Tapping the heat in the earth's mantle I believe is a large resource which we should consider when we are looking at sustainable ways to generate electrical power. I have an aquaintance who used to work in the oil business, and he says that in Alaska the oil comes out of the ground white hot. The deeper you drill into the earth's crust, the hotter it gets.

The heat inside the earth is a constant, whereas the sun and the wind are fickle; they can be intermittent sometimes.

Dams for hydroelectric power are also a very important thing to consider. They are also very reliable - you know exactly how much electrical energy potential is piled up behind that dam at any given time. All of Canada is powered by hydroelectric power - and 90% of Washington State is as well. Yes, dams are tough on migrating fish... but given the scope of the ecological disaster that humans are causing globally, I don't think that should be our greatest concern. We will need to really expand electricity generation in north america in order to transition to electric (and hydrogen) powered vehicles. I think that if all the boats in the shipyards and all the cars in the cities were powered by clean energy, there would be a substantial benefit to the ecosystems at the river deltas which flourished so wonderfully before all the big human habitations were built there.

So, without further ado, here's a film about a company in Australia which is making strides in steam geothermal power generation.