PROJECT EASY GREEN

Utility-scale storage is the Holy Grail to many in the industry. Some would say it is just around the corner, while others argue it is floundering outside of the realm of commercial viability.

During a recent webinar, Utility-Scale Storage: Determining the Best Investment Strategy for Utilities, a group of experts tried to tease out the drivers that are pushing the industry forward, as well as those that are holding it back.

There were varying opinions about what holds the most promise for storage on the grid, but there was also a consensus that it was time to move out of the starting gate and ramp up the real-world learning curve.

“In the past year, a lot of good things have happened,” said Imre Gyuk, program manger for energy storage research at the U.S. Department of Energy. He pointed to the deployment of $185 million in stimulus funds for storage projects and federal and state legislation.

Gyuk also highlighted many of the demonstration projects, from wind firming in California to community battery storage at American Electric Power to flywheel projects with New York Independent System Operator, as examples of technologies making forays into the field.

Storage, of course, is not monolithic. Flywheels, like those erected in New York by Beacon Power, only store energy for a few moments: the devices serve to balance power delivery. Batteries — which sport a chemistry cookbook that includes lithium ion, sodium, zinc, fiberglass and other variants — store energy for intermediate periods. For persistent power storage, there's a raft of compressed air startups like Bright Energy and SustainX, as well as energy storage via water and gravity. In general, the less time you have to store energy, the more market-ready your technology is at the moment. Further out: ammonia and liquid metals.

The leap out of the lab is significant, but huge challenges remain. The community storage projects, for example, which could someday make use of electric vehicle batteries after their useful lifespan inside the car, have some basic issues. “Are there issues with the transformer and this [battery] sitting next to each other?” asked Melanie Miller, senior project manager at Duke Energy. “It’s easy to put storage in a lab setting. You don’t have to worry about digging up someone’s front yard.”

The logistics of simply finding a suitable site for storage is just one issue. Duke also has battery storage paired with solar projects to understand how to most effectively use it for peak shaving and, in a separate project, for frequency regulation. “We’re trying to pair multiple components to get the biggest value,” she said. 

More bang for your buck will be the secret for storage success in coming years. While some technologies regulate voltage and others can store more energy to dispatch at peak, experts agree that solutions that meet the specific needs of a utility are going to get deployed even if they’re not completely optimized. For project managers, it’s really important to understand those hyper-local issues to get the most out of storage, according to Rahul Walawalkar, vice president of emerging technologies and markets for customized energy solutions. He also said that round trip efficiency will be a key issue for any technology. 

Others agreed that carefully weighing the different options for specific applications will be key. “When we talk about benefits, they’re entirely dependent on the time you operate and where you are,” Haresh Kamath, strategic program manager for EPRI, said during the webinar, which was hosted by Smart Grid Today. “If you’re justifying cost on those very variable targets, you have to be careful.”

Many demonstrations are already underway to better understand how storage can work best in different applications. The DOE helped fund 16 projects, including a 25 MW/3-hour battery plant for the Modesto, Calif. Irrigation District to firm 50 MW of wind. At PJM, stimulus funds helped install a 20MW flywheel storage facility. Pacific Gas & Electric is planning a 300 MW/10-hour compressed air storage facility in Tehachapi, Calif. Unlike utility projects, which can be viewed as proprietary, storage is likely to result in a lot of information sharing, as the need for it is already overdue. AEP Ohio, which is just starting a community energy storage pilot, said that all of its data from the project will be open source.

Aside from gaining a more complete understanding of how storage will impact the grid, FERC’s ruling earlier this year about pay for performance for grid storage, which requires grid operators to pay more for faster-ramping resources, is also pushing the market towards commercial viability. Walawalkar is optimistic, betting that there’d be at least a half-dozen technologies on the market by 2015. Even with changes in the market, Kamath didn’t expect to see a standardized grid-ready product until after 2015, and maybe closer to 2020. “We need to have something that’s a lot more than a science project,” he said. 

Turn a glass upside down and plunge it into a sink filled with water.

You’ve just demonstrated the operative principle behind a compressed air storage system being developed by startup Bright Energy Storage Technologies that — conceivably — could deliver large amounts of power for 2.5 cents to 6 cents per kilowatt hour.

