Building grid-scale batteries isn’t as simple as stacking lots of smaller batteries in a storage container, plugging them all in and walking away. Someone's got to keep an eye on the system, managing and optimizing its output over time, diagnosing and replacing battery cells as they degrade and break down, and otherwise keeping the system operating as it's meant to.
Spider9, a Northville, Mich.-based startup with battery management technology out of the University of Michigan, has set its sights on this challenge and announced its first grand-scale project: managing a 2-megawatt-hour lithium-ion battery array that’s connected to a solar farm being built by Greek solar developer EasyPower.
The project, sited on an as-yet-undisclosed island in Europe, is expected to be installed early next year, and is aimed at providing load-shifting, firming and power-factor-correction capabilities to that intermittent solar resource.
Spider9’s Operating System for Energy, or OSE, is aimed at “intelligently managing the architecture that supports that energy storage,” Glynne Townsend, Spider9’s founder and CEO, said in a Wednesday interview.
As a former executive at lithium-ion battery maker A123 Systems, Townsend is intimately familiar with the real-world ways that batteries originally designed for automotive or other smaller-scale applications are being put together to serve the grid. The problem with many of today’s grid-scale battery arrays, he said, is that their nameplate capacity -- that is, how much energy and power they can theoretically deliver -- can quickly degrade over the course of day-by-day, year-after-year operations.
The makers of “a lot of other architectures will hide behind saying, ‘That’s a problem that we’ll face ten years from now,’” he said. “They just want to sell it as cheap as they can, and put out a warranty that may be worth something, or may not be worth something.”Building Grid Batteries to Optimize Long-Term Costs, Benefits
Take the problem of individual battery cell degradation, which can negatively affect the performance of the system as a whole. Spider9’s technology can remotely isolate those cells while keeping the energy storage system running. That, in turn, helps keep the array close to its nameplate voltage output, while also ensuring that the remaining batteries aren’t being forced to work harder to make up for the degraded or failing cells, which can decrease their reliability and lifespan over the long run, he said.
Spider9 and its partners have also designed the system so that individual cylindrical cells, organized in 24-cell blocks, can be removed and replaced without shutting down the entire system to do so, instead shutting down just the block in question. That can allow grid-scale battery arrays to keep running and making money on a 24-7 basis, with much-reduced operations and maintenance costs, he said.
“When you look at the total cost of ownership and the service cost, we’re going to be 50 percent lower than the competition,” he said. Those costs, while not often included in the upfront costs of energy storage systems on a kilowatt or kilowatt-hour basis, can quickly add up over the long run, he said.
Simply adding in the on-site maintenance to keep that system running can add $30,000 to $50,000 a year, he said -- costs that Spider9’s automated monitoring and management system can bring down to a few thousands of dollars per year. Then you’ve got to calculate the lost opportunity costs associated with bringing the entire system offline to do maintenance or replacement, versus Spider9’s approach: “Our batteries never go down,” he said.
Add in the active battery management features that Spider9 is claiming, and the fact that the company's product is “20 percent more efficient on a battery discharge cycle, through a combination of active balancing and reconfiguration of the voltage strings, to keep high efficiency going across an inverter” that transforms the battery’s DC power to grid-ready AC power, he said.
While the industry hasn’t yet come up with the terminology to describe these lifetime costs, Townsend suggested that a dollar-per-watt of usable energy, over total lifespan, might be one way to calculate it. “That’s the true metric, where the industry should be,” he said.The Competitive Landscape for Grid-Scale Batteries
Judging the long-term costs of competing grid battery architectures is a tricky task right now, of course, given that most of them have just been installed in the past few years. It will likely take years for the various pilot projects and commercial-scale deployments out there to prove just how well they stand up over time.
In the meantime, there are many different ways to optimize the battery-grid interconnection, from the smallest to the largest scales. On the battery systems side of the equation, many manufacturers have built their own battery management software (BMS) systems to manage thermal and electrochemical variables within the batteries themselves, and startups such as Sendyne and Qnovo are working on technical solutions to these challenges as well.
Scaling those individual batteries up to grid scale adds a set of challenges that software can help manage. Battery makers like A123, General Electric, Johnson Controls, Saft, LG, Panasonic, NGK, Samsung, BYD, Xtreme Power and others are adding more sophisticated interfaces and controls aimed at meeting grid needs, either via internal development or by partnering with others.
Since it launched in 2011, Spider9 has raised less than $10 million from undisclosed investors, and has been working with unnamed lithium-ion battery makers to manage and optimize battery systems. Those tests, conducted at Element Testing Materials (formerly Detroit Testing Laboratory), have been applied to arrays ranging from 5 kilowatt-hour configurations up to 75 kilowatt-hour configurations, the latter being the basic building block going into the megawatt-scale system the company is building with EasyPower.
Spider9 wants to build up commercial-scale product through its own brand, Townsend said. The firm is working with an unnamed U.S.-based lithium-ion battery partner to package its software into systems now available in smaller-scale configurations, and is seeking UL certification for its latest configuration.