Renewable Energy — Solar, Wind, and Hydroelectric Power

Renewable energy sources draw on flows that nature replenishes continuously, offering the promise of power without fuel depletion or, in operation, greenhouse emissions. Their central difficulty is that these flows are diffuse and often intermittent: sunlight and wind are spread thinly over large areas and vary with weather and time of day. Harnessing them efficiently is therefore as much a challenge of scale and storage as of physics. This lesson examines the three most important renewable technologies and derives the key relationships that govern their output.

Solar power captures energy directly from sunlight in two distinct ways. A photovoltaic cell (solar PV) is a semiconductor device that converts light straight into electricity through the photovoltaic effect: incoming photons free