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Geothermal may beat batteries for energy storage

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Re: Geothermal may beat batteries for energy storage

#161

Post by jonstewart »

xienze wrote: post #156
jonstewart wrote: post #80

Earlier quoted context omitted.

It is probably far more cost effective to buy a new air source heatpump. They’re so efficient and work well at low temps now. I have infloor radiant heat at a rural house in upper Midwest, have thought a lot about using solar heat pipes and adding a storage tank, and it’s all so fiddly, pipes and pumps and manifolds and glycol and maintenance, all custom, all expensive. I’m almost certainly better off with PV panels…

> They’re so efficient and work well at low temps now. Can someone provide me model numbers for these heat pumps that “work well” at low temperatures? I’ve been through more than a few over the decades and currently have a Trane from last year and yep, still doesn’t hold up very well once the temperature hits freezing. Don’t get me wrong, I like heat pumps, but my eyes roll into the back of my skull when I hear over…

Fujitsu XLTH: https://www.fujitsugeneral.com/us/residential/technology/xlt...

Mitsubishi Hyper Heat and H2i Plus: https://www.mitsubishicomfort.com/articles/what-is-a-heat-pu...

Efficiency with these heat pumps severely decreases when temps go below 0F, but they still produce heat.

Their sites are admittedly not all that clear. GreenBuildingAdvisor.com has a ton of useful info on it, like https://www.greenbuildingadvisor.com/question/cold-weather-p....

Re: Geothermal may beat batteries for energy storage

#162

Post by throw__away7391 »

soperj wrote: post #160
dahfizz wrote: post #108

Earlier quoted context omitted.

> Why there are no water storages on the roof. Quick math - 100 gallons of water 15 meters up off the ground has enough potential energy to run a microwave for 30 seconds. Gravitational storage is pathetically weak. It only makes sense on massive, massive scales. In a residential setting, the storage will never outweigh the extra cost and risk of having so much water on your roof.

they do it a lot in NZ. Solar hot water heating.

Solar hot water is great, but that's not gravitational storage, e.g. pumping water up a hill with pumps and later using the flow of water back down to generate power.

Re: Geothermal may beat batteries for energy storage

#163

Post by SECProto »

cupofpython wrote: post #113
merely-unlikely wrote: post #90

Earlier quoted context omitted.

> I was always wondering why there are no systems converting the unused electricity in potential energy by moving water to a higher ground There are a bunch of pumped storage facilities around [1]. But they work best at massive scale, so suitable locations are somewhat limited. Plus they are expensive to build and often face environmental protests (similar to building dams). Still, it's a solution I'm a fan of. [1] h…

emphasis on massive scale. Moving 500,000 kg (over 1 million pounds) 7.5 meters (~25 feet aka the height of a house) will give you about 10 kWh of energy. This is equivalent to running a 425W device all day, like a small air conditioner. The relationship is linear. Double the weight or the distance to double the energy. All of the metal at a scrap yard I know of amounts to less than half that weight, for reference. I…

> All of the metal at a scrap yard I know of amounts to less than half that weight, for reference.

That's not a great reference point when you're trying to visualize to pumped storage, as water is 1t/m3 while steel is up around 7 or 8. Also, 500t of steel at a scrapyard seems very small - 70m3?

A better reference might be a back yard pool, which might be in the 30-40t range - so like lifting 15 back yard pools the height of your house to power a tiny AC.

Re: Geothermal may beat batteries for energy storage

#164

Post by sidewndr46 »

dahfizz wrote: post #108
cookiengineer wrote: post #68

Earlier quoted context omitted.

This reminds me a lot of the Earthship community in the middle of the desert, which always focusses on smart ways of reusing water for different purposes, and by not wasting water as much as possible. The houses usually have a clean/grey/blackwater + a rainwormbox system to process fecals and reuse it for growing plants. Their air conditioning system is basically just a pipe in the ground where the hot air flows thro…

> Why there are no water storages on the roof. Quick math - 100 gallons of water 15 meters up off the ground has enough potential energy to run a microwave for 30 seconds. Gravitational storage is pathetically weak. It only makes sense on massive, massive scales. In a residential setting, the storage will never outweigh the extra cost and risk of having so much water on your roof.

Secondary point: most residential structures are not designed to have 1000s or even 100s of gallons of water stored on the roof. Even 100 gallons is a huge amount of static load to add to a structure.

Re: Geothermal may beat batteries for energy storage

#165

Post by xienze »

spywaregorilla wrote: post #153
bagels wrote: post #117

Earlier quoted context omitted.

