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Green-Energy Storage: 'The Next Big Thing'

For California to reach its ambitious climate-change goals, it must figure out how to deliver electricity when the sun isn't shining and the wind isn't blowing.

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For the past decade, California has been a leader in the clean-energy revolution. Groundbreaking state laws require our major utilities to purchase 33 percent of their power from renewable sources by 2020. And some green-energy experts expect that mandate to rise to 50 percent or more in the following decade. To date, the rapid growth of solar and wind power has fueled the move to renewables. But for California to fulfill its green-energy future, it must solve an important problem: how to deliver electricity to consumers when the sun isn't shining and the wind isn't blowing.

We rely on what's essentially a 19th-century technology — the electrical grid — to deliver power to our homes. The grid encompasses power plants, high-voltage transmission lines, local circuits, and just about everything they touch: whatever it takes to generate and distribute power. Throughout the 20th century, the concept evolved and improved, and grids of various sizes began delivering power more reliably to ever more places in the United States and around the world.

But in the 21st century, a major shortcoming of our existing grid looms large: Electricity dissipates instantly on it. This use-it-or-lose-it system is a problem for wind energy, since wind blows strongest at night, when demand for electricity is low, and for solar energy, which can't provide power once the sun goes down, or when a cloud passes overhead. That means considerable energy from wind and the sun is lost if it isn't used at the moment it's available.

On top of that, the intermittent, sometimes unpredictable energy output of solar panels and wind turbines can spell trouble for our outdated grid, like large-scale blackouts and brownouts or surges on local circuits that can fry electronics.

In short, the system needs an upgrade. It needs a buffer to help balance supply and demand, without which the grid can suffer catastrophic failure. It needs a sponge to soak up excess power and deliver it at peak times. It needs a regulator to smooth out the steep peaks and valleys that result from solar and wind ramping on and off with the weather. And it needs to do all this while meeting the country's most stringent greenhouse gas-reduction targets in a state that is forecasted to continue growing in population, and therefore energy demand, for decades to come.

What the grid needs — California legislators, utilities, and entrepreneurs agree — is energy storage.


With the solar and wind industries safely ensconced in California and the energy they produce critical to our state's grid (renewables now account for at least 20 percent of our power), electricity storage represents the next evolutionary stage of our energy system. Yet evolution may be too soft of a word; what storage could mean, years down the line, is nothing short of the total transformation of a rigid, over-engineered grid reliant on fossil fuels into a flexible, efficient, and, most importantly, carbon-free grid capable of responding in real time to fluctuating supply and demand.

The energy storage industry remains nascent, to say the least — as do its various technologies, including multiple kinds of batteries, compressed-air storage, flywheels, and advanced chemical processes, at least on a commercial scale. But UC Berkeley professor Dan Kammen, a world-renowned expert on renewable energy, suggests that by 2050 storage could displace all of our state's natural gas power plants, which currently play the role of a buffer and peak-hour supplier, to represent roughly a quarter of the state's total demand, or about 20 gigawatts of capacity. Today's figure is somewhere in the tens of megawatts.

"We're talking about creating a whole new sector, but I'm pretty confident," Kammen said. "Storage is going to be the next big thing."

He's not alone in thinking so. Many state leaders agree, including two from the East Bay who are spearheading California's charge to integrate energy storage into the grid. Just as California has led the nation in adopting renewable energy — thanks to its aggressive renewable portfolio standard (RPS), which was enacted in 2002 — it is now on the brink of becoming the first state in the nation to not just support storage, but require it.

Three years ago, in September 2010, then-Governor Arnold Schwarzenegger signed into law Assembly Bill 2514, authored by state Assemblywoman Nancy Skinner. Known as the California Energy Storage Bill, AB 2514 directed the California Public Utilities Commission to consider instituting storage procurement targets and mandates for the state's three large investor-owned utilities.

After years of review, CPUC Commissioner Carla Peterman, who is currently pursuing a Ph.D at UC Berkeley and who lived in Oakland at the time she was appointed to the commission, delivered the CPUC's proposal in June: a mandate requiring Pacific Gas & Electric, Southern California Edison, and San Diego Gas & Electric to cumulatively install 1.3 gigawatts of energy storage by 2020 (each has individual targets included in the proposal). By next year, the utilities will have to come up with two hundred megawatts total: ninety each for PG&E and SCE and twenty for SDG&E.

