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Building on battery storage with solar and wind power

E.ON Climate & Renewables, which earlier this year completed its first utility-scale grid-connected lithium-ion battery storage project in the United States, has since added storage facilities to two existing wind farms in Texas.

By Vicky Boyd

Representatives of E.ON Climate & Renewables, which earlier this year completed its first utility-scale grid-connected lithium-ion battery storage project in the United States, have only to look as far as the electric car industry for their success.

"This is a technology that's really taken off, and it's really being built upon the gains made in the electric vehicle market," says Mark Frigo, E.ON vice president of energy storage North America. "Utility-scale batteries are being manufactured in the same factories as electric vehicles. That is dramatically driving down the production costs of these batteries worldwide."

The company's inaugural foray into North America involved the 10-megawatt (MW) lithium-ion Iron Horse Energy Storage and Solar Project that will provide frequency response and voltage control to Tucson Electric Power under a 10-year contract. It was paired with a 2.4-MW solar project, both of which were built at the University of Arizona's (UA) Science and Research Park southeast of Tucson, Arizona.

The battery and solar project is also the first for phase two of the Solar Zone—223 acres that the university touts as one of the largest multi-technology renewable-energy demonstration sites in the world.

Bruce Wright, UA associate vice president of Tech Parks Arizona, says the university will issue a formal call for new projects by September for phase two but not for new solar arrays. The new projects will focus on energy storage, grid optimization, and microgrids, distributed solar systems, and integrated and embedded solar materials.

Shortly before the Iron Horse project and PV array went online this spring, E.ON announced it was adding two 9.9-MW lithium-ion battery storage facilities to its 249-MW Pyron wind farm in Scurry and Fisher counties, Texas, and its 197-MW Inadale wind farm in Nolan and Scurry counties, Texas. Both wind farms went online in 2009.

The Texas Waves energy storage projects are designed to provide ancillary services to the Electric Reliability Council of Texas (ERCOT) market and increase system reliability and efficiency by quickly responding to shifts in power demand.

"The key is the world is going to a more carbon-neutral power source," Frigo says. "Coal plants are continuing to be closed, so you have to get power from somewhere, and renewables are filling the bill. But you have the problem of intermittency. Now energy storage is a big part of the solution to the intermittency issue."

Battery storage can be classified as either short term, providing energy for 15 to 20 minutes, or long term, providing stored energy for hours rather than minutes.

In the case of Iron Horse, the project is designed to provide short-term storage to help with grid stabilization. This becomes even more critical in regions with a high concentration of renewable energy production, such as solar in California and Arizona, or wind in west Texas.

 
  

"In the middle of the day, if you add more solar to the system, you have a massive influx of generation, and this massive amount of generation gets ramped up extremely quickly," Frigo says. "It puts strain on the grid, and you need to be able to match the demand accordingly. The focus is energy storage that can help with the ramp up and down—it can effectively smooth out that generation."

Most people are familiar with lithium-ion batteries used in digital cameras, laptop computers, and cell phones. But Frigo says lithium-ion is a general term, and there are actually several types based on slightly different chemistries.

"It really depends on the cost," he says of commercial applications. "Some are more expensive, but they have better performance. Some have slightly different safety characteristics than others. It's really, what is the application for the utility? Is it for short-term service or long-term storage?"

The battery storage used in the Iron Horse project, for example, is lithium titanate oxide or LTO.

After evaluating various battery options, Frigo says E.ON went with that particular system because of its high reliability. In addition, Tucson Electric Power (TEP) wanted short-term storage that could be used to maintain the required balance between energy demand and supply, helping to maintain reliable service for customers during periods of high energy demand by supporting stable voltage. LTO is also operational under temperatures ranging from minus 30 to 75 degrees Celsius (minus 22 to 167 degrees Fahrenheit).

Much of E.ON's early battery storage development was conducted in Europe—the firm's parent company is based in Essen, Germany.

E.ON decided to expand into the U.S. about 18 months ago. Frigo says, "We noticed that the cost of lithium-ion technology was coming down to the point where it was becoming economically feasible for commercial installations on a large scale in the U.S. That was kind of the tipping point."

E.ON already had a long-standing business relationship with TEP, having built the 6.6-MW Tech Park Solar and the 13.2-MW Valencia Solar projects in Tucson, and the 17.2-MW solar facility at Fort Huachuca Army Base near Sierra Vista, Arizona.

 
 E.ON Climate & Renewables combined the solar and battery components within the Iron Horse project to take advantage of the 30 percent federal renewable energy tax credit. By combining the battery storage with the solar, it is now an integral part of a renewable energy project, and the investment tax credit on the entire project effectively lowers the cost.
  