The company’s core technology consists of a long, flexible polymer/glass bag shaped like a giant sea cucumber. One end of the bag is attached to an air hose on the surface. The other end is open to the sea. Sand from the sea floor anchors the open end of the tube to a sand flat 140 meters below the surface.

To store energy, generators on shore will compress air and funnel it to the bag. While some air can bubble out the open end if overfilled, the majority of it stays inside, in the same way air stays in the upside down glass or when you blow into a straw.

When needed, the air can be quickly dispatched.  Sea water (or water from a large lake) fills the void until more air gets sent down.

The potential low cost of the technology derives from the fact that Bright doesn’t need high pressure storage tanks or lots of active mechanical equipment. The body of water does most of the work.

“We design for no moving parts and no metal,” says chief technology officer Brian Von Herzen. “Sand at the sea floor is 100 times less expensive than steel. It is free at the bottom of the ocean. The main expenses for the ballast are the permit and installation.”

Compressed air storage — the cheapest way to store energy according to many — barely exists as an industry now. Only two large-scale compressed air facilities currently operate in the world. The concept, however, has uncorked the creativity of engineers and designers all over. Some of the more notable startups include SustainX (compressing air with the help of water vapor), secretive LightSail Energy (founded by an entrepreneur who entered college at age 12), General Compression (cost-effective underground storage) and Isentropic Energy (hot gravel). Some others are also looking at Bright's idea.

At 140 meters below the surface, Bright can store enough air for approximately 1 gigawatt-hour of power in a square kilometer of sea real estate, he said.

The main expense lies in building the tube to refill the bag and to allow for grid connection. Horizontal drilling techniques are employed and the air spout is located close to shore. A self-standing system with its own generator could produce power for under 6 cents a kilowatt hour, he said. If you could latch onto a generator at an offshore wind farm, the costs could potentially drop to 2.5 cents.

Storms? Debris? Sharks? Wave and tidal companies have seen their valuable prototypes shredded by the sea. Those systems, however, mostly float on or near the surface, the most turbulent place in the ocean. At 140 meters down, the ocean is far calmer. Below 70 meters, hurricanes can have little effect, Von Herzen said.

“The deeper you go, the better it gets,” he added.

The air is also only stored at two pounds per square inch of pressure over ambient conditions, so Bright doesn’t have to worry about rips or tears caused by excessively high pressures.

The technology also dovetails well with ocean conservation efforts. Imagine a checkerboard of ocean real estate: one square kilometer is given over to fishing, while the neighboring square kilometer is used for storage. Fish suddenly have protected habitats, but protected environments that are close enough and small enough to placate the fishing industry. Ideally, it could become a model for sustainable aquaculture.

The company will conduct a trial later this year.

The biggest obstacles are permitting and planning and skepticism. It’s a bag in the water. Can it last 25 years? What happens if leaks develop? What if the ballast shifts and the air rushes out the other end? Utilities are accustomed to getting their power from large-scale coal plants.

“Utilities are not used to being entrepreneurial organizations,” he said.

One group likes water and air. The other prefers heat and earth.

It sounds like a panel that Aristotle might have moderated 2,500 years ago, but actually it marks the difference between two different approaches in modular compressed air energy storage.

SustainX, a well-funded spin-out from Dartmouth College, has come up with a modular energy storage system that relies on water to prepare a mass of compressed air that can later be delivered to a turbine. A 40-kilowatt prototype exists, and in 2012, a 1-megawatt system for AES should be ready.

LightSail, a somewhat secretive startup funded by Khosla Ventures, is taking a similar approach.

England’s Isentropic Energy compresses gases for turbines too, but instead of water, the active ingredients are two gravel-filled tanks:  a cold one with rocks at minus 160 degrees Celsius and a hot one with rocks at 500 degrees Celsius.

In Isentropic’s system, the gas only gets compressed to around 174 psi, but it radically changes temperature. When it comes out, it is at a high pressure and temperature, said CEO Mark Wagner.

In the SustainX and LightSail systems, the gas stays at close to room temperature throughout the cycle, but it gets compressed to 3,000 psi so it comes out at an extremely high pressure.

Who’s right? Utilities will ultimately have to determine that through rigorous testing, but here are the basic differences. Compressed air remains far cheaper than batteries or other means for storing energy, according to EPRI and others. Modular units like these have an advantage over geologically-based storage in that they can be made in different sizes and be placed virtually anywhere on the globe. (General Compression, which just raised $54.5 million, concentrates on geological compressed air storage that uses wind turbines to compress air. So it's mechanical compression, but different in its market approach than these three.)

