There is no perfect source of energy but humans have some options besides fossil fuels. One of these is solar power, and that is a good bet for the future compared to nuclear, wind, geothermal , hydroelectric or biofuels.
Even so we don’t yet know how to use all the sun- photovoltaics- available for heating, thermal heating with mirrors and directed into a turbine. However, in many regions like California and Texas- maybe not Boston, the solar power will be getting cheaper so that it’s only 2X the cost of coal heat. At the same time solar energy needs more technological solutions to boost up efficiency and invent better storage options. We can expect this to happen but who knows when.
As for nuclear power we do not yet have either a perfect storage or recycling system: dry cask storage is not safe enough to take care of waste cheaply and well. Nuclear does take care of greenhouse gases though. So that is why it accounts for 20% of American energy.
Wind power is the most popular around the US and of course Germany too. Here in Boston the windmill farm offshore might take care of one (2005 level) full year of the US national energy demand. However people have to tolerate 50 ft. towers only 7 miles off the coast. Most people think that new technology will grow fastest in the wind area above all.