The specifics of the proposal — including the very notion of a mandate, which is opposed by some stakeholders, including the utilities themselves — were merely a starting point. An updated proposal will be issued this week; then it, too, will be subject to review and another round of comments. A final ruling is expected on October 3.

Skinner, for her part, was encouraged by the CPUC's opening volley. "I've been very, very pleased that Commissioner Peterman has proposed targets," she said in an interview. "Part of the purpose of my bill was to send that market signal, and then as the market responds, to then have appropriate targets so that we can as a state, help ensure the reliability of our grid. ... We often have to get ... a little ahead of the curve to make sure that we properly incentivize the technologies."

Her support for storage isn't all about renewables, either. She said she'd like to see utility-scale storage displace the need for new natural gas "peaker plants," which are expensive to operate, as well as dirtier and less efficient than traditional gas plants. Most are designed to operate just a few times per year, and are used only to generate emergency power when demand spikes during summer heat waves.

Peterman shares Skinner's view on storage, and has made no secret of her support for government intervention in renewable-energy markets; her research at Cal addresses the impact of public policy on reducing photovoltaic costs. "There's been a growing appreciation that as you introduce renewables, you have to introduce other technologies that can keep energy at a constant flow," she said. "Storing energy allows us to use it at higher-value times without creating the other air emissions you would have from burning fossil fuels. The technologies are emerging, so they are high-cost. But they are also high-benefit."


East Bay startup Primus Power is banking on energy storage — and batteries in particular — being the way of the future, mandate or no. The 25-employee company, established in Alameda in 2009, is now fine-tuning its first generation of commercial batteries and has secured contracts to ship its very first units up and down the West Coast starting next year. To date the company has received $17 million in grants from the California Energy Commission and the US Department of Energy, in addition to at least $15 million in private financing.

At Primus' 16,000-square-foot lab in Hayward (where the company moved from Alameda in 2010), director of product management Andrew Marshall showed off the company's key product, an "EnergyPod" that includes a group of twenty-kilowatt batteries arranged inside a standard twenty-foot shipping container in two rows of seven, with a narrow aisle down the middle. This container-based system, designed for portability and easy scalability, is popular among other utility-scale battery manufacturers.

What's different is the batteries themselves — though it's still early enough in the storage game that many applications remain technology-agnostic. Primus Power's batteries, which contain thirteen patented technologies (Marshall says the company has filed for another sixteen patents), can store energy for up to four hours using a "flow battery" system in which an electrolyte solution (in this case zinc bromide) is passed through an electrochemical cell to charge and discharge electricity.

In standard configuration, eight 250-kilowatt EnergyPods will be paired with one "power box" — a set of inverters, connections, and other components required for grid integration — producing a single unit with a total storage capacity of 2 megawatts of energy.

Starting next year, 112 of Primus' pods are headed to the Modesto Irrigation District to store and regulate the energy output of the small utility's new 25-megawatt solar-panel system, which was completed late last year. Two pods are also going to Puget Sound Energy, a utility serving a large swath of the Pacific Northwest, as part of a project to evaluate the role of storage in balancing the output of various large wind farms in the region. And one pod will ship to the Marine Corps Air Station Miramar in San Diego, which is building a small, independent, storage-dependent "microgrid" to ensure energy stability on the base, which experienced a disruptive blackout in September 2011.

"It's all around making the grid cheaper, cleaner, and more flexible," said Primus Power CEO Tom Stepien. "All the macro trends are pointing to storage. It's a question of when, not if, for sure. ... As the cost of these units come down, we'll find more and more ways to use them.

"It's early," he allowed, "but everything is pointed in the right direction."


In California, momentum is building fast for green-energy storage. This week, San Jose welcomes the Energy Storage North America 2013 conference (September 10-12) and it's expected to host as many as five hundred attendees and seventy speakers from countries including Italy, Africa, and Japan, said Berkeley resident Janice Lin, executive director of the California Energy Storage Alliance, which will co-organizing the conference. Commissioner Peterman will be a keynote speaker.

Then, in mid-October, San Diego will host the Electrical Energy Storage Applications and Technologies 2013 conference, organized by the Department of Energy, Sandia National Laboratories, and the Electricity Storage Association, a trade association founded in 1991 to promote energy storage systems worldwide.