SustainX. The key intellectual property behind the company is a proprietary compression/expansion motor powered by a hydraulic transmission compresses the air.

The transmission functions essentially the same way as a portable hydroelectric dam: a large volume of water with the help of gravity is harnessed perform mechanical work. Dax Kepshire, co-founder and general manager, wouldn’t describe it much beyond that, but agreed loosely with the hydroelectric analogy.

The motor can also be used for functions other than compressing air.

While getting compressed, water vapor is employed to cool the air. Cooling is important during compression. Gases heat up as they get compressed, and that increases the amount of energy required to compress the substance. In the few underground compressed air storage facilities in the world today, the energy required to run the gas turbines compress the air comes roughly to about 50 percent of the energy stored. SustainX, he said, has an energy density of seven times more than conventional systems.

“We are spraying water directly into the cylinders,” he said.

The heat extracted with the vapor is subsequently stored in, yes, another body of water. Water is employed as a heat sink because “Water has the best specific heat of any substance on the planet,” he said. The compressed air, meanwhile, is stored in the same sort of tanks used by fossil fuel companies to store compressed natural gas: pressures of 3,000 psi do not present a problem, he said.

When the air gets released, the heat from the reservoir gets injected back into the air as it expands so that when it gets to the turbine, it is a rush of fast-moving air at ambient temperatures. In a sense, air is just a medium for energy created by water.

“We want to maintain the temperature constant in compression and expansion,” he said.

The company, he added, has also figured out techniques for removing the water vapor from the compressing air to eliminate the possibility of internal corrosion. Additionally, SustainX may not only be seen at modular facilities: the hydraulic pumps and other aqueous tools can be used at cave storage facilities, he added.

Isentropic Energy.  By contrast, Isentropic thrives on the heat generated in the compression process. Its proprietary compression/expansion engine compresses captured argon to around 12 bars of pressure. The compression heats it up to 500 degrees Celsius. The hot air is then passed through gravel, transferring the heat to the gravel in the same way steam heats rocks in a sauna.

The heat returns to ambient temperatures but stays at 12 bars. It is then passed to another chamber where it expands. The temperature drops to minus 160 degrees Celsius and the pressure goes back to normal.

When a utility needs energy, the air goes through the process in reverse, delivering 500-degrees-Celsius, 12-bar air to a generator. Discharge takes a few seconds.

Isentropic’s compression engine runs about $500 a kilowatt, but the gravel only runs about $25 a kilowatt-hour. In total, an Isentropic system will cost $87.50 per kilowatt-hour installed, claimed CEO Mark Wagner.

“Temperature difference is the cheapest way to store energy,” he said.

Storing the heat in gravel also reduces the level of pressure required, he added, which in turn reduces the cost of the storage tanks.

Kepshire wouldn’t give numbers, but reiterated that his company would be competitive with gas turbines when it came to delivering power.

The results should be interesting.

SAN JOSE, Calif. — Zinc isn’t as cheap as dirt, but it’s close, which is why it still belongs among the viable options for energy storage, say advocates.

Zinc costs $2 a kilogram, according to Gregory Zhang of the International Zinc Association. The world has reserves totaling 1.9 billion tons. If you wanted to store 10 percent of the energy that will get generated by the world’s wind turbines in 2020, you would only need 2.3 million tons of zinc.

The world produces 30 million tons a year.

“The world will never run out of zinc,”  he said during a presentation at the Energy Storage Association annual meeting last week.

The material isn’t perfect. Companies such as Revolt Technology and PowerAir have touted the material for years. APET from Taiwan even showed us the Zincmobile at the Frankfurt Auto Show 1.5 years ago. (That's APET's battery in the photo.) But it’s still not mainstream. Carbon dioxide can clog the air intake, while corrosion, inadequate electroplating of electrodes, mineral degradation and electrolyte degradation remain problems too. Many zinc batteries can’t survive more than 100 charging cycles. PowerGenix, which has sold nickel zinc rechargeables for a few years, has managed to get around the charge cycle issues but it's generally still an industry problem.

But besides being cheap, zinc also packs a wallop of power. A kilogram of zinc contains enough energy for raising five cubic meters of water 100 meters. Energy is harvested by combining zinc with oxygen and catalysts. Zinc oxide, one of the byproducts of the first reaction, subsequently becomes a source for zinc. The zinc/zinc oxide reaction is essentially infinitely renewable.

