm, feeding up to 70 kilowatts of renewable electricity directly to PGE customers.

Leftover materials are processed through a solids separator into relatively odor-free fibers and liquids that can be used for commercial nursery or farm soil applications. For more, visit Introducing Biogas.

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Geothermal

Geothermal energy is derived by harnessing the heat from the earth’s core, some 4,000 miles deep, where temperatures can reach 9,000 degrees F and higher. This heat flows outward and upward through the surrounding layers of rock, sometimes actually melting the rock to magma.

This magma typically remains below the earth’s crust, heating nearby rock and water to near 700 degrees F. While some of this hot water reaches the earth’s surface as hot springs or geysers, most stays trapped deep underground.

Geothermal power plants make electricity by using wells to pipe this underground steam and hot water to the surface, where it is converted into electricity.

Not only is geothermal energy clean, it is also the most reliable of all electricity sources. Geothermal plants regularly operate at 90 percent or more of their rated capacity year-round.

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Wave

Oceans offer a vast, untapped source of clean, renewable energy. Experts estimate that 0.2 percent of the ocean’s energy could power the entire world.

In recent studies, Oregon State University has created three prototypes of devices that could be used to harness wave energy. One of the most promising involves a buoy inside which an electric coil surrounds a magnetic shaft.

While the coil is secured directly to the buoy, the magnetic shaft is anchored to the sea floor. Waves cause the coil to move up and down on the fixed magnetic shaft, generating electricity.

The research team pictures an array of buoys, or “wave park,” placed one or two miles offshore in about 100 feet of water, making it virtually impossible to see from land. OSU hopes to have a prototype in the ocean by summer 2008 for testing.

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