Tham khảo tài liệu 'the complete guide to the toefl ibt part 2', ngoại ngữ, toefl - ielts - toeic phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Section 2 Guide to Listening 11 source It has to be environmentally friendly . . . nonpolluting in other words. And what else Renewable. Not like oil or coal. When you use those bang they re gone they re used up. Renewable sources keep replacing themselves. Okay so we discussed solar power and wind power one day . . . and tidal energy energy from the waves . . . hydroelectric power from waterfalls we discussed that too . . . and in our last class we talked about one kind of geothermal energy hydrothermal energy. That s the energy that comes from hot water from hot springs under the earth. In places like oh say Iceland parts of New Zealand where you have these uh features this can be a very good source of heat and power. But unfortunately hot springs aren t found all over the world. Okay well there is another source of geothermal power called hot dry rock. That s hot dry rock or HDR. Ever heard of it No eh Well the chances are you ll hear a lot about it before long. How does HDR energy work Well in theory anyway . . . and let me stress I say in theory . . . it s pretty simple. You use oil-well drilling equipment big drills and you punch two holes down into the earth about oh maybe two miles five kilometers maybe that s about as far as you can drill into the earth for now at least. Down there deep in the earth there is this extremely hot cauldron of rock of granite. So then you pump water from the surface into the first tube. The water goes down to the hot rock and becomes superheated. Then the superheated water rises up the second tube oh I forgot to mention that these two tubes are interconnected this hot water rises up the other tube and you use that to heat up a volatile liquid do I need to go into what I mean by that No Okay. So then this volatile liquid turns into a vapor a gas and you use it to turn an electrical turbine and . . . bingo you have electricity And then when the water has cooled down you just send it down the first tube again so that you don t .
