The biggest disadvantage to all renewable energy sources is that conventional utilities aren't fully capable of incorporating the new technologies to make energy. There are still technological and cost barriers (solar panels are still fairly expensive, for example) but as the price of generating energy conventionally continues to rise, and along with the improvements in technology and manufacturing, components needed to generate renewable energy will become cheaper. To some degree, this is in effect -- and, at least where near I live, windmills are now finally appearing alongside power plants. Much of the "alternative" energy systems are most effective if situated at your home; this is perhaps the most difficult philosophical obstacle from a corporate standpoint, which is attempting to incorporate them into a big distributed system. Why have solar panels hooked into the grid, and lose much of the energy in transit? Why not directly connect panels to the home? What would the big distributed system do then?