electricity, can help address these challenges. Renewable energy is an attractive option because renewable resources available in the United States, taken collectively, can supply significantly greater amounts of electricity than the total current or projected domestic demand. These renewable resources are largely untapped today.
There are, however, important disadvantages to the use of non-hydropower renewables for electricity generation. The energy available from renewable resources is less concentrated than that provided by fossil-fuel or nuclear power, posing significant challenges to the development of renewable resources for electricity generation on a large scale. Generation must occur at the site of the resource and accommodate the temporal fluctuations characteristic of some non-hydropower renewable resources. At high penetrations of non-hydropower renewable sources, electricity system operators must deal with spatial and temporal constraints to integrating the generated electricity into the electric grid in ways that ensure a reliable, controllable supply of electricity. Large penetrations also will result in land-use requirements that in turn can lead to instances of local opposition to the siting of generation and transmission facilities.
In turn, the use of renewable electricity provides some significant advantages over the use of fossil-based electricity. Many types of renewable electricity-generating technologies can be developed and deployed in smaller increments, and constructed more rapidly, than large-scale fossil- or nuclear-based generation systems, thus allowing faster returns on capital investments. Generation of electricity from most renewable resources also reduces vulnerability to increases in the cost of fuels and mitigates many environmental impacts, such as those associated with atmospheric emissions of greenhouse gases and emissions of regulated air pollutants. Further, distributed renewable electricity generation located at or near the point of energy use, such as solar photovoltaic systems installed at residential, commercial, or industrial sites, can offer operational and economic benefits while increasing the robustness of the electricity system as a whole.