Solar-power replacement as a solution for hydropower foregone in US dam removals

There is a growing dam removal movement in the United States, driven in part by environmental, safety and cost considerations. These include electricity-producing hydro-dams, many of which are ageing and will require substantial maintenance or removal over the coming decades. However, hydropower has been and remains an important source of energy for the development of the United States, presently generating about 6% of the nation’s electricity while providing essential grid services. As a potential solution to the conflict between these imperatives, industrial-scale photovoltaics (PVs) could be used for replacement of the energy foregone from hydro-dam removals either by installing the PV infrastructure in the area formerly inundated by the dam reservoir or through offsite replacement. Presently, the total PV generation in the conterminous United States is 35,919 GWh yr⁻¹, or approximately 13% of hydropower generation. On the basis of actual hydropower generation in the conterminous United States in 2016 (that is, 274,868 GWh yr⁻¹), we estimated that 529,885 ha of PVs would be needed to replace the generation of all 2,603 hydro-dams—an area approximately equal to the land size of Delaware. PVs could replace the total annual energy produced from these dams while requiring only 13% of their existing reservoir area. If all the hydro-dams in the United States were removed and only 50% of the emergent land was used for PVs, 945,062 GWh yr⁻¹ power could be generated, which is 3.44 times the current hydropower generation. These analyses are theoretical and do not consider costs, which would be highly site specific. Replacement by PVs without energy storage could not replicate the dispatchability and grid services provisions of existing hydropower facilities; however, improving battery storage capabilities may ameliorate this shortcoming. We suggest that PVs could replace much of the annual electricity output of hydro-dams in the United States while using substantially less land area and providing considerable environmental and ecological benefits.