How to Store Solar Energy
by Hal Bernton
The Snohomish County PUD dedicated its first battery system Thursday
designed to store power from wind or solar generation for later use during high demand.
Steve Klein is an advocate for wind and solar power, but as chief executive of Snohomish County Public Utility District he also has plenty of experience with their drawbacks.
When the sun sets, solar cells cease generating, and when gusts die down, wind electricity plummets.
"They are intermittent," says Klein. "They are there, often times when we don't need them, and not there when we do."
Klein is hoping for big changes in the years ahead, when a network of batteries would enable the utility to bank some of this energy and then feed it into the grid during times of peak demand.
On Thursday, in a step toward that future, the Snohomish PUD dedicated its first battery, a lithium-ion system about the size of a shipping container that has been installed at a South Everett substation.
The one-megawatt system, developed by Mitsubishi and GS Yuasa, is able to store enough power for about 400 families for one hour.
The project is part of a broader effort, partly funded through $14.3 million from the state's Clean Energy Fund, to test new battery and smart-grid technologies at Snohomish PUD, Puget Sound Energy and Avista.
The fund was launched by Gov. Jay Inslee, who was in Everett on Thursday for the dedication, as part of his push to reduce fossil fuels' carbon emissions that contribute to climate change.
In an industrial hub of Western Washington, the Snohomish PUD has been able to meet an expanding load demand from more than 327,800 customers largely without coal or natural-gas-generated electricity. Instead, it has relied on hydropower supplemented with nuclear, wind and smaller amounts of other renewable energy sources, such as rooftop solar installations and landfill gases.
But the power supply in recent years has become more volatile, and that makes it more difficult for the utility to keep demand and power resources in equilibrium.
"We went in less than two years from zero wind in our portfolio to 8 percent of our portfolio on an average basis," Klein said. 'We could go into the hour perfectly balanced, but 15 minutes later some 200 megawatts of our wind resources would go to zero, and we're scrambling."
Other utilities using increasing amounts of renewable energy also are facing challenges, particularly in California where large-scale solar as well as wind power are pouring into the grid and utilities are required, over time, to dramatically expand storage.
Klein hopes that batteries can help ease such strains.
But the technology is expensive, piling on substantial costs to harnessing solar and wind energy. Some of the early battery systems haven't worked very well, and more work needs to be done to develop standardized systems that can be reliably integrated into the grid.
"The last thing you want to do is to plug in something you can't trust," he said.
Snohomish PUD, which received $7.3 million of the state grant money, will test three battery systems.
Two of these systems use lithium-ion batteries, the technology used in electric cars and computers.
A third involves vanadium-flow batteries that store energy in liquids. This system will be housed in 20 shipping containers and be capable of storing about eight hours of power for 750 families.
The electrolyte chemistry was developed at Pacific Northwest National Laboratory in Washington, and the battery is being supplied by UniEnergy Technologies in Mukilteo.
These batteries have a long life and are flexible in their charging, which gives them some advantages for use by utilities.
"You can cycle the battery deep or shallow as much as you want, and you can use it as much as you want without causing degradation," said Russ Weed, a vice president of UniEnergy, which is working to develop national and international markets for the battery.
Software is another key component. It has been developed for the Snohomish PUD by 1Energy Systems, a Seattle company founded in 2011 by former Microsoft executive David Kaplan.
1Energy Systems has come up with "open standards" software that regulates battery operations and communicates with the grid.
"We have sold our system to a half-dozen different utilities, but Snohomish PUD was our first," Kaplan said.
The performance of different battery systems will be analyzed by Pacific Northwest National Laboratory. The hope is that this effort will contribute to a new generation of more efficient, and more affordable, battery systems.
"The goal is, if you track us over the course of all this, a year or two out, you should see the price of what we're paying fall down dramatically," Klein said.
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