TEP put out a request for energy storage proposals in June 2015. E.ON was selected to build the combined storage and solar project the following year. The project is one of three recently undertaken by TEP examining different types of energy storage systems. The Tucson utility provides electricity to about 417,000 customers in southern Arizona.

The goal is to identify when and where installation of additional storage systems would be most beneficial to TEP. This will be an integral part of its plan to add 800 MW of new renewable capacity by the end of 2030, boosting its total renewable energy portfolio to about 1,200 MW, according to the utility. If it comes to fruition, TEP will obtain at least 30 percent of its power from renewable resources, twice the level required by 2025 under Arizona's Renewable Energy Standard.

Carmine Tilghman, TEP senior director of energy supply and renewable energy, says the utility relies on partnerships like those with E.ON and Tech Parks Arizona to build cost-effective energy resources for the community.

"It's easy for us as an electric utility to look ahead and see that the world is changing and that we need to adapt to it," he says. "We need to bring new innovative technologies to help ensure the safe, affordable, and reliable electric grid of the future. Projects like this are going to integrate even more renewables. It will allow us to integrate bigger, larger projects, transition away from fossil fuels, and move toward a more sustainable energy resource portfolio."

Battery storage projects, such as Iron Horse, can be built anywhere within the system as long as they are within the grid. Frigo says E.ON combined the solar and battery components within Iron Horse to take advantage of the 30 percent federal renewable energy tax credit.

"By combining the battery storage with the solar, it is now an integral part of a renewable energy project, and we can take a 30 percent investment tax credit on the entire project," he says. "It effectively lowers the cost of the project."

The reduced cost allowed TEP to build not one, but two, energy storage projects for what it had originally budgeted for a single project.

 
The Iron Horse project is designed to provide short-term storage to help with grid stabilization. This becomes even more critical in regions with a high concentration of renewable energy production, such as solar in Arizona and California or wind in west Texas. 
  

Permitting was fairly straightforward, with only University of Arizona approval required since the project was being built in the university's research park.

"As it [battery storage] is new technology, most counties and cities haven't had an opportunity to establish guidelines specific for this, so they are using what they have done for solar in the past," Frigo says.

Once approval was obtained, the project moved briskly. "We got our storage batteries delivered in January, and we were effectively operational in April," he says. "It was less than four months once they arrived on site." An official ribbon-cutting ceremony was held for the commissioned project on June 1.

Landis+Gyr designed, engineered, and supplied the 10-MW containerized project that was based on Toshiba's SCiB battery technology. Signal Energy LLC and CSI Electrical Contractors Inc. served as subcontractors. Parker Hannifin Corporation was selected as the inverter supplier for the batteries. Parker's inverter technology is said to offer precise control of the energy supply to match demand, helping utility customers improve grid stability and lower energy costs for consumers.

On the solar power side, the 10,350 panels for the project were from JA Solar, with SunLink racking and PV inverters from Huawei.

Heavy cranes were brought in to unload Conex boxes from delivery trucks and position them in the tech park. The batteries, each about the size of a stereo system, were assembled in racks, connected together, and installed in the boxes. Although the LTO batteries can withstand a wide range of temperatures, heating, ventilation, and air-conditioning equipment was installed in each box to minimize extreme environmental conditions and boost battery efficiency. Altogether, the project occupied the equivalent of 2.5 boxes.

Although many of the components were fairly modular, Frigo says Landis+Gyr was on-site to help with specific installations. The contractor also tied the solar panels into inverters to convert the DC to AC. A substation was built to handle 34.5 kilovolt lines from both the inverters and batteries and to step up output to the grid.

The brains behind the battery storage system come from Emeryville, California-based Greensmith Energy Management Systems, which Frigo described as "one of the premier integration software companies in the energy storage business."

The company's GEMS software control platform provides real-time monitoring, integrated control, and system optimization.

Daily peak energy consumption is a constantly moving target affected by demand growth, energy efficiency, temperature, and other factors. The platform optimizes performance to provide a fast response when called upon throughout the day while storing enough energy to discharge when it's needed most.

When the grid has a critical issue, it sends a signal directly to the batteries, Frigo explains. The software recognizes the signal and tells the batteries how much power to send to the grid to mitigate the problem. All of this needs to happen in milliseconds.

"We think they have a high-quality product, which is the 'secret sauce' of making the system work because it's very much automated," Frigo says of GEMS.

Greensmith Energy is also supplying the software control platforms for E.ON's two west Texas battery storage projects.

 


July/August 2017