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'Freeze-thaw battery' stores electricity long-term for seasonal release

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Re: 'Freeze-thaw battery' stores electricity long-term for seasonal release

#51

Post by mechagodzilla »

credit_guy wrote: post #49

Sorry to be a killjoy, but $6/kwh is at least 20x too expensive. In 2021, the average price of electricity in the US was 14 cents/kwh. Assuming you charge with free electricity, your charge-discharge efficiency is 100%, there is no capacity loss over the years, and your cost of capital is zero, you need more than 40 years to break even at that price. All the 4 assumptions above and a few others (zero installation and…

I think you misunderstood the article - they're talking about the capacity of the battery in terms of kilowatt-hours, not its cost relative to round-trip efficiency. If the cost were $6/kwh, you could build a 100kwh battery for $600, and charge/discharge that many times. I think this is supposed to be interesting both for its relatively cheap materials (and useful level of energy density), and its ability to be 'frozen' in a room-temperature charged state for long periods of time without much loss of charge.

Re: 'Freeze-thaw battery' stores electricity long-term for seasonal release

#52

Post by KennyBlanken »

pjc50 wrote: post #27
KennyBlanken wrote: post #15

Iron flow batteries already exist commercially, are even more non-toxic/safe, and they don't require heating up (and keeping hot, while using) the battery. https://essinc.com/iron-flow-chemistry/ The utility industry isn't really that interested in storing power for an entire season. Very little ROI compared to a system that allows them to balance minute-to-minute or day/night...or transmission infrastructure improve…

I've never really seen the advantage in going off grid per se , since it increases the amount of wasted capacity in both generation and storage, and running a few wires is cheap enough in urban environments. The most efficient arrangement might be a global grid.

Utilities around the US are working in numerous states to get favorable legislation letting them pay a fraction of what they do now for solar and wind energy fed back into the grid by residential and commercial customers. Once you even out your meter and reach net generation, any further generation into the grid you'll soon be getting bupkus for. Sorry, but I got better things to do than line the pockets of my state's for-profit utility company.

In rural areas, getting connected can mean tens of thousands of dollars...if they even offer it to you at all.

No matter where you are, you have to pay a monthly connection fee. It really adds up, and given how cheap solar and wind are now, you don't really get anything for it. Battery storage systems a couple years ago were very expensive, but prices are crashing and safer tech like lithium iron phosphate are becoming more commonplace. Heatpump systems have gotten so efficient that I'm pretty sure my next furnace isn't going to be a furnace, but an electric heatpump.

In my area, we lose electricity for a day or so in the winter, 1-3x a season. A year or two ago we were without power for 3 days. Everyone has generators; expensive, noisy/annoying (especially given they conduct a weekly "exercise"), wasteful, polluting, and expensive to maintain.

Having at least a large battery backup would mean I don't freeze, I can cook, take a hot shower, do my laundry, and my food doesn't spoil. And I don't need to pay the electric company for a product that just isn't very reliable and is increasingly irrelevant.

Re: 'Freeze-thaw battery' stores electricity long-term for seasonal release

#53

Post by SECProto »

sacrosancty wrote: post #47
xvedejas wrote: post #46

Earlier quoted context omitted.

This is a useful thing: storing energy in a phase change makes it easier to keep the energy stored for a longer period of time compared to if there was no phase change. The difficult part is that steam is much farther from ambient temperatures than ice is (and also that it is far less compact). Newton's law of cooling means that the larger the temperature difference, the faster the heat loss, so steam would require m…

Besides insulation, there's no hope of storing thermal energy as steam because the density is 1000 times lower than ice or water while the specific heat is similar, so the heat capacity per unit volume is about 1000 times lower.

Storing heat as steam is actually very good and efficient - as long as you're storing the heat for location shifting, not temporal shifting. It's regularly used in combined heat + power plants

(Yeah, I know I'm being both pedantic and off topic, since the discussion here is specifically about seasonal storage)

Re: 'Freeze-thaw battery' stores electricity long-term for seasonal release

#54

Post by credit_guy »

mechagodzilla wrote: post #51
credit_guy wrote: post #49

Sorry to be a killjoy, but $6/kwh is at least 20x too expensive. In 2021, the average price of electricity in the US was 14 cents/kwh. Assuming you charge with free electricity, your charge-discharge efficiency is 100%, there is no capacity loss over the years, and your cost of capital is zero, you need more than 40 years to break even at that price. All the 4 assumptions above and a few others (zero installation and…

I think you misunderstood the article - they're talking about the capacity of the battery in terms of kilowatt-hours, not its cost relative to round-trip efficiency. If the cost were $6/kwh, you could build a 100kwh battery for $600, and charge/discharge that many times. I think this is supposed to be interesting both for its relatively cheap materials (and useful level of energy density), and its ability to be 'froz…

Seasonal storage means you charge in the summer and discharge in the winter. One cycle per year. You need 40 years to sell electricity 40 times.

