I don't think the water goes straight down into the earth's core, in fact I can guarantee that. I think that the geologists would be looking for cooling bodies of magma traveling up through the crust as they become granite. These are hot and close-ish to the surface, and so drilling a hole into one can make economic sense. The rock just cools faster as it becomes granite - cooling which normally could take millions of years. The deepest drilled today is only a bit above 10 km., and so pumping water down to the core thousands of miles down would be quite the ambitious plan!

You're right of course, Karl. I was using 'core' to suggest 'beneath-the-earth's-surface' and trying to be a bit economical with my words. As you point out we haven't drilled super deep just yet, and when we do it's cost billions of dollars. The plan in Australia is to find those locations where the granite is closest the surface to minimise the depth of drilling and therefore cost, making the venture more profitable.

Before anyone mentions it I would like to point out that yes, there are some emissions from geothermal plants including various sulfurous gasses and CO2. But it is a relatively cheap technology (cheaper than nuclear), with considerably lower emissions than the burning of any fuel and with new fractured rock technologies plants can be built just about anywhere (compared to older technologies that required hot aquifers). So its not such a bad deal.

I'm starting to look into geothermal, although the cost is such that I probably won't be able to afford it for a few more years. But my dad is convinced that if every house in my city turned to geothermal, the system wouldn't work because the net result would be to cool the earth. That kinda seems like one of those knee-jerk naysaying things (like wind turbines kill birds, or hybrid cars aren't worth it) but is there merit to what he says?

I am not a geologist or volcanologist, but it is a passing interest. Is there any downside to extracting so much energy faster than it is already flowing to the surface through natural vents? Is there any potential benefit, other than the lower greenhouse emmissions and cleaner atmosphere.

I for one, don't see nuclear as ugly, nor do I see it as a panacea. I have a similar concern about nuclear that the energy relead through fision, if used for every source of electricity, would still add too much energy to our environment, causing further warming. On the other hand, I think there will be some need for nuclear power plants in the mid to long term, and more than we have right now. Ideally, we would find a key to effective, cheap, clean, and safe fusion power, augmented with solar, wind, geo-thermal, hydro, tidal, etc. Maybe than we can put the exhaust of any fossil fuel burning plant through some kind of carbon sequestration, biomass and organic material processed into oil, which has been discussedo n this site. Pump said carbon rich byproduct into old oil fields, thus controlling the balance of CO2, and having emergency stores of energy.


Sorry for the rambling, but I guess the short point is that there are so many options, and relying on anyone of them would be folly. I know that wasn't the point of the article, but I guess it seemed nuclear was being dismissed as it won't solve everything, which is the same excuse people use against solar and wind around here. The same part of me looking forward to reducing/eliminating my commute gets excited that we are on the cusp of having energy abundance through so many different sources of energy. And yes, that abundance will be reached in part by conservation. It is easier to have an abundance of what we don't over use.

DG, in our original post on hot rocks, one of the reports referenced suggested that all of Australia's electrical energy could be supplied for next 7,500 years, so your Dad may be being a tad alarmist. Of course this is all supposition, as no such 'hot rock' plant is yet in commercial operation.

Old Wolf, there are said to be some side effects, such as minor earth tremors, so hot rocks plants are expected to be located away from built-up areas, which might result in some loss of energy due to transmission. But we already have this issue with existing technologies. One other downside may have to do with the saline water mixture used. If this needs to be expelled from the loop at some stage, its disposal will require consideration. But I'm willing to bet salt water's half life is somewhat less than spent plutonium rods.

And you are absolutely correct that there is no singular silver bullet to kill global warming. It will need to be a grab bag of whatever works, without further jeopardising an already tenuous future.

I beleive there is currently a large-scale porject in Norway or Sweden exploring this type of energy. I think the difference between this and standard geothermal is the depth required to reach the much hotter temperatures.

Okay, I'm not a geologist, either, but I know that the reason the Earth is hot isn't just because of leftover energy from when it was formed. Rather, the constant gravitational forces exerted on it from the Moon and the Sun is enough to keep the core as hot as it is. (It may not even be "molten" but of a theorized crystalized iron mass, oriented North-South.) The other thing going for us in keeping the Earth as warm as it is, is the distance from the Sun. At almost 8000 miles in diameter, I think we have more than enough hot mass under the crust to satisfy any geothermal needs for a time probably longer than the human race's lifetime on the planet ;)

And, doesn't the temperature rise by a degree F for every 50' down you go? Seems we'd get to geothermal temps a lot sooner than 10km...