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Geothermal may beat batteries for energy storage

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Re: Geothermal may beat batteries for energy storage

#91

Post by jonstewart »

teucris wrote: post #86
londons_explore wrote: post #83

Earlier quoted context omitted.

Even a modern air source heat pump typically doesn't beat gas for $/kwh. Even in europe where gas prices are sky high, electricity still costs more when you look at the seasonal efficiency of heat pumps, which is typically advertised around 4.4, but various studies show that in most real world scenarios you typically won't reach the quoted lab numbers, so expect to get more like 2.5-3.0. Study: https://www.sciencedir…

Thus the solar panels. So long as the installation proves to make financial sense, the PV production offsets the heat pump efficiency, even in winter months.

Selling PV electricity back to the grid is almost always many times worse, depending on state incentives, than consuming the electricity. For example, my utility sells electricity to me at 9 cents/KWh, but only buys from me at 2.5 cents, and charged me a fixed monthly fee for the meter to boot.

If the commenter’s house doesn’t have gas, then it doesn’t seem to make sense to install it, and the price differential in the US isn’t as great as in the UK (how’s that Brexit thing working out?).

Re: Geothermal may beat batteries for energy storage

#92

Post by jillesvangurp »

killjoywashere wrote: post #31
jillesvangurp wrote: post #24

Earlier quoted context omitted.

It can work, it's just a cost equation. You need a large amount of mass to get meaningful amounts of energy stored. So pumped hydro is nice because you are basically using natural reservoirs and some cheap pumps and pipes. A water tower needs to be built first and only stores a limited amount of potential energy. The problem is not the efficiencies but the cost of building a big enough tower. A tower with the same ca…

Why would you need a water tower? If you're in flat geography at sea level, you could probably access tidal energy to drive generators. If you're flat and far from water, couldn't you dig a shallow hole and a deeper hole, and put the generator and pumps in between? I mean, even in Kansas it's not that hard to find an elevation difference of 50 feet.

It's just an example from the comment I replied to was using; I agree it's not a very feasible thing to do. But I used it to illustrate the difference in cost between that and pumped hydro using natural reservoirs. The point being here that you'd need a stupidly large amount of water towers to come close to the amount of energy you can store in a pumped hydro reservoir

Whether it's a water tower, a big crane, or whatever that holds the mass that you then use to drive a generator. You have to build it or use nature to have some natural height difference. Building infrastructure like that is expensive. So nature is preferable and way cheaper.

I come from a relatively flat part of the world; so that's not really an option there. Gravity based batteries are nice where they can be done cheaply. But otherwise probably not ideal.

Re: Geothermal may beat batteries for energy storage

#93

Post by teucris »

jonstewart wrote: post #91
teucris wrote: post #86

Earlier quoted context omitted.

Thus the solar panels. So long as the installation proves to make financial sense, the PV production offsets the heat pump efficiency, even in winter months.

Selling PV electricity back to the grid is almost always many times worse, depending on state incentives, than consuming the electricity. For example, my utility sells electricity to me at 9 cents/KWh, but only buys from me at 2.5 cents, and charged me a fixed monthly fee for the meter to boot. If the commenter’s house doesn’t have gas, then it doesn’t seem to make sense to install it, and the price differential in t…

Huh. We have a 1:1 credit system here in Washington.

Re: Geothermal may beat batteries for energy storage

#94

Post by jonstewart »

2Gkashmiri wrote: post #87
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…

interesting. i have a PV system. i want to use the half installed central heating system (only piping laid down) (no boiler or FCU/room unit) and i have this crazy idea. use solar water heater to heat water, that feeds into a water storage tank, that water gets heated MORE by an air source water heater and a small circulation pump uses that water storage to heat the house. i am hoping, since we currently have 0 whole…

I assume you’re on the grid?

Yeah, sadly, it’s crazy. Solar heaters are expensive and require a large area to get decent BTUs out of. If you can find free solar heaters that someone’s giving away, that can make the difference, but they’re often a few thousand dollars and that’s about equivalent to a Fujitsu or Mitsubishi heat pump base install, especially when you factor in all the extra plumbing and pumps to/from the solar thermal array.

WORSE, there’s maintenance. You’ve got the potential for leaks (probability rises to 1.0 over the years), and you have to worry about the water freezing. That can be mitigated by using a glycol mix, but then you’ve got glycol and that lowers the efficiency.

