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Comment by mdorazio | Hacker News Reader

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.

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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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