By contrast, titanium and silicon oxide reactions can’t be reversed in the same way. Iron and lead have lower energy densities and lithium and sodium, which can pack quite a bit of energy, aren’t as stable.

Mike Oster, CEO of EOS Energy Storage, says the company's zinc air batteries for grid storage will cost $1,000 per kilowatt-hour when they come out next year. The first battery pack will be a capable of storing 6 megawatt-hours of power. The device will fit in a 40-foot storage container. The pack will be made from 50-kilowatt/300-kilowatt-hour modules. (EOS used to be Grid Storage Technologies.)

Though the starting price will be more expensive than lithium-ion grid batteries, the price will drop to $650 and $400 per kilowatt-hour in subsequent years.

The key to the battery is a novel aqueous electrolyte that helps ameliorate many of the problems listed above. (Aquion Energy has a sodium battery with an aqueous solution. Water and air seem to be two of the more popular ingredients in batteries these days. Maybe bread is next.)

The response time can be measured in milliseconds, Oster added.

Regardless of whether you become a zinc nut or not (personal disclosure: I'm a huge fan of the idea), Zhang did raise an interesting dichotomy to think about when considering energy storage technologies. The market can be divided into two categories: storage technologies that depend on mechanical devices like flywheels, batteries and capacitors and storage technologies that depend on materials like hydrogen, air or chemical changes. Material storage plays will always be cheaper because capacity can be added at marginal costs.

Differentiating between the two isn't always easy. Compressed air systems store energy in mechanical systems. Hydrogen needs fuel cells and zinc requires batteries. But in the case of zinc, ammonia and hydrogen, the mechanical elements mostly function as container. The energy is stored through molecular action. Similarly, the energy in a pumped hydro system comes from gravity. It's an interesting way to look at things.

ElectronVault later this year will take the wraps off of a technology it claims will make it easier for you to get into the market for electric cars and energy storage.

The company, run by the husband-and-wife team of Rob Ferber and Linda Maepa, has developed a technique for quickly, cheaply and comprehensively wiring batteries together to form a battery pack. Wiring batteries together in a notebook pack is simple: notebooks only have six to nine cells. But an electric car like the Tesla Roadster can have thousands, and the number grows when you contemplate multi-megawatt storage facilities. Incomplete or damaged connections can create problems, while some of the more sophisticated technologies, such as laser welding, can be expensive.

ElectronVault has come up with a single-step process that functions in a parallel, rather than serial, fashion. The number of cells in a pack is not an inhibiting factor and it is compatible with existing manufacturing equipment and processes.

"All of our technology is between the cells and the power terminals. [...] We're an electric joining technology," Ferber said. "It replaces all current joining technologies."

Just as interesting, ElectronVault's business model will, ideally, give end-users more bargaining power in the storage business. The company plans on licensing its know-how to car companies and others. Thus, instead of having to buy completed battery packs from manufacturers, they will be able to buy cells and, with ElectronVault's know-how, weave a battery pack together themselves. As an added bonus, these battery packs will be able to mix and match cells from different manufacturers, ameliorating spot shortages.

Will the company make it? Who knows, but we love covering mystery startups here, particularly those founded by people with a track record. Prior to ElectronVault, Ferber was a science director at Tesla, where he worked on batteries; he also helped AC Propulsion retrofit a Scion for electric drive. While in grad school back in the '90s, he got recruited to serve as the first CTO of eToys.

Licensing in batteries is a growing phenomenon. Argonne National Labs licensed battery technology to LG Chem and General Motors. Meanwhile, battery component makers Envia Systems and Amprius recently raised $17 million and $25 million, respectively. Licensing is never easy. Most potential licensees prefer to avoid it and risk lawsuits. But in cars, an opportunity may exist. Large manufacturers, particularly in emerging nations, want to gain early market share and don't often have the technical expertise in-house. (Keep an eye on Porous Power and PolyPower, too.)

The company's process complies with the warranty terms of the majority of battery cell manufacturers. Right now, the company is in discussions with Chinese vehicle makers, as well as grid operators in South Africa.

But what is it exactly? Again, Ferber's not saying, but he said to think broadly about botany. More information will likely come out at a user conference this fall in China.