Re: What? Have these people learned nothing?
>You need to learn how to do the numbers...
Actually I just spent two minutes on Wikipedia to check your numbers, and you are quite wrong.
(for the records I used to work in the Geothermal industry, but just wanted to check my facts were up to date)
>For power generation, even with specialised turbines, you'll need a steam source at about 180-200C >minimum.
With binary / closed cycle plants, you can generate power from about 120C up (remember you can boil a number of fluids with relatively low grade heat sources; and with geothermal needing no fuel, and no emssions, you can afford to have low efficiency levels)
>The typical rate of increase of temperature as you drill down is around 20C/km.
References I have say 25 to 30C per KM. But there are many places around the world including in Europe which have localised spots such as hot springs with much greater heat at shallow depths.
>That means you need bores of the order of 10km/33,000 feet
No, not unless you are drilling somewhere dumb, and need to get 200C flows.
> the record for vertical drilling is a small fraction of that (for example, the bottom of the Bowland >Shale formation is about 8,000 feet down).
Wrong - the record is the Kola superdeep borehole which is 12 kilometres down. Typical deep wells are only about 3km (not what I would call a 'small fraction') but in the search of oil, companies are getting experience in drilling deeper. Not that you need to go more than 1 or 2 KM down if you select
your drill site well.
>Even were you able to economically drill that deep, you still need more complexity - the old >Cambourne "Hot Rocks" project relied on drilling two bores a few metres apart and explosive >fracturing the rocks between them (it's far too deep, and hence ground pressures too high for >hydraulic fractuturing), pumping water down one bore and getting steam up the other. They found it >wasn't viable - the fractures tend to close up, and even if they don't you fairly quickly deplete heat in >the area between the bores.
Wrong again. Rosemanowes Quarry dates back to the 1970's and pretty much proved the process works, but the site was experimental not commercial (the data helped feed into a well bore simulator I worked on).It lead on to Soultz and other 'Hot Dry Rock' sites.
>Even if you restrict yourself to volcanic areas, the potential's not that big. The Icelanders reckon >their total generation potential is about 2,000 to 2,500 MW - about 2/3rds that of Hnkley C.
Pretty silly example as Iceland currently has a total generation capacity of under 3000.MW, and that is more than enough; average consumption per person is very high compared with the rest of Europe and most power goes to smelters. They could probably actually power the entire island with geothermal, so potential is pretty significant, but no need to when they have plentiful hydro resources. And nuclear would be silly in the Icelandic case.
Not to derail that nukes make more sense in the UK case, but spend a few minutes to understand the real numbers and you see that geothermal has a part to play in many countries, along with hydro, wind, solar and nuclear.