[jillesvangurp]

The 300 degrees is needed to get enough steam pressure to drive a turbine. You need the temperature gradient basically to get that. It's all about efficiencies. A lower efficiency basically means you need to pump more water through, which means more drilling, which raises the cost.

Heat exchange pumps work with much lower temperature gradients which is great for heating a building or some water since you don't need to drill that deep. But it's not very efficient for generating electricity. There actually are some companies that can use heated water in your boiler as a battery and generate electricity from it but that is more from the point of view of using the energy you are storing anyway instead of letting it cool down. So a lower efficiency is acceptable for that.

The open question mark for geothermal is if the cost of drilling will ever be low enough to compete with solar and wind + batteries. Solar and wind are a lot cheaper per kwh but of course intermittent. There are various ways of fixing that that basically involve using some form of battery. You can think of geothermal as a battery where the fully charged battery simply is our planet. Nice if you can get to it but not necessarily cheap enough compared to other ways to store energy. Getting to it involves expensive drilling projects and operating a lot of plumbing to get energy out of it.

An example of a battery that is pretty cheap is a thermal mass based batteries. It is basically the same material (i.e. rocks) plus some insulator. Given enough mass, you can store quite large amounts of energy for very long and there are some companies starting to do exactly that. Several companies are working on those. It's all going to boil down to cost per kwh in the end. wind and solar converging on about a cent per kwh. Batteries tend to be more expensive but still cheaper than burning gas/coal. Geothermal sits somewhere in between. It could be cheaper in some places long term. But then batteries are also getting cheaper.