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No Dice: storage can’t solve wind energy gamble

October 16, 2020

Here’s the theory: take a wind turbine, smooth the intermittent surges to a steady pulse, send it out to the grid.

Here’s the schematic:

If this works from minute to minute and hour to hour, it is because turbines currently send their small output to a large grid with plenty of capacity from natural gas to stabilize the unpredictable output. 

But what if this kind of renewable energy was all the grid relied on? What would a storage system look like that has the capacity to keep a reserve for the weeks when little to no electricity is available?

To answer that question, Chris Kapsambelis used two years of data from a 1.5 megawatt (MW) turbine in Fairhaven MA. Its output in a day could range from a high of 36,000 kilowatt hours (KWh) down to zero. Read his report.

He graphed peak storage In May. Ideally that means the slow discharge through late summer leaves enough to carry subscribers through the autumn, when the wind on the South shore picks up again.

He established a break-even level of 8640 kilowatt hours. More than that and energy is added to the battery, less than that and energy is drawn down.

So far so good. 

Then Kapsambelis recalculated his assumptions about demand on the system. If the grid operator drew 5 KW more power from the battery,  a 1.4% change, the grid could experience blackouts at any point between mid-September and mid-October. 

If that weren’t enough of a worry, he found that the battery would need to be large enough to store 500 MWh. But wait! The largest storage field in the world, the Hornsdale Power Reserve in Australia, “can only store 129 megawatt-hours, which is about a quarter of the storage needed for just one small wind turbine.”

Chris Kapsambelis has news for us: energy storage for wind power is not possible.

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