Technologies that could help break fossil-fuel dependence.
• Solar Energy: We can harness the sun’s power using several technologies. The first uses solar cells that convert sunlight (photons) directly into electricity (voltage), a process called the “photovoltaic (PV) effect.” This technology frees electrons from atoms, allowing them to flow through the solar-cell material and produce electricity. The cells usually are combined into modules mounted in “arrays,” or flat plates positioned flush on south-facing rooftops. Between 10 and 20 arrays provide enough power for a household.
• Passive Solar Heating: Another way to use the sun’s energy to warm your home is through passive solar heating. If your house is large, south-facing windows, you’ve already experienced this phenomenon. By adding walls and floors made of concrete, brick, tile and other masonry materials that absorb heat, your home especially becomes its own heat source. These surfaces heat up during the say and slowly release the heat throughout the night; dark colored materials are most effective.
•Wind Power: Wind-energy systems create electricity using turbines and generators. Air flows past the turbine’s rotor, which looks like an airplane propeller, causing it to spin. This drives the generator shaft, producing electricity.
•Hydroelectric Energy: If a stream or small river runs through your property, you might be able to use water to generate electricity. Your stream needs a sufficient quantity of year-round, falling water. With this system, turbines and generators convert energy from flowing water into electricity or mechanical energy. So-called micro-hydropower systems can generate up to 100 kilowatts (kW) of electricity; 10 kW provides enough power for a large home.
• Geothermal Energy: You also can get power directly from the earth. Renewable geothermal resources can heat and cool your home, saving you up to 80 percent over fossil-fuel energy. One popular way homeowners tap geothermal energy is with a heat-pump system buried beneath the earth’s surface. The systems work well in North American latitudes where the upper 10 feet of ground maintains a constant temperature of between 50°F and 60°F. Heat exchange and air-delivery systems distribute warm air from underground to the home during winter; cooler air is brought up during summer.
-How your system can pay for itself: If you have a renewable-energy system that’s connected to the grid, your utility company will pay you wholesale rates for excess power your system produces, measured by an extra meter, installed at your expense. Your system also can help pay for itself through a process called “net metering”, which actually spins your existing home electricity meter backward, allowing you to use the excess electricity you produce to offset electricity you use from the grid to other times. Net-metering works especially well with renewable-energy systems that provide intermittent power generation, such as wind and solar energy.
(Resources and some information pulled from: Natural Home, American Wind and Energy Association, and U.S. EPA Green Power Partnership of America)
Comments
Eventually 10 billions will want to live like 1 billion now do. That means world energy use will increase from present ~5 TW equivalent to 50 TW equivalent. This limits any energy choice to using less than 0.1 kg-Fe/W. Otherwise you run out of stuff. Nuclear, coal, natural gas, and oil roughly meet this criterion. "Renewable energy" ends up needing roughly 1 kg/W, sometimes much more than this. The solar PV system in Malmo Sweden has a 154 ton (tonnes?) mass and is reported to produce 10 kW. This is apparently averaged over 24 hours, because its ~1500 m^2 should produce roughly 150 kW nameplate, assuming a 10% solar PV efficiency. Even 150 kW at 154 tons is 1 kg/W. Solar-thermal using ammonia-H2O energy storage and sheet metal collectors also is about 1 kg/W. Windmills are about 0.1 kg/W nameplate,but 25% utilization (DOE, Spain, CA ISO data), 50% storage loss, 10% line loss gets to the magic 1 kg/W. "Wet" geothermal produces ~1 mile^3 hypersaline effluent Per GWe-y.
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