Renewable energy comes from sources that are free and cannot be depleted. Two types of renewable energy that can be harvested and used easily in buildings are solar and wind power.
Photovoltaic cells, or panels, harvest energy from the sun, which is an unlimited global resource. Solar power can also be used for hot-water heating systems, especially in sunny climates where passive collection from rooftop systems is easy and dependable.
Wind turbines create energy by a wind-driven rotor that turns a generator. Turbines must be placed well above surrounding structures. At the University of Chicago 5% of the energy used in residence halls is provided by wind power.