This would baffle consumers, of course, but would be perfectly correct thermodynamically. Table 1 shows the basic energy types and other characteristics associated with each renewable energy resource. The type of energy may restrict how the resource can be used or at least imply that some uses may be more economical than others. The second characteristic, intermittence, is an issue for some resources but not others. In biomass, for example, the energy is locked in chemical bonds and can be released when needed, whereas the kinetic nature of wind means that it must be used when available.
Spatial variability refers to the range of the resource across a given region.
Biomass yields, on the other hand, can vary 30-fold from fertile regions to infertile ones, due to variations in soil and rainfall. Although Table 1 lists seven resources, in reality almost all are derived from the sun. Solar energy is the source of our weather, heating up the atmosphere, driving winds, and dictating the hydrologic cycle. Ocean waves are in turn produced from winds, and ocean temperature gradients result directly from absorbed sunlight. The energy fixed in biomass is likewise converted from sunlight via photosynthesis.