Ram Power, a Nevada geothermal corporation, has successfully drilled a well in the Imperial Valley which they say could produce 8-10 MW of power (1 MW can power 750-1,000 homes). The area currently produces 600 MW of geothermal power and they say the potential geothermal capacity for the area is a staggering 22 GW, about equal to 22 big coal or nuclear plants. While any actual production would certainly be much less than that, it would still be huge. They plan to build three 50 MW power generation facilities in the area and view the valley as perhaps the biggest geothermal area in the country.
This type of geothermal energy pumps hot water from deep within the earth, uses it to power turbines, and then usually pumps it back. Since the water is always hot, the power generation is steady, which gives it a big advantage over wind and solar. There are two other types of geothermal as well. The heat from the water can be used to directly heat buildings, and in ground-source heating and cooling, the steady temperature of about 50 degrees just a few feet underground is used to heat and cool homes. Both of these techniques are used worldwide, and are effective and economical.
California already has the biggest geothermal power plants in the world at The Geysers in northern California, which produces 725 MW. However, they use evaporative water-cooling and lose 60-80% of the water in the process. This is where things can get a bit iffy for geothermal. The process needs massive amounts of water. So, The Geysers is now pumping 11 million gallons of treated wastewater a day from nearby communities on a 40 mile pipeline, then injecting it into the wells to create steam from the hot underground rocks. This process hardly seems sustainable.
The Geysers is also old. A newer technique called binary cycle pumps the hot water up, sends it through a heat exchanger where it heats a second liquid, usually isobutene, which powers the turbines. The water is then pumped back down a different well. Thus, it is a closed-loop, with no water loss. Clearly, this is a vastly cleaner and more efficient way of creating energy.
Enhanced geothermal systems pump liquid at high pressure deep into the earth to break up rock and make it more permeable. This process is called fracking and is controversial. It has been banned in some areas because the process caused small earthquakes. But the potential is huge and research continues. Gtherm says they have developed a method of deep geothermal with no fracking or pumping up water because the heat exchanger is deep within the well itself.
Geothermal has always been the overlooked source of renewable energy. However, it has huge potential, especially in California. Perhaps one day California will generate much of its electricity from closed loop geothermal, which would provide steady amounts of clean, renewable energy.