The Intermittency Problem                                                       
Many renewable technologies are by nature intermittent producers of electricity. The Sun only shines for so many hours each day, and winds unpredictably come, fluctuate and go. These conditions are at odds with both fixed and variable demands on the grid, and nuclear, coal- and gas-fired generators need time to “spin up” when renewable sources become unavailable.


Even if every rooftop in a given area were covered with “solar” (photovoltaic) panels, they would all be producing electricity for the exact same number of hours each day. Unfortunately, these relatively few hours of production do not very closely parallel the demand curves which power companies must meet.

Solar Thermal

The power of concentrated sunlight can be demonstrated with a magnifying glass. Baseline production from heliostat/tower and parabolic trough systems produce extremely high temperatures and perform well in high insolation areas. Lower temperature systems can work well in less favorable locations.

Image courtesy of Powermag

The red line in the 12-hour “snapshot” above illustrates the challenges power companies face in trying to meet fluctuating demands using intermittent sources. The downward and upward spikes indicate the times when wind (as is also true for solar) energy production and demand are out of synch.

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