Nuclear power has a bad reputation today.  For its history of several devastating events. Nuclear power in general is dangerous source because it involves radiation. Any damage to the power plant is potentially devastating for the surrounding environment. As it happened in Japan the earthquake and tsunami caused equipment in japan to malfunction and caused nuclear meltdown resulting in leak of radioactive material.
Out of all energy sources outside damage to the facility is most dangerous if its Nuclear power plant. Because it packs so much radiation any kind of incident may turn surrounding area into a nuclear waste.
Nuclear power if ensured its safety is potentially best source of energy so far.

Iceland is a cold country but under its surface there is boiling liquid rock. Iceland managed to live off earths natural energy source and today whole country’s electricity depends on it. Using Geothermal energy as energy source is clean renewable energy source, currently in U.S the project is being developed which would supply U.S for around 10% of its electricity. Iceland basically drilled down hot reservoirs under surface and use the steam that it produces to wind up turbines, which is then transferred into electricity. Geothermal Energy produces no greenhouse gases and is one of the cleanest renewable energy sources.

Stirling engine is using fire to heat up gas in special cylinder. As gas heats up it expands moving the piston and thus producing mechanical energy. Really big downside of this engine is having the gas in cylinder cool down and repeat the process. Other then that very similar to petroleum engine. Moving piston and producing energy. I see why this type of energy production never got as much action as coil or oil did. It is not efficient when compared to them at all. and efficiency is all that matters, it makes all the difference in the world. Today it does have small usage today for single reason, it is more quite then other alternatives. So machines such as military Submarines or small yachts come with built in Stirling engine. But as far as big industry usage is concerned, it gets overrun in competition by alternative engines.