I always wondered if we could use the earths natural heat deep underground by boring a loop through it, pump water in it one way, and extract steam from the other end to run turbines. This could effectively be done indefinately, would create no waste, and produce clean, green power...<br><br>It would be a massive engineering feat in some places, as drilling deep is hard and making it a clean loop with a material that is heat resistant but not insulating...but I dunno, maybe in the future we have "Geothermal powerplants" everywhere...,(reply>), @Maggie Mez Sweet.,(reply>), It already exists. We do it in the netherlands. You need to drill 2 to 5 km deep and then you can use the heat.