I could point to a study citing dozens of solid sources, but the bottom line is this:
Geothermal is great where it's available (California).
Wind power is great, when the wind is blowing.
Hydro is great, where it's available, but requires a 100 mile reservoir.
Solar panels, which catch energy several l hours per day, are super expensive crap. As in it costs TEN TIMES as much as natural gas. A $1,500 / month home electric bill? No thanks.
Geothermal, wind, and hydro can each provide 2%-5% of our power needs. The rest needs to be provided by either fossil fuels or nuclear. The co-founder of Greenpeace agrees that nuclear is the only feasible option, since he doesn't think fossil fuels are feasible long term.
Looking at the safety record of each option, coal is the worst, hydrothermal is the second most dangerous. Nuclear is the safest (by far).