Wednesday, April 17, 2013

The Reliability of the Sun and the Wind

The electric utility industry often complains that renewable energy proponents don’t pay enough attention to the intermittency of renewable resources.  A common refrain is “the sun doesn’t always shine and the wind doesn’t always blow.”  The industry then reminds us that, for a reliable electricity grid, supply and demand must be in balance at all times. The implication is that this will be impossible if we rely heavily on renewable energy.

A new report published by the Civil Society Institute models a year 2050 scenario in which renewable energy is used to generate about half of all electricity in the US, and the lights still reliably come on.  In the scenario, about 22% of demand is met by solar (almost all PV), 16% by wind, 8% by hydro, and 5% by biomass. The rest is supplied primarily by natural gas and nuclear energy.  The scenario includes no coal-fired generation.

The authors explain that the intermittency problem of solar and wind is greatly reduced when you consider generation on a regional rather than local scale. Also, weatherpeople are actually pretty good at forecasting available solar resources (i.e. cloud cover) and wind resources (i.e. wind speed) on the time scale that’s needed for sophisticated grid operators to balance supply and demand – namely, several hours ahead of time.  It also helps that as a general matter, solar electricity is most plentiful and reliable when we most use electricity: during daylight hours. To the extent that disparities between energy supply and demand occur in the 2050 scenario, the report shows that reliability can be achieved using interregional transfers of electricity, energy storage, demand response, and other available approaches.

So it seems we can build electric power systems that bank on the reliability of the sun and the wind.  A new refrain could be “the sun’ll come out tomorrow, bet your bottom dollar that tomorrow, there’ll be sun!” and we can recall that our forebears didn’t name places Windy Mountain, Windy Plains, and the Windy City for nothing. 

- Lesley McAllister

http://lawprofessors.typepad.com/environmental_law/2013/04/the-reliability-of-the-sun-and-the-wind.html

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