A (Load) Balancing Act: The Challenge Of Clean Power As new solar and wind energy projects come online in California, electricity grid operators are struggling to smooth out the irregularities in power that come from renewable sources. They are exploring huge batteries and flywheel technology, but such devices are expensive and have limitations.
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A (Load) Balancing Act: The Challenge Of Clean Power

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A (Load) Balancing Act: The Challenge Of Clean Power

A (Load) Balancing Act: The Challenge Of Clean Power

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This week, we're taking a look at California's clean energy goals, in collaboration with KQED in San Francisco. Solar and wind power are booming in the Golden State. But there are times when the sun doesn't shine and the wind doesnt blow. So California utilities are hoping to smooth out those bumps by doing something rarely done on the grid today - storing electricity. Lauren Sommer has more.

LAUREN SOMMER: Inside an unmarked building outside of Sacramento, dozens of people are glued to computer screens.�

Mr. DAVE HAWKINS (California Independent System Operator): So did you look at the load curve yesterday?

SOMMER: On the wall, theres a display plotting a big red line, showing how much electricity California is using right now.

So these are the people that are keeping the lights on.

Mr. HAWKINS: Yep, this is the real-time operations.

SOMMER: That's Dave Hawkins. He's showing me the California ISO, or Independent System Operator. The ISO is the traffic cop of the state's electric grid. Its job: To forecast how much electricity the state needs, and to make sure that it's supplied. And it's done every four seconds.

Mr. HAWKINS: Our electric grid today, as we've built it and manage it, is a huge just-in-time delivery system - just in time.

SOMMER: Hawkins says in order for the lights to come on when we flip the switch, energy supply and demand have to be in perfect balance.

Mr. HAWKINS: And if we don't get all the numbers correct, then there's some major imbalances and some unpleasantness that happens in the system.

SOMMER: Today, most of the state's energy comes from natural gas plants, which produce a steady power supply. But record amounts of wind and solar power are being switched on every year. And because the sun disappears behind clouds and the wind dies down, renewable power is variable.

Mr. HAWKINS: The curves that are showing up so far are pretty erratic. You'll see 40, 50, 60 percent change in the output in a very short amount of time.

SOMMER: Better weather forecasting could help the ISO anticipate the fluctuations, but Hawkins says they'll need something else to fill in the gaps.

Mr. PRAVEEN KATHPAL (Market and Regulatory Affairs, AES Energy Storage): We're looking at what we call Project Sano. It's a two-megawatt energy storage unit.

SOMMER: Just outside of Los Angeles in Huntington Beach, Praveen Kathpal of AES Energy Storage shows me one of the biggest batteries in the state. From the outside, it looks like a simple shipping container.

Mr. KATHPAL: It's pretty unspectacular to look at, which is good. We don't like excitement in the power business if we can avoid it.

SOMMER: The container is packed with small lithium-ion battery cells.

Mr. KATHPAL: Approximately 83,000 of those cells within this container.

SOMMER: This test battery holds enough power for 1,500 homes. Kathpal says grid operators can use the electricity to smooth out the second-to-second fluctuations on the grid. Batteries and other energy storage technologies could also be used for longer-term storage, especially for wind power.

Mr. DAN RASTLER (Program Manager, Electric Power Research Institute): Unfortunately, a lot of the wind blows at night, and we don't want to spill wind, you know.

SOMMER: That's Dan Rastler. He's with the Electric Power Research Institute, a group in Palo Alto sponsored by the nation's utilities. He says if nighttime wind power could be stored in batteries like these for several hours, grid operators could use it during the day, when energy demand is highest.

Still, there's one big problem: Batteries and other storage technologies are expensive. At its best, battery storage costs twice as much as traditional power sources. That's kept most utilities away. But Rastler says the federal stimulus funding could change the game.

Mr. RASTLER: It's been huge. I believe it's around $250 million of stimulus funding, really is jump-starting a number of really key demonstrations.

SOMMER: Several of those demonstrations, or pilot projects, are being led by California's largest utilities. But given the cost, scaling up energy storage could take decades, and California's utilities are on a tight timeline. They're required to get one-third of their electricity from renewable sources by 2020.

For NPR News, I'm Lauren Sommer.

WERTHEIMER: At our Web site, you can learn how California plans to bring this renewable energy online and explore the new technology that will help make clean power possible. That's npr.org/science.

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