Discovery Guides Areas


Why Not the Sun? Advantages of and Problems with Solar Energy
(Released December 2008)

  by Ethan Goffman  


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baseline or baseload power: Power that supplies a constant energy need, often supplied through coal or nuclear plants.

bulk or wafer-based photovoltaics: Cells that convert energy from the sun into electricity, generally through the medium of silicon.

demand pricing: Policies tied to the changing value of energy depending on demand. This generally makes solar energy more valuable as it is usually strongest during mid-day when demand is high.

externalities: According to one source, "a technological externality is the indirect effect of a consumption activity or a production activity on the consumption or production possibilities available to some other consumer or producer" ( For environmental purposes, an externality is a cost inflicted on the environment-and indirectly on those who use or depend on the environment-not borne by those who inflict the cost.

feed-in tariffs: Tariffs that require extra payment for solar energy on the grid; the money then goes to individuals who have installed solar. This system incentivizes not only solar installation, but installation of the most efficient solar possible.

insolation: The amount of solar radiation area received by a surface at a given time.

intermediate-load electricity: Power that is needed in addition to baseline power as a result of increased demand; often this comes from natural gas, solar, or wind.

kilowatt hour (kWh): A unit of energy equivalent to the work done by one kilowatt (1 kW) of power expended for one hour. This is more formally expressed in joules: one Kilowatt-hour equals 3,600 joules.

law of unintended consequences: A maxim that actions often have unintended consequences. It has been used to critique government programs, and applies also to environmental impacts.

net metering: Solar energy that is fed back into the electrical grid, causing the meter to run backwards.

parabolic troughs: Currently the standard form of solar thermal used in large power plants. They consist of "long parabolic-shaped rows of mirrors focus sunlight on fluid-filled metal tubes encased in glass. The heat collected drives steam generators similar to those that run coal-fired power plants." (Woodside)

renewable portfolio standards (RPS): Laws that require utilities to a minimum fraction of their energy from renewable sources by a certain date; RPS is a form of environmental target.

thin film: Solar cell technology which employs a variety of metals (or sometimes silicon) and is easily manufactured and installed. Thin film technology is currently less efficient than bulk or wafer based cells.

watt: A unit of energy equal to one joule per second.