The Good Thing about Fluctuating Wind and Solar

Wind and solar complement each other as renewable energy sources, says Geoffrey Heal, Chazen Senior Scholar and Donald C. Waite III Professor of Social Enterprise. He spoke at the Chazen Institute’s India Business Initiative conference in Mumbai on January 15, 2018.
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Now the downside of wind and solar is they can be erratic. Wind fluctuates widely; it can be forecast up to a day or so ahead but not much more than that, though offshore winds are more stable and predictable. And solar power of course varies over the course of the day, though solar power is very predictable, and it has the nice property that it’s strongest in the middle of the day when the demand for electricity is at its highest. So there’s something quite good about solar power there.

This shows you what I mean when I say that wind fluctuates a lot. This is the output – the aggregate output of all wind power stations in the United Kingdom over one quarter. And you can see it fluctuates wildly from almost 2 gigawatts down to almost zero within a day or so. Wind can drop away, you can have a 25 mile an hour wind now and you have zero wind in 4 or 5 hours from now.

So integrating something which is as variable as that into the grid can be quite a challenge for the people who manage the grid, and that’s something we have to talk about.

This is the output of solar power in California; this is one day from March of last year. The yellow curve here is the output of solar power stations in California. As you can see, it’s very predictable: starts at 6 am, finishes and 6:30 pm, and reaches a peak in the middle of the day, which is when the demand for power is highest. So that’s actually quite nice.

The other thing you might notice from this diagram is, this blue line here is wind. Wind is lowest in the daytime when solar is high, and highest at nighttime when solar is low. So wind and solar do tend to complement each other in many geographies – with wind being stronger at night and solar being stronger during the day, so you put the two of them together, you get less fluctuation on aggregate than either on its own.

About the researcher

Geoffrey Heal

Geoffrey Heal, Donald C. Waite III Professor of Social Enterprise at Columbia Business School, is noted for contributions to economic theory and resource and...

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