August 30th, 2015 by Tina Casey
Flow batteries offer a promising solution for utility-scale wind and solar energy storage, and the US company UniEnergy Technologies is part of a new demonstration program in the Pacific Northwest that pits the technology against lithium-ion batteries. When its flow battery was fully commissioned earlier this summer, UniEnergy’s press materials raised this point: “The Uni. System’s levelized cost ($/total GWh delivered over 20-year life) is multiple times lower than the cost of lithium-ion systems such as Tesla.”
CleanTechnica took note of UET’s energy storage challenge to Tesla back in June, and a couple of weeks ago the company’s VP for Business Development, Russ Weed, graciously took to the phone lines with us and discussed the background behind that claim.
About Those Flow Batteries…
Before we dig into the details, first take note that the challenge refers to large-scale stationary energy storage, not to the residential-scale Powerwall or electric vehicle batteries offered by Tesla. While flow batteries are beginning to emerge as a potential EV technology, they’re not quite there for that application.
For those of you new to the topic, flow batteries literally “flow.” They generate a charge that occurs when two liquids flow adjacent to each other, typically separated by a thin membrane:
Flow batteries are particularly attractive for wind and solar energy storage, partly because they can be idled for long periods without losing charge. The two liquids are stored in tanks, which can be called into action quickly when needed.
About That UET-Tesla Comparison…
Take a look at the schematic at the top of this article, and you’ll get a sense of where UET is coming from. The company took a 100 MWh utility-scale energy storage image from the Tesla website…
… and overlayed it with an equivalent in UET flow battery modules (those are the blue-capped figures at the top edge of the Tesla array in the first image). Weed went over the comparison with us, and aside from the numbers, one clearly visible difference is the footprint. Flow batteries don’t involve the same thermal management considerations as lithium-ion batteries, which enables more flexibility in configuration. All else being equal, if a smaller footprint is a big priority, chalk up a point for flow batteries.
Weed also made the point that, in terms of simplicity, flow batteries offer some distinct operational advantages, particularly in terms of SOC (state of charge) management. Simplicity also factors into end-of-life issues, including lithium recycling/recovery.
The Bottom Line
In addition to the overlay for a 100 MWh array, UET has also prepared a side-by-side cost comparison of its flow battery against a “competitive” lithium-ion array and Tesla’s offering.
The full contents of the comparison are proprietary but we can share some of the factors that UET considered, including state-of-charge flexibility, capacity fade, and lifetime capacity. UET also derived some of Tesla’s information from a third-party source, namely Germany’s Karlsruhe Institute of Technology (for the record, UET also notes that precise data on its competitor is difficult to assemble).
When UET assembles all of the lifetime expenses for its flow battery and divides that figure by lifetime discharge, the result is a “simple” Levelized cost of 16.7 cents per kilowatt-hour. UET notes, though, that flow batteries can cycle twice daily, not just once. Factor that in and UET arrives at 8.3 cents per kilowatt-hour.
That figure, reportedly, amply backs up the “multiple times lower” claim referred to at the top of this article. Keeping in mind that lithium-ion batteries degrade over time, UET’s calculations for “competitive” lithium-ion work out to 37 cents per kilowatt-hour over five years. For the battery offered by Tesla, UET arrived at $1.16 per kilowatt-hour for 19 months, and $1.54 per kilowatt-hour for seven months. (Note that estimates from CleanTechnica director Zachary Shahan for the daily cycling battery from Tesla over the course of 15 years came to 10 to 25 cents per kWh.)
Without seeing the math behind the math, you could shrug off those figures. However, there is a broader point at play. As new energy storage technologies come on board, it’s evident that a conventional calculation of levelized costs is just one tool — though a very important one — in the energy storage planner’s toolkit. Other factors like grid integration, scalability, siting flexibility, aesthetics, and customer also factor in. Energy storage technology is diversifying, and that’s a good thing.
We’re also convinced that Tesla is going to come right back with some facts and figures of its own, and if you have any ideas about that, drop us a note in the comment thread.
About That Energy Storage Diversity…
Regarding energy storage diversity, let’s take a closer look at that aforementioned smart grid project. It’s a $14.3 million, three-part, comparative, wind energy storage demo being undertaken by the State of Washington with technology support from the Energy Department’s Pacific Northwest National Laboratory (PNNL).
As a PNNL licensee (group hug, taxpayers), UET is providing flow battery arrays for two utilities in the demo. Here’s the rundown from PNNL:
Avista Utilities of Spokane, Wash., was awarded $3.2 million. Its project includes installing a UET flow battery in Pullman, Wash., to support WSU’s [Washington State University’s] smart campus operations. PNNL will collaborate with WSU to develop a control strategy for this project…
Puget Sound Energy of Bellevue, Wash., was awarded $3.8 million. Its project includes installing a lithium-ion battery. As part of a previous project that was jointly funded by the Bonneville Power Administration, Primus Power, Puget Sound Energy, and DOE, PNNL analyzed the costs and benefits associated with installing energy storage at various sites within PSE’s service territory.
Snohomish County Public Utility District No. 1 of Everett, Wash., was awarded $7.3 million. Its project includes installing a UET flow battery and a lithium-ion battery…
According to Weed, Avista Utilities had been looking into a lithium-ion energy system several years ago but was put off by some of the challenges that arose during an earlier grid integration project in the neighboring state of Oregon (this one).
The Washington State demo offered Avista an opportunity to deploy a UET battery on-site at the leading electrical grid innovator Schweitzer Engineering Laboratories in Pullman. The new array will enable Avista to level out demand spikes, and Schweitzer will also use it to sub in for diesel generators during power outages.
PNNL will monitor and analyze the full three-part project and compile use case data designed to help utilities and regulators understand how different energy storage solutions perform over the long run, so stay tuned.