San Diego is pursuing storage more aggressively than perhaps any other city in the state. Earlier this summer, the CPUC authorized San Diego Gas & Electric to spend $26 million (it had originally applied for $55 million) on research, development, and demonstration of energy storage projects — a first for utilities in the state.

Residential rooftop solar penetration is as high as 50 percent in some San Diego-area neighborhoods, said Lee Krevat, Smart Grid Director for SDG&E, and total concentration across the utility's territory is likely unsurpassed statewide.

"The number-one benefit of energy storage that is urgent enough to already be investing in it is to smooth solar energy," Krevat said, referring to weather-induced dips and surges in solar energy output, a persistent issue in coastal San Diego. "We have data that we've measured on specific circuits where there's a high concentration of solar energy, and it causes voltage swings, especially when we have the marine layer burning off. It changes from second to second. Our old equipment is electromechanical, so it just can't react fast enough. By the time it reacts, the clouds have moved to a different area."

Most new battery technologies, however, can respond in a fraction of a second, smoothing the power supply in real time and avoiding solar's potentially harmful hiccups — including the backwards flow of energy on local circuits that can result when sunshine is high and demand is low. "We think storage is a very important piece of California's energy future, and really the world's energy future," Krevat said.

However, not all of California's major utilities are so enthusiastic — especially about the possibility of the CPUC handing down another mandate. But storage, whether paired with large-scale solar and wind plants, installed in local circuits, or even set behind the meter at private homes and businesses, can be a boon to utilities by increasing the reliability and quality of the energy supply and reducing the likelihood of outages. It also allows utilities to profit by storing energy when it's cheap (like overnight) and selling it at peak times: a classic case of buying low and selling high.

This is something that San Diego Gas & Electric, and, to a lesser extent, Pacific Gas & Electric, have begun to embrace. PG&E announced in May the completion of a four-megawatt, six-hour battery pilot project in San Jose designed to help study how sodium-sulfur batteries in particular can benefit the grid. And the utility has received $25 million from the Department of Energy and $1 million from the California Energy Commission to demonstrate a compressed-air storage plant, where excess wind energy will be used to compress air in a depleted natural gas reservoir. The air can later be drawn upon during high-demand periods to produce electricity by releasing it through a turbine. PG&E is still searching for a suitable site. When completed, the facility will be the third of its kind in the world, and the first in the Western US.

One goal of the project is to assess the cost-effectiveness of compressed-air storage on today's grid. It's a critical point, as both Skinner and Peterman designed their proposals to that ensure that storage is only required to the extent that it is, over time, no more costly (and ideally less so) than using other options, including natural gas plants, to stabilize the grid. "What we're trying to achieve here is encourage storage that has a cost, but not a cost that would exceed" the cost of generating electricity, Skinner said.


California can technically meet its ambitious 2020 RPS goals without adding much more storage than currently exists on the grid, said Cal's Dan Kammen. But if we look beyond 2020 into 2030, he said, when the renewable-energy target could be elevated to 50 percent or more, and eventually 2050, when he projects that natural gas could be phased out entirely, storage becomes much more critical.

"If we don't begin by getting storage deployed now, then in that 2020 to 2030 timeframe, we won't be ready," he said. "It's clear from the models that if we can begin to deploy these advanced technologies sooner, we can gain more information about them and bring down the price."

Yet California isn't the only state with big plans for energy storage. Kansas and Texas, both of which have high concentrations of wind energy, are actively considering storage at both policy and technology demonstration levels, said Brad Roberts, executive director of the Electricity Storage Association.

In addition, a ruling from the Federal Energy Regulatory Commission in October 2011 has spurred large storage projects in the Eastern United States by offering financial incentives to grid operators for using storage — instead of coal and gas plants — to regulate voltage frequencies.

Imre Gyuk, who heads the DOE's energy storage program — and who will be another keynote speaker at the San Jose conference this week — believes 2013 represents a turning point in the energy storage field worldwide. California, and the nation at large, are out front — for now.

"Storage is a reality," Gyuk said. "It's growing in the United States. It's growing in China like crazy. The entire Pacific Rim is just bursting to get into this. Europe is taking it up.

"But they're all behind us. We need to take some leadership in this," he cautioned, citing California's proposed mandate as a model. "We don't want to let happen what happened with photovoltaic panels."

Correction: The original version of this story misstated Brad Roberts' first name and the name of the organization in which he is the executive director. It is the Electricity Storage Association, not the Energy Storage Association.

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