And then you have to think about climate. Is it reliably sunny in the winter? Or is it only sunny 1 out of 3 days, with long stretches of gray days? You are probably better off plowing that money into efficiency/insulation improvements to lower the overall heat load (and those improvements often have zero maintenance).

I’d suggest looking into an air source heatpump that can produce domestic hot water, paired with a large storage tank. Check out Artic Heat Pumps: https://www.arcticheatpumps.com/

Re: Geothermal may beat batteries for energy storage

#95

Post by photochemsyn »

Hot dry rock schemes have been around for a while (apparently dating back to a project in 1970 in Los Alamos NM), but for it to work it seems you need some specific rock types. For example, one project only recovered 3% of the injected water due to losses into fractures. Here's a historical overview:

https://www.sciencedirect.com/topics/engineering/hot-dry-roc...

Re: Geothermal may beat batteries for energy storage

#96

Post by bobthepanda »

merely-unlikely wrote: post #90
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…

> 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…

Also, any sort of hydro-based solution is susceptible to drought evaporating water below sufficient operation levels.

Re: Geothermal may beat batteries for energy storage

#97

Post by lotharcable »

moffkalast wrote: post #8
jillesvangurp wrote: post #7

Interesting option. It's all about the cost and efficiencies in the end. Converting electricity into heat and then back into electricity is a lossy process that is constrained by the second law of thermodynamics. Basically generating heat is easy and efficient. But converting it back to electricity is typically less than 50% efficient. Basically, it's several energy conversions in one process: you use electricity to…

I wonder if it would be possible to scale down pumped hydro to something the size of a tall water tower. Probably not worth it due to the small height difference and volume, and you'd also lose efficiency due to the smaller turbine, but I still do wonder what the actual figures are like for something like that. Especially in cost per kWh stored compared to lithium.

It is 100% possible.

The problem is that it's monumentally expensive. You will need to have a pretty big water tower to handle enough energy to run a microwave for a hour.

P.E. = mg(h)

So say we have 2,000 liters of water that is 50 meters high.

2000kg * 9.81m/s^2 * 50 * 80% efficiency = 784,800.0 joules.

Say you have a 1100 watt microwave. A watt is 1 joule per second. That gives you enough energy to run that microwave for about 11 minutes.

A better example would be existing municipal water towers. A 500,000 gallon water tower that is 129 feet tall costs about 2 million dollars. This is based on a public notice I found for a city in the USA.

That is 1892700 liters and 39 meters. I am guessing that the average height the water actually falls is 25 meters.

The average American household uses about 30Kwh per day. Which is 108,000,000 joules.

1892700 * 9.81 * 25 * .80 / 108,000,000 = 3.4

So 2 million dollars for 3.5 households-days worth of energy.

I don't know if having 1 days worth of energy is too much or too little per household.

And beyond the cost of the tower itself you need the generators and lines and holding pond for the water. Or underground tank or whatever you want to use.

It's very expensive.

However it is probably the cheapest option right now as far as current technology goes.

It would probably be cost effective for a off-grid shack in the woods, though.

Re: Geothermal may beat batteries for energy storage

#98

Post by martin_a »

rootusrootus wrote: post #73
ed312 wrote: post #64

Earlier quoted context omitted.

Based on some extremely back of napkin math (e.g. doing one of those activities where you cycle to power a light bulb) that seems pretty far off. Was the flow rate extremely low? Have a link?

Sounds like this one: https://www.youtube.com/watch?v=CMR9z9Xr8GM They do say it is about equivalent to a single AA alkaline. It is not exactly an optimized efficient setup, but still, it gets the point across. Pumped hydro is a grid scale option, in places that have the ability to store a lot of water.

That's the one!

Re: Geothermal may beat batteries for energy storage

#100

Post by titzer »

londons_explore wrote: post #83
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…

Even a modern air source heat pump typically doesn't beat gas for $/kwh. Even in europe where gas prices are sky high, electricity still costs more when you look at the seasonal efficiency of heat pumps, which is typically advertised around 4.4, but various studies show that in most real world scenarios you typically won't reach the quoted lab numbers, so expect to get more like 2.5-3.0. Study: https://www.sciencedir…

That's kind of disappointing news. I had a skim through the article and was surprised to find that it's all based on models. There wasn't a single empirical measurement of an installation of either kind. Not that I don't believe in modeling and its usages, but I am going to radically discount the findings of this paper because there was no actual experiment performed here, just fiddling with models.
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