I know they heat their homes with the geothermally warmed water, but their electricity rates don't seem to be significantly different than most places. "Iceland, March 2022: The price of electricity is 0.139 U.S. Dollar per kWh for households."

Iceland has the cheapest electricity in the world. They run heat under their roads so they don't need to be plowed. Aluminum is shipped to Iceland to be smelted just because the energy is so much cheaper. Iceland's electricity usage per capita is 4x that of the United States, and more than 2x the next highest country (Norway). They're the largest producer per capita as well. The population is not large, mind you, but…

> Iceland has the cheapest electricity in the world.

Come again? If the parent post about about $0.139/kWh for households is correct, I can assure you there are many places in the US cheaper than that.

Re: Geothermal may beat batteries for energy storage

#166

Post by starlust2 »

psadri wrote: post #158
psadri wrote: post #112

Earlier quoted context omitted.

energy storage density of heating water >> lifting water. 1m^2 of water heated by 50C (20C → 70C) = 58KWh lifting 1m^2 of water by 10 meters (~ 3 stories!) = 0.03Kwh :-(

I think in the future we will see more homes with: Gray water recovery Thermal batteries (hot and cold) - Excess solar energy can be use to "charge" the hot or cold reservoirs for later use depending on season. Effluent heat recovery - Home appliances generate lots of heat (clothes driers, ovens, refrigerators, ...) that is currently vented to the atmosphere. Capture and use it to "charge" the hot battery. - I'd imag…

> Lots of home appliances generate lots of heat (clothes driers, ovens, refrigerators, ...) that is currently vented to the atmosphere. it'd love to capture that and use it to "charge" the hot battery.

I've seen systems that use waste heat from central A/C to heat a swimming pool. In addition to the condenser they have a heat exchanger connected to the coolant line. Pool water is pumped through the heat exchanger and back out to the pool.

Re: Geothermal may beat batteries for energy storage

#167

Post by starlust2 »

jws wrote: post #134
distances wrote: post #107

Earlier quoted context omitted.

This may work in mild climates, but the areas where winter heating is most needed will have the solar panels under a bed of snow during the winter months. Additionally, winter months are usually the cloudy ones. It's not very uncommon to have just a couple of sunny days per month in European winters, driving down solar gains even if there's no snow cover.

It's not as bad as this. In climates where you will have a bed of snow during the winter months, your optimum tilt angle for a fixed solar panel is something like 30° off of vertical or steeper. I find that on mine the snow falls off since it is a south facing, steep, dark surface. You engineer to make sure you have enough energy captured each month to meet that months needs. That might lead you to a tilting mount, o…

They are on a pole on your roof or you moved them to the ground?

Re: Geothermal may beat batteries for energy storage

#168

Post by bergenty »

tyfon wrote: post #34

There is a school close to where I live that does something like this. During the summer they heat the bedrock using solar panels (thermal and electric via a heapump) to heat the bedrock far down using water pipes. In winter they extract this energy for heating, electricity and hot water making the school self sufficient for energy. Here is a write-up from the municipality about it, but it's in Norwegian https://www.…

Wait how long does that heat last. I wouldn’t imagine more than a week since it’s not insulated?

Re: Geothermal may beat batteries for energy storage

#169

Post by spywaregorilla »

xienze wrote: post #165
spywaregorilla wrote: post #153

Earlier quoted context omitted.

Iceland has the cheapest electricity in the world. They run heat under their roads so they don't need to be plowed. Aluminum is shipped to Iceland to be smelted just because the energy is so much cheaper. Iceland's electricity usage per capita is 4x that of the United States, and more than 2x the next highest country (Norway). They're the largest producer per capita as well. The population is not large, mind you, but…

> Iceland has the cheapest electricity in the world. Come again? If the parent post about about $0.139/kWh for households is correct, I can assure you there are many places in the US cheaper than that.

If you're asking for some contextual explanation why that $0.139 is not a sufficient figure to explain the issue, consider reading the rest of my post past the first sentence.

Re: Geothermal may beat batteries for energy storage

#170

Post by jws »

starlust2 wrote: post #167
jws wrote: post #134

Earlier quoted context omitted.

It's not as bad as this. In climates where you will have a bed of snow during the winter months, your optimum tilt angle for a fixed solar panel is something like 30° off of vertical or steeper. I find that on mine the snow falls off since it is a south facing, steep, dark surface. You engineer to make sure you have enough energy captured each month to meet that months needs. That might lead you to a tilting mount, o…

They are on a pole on your roof or you moved them to the ground?

I moved them to the ground. The roof pitch is about 1:1 and I’m not feeling like trying to stick to it any more. The pole puts everything at a comfortable working height.
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