Vanadium-Flow Batteries: The Energy Storage Breakthrough We've Needed | Hacker News Reader

Vanadium-Flow Batteries: The Energy Storage Breakthrough We've Needed

forbes.com

32 pointsaburan2811 comments

The cost of storage is the most interesting claim: 5 cents per kWh, amortized over the system life. If everything else about the article was identical but the cost was 40 cents per kWh then this would be just another chemistry experiment too expensive for widespread use. So I was really hoping to find more details about the cost number -- what modeling assumptions went into it, what sort of lifetime is warrantied from the manufacturer, whether the cost is genuinely based upon current prices or is one of those malleable "in a few years..." projections.

Everything that they have disclosed, technology-wise, looks believable and good. But past vanadium redox flow batteries have been fairly expensive per cycled kWh and I thought that was more about the relatively high price of vanadium than about the temperature/solubility limits of all-sulfate electrolytes. If the mixed-acid electrolyte really is the main enabler of the impressively low claimed cost, I'd like to read how. Mostly I'd like to read supporting evidence behind the "5 cents" number.

For my purposes anything under $AU0.18/kWh extracted means I can say goodbye to the grid and imminent surcharge for having PV on my roof.

Usable membrane-less version of flow battery IS the breakthrough. Still, that article didn't even mention that. Membrane is the weak point of the technology, it's expensive and with limited resource.

P.S. Technology of flow batteries is very promising (at least for consumers with size down to cars) but the article is not.

Wiki so much better: https://en.wikipedia.org/wiki/Flow_battery

My understanding of the chemistry is that they are using Vanadium Chloride which is not listed in the Wikipedia article. What is mentioned in Wikipedia are membrane cost/stability issues with Bromide. I could imagine the latter is more reactive but I'm definitely not a chemistry buff.

Their view of the chemistry:

> using a molecule developed at the Pacific Northwest National Laboratory. PNNL’s breakthrough was to introduce hydrochloric acid into the electrolyte solution,

What I found also newsworthy is that the largest battery soon will be China with 800MWh. That is a typical US nuclear reactor providing power for 1 hour - nothing to sneeze at.

What is also newsworthy is the cost which is also an indication that they got some handle on membrane cost. They are claiming 5cent/kWhr which would be a game changer as it is lower than generating it.

Somewhat misleading title. This is an energy storage breakthrough specifically for utility-scale storage, but will likely never be practical at the scale of a home or car battery, and definitely never at the scale of electronics. As the article points out, the big benefits here are longevity, safety, and cost per kWh stored, not energy density.

isn't that the big problem with renewables and grid, that energy production doesn't match consumption over the course of the day?

Yes and no. It depends what kind of renewables we're talking about, and where they are. My favorite solar tech is solar-thermal (CSP power plants look really awesome), which effectively stores the collected solar energy as thermal energy and uses this to drive turbines. As a result, it can produce power to meet demand over a 24 hour cycle if you put it in a desert. Hydroelectric power is also renewable and can produce power whenever it is needed (assuming the reservoirs don't go dry). The problem comes from wind turbines, which produce fairly consistent power over a 24 hour cycle and don't have a way to store it at night when demand drops, and also from rooftop solar installations, which obviously only work during the day.

Sorry. This is the first time I am hearing about this tech.

Why couldn't it be practical at the scale of a home? Say if you have a large backyard?

It can be practical at home scale: https://www.zcell.com/

Only kind of. Zcell costs about 4x a Powerwall of the same capacity ($13k USD vs. $3500 USD) and has the same warranty duration (10 years), which to me means they're expecting it to last about the same amount of time in normal use. It's a decent alternative if you don't want Li-ion for some reason, but definitely not a good solution cost-wise in the home storage space. As others have pointed out, the benefit of flow batteries is that you can scale the tanks very large to add capacity without raising the cost too much, whereas Li-ion type batteries scale cost with capacity fairly linearly.

They make the most sense for large installations because you can increase the capacity largely by just increasing the size of the tanks storing the anode/cathode liquids. The rest of the system (pumps, membrane, etc.) stays the same for the most part and can be thought of as a fixed cost that you must pay for regardless of the tank size. So, you can potentially make a really long lasting battery with a low cost/kWh by scaling the tanks so they store a lot of anode/cathode liquid. If you try to make a really small version of a flow battery, the cost of the pumps and membranes and general system stuff will probably dominate and give you a high cost/kWh.

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