Re: 'Freeze-thaw battery' stores electricity long-term for seasonal release

#55

Post by ClumsyPilot »

mschuster91 wrote: post #26
KennyBlanken wrote: post #16

Earlier quoted context omitted.

> some other people would have already proposed such things. Geothermal heat pumps. Been around for decades. Expensive to install due to drilling the well or laying the field, but very efficient.

Geothermal energy is risky AF though. Even with shallow drilling depths, you risk hitting anhydrite and, in combination with water, massive damage like in Staufen [1]. [1] https://de.wikipedia.org/wiki/Hebungsrisse_in_Staufen_im_Bre...

Geothermal energy for power generation and heat pumps for heating homes are totally different systems. It's like comparing a fireplace in your house to a nuclear power plant.

Re: 'Freeze-thaw battery' stores electricity long-term for seasonal release

#56

Post by ClumsyPilot »

snewman wrote: post #22
a9h74j wrote: post #17

Tangent, but in the seasonal storage context. Apparently, according to a reported simulation, if you (1) take a ca 15m x 15m house thermally in contact with the ground, (2) insulate the ground outside to a radius of ca 40m, and (3) heat the interior to say 25C, then (4) evenually (50years?) the ground itself under the house will come up to a steady temperature consistent with that. Even if the simulation was correct,…

Gradual heating of the ground is definitely a thing; over the decades, certain London Tube lines have drifted from pleasantly cool to sweltering: https://www.wired.co.uk/article/central-line-temperature-lon...

Yes, people are literally dying in the heat from heart attacks because city planning won't allow TFL to knoxk down a house sp they cam build a ventillation shaft

Re: 'Freeze-thaw battery' stores electricity long-term for seasonal release

#57

Post by a9h74j »

gnorme wrote: post #23
a9h74j wrote: post #17

Tangent, but in the seasonal storage context. Apparently, according to a reported simulation, if you (1) take a ca 15m x 15m house thermally in contact with the ground, (2) insulate the ground outside to a radius of ca 40m, and (3) heat the interior to say 25C, then (4) evenually (50years?) the ground itself under the house will come up to a steady temperature consistent with that. Even if the simulation was correct,…

I'd love to read more about this simulation, have any links?

I am unable to find a link, and IIRC this was reported 10 years ago or so. I recall an attribution to German designers or architects. I cannot remember where exactly it was reported, but I remember it as moderately plausible reporting, although not in a journal.

A quick estimate with soil:

Take a specific gravity of 2.7 gm/cm^3, a specific heat of 0.2 cal/gm-K, and 1 cal ~ 4.2J ~ 4.2 W-sec. For a cube 25 m (2500cm) on a side, if I am not mistaken this suggests a thermal inertia of about 3.5E10 W-sec/K.

Now take a thermal conductivy of 1 W/m-K. For a slab of 25m x 25m, also with a thickness of 25m, we get a net conductivity of 25 W/K .

Then 3.5E10 W-sec/K divided by 25 W/K gives 1.4E9 sec . Given 3E7 sec/year, that suggests about 47 years.

Aka a 50 year time scale.

Of course this assumes a low water table.

Re: 'Freeze-thaw battery' stores electricity long-term for seasonal release

#58

Post by mabbo »

frosted-flakes wrote: post #40
bombcar wrote: post #25

Earlier quoted context omitted.

The cube/square law also applies in the opposite direction, this is why it takes longer for lakes to freeze and why the Great Lakes never do. I believe at least one university on the Great Lakes does heating and cooling with pipes deep under the lake.

The Great Lakes do occasionally freeze over significantly, though never completely. 2013-2014 was one such winter, when ice coverage reached 92% across all five lakes. That's quite unusual though. And the city of Toronto uses lake water for cooling. Heat from a downtown cooling loop is dumped into the city's drinking water supply, bringing the temperature up to around 13° from 6° (if I remember correctly).

Not just drinking water. The cool water is pumped into buildings to work as the air conditioner for a lot of the big buildings.

Re: 'Freeze-thaw battery' stores electricity long-term for seasonal release

#59

Post by alexchamberlain »

nikanj wrote: post #42
jessriedel wrote: post #34

For more on the general problem of storing thermal (rather than electrical) energy on a seasonal basis see https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storag... I was especially surprised to learn that serious attempts at storing heat in soil and rock have been made https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storag... https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community which in the winter…

Furthermore, we have a real problem with the soil storing heat: https://citymonitor.ai/transport/londons-tube-has-been-runni...

Stupid question: can we harness this 100 year old heat to power something today?

Re: 'Freeze-thaw battery' stores electricity long-term for seasonal release

#60

Post by thescriptkiddie »

alexchamberlain wrote: post #59
nikanj wrote: post #42

Earlier quoted context omitted.

Furthermore, we have a real problem with the soil storing heat: https://citymonitor.ai/transport/londons-tube-has-been-runni...

Stupid question: can we harness this 100 year old heat to power something today?

Yes

https://www.newcivilengineer.com/innovative-thinking/harness...

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