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Comment by mcculley | Hacker News Reader

Do you have some idea on how to do storage cheap at scale? There is a lot of money for anyone who has an easy technical remedy.

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My company is working on this. 50 kWh modules, similar cost/kWh to battery storage, but no lithium or rare earths. Optimized for daily 0-100% cycling.

http://www.vortical.io

I hope flywheel storage takes off (no pun intended) it seems such a logic solution when compared with water elevation or chemical solutions. Why hasn't it gone mainstream yet?

I remember being really hyped about flywheel energy storage... 20 years ago. I wonder if it has become more viable since then? And if so, what changed to improve viability?

https://beaconpower.com/carbon-fiber-flywheels/

These guys have two projects (check their operating plants) using flywheels. They're used for frequency regulation. About 20MW each.

They have become more viable thanks to higher efficiency motors/power components and magnetic bearings, among other things. The biggest drawback is still cost, which is what we're tackling.

In the past they have been made to work, but they were not much better than batteries. With the price of batteries dropping like a stone I suspect they are going to have an even harder time competing.

There are several differences from batteries. Generally the benefits are faster charge and discharge rates, unlimited cycles without degradation, no lithium or rare earths needed, and wider operating temperatures.

They are not good at long term storage though, as the self discharge rate is high. And historically they have been expensive.

Cost, mainly. Most flywheels use exotic components, expensive magnetic bearings, must work in a vacuum, etc.

Interesting! But 50kWh seems pretty small for (macro-) grid applications. How big are these units? Seems like most grid installations would want on the order of hundreds (~10MWh) to a few thousand (~100MWh) of these.

Or do you plan to focus more on microgrids?

The focus is on microgrids, but they're modular and can be installed below grade so you can add as many as needed. Approximately 2m diameter by 1m tall.

We're still working out costing, but it might even make sense for residential use to take advantage of time-of-use rates or energy arbitrage. Other applications are industrial processes that require high power for short periods.

Cool! I'll definitely be following your progress with interest :)

Hopefully constructive feedback: I would put that residential thing further down on your list. I think that stuff tends to be too complicated unless / until you can aggregate a lot of loads (eg. I think Tesla only recently recently started doing this stuff residentially. Probably awhile before you reach their scale...)

https://www.tesla.com/megapack

https://electrek.co/2023/04/19/tesla-reports-massive-increas...

https://lorenz-g.github.io/tesla-megapack-tracker/

(on a smaller scale, to date, Tesla has deployed Powerwalls and Powerpacks at more than 50,000 sites worldwide; their Lathrop, CA facility is ramping to manufacture 40GWh/yr of capacity)

Two things: (1) Price signals have to be further clarified especially at a utility level for ancillary services (2) Battery system prices have been dropping quickly mainly as a function of Chinese manufacturers building out quickly e.g. CATL. Tesla is also helping.

Competition is already there - its next how do you deploy your development costs for winning those assets.

Dual feed power line, one for home electrics, one for immersion heater. Store excess renewably generated energy in household hot water tanks during the day, to be used in the evening in place of fossil-fuel generated supply, which also evens out load peaks as a side effect. This also works well with home solar.

I don’t understand. How do you convert hot water to electricity in the evening?

The Seebeck effect will definitely have less than 8% efficiency with 80C water. Perhaps GP means that the hot water will already be available to use for hygiene and laundry, which for those with an electric water heater, is a large portion of the household power draw.

I'm not sure if a household sized water tank-full could provide heat over the course of a cold night, and whether a heat exchanger for air heating or water pipes would be more efficient. I suppose it depends on the insulation and placement of the ducts and pipes and how much of the heat makes it to and through a wall.

I did some very crude calculations but assuming 50 gallons at 60C and 1000W energy loss per hour from a moderately insulated house on a 50F night, the full water heater could keep the house at 70F for 5.14 hours. Someone with more recent practical physics usage is welcome to check this figure.

You don't. It's stored energy. If your hot water is already heated, you save on the energy required to heat it in the evening.

just use it durectly fir showers and heating the house

That is a good idea for places that need heat.

Do the opposite (make lots of cold water) for places that need cooling. Am I missing something?

The energy difference between ambient-temp-to-frozen and ambient-temp to steam is much larger. I would think that this affects scalability.

I live in a city center that uses chilled water for some use cases, but it certainly does not seem scalable enough to be an "easy technical remedy" to the issues of distribution being expensive.

A home central A/C would use a volume of ice of maybe a cubic meter, if that. This doesn't seem excessive.

Not at all. Peak shaving with approaches like this is fairly common with utilities. Lots of them will give huge rebates on smart meters in exchange for this.

I think grid load management for water heaters is already fairly common. I've basic versions of the concept in use by a coop in South Carolina, and I can't imagine them being anywhere near the bleeding edge.

On the west coast, there are pumped hydro storage projects in Southern Oregon (500MW) the Columbia River (~1GW) , and Nevada (~1GW).

These are targeting 8-10 hours of sustained power when needed.

Solar pairs well with hydro - a reservoir is basically a big battery that you recharge by pumping water uphill.

Any idea what the efficiency loss might be?

I’m sure the loss is very high, but maybe could be overcome with ample solar inputs?

Modern pumped hydro has a round trip efficiency of around 80%, I understand.

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