Lets see, Volume 35, chapter 16, page 742 of Things Rhythmdvl Doesn’t Understand: Energy Production
If one has a readily accessible heat source, creative engineers can exploit it to generate electricity. Not too far (as oil drillers think) down in the Earth, pressure from upper rocks creates significant heat. Drilling, while not cheap, is a fairly well known technology. So, what is stopping someone from drilling deep enough so that the temperature would boil water, but not melt machine parts, and installing a few pipes to generate steam? One pipe down with a one-way valve could get water down there. The surrounding rock would turn it to steam, and a turbine attached to the exhaust pipe generates electricity. Capture the expanded steam past the turbine, condense it, and dump it back in the incoming pipe. Rinse and repeat.
Granted, the setup would be a bit more complicated than that, but where does it get technically impossible or technically impractical? Sure, coal is relatively cheap here, but there must be plenty of places that would enjoy being off the grid. Even a farm of such devices shouldn’t take up too much real estate, and once the initial drilling process is completed, what environmental harms or costs are there?
So, what am I missing? If it did work, I’d think someone out there would already be doing it (unless they fell victim to the great oil conspiracy :rolleyes: ) so I can only assume there is a good explanation. Anyone?
Geothermal energy is successfully exploited, you can read a bit about it at the World Bank’s Geothermal Energy page.
Geothermal exploitation is relatively young, and drilling a geothermal well exposes the operator to all kinds of conditions that are not problems with oil and gas wells, or are at least not as problematic. But these technical problems are under assault by industry, and as they are conquered, and with an accompanying improvement in geothermal economics, perhaps earth heat concentration can assume a more prominent place amongst the energy deposits exploited by man.
I believe you can buy geothermal heat pumps for residential heating and cooling, but I have no idea how cost effective they are, and since I doubt they’d be as deep, or constructed to deal with the extreme conditions a power plant geothermal borehole must, I imagine water supply (and return) is a problem.
Also, geothermal energy production will only be efficient in places with a high geothermal gradient, which varies mostly as a function of crustal thickness (i.e., proximity to the mantle) and whether or not magma is present at some depth in the subsurface. Just off the top of my head, I can think of three places where geothermal energy is being currently exploited, or at least experimented with: Long Valley, California (Magma in the subsurface), Northwesternish Nevada (Thin crust), and Iceland (built on super-thin oceanic crust AND has lotsa magma in the subsurface). Find some place in the stable continental interior overlying nice, thick crust, and you’re just going to have to drill way too deep to make it efficient.
…and Clear Lake, California, too. Somewhat recent volcanism there, and it overlies flimsy crust. Oh, and also in the Brother’s Fault Zone area in the Oregon Plateau (from Burns and Harney westward to Newberry volcano, Bend, Sisters, and that area… which is also starting to bulge with new magma!)
Geothermal energy has a few problems, besides the sheer expense of drilling far enough to meet the specified conditions. I read a few articles about this power source several years ago, sorry about not being able to find them, but they mentioned a rather nasty corrosion problem involved.
No problem. Just repair the turbine blades, pipes, and what-have-you when they’re too corroded to work very well. But how are you going to pull pipes several hundred meters out of the ground to replace them? Metal pipes of suitable dimensions will eventually snap under their own weight, I should think, if one tries to pull them bodily out of the ground.
No problem. Just get a very hard-to-corrode material, so you don’t need to replace them. Gold comes to mind, and I’m sure there are certain plastics/ceramics/alloys the chemists are coming up with to handle this problem. That pretty much handles that problem there.
All in all, I do support geothermal energy. I think it’s a better proposition than plopping a couple dozen highly dangerous nuclear plants, or a couple hundred dozen fossil fuel plants. Geothermal energy is a good source, at least until practical fusion power comes out of the labs.
Also, never underestimate operations and maintenance costs of these sorts of systems. For a somewhat related example, one can look at seasonal thermal energy storage (STES) using acquifers. The O&M costs can be outrageous on these things in some areas of the nation, due to the high mineral content of the water.
Here, I found a site that explains a few things about geothermal power, including the different methods of going about the process of power generation.
I do beleive that Iceland uses a lot of geothermal power to heat buildings and houses. There’s not much else they can burn; and I wouldn’t want a gigantic propane tank sitting behind my house right beside a volcanic crater. It’s also cheaper for them since they are rather isolated and the magma is so near the surface anyways.