For eight years politics have kept geothermal power under funded and hidden from view in the US. Meanwhile, in California geothermal power has quietly grown to where in 2007 it produced 2.3 times as many killowatt hours as wind and 23 times as many as solar power! Since geothermal plants produce power continuously, a megawatt plant produces as many kilowatt-hours as 3 MW of wind or 5 MW of solar power.
Now that California has shown the way, many other western states are drilling geothermal wells at a rapid pace. But until recently federal support was totally lacking. The Senate has been a big stumbling block with many states in the pocket of coal and oil interests. Also, Eastern states feel left out because drilling expense is much higher there because the hot rocks are deeper. With better drilling technology Enhanced Geothermal Systems can work virtually anywhere.
Google just invested $10 million in EGS Geothermal, including $4 million to Potter Drilling who have a new technique that can drill hard rock five times faster. Drilling costs currently grow exponentially with depth because drill bits must be periodically brought to the surface to be replaced. Drilling technology development has been driven by the needs of the oil industry, which uses smaller bore wells, often in soft sedimentary rock.
We have already drilled a lot of holes to pump oil out of the earth. In Texas alone they have drilled over 600,000! Many of those wells are so deep that the oil comes up hot enough to be useful for power generation. Water flooding is used in many of the wells to push oil out from cracks in the rocks. In the Gulf States alone over fifty billion barrels of hot water a day are produced this way. This water is considered a nuisance because it must be separated from the oil and disposed of or reinjected. Much of this water is hot enough that it could be used to generate electricity — just like water from a geothermal well. In fact, similar water injection can make geothermal power practical anywhere because there are hot rocks underfoot everywhere on the planet.
The oil and gas industry has made great progress in recent years with drilling technology. There has been a gold rush to retrieve natural gas from shale deposits, which were previously considered uneconomical. They now routinely drill very deep wells that turn horizontal for several thousand feet. They then fracture the rocks all along the horizontal run to let the gas out of the shale. This fracturing of the shale used to take months of work but new techniques allow fracturing five zones in 30 hours. (To see an amazing movie of how this works click on "Excape" here.)
All of these tricks are perfect for EGS geothermal, where you need to run water over a large area of hot rocks deep underground to extract the heat. Rocks aren’t very good conductors, so if you want to pull a lot of energy out of them you must do it over a large area or they will just cool down. The moving water moves the heat like a conveyor belt up to a turbine above ground.
To generate significant amounts of geothermal power we will have to extract heat from a very large area. This means an incredibly large number of holes will have to be drilled — many more than the 600,000 oil wells in Texas. Oil carries much more energy than hot water: In a typical oil-fired power plant, one gallon of oil can generate about 40 kilowatt-hours. It takes about 350 gallons of 350° F water to generate the same amount in a geothermal plant. Clearly, we will need to drill a lot more holes it we’re going to power the world with geothermal power instead of oil.
If we can learn to drill larger boreholes and run them horizontally with fracturing we may be able to draw heat from a large area of hot rocks with much fewer holes. This would be a major breakthrough, building on the innovations already developed for extracting gas from shale. Some of these deep, hot shale deposits are in coal country: The Marcellus shale in Ohio, Kentucky, West Virginia, Pennsylvania and New York could provide clean geothermal power without having to ruin the countryside. Politically, this could be very important, as the coal states have often blocked green energy legislation.
There are also high heat flow areas in other states such as Illinois and New Hamshire. The Haynesville shale in Texas and Louisiana is very deep with bottomhole temperatures averaging over 300° F. Even North and South Dakota have hot aquifers that may be usable for geothermal power. The problem is that because of political deadlock we haven’t even been looking for geothermal resources outside of California until recently. Germany and Australia started looking a few years ago and have found rich resources. We need to get our oil and gas exploration companies busy working on geothermal. They don’t do it now because the billions in subsidies that apply to oil and gas don’t apply to geothermal development. We desperately need new laws that will level the playing field and recognize the staggering hidden costs of fossil fuels.
Please read full by jcwinnie
