Can "enhanced geothermal" solve our energy problems?

Most Manitobans are familiar with geothermal energy in its mild form, the "heat pumps" used for heating and cooling buildings. What fewer people realize is that if you drill deep enough, it gets hot enough to boil water, which can be used to spin turbines and thus drive generators. The Guardian's Damian Carrington thinks it offers all the benefits of nuclear fission, without the problems:

By mass, 99.9% of the Earth is hotter than 100C. That means that not far below our feet is the power to boil unlimited water and generate clean, renewable energy. Is the UK throwing all it can at this extraordinary opportunity? Of course not, who do you think we are? Germans?

That contrasts strikingly with the more glamorous sister of deep geothermal energy, nuclear power. Both ultimately tap the heat generated by the decay of radioactive elements. Geothermal plants send water down holes to bring to the surface the heat from natural radioactive decay deep in the mantle. Nuclear power mines the radionucleides, concentrates them, sends them critical and then wonders what to do with the leftover mess - not very elegant by comparison.

The coalition government has pledged that nuclear power will receive no taxpayer subsidies. But it can receive financial support by other means which are subsidies in all but name.

So what support is there for deep geothermal projects? Nothing. As Tim Smit - founder of the Eden project where one of just two projects in the UK is sited - put it last night at a Renewable Energy Association event in Westminster: "I'd like the same 'lack of support' the government is giving to nuclear."

Geothermal energy has been tapped in the UK since Roman times, via the hot springs at Bath and elsewhere. Shallow geothermal projects - such as ground source heat pumps - are slowly growing. But even Decc's own and very conservative estimate is that deep geothermal - a few kilometres down - could provide 10% of the UK's electricity.

And how! It runs 24 hours a day, so perfect for baseload. The water circulates in a closed-loop, so it's clean and sustainable. It is virtually zero carbon and the plants have a small surface footprint, so it's pretty NIMBY-proof.

Sounds like a great idea. Carrington isn't the first to suggest this either (I heard Gwynne Dyer advocating it on the radio several years back, for instance). Of course, it's not entirely trouble-free; there is some evidence linking deep geothermal systems to earthquakes in some cases, and I also wonder about localized problems from the release of subterranean gases (such as sulphur dioxide) when you drill several kilometres into the ground. Still, it's worth looking very seriously at this as an alternative to coal and natural gas (and eventually fission).