The University of Michigan’s Center for Sustainable Systems has developed since 2001 a growing set of factsheets that cover topics including energy, water, food, waste, buildings, materials, and transportation systems. The Energy category includes the Factsheets on Biofuels, Geothermal Energy, Nuclear Energy, Photovoltaic Energy, the U.S. Energy System, US. Grid Energy Storage, U.S. Renewable Energy, Unconventional Fossil Fuels, and Wind Energy.