Clean Power

Published on November 24th, 2011 | by Nicholas Brown


Solar Backup Myth

November 24th, 2011 by  

Rooftop solar panels.

MYTH: Solar Power Isn’t Green When It Requires Backup Gas Power Plants:

Solar opponents often argue that solar power plants create the need for additional power plants. The first problem I noticed with this argument is that the installation of additional electricity generation capacity does not create the need for more electricity.

That is illogical. If you were to cancel the construction of a solar power plant, then this means that electricity would have to come from another power plant, and that is likely a natural gas one. The natural gas power plant would have to operate and burn gas 24 hours per day.

If the solar power plant was installed, then that same natural gas plant would back it up at night, and would operate only a fraction of the time, and, hence, burn a fraction of the gas that it normally would.

During the day, when solar irradiance fluctuates, a relatively small (compared to an entire day of backup) amount of energy storage (batteries are an example) could back up the solar power plant with the excess energy stored from sunny periods.

Second: Such people argue that the natural gas generators required are unable to scale electricity generation up or down when solar power production decreases or increases, respectively. Therefore, they have to stay on all the time.

Note that while some power plants can take hours to start (especially coal and nuclear plants), modern gas peaking plants can start in 10-20 and hydro generators can start almost instantaneously.

The solution to the problem above, nonetheless, is pretty simple — set up an hour (or even less) of energy storage that the solar panels would keep charged, and if it becomes cloudy, the battery will back up the solar power plant by providing electricity for up to an hour, which is plenty of time for the natural gas or hydro power plant to start.

One hour of energy storage is inexpensive and the energy storage would act as a buffer for solar power. Another characteristic about solar panels that complements that is they already generate DC, so no AC to DC conversion is required to charge the batteries.

Related Articles:

  1. World’s First Solar Power Plant that Works at Night Constructed
  2. Solar Thermal Electricity: Can it Replace Coal, Gas, and Oil?
  3. Backing Up Solar Power Plants

Photo Credit: SolarShop

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About the Author

writes on CleanTechnica, Gas2, Kleef&Co, and Green Building Elements. He has a keen interest in physics-intensive topics such as electricity generation, refrigeration and air conditioning technology, energy storage, and geography. His website is:

  • Dcard88

    Also, moderately cloudy days will still produce up to 50% power and heavy clouds will produce 5 to 10% (most technologies)

    • Anonymous

      Thanks for the note/point.

  • Jnffarrell

    Electric companies charge ratepayers for peak power needed only on the hottest and sunniest days. Moreover they ship high priced power across thousands of miles of electric grid payed for by rate payers. Distributed power at home and at Walmart prevents power failures and rotten food for thousands, not to mention preserving comfort and safety for thousands of old people who have retired to the desert.

    Shame on power company lobbying for less safety for old people. Time for Sen. Grassley to speak up against PG&Es ‘death lobby.

    • Anonymous

      Nicely put 😀

  • Anonymous

    Modern gas peaking plants can go from full stop to full speed in 10-15 minutes. Much less than an hour. Hydro generators are essentially instantaneous.

    Solar input, if it’s from a number of arrays spread across an area, does not suddenly turn on or off. Clouds move across a region in a gradual and predictable pattern.

    Some really interesting stuff is happening with battery technology. We may see new, very inexpensive battery storage in production in the next year or two. When that happens solar and wind are going to take a lot of natural gas off our grids.

    • The most recent battery technologies certainly are promising.

    • Anonymous

      Thanks! I updated that line. Any chance you’ve got links for those numbers that we could stick on that text?

      • Anonymous

        Here’s a good site with basic info on various fossil fuel generation methods including startup time.

        Note that the turbine portion of combined cycle gas plants are fast to come up but the heat/steam portion takes 1.5 to 3 hours to climb to speed. That does mean that combined cycle can be used for peaker power if needed.

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