Their technical development is necessary. But, perhaps the most important one is the fact that they generally require large land areas. For example, if one were to grow enough biomass to supply the energies now supplied to the world by oil, one would have to grow crops at very high rates of yield over the entire continental United States. Another difficulty is the lack of availability. Biomass can be grown and stored, but those technologies that depend upon direct sunlight, such as photovoltaic cells or solar-thermal technologies only operate well when the sun is shining.
Wind power varies with time, but in a different way.
And, none of them can be guaranteed to operate and supply energy at times when people wish to use it. Certainly, solar technology at nighttime is not feasible without energy storage, which adds complexity to any system, as well as cost. Nuclear power also supplies about ten percent of the world s energy supply when we count it on a primary energy basis. Its technology is further developed than most of the solar technologies, but it definitely faces a different set of social and political problems that must be resolved if its use is to grow, and if it is to become a significant source for the future. I ve been very up-front in pointing out there are problems.