European eclipse sheds light on solar power challenges

Dan Weissmann Mar 20, 2015
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European eclipse sheds light on solar power challenges

Dan Weissmann Mar 20, 2015
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For lots and lots of Europeans, the continent’s biggest solar eclipse in many years meant excitement.

But for a few Europeans — grid operators and utility workers — it meant distinct unease. Especially in places like Germany and Italy, where solar power has grown to be a significant part of the electricity supply.

Managing the grid when the sun suddenly went away was a serious concern. And it cast light on a big challenge as renewable energy grows: integrating it into the grid.

Of course, it does get dark every single night. But not all at once. Sunset and dusk add up to an hour or so, which gives power producers time to spin up other generators.

The lead time is important, because the big challenge for grid operators is balancing out supply and demand in real time.  

“A fossil-fired generator is not like a stereo,” says Anthony Paul, a fellow at the think tank Resources for the Future. “You can’t just turn the volume from five to ten, in an instant.”

Generators take time to ramp up. And down. What happens when the sun comes back, and you’ve still got all that power from your other sources?

Maybe an overload. In Europe, people worried about blackouts.

That didn’t happen, but the episode shows why, even with just regular events — night falling, or clouds rolling in — solar means extra work for grid operators.

One big piece of work is accommodating what’s called “distributed generation” like rooftop solar. The grid isn’t really built for it.

“Traditionally, our grid has been a one-way street,” says John Larsen, a director at the Rhodium Group. “You’ve got all these power generators, and they shove all the power through the transmission lines, down through the distribution network into your house.”

Distributed generation like rooftop solar means changing that traffic flow. “You’re turning it into a two-way street,” Larsen says.

And the existing street may not be wide enough to handle traffic in both directions.  

For instance, the amount of distributed generation power coming up from parts of Germany’s grid is now six times as much as formerly went out to them, says Ben York, a research engineer at the Electric Power Research Institute.

He picks up Larsen’s traffic-pattern analogy. “If you had originally two lanes lanes going one way,” York says, “you’ve got to add six or seven lanes going back the other way.”

He says Germany is looking at a $30 billion investment to create those lanes in the next few years.

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