What's the Difference Between Solar Energy and Solar Power?

Scott, I'm confused about the use of the terms solar energy and solar power. Is solar energy both a type of energy and a type of technology? Is solar power both a type of power and a type of technology? It seems like the terms get mixed up and used interchangeably, like kWh and kW do even though these units describe two different things. What are the general differences between solar energy and solar power? Thank you. -- Lee K.

Lee, this is a question I get often, and believe it is worth addressing. Solar "power" usually means converting the sun's rays (photons) to electricity. The solar technologies could be photovoltaics, or the various concentrating thermal technologies: solar troughs, solar dish/engines, and solar power towers.

Solar "energy" is a more generic term, meaning any technology that converts the sun's energy into a form of energy—so that includes the aforementioned solar power technologies, but also solar thermal for water heating, space heating and cooling, and industrial process heat. Solar energy includes solar daylighting and even passive solar that uses building orientation, design and materials to heat and cool buildings.

Now in the early 1980's, I was Political Director of the Solar Lobby, formed by the big nine national environmental groups, that embraced all solar technologies—which we viewed as wind, hydropower, and biomass, along with the long list of traditional solar conversion technologies.

The thesis, which is correct, is that the sun contributes to growing plants, wind regimes, and evaporation and rain (hydropower), so that all the renewables are part of the solar family. Now, of course, most would argue that geothermal, and tidal and wave (effected by the gravitational force of the moon) are not solar, but we included these technologies as well.

While I have this platform on solar terminology, I am routinely annoyed by media stories about solar cells (which they assume describes photovoltaics). Photovoltaics technology has changed over the decades from groups of silicon cells wired together under glass to make a photovoltaic module (panel), to various thin film materials deposed on glass, metal and plastics, and including the newer nanotechnology photovoltaics incorporating light sensitive dyes.

While solar exerts could nitpick that these are indeed other types of embedded solar cells, I would venture, the term is outmoded. The word "photovoltaics" for the direct conversion of sunlight to electricity is sufficient.

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