The future of renewable energy appears to be bright even if the very near future remains murky. As the consequences of global warming grow more and more clear, it seems almost certain that renewable energy sources will play an increasingly large role in global power generation. One fine example might come from Warren Buffett's purchase of a California solar plant from First Solar (FSLR) last year through his company Berkshire Hathaway (BRK.A). The transaction was made all the more attractive because of lucrative contracts that were made possible by state legislation in California calling for a third of the state's electricity to come from renewable sources by 2020. However, this doesn't just mean more solar, wind, and biofuels. Renewable energy comes from a variety of different sources, many of which haven't entered into popular consciousness.
Individuals who don't take a specific interest in science are much less likely to have heard of geothermal energy, but worldwide installed capacity exceeds 10,000 megawatts with the United States leading the world in generating geothermal power with a capacity of over 3,000 megawatts. The concept is pretty simple. The earth has a heat content of 10 to the 31st power joules, an enormous amount of energy. While harnessing that power is difficult because of the earth's crust, there are ways to use the naturally occurring heat of the earth to generate electricity through a variety of different methods. Most involve the drilling of wells in volcanically active areas and then powering a turbine with steam generated from the heat underground. The most common plant in use is what's known as a flash steam power plant, which are powered by high-pressure hot water from underground.
Also referred to as "Marine Energy" or "Marine Power," using the ocean's natural movements and heat to generate electricity can be an appealing proposition (if notably less exciting to anyone living in Kansas). According to the International Energy Agency's 2007 annual report, the ocean has the capacity to produce as much as 15,000 gigawatts of electricity through currents, thermal power, tides, and waves. One of the biggest issues with wind and solar power is their unpredictable nature. Weather patterns can affect the output of solar plants and wind farms, and solar plants won't produce energy at night. Ocean-related sources can prove to be much more consistent and reliable, making them appealing potential power sources. Marine current power is generated by harnessing the kinetic energy of ocean currents like the Gulf Stream. Wave and tide sources of power are very similar concepts, finding ways to power turbines using the naturally occurring kinetic releases of the ocean. Ocean thermal power utilizes the difference in temperature between cool deep waters and warmer surface waters. However, perhaps the most interesting form of electricity drawn from the ocean is osmotic or salinity gradient power. The method uses the difference in salinity between ocean water and river water to power osmosis with ion specific membranes that generates power.
Different Solar Methods
Solar is probably the most recognizable form of renewable energy, but it's not as well known that there are many different ways of collecting solar energy beyond the photovoltaic cell. Solar plants are being built that utilize a variety of new methods that break free from classic array of panels. The most common methods involve using mirrors and lens to focus solar energy onto one small area and harness the thermal power it carries. The concentrated heat is then used to power turbines that generate electricity. The most developed of these methods is called the parabolic trough, where curved mirrors concentrate the sun's energy towards a pipe in the middle, which contains a working fluid that is heated and then used to heat water to power a turbine. Other solar plants involve focusing solar energy onto a single tower in the middle of an array.
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