Are solar, wind and marine power too intermittent to be useful?

Electricity generated from renewable sources such as wind, marine and solar helps to cut carbon emissions by reducing the need for fossil fuel power generation. Renewable energy can also diversify supplies, helping to make a power system more resilient to failures and less exposed to fluctuating fuel prices. However, renewables pose a challenge in the form of intermittency, as their output varies with the available sunlight, wind speeds and wave activity.

Giant wind turbines are powered by strong prevailing winds near Palm Springs, California. Photograph: David McNew/Getty Images

In off-grid situations – for example in remote regions of developing countries – intermittency is typically dealt with using a battery, which gets charged up when power is available and stores the electricity until it's needed. But most of the world's renewables power sources are connected to an electricity grid and in this situation intermittency can be accommodated by varying the output of fossil fuel power plants.

Even on a grid with no renewables, fossil fuel plants needs to be adjusted over time to match demand to supply and allow for power station breakdowns. When renewables are included in the energy mix, the output of these fossil fuel plants may need to be adjusted more frequently. Some power stations will run below their maximum output to allow this, and additional fast-responding plants may be needed. Efficiency may be reduced as a result. But overall, these effects are usually much smaller than the savings in fuel and emissions that renewables can deliver

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