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Geothermal may beat batteries for energy storage

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Re: Geothermal may beat batteries for energy storage

#81

Post by dmurray »

ed312 wrote: post #64
martin_a wrote: post #11

Earlier quoted context omitted.

I saw a video like a month ago on YouTube where somebody pumped something like 250 liters of water on his roof (7 meters elevation, if I remember correctly) and let it run through a homebuild generator. The power capacity of that setup was like that of an AA battery, if I remember correctly. You need huge amounts of water and lots of height difference.

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?

250 litres x 7 metres is 1750 kilogram-force-metres.

Wolfram Alpha [0] says this is about 5 Watt-hours, and gives some other handy comparisons:

> ≈ 0.45 × metabolic energy of one gram of fat ( ≈ 38000 J )

> ≈ 0.63 × energy released by burning 1 gram of ethanol ( ≈ 27000 J )

> ≈ metabolic energy of one gram of sugar or protein ( ≈ 17000 J )

> ≈ (0.02 to 0.09) × typical kinetic energy of a car at highway speeds ( 200000 to 900000 J )

> ≈ 0.5 × typical battery energy content of an alkaline long-life C battery ( ≈ 9.6 W h )

> ≈ 0.55 × typical battery energy content of a nonrechargeable Lithium-Thionyl Chloride AA battery ( ≈ 8.6 W h )

> ≈ 0.92 × typical battery energy content of a carbon-zinc D battery ( ≈ 5.2 W h )

Gravitational potential energy is just really, really low energy density. Fortunately it's reasonable to have pumped-storage reservoirs that contain trillions of litres of water.

[0] https://www.wolframalpha.com/input?i=1750+kg+metres+in+watt-...

Re: Geothermal may beat batteries for energy storage

#82

Post by Schroedingersat »

mschuster91 wrote: post #51
Schroedingersat wrote: post #26

Earlier quoted context omitted.

The total budget for any given power source is surprisingly close to 100TW. Geothermal, you'd cool the crust and have to drill far deeper than is possible to exceed 50TW for long. Wind, if you exceed somewhere in the 1-10W/m^2 you slow down the wind and create turbulence. Solar, if you use more than ~1% of the land you're radically altering the albedo and habitat (so maybe up to 200TW). Fossil fuels create GHG and ru…

> Solar, if you use more than ~1% of the land you're radically altering the albedo and habitat Both of these may actually turn out to be beneficial. Putting up solar panels above agricultural land ("Agri-PV") is not just avoiding clobbering up arable land with PV panels, but also has benefits for the plants [1]: they need less water because less sun directly hits the plants and heats up the soil which means both more…

Agri-PV is one way of using the thermal budget (and a great one from a habitat-harm perspective as it causes a net reduction in human-occupied land).

The albedo problem is the opposite of what your are thinking as it is another source of radiative forcing from putting a mostly black thing in the sun.

A Shockley-Queisser limited solar panel mostly only reflects IR. So where your plants/dirt might have an albedo of 0.3, the solar panel absorbs 80-95% of the light (albedo 0.05 to 0.2). 20-30% becomes electricity (and later thermalises when used).

This gives you a net forcing on the order of 100-250W or so _somewhere_ on earth for every m^2 of pv. If you cover too much land the radiative forcing is on the same order as GHG, hence the ~1% limit. 200-300W of work for 100-250W of new heat is a pretty fantastic deal compared to other options though.

Putting it above existing asphalt or a similar surface is 'free' because albedo is already 0.1 there. Similarly wind is free from a radiative forcing perspective.

Putting the panel in existing (light coloured) desert is much worse because deserts have an albedo around 0.4-0.6 so you are making 400-550W of new heat for your 200-300W of work.

This also leads to the interesting thought of placing bifacial tracking modules sparsely on low albedo dead surfaces and painting the surface white for a net reduction in thermal forcing (is there a 1000km patch of volcanic rock somewhere? Gobi desert?)

In the same framework, every joule of nuclear energy is a new watt of heating, and if it is from a steam engine, it's more like 3W (or even 5W once you include post-reactor heat as well as xW of heat for every 1W of pre-reactor work inputs of mining, milling, and enriching low quality ore).

Of course these all only become relevant if we slash carbon intensity to under 2% of what it is today and continue trying to grow our energy usage exponentially.

Re: Geothermal may beat batteries for energy storage

#83

Post by londons_explore »

jonstewart wrote: post #80
LinuxBender wrote: post #67

Many of the greenhouse Youtube channels I watch do a smaller DIY version of this. They have either dark barrels of water in the greenhouse with the windows facing south to the sun, or a thin metal wall filled with clay and pipes acting as a sun-heat-battery. They pump the water through the barrels or clay battery into pipes that are under ground to store the heat. In winter time they extract the heat from the ground…

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.sciencedirect.com/science/article/pii/S037877882...

Re: Geothermal may beat batteries for energy storage

#84

Post by Bakary »

swayvil wrote: post #20
newyankee wrote: post #17

More the competition the better for the world. I still feel a well designed Lithium Iron Phosphate or Sodium based battery with > 5000 cycles can prove very cost effective if used properly. The high no of cycles reduces the levelized cost of storage significantly. Difficulty is scaling this to beyond 1-2 days at most.

Competition is just a euphemism for fighting. You're saying that more fighting is better. Isn't that crazy? You'd think that fighting would be wasteful and upsetting. That peace would be better. It's a crazy world.

Forget the word competition. Just think of it as smart people having an incentive to produce something with beneficial effects or externalities for once.

Re: Geothermal may beat batteries for energy storage

#85

Post by flavius29663 »

snarfy wrote: post #4
nullish_signal wrote: post #2

One wonders what the limits of "Thermal Heat" are from small "wells"(???) up to the heat content of the Earth's ore (Heat relative to sea level) How much heat is generated by Earth's gravity onto itself? How "renewable" is Geothermal energy, truly?

About 47 terawatts https://en.wikipedia.org/wiki/Earth%27s_energy_budget#Earth'...

That seems terribly low, but apparently it's correct (humans need right now about 18TW). This means a lot of Earth's heat is actually coming from the sun itself.

One small nuance: the OP asked about the heat generated by Earth's mass. The 47TW is split between the original heat from the formation of the Earth and the nuclear decay of radioactive elements.

Re: Geothermal may beat batteries for energy storage

#86

Post by teucris »

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…

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.

Re: Geothermal may beat batteries for energy storage

#87

Post by 2Gkashmiri »

jonstewart wrote: post #80
LinuxBender wrote: post #67

Many of the greenhouse Youtube channels I watch do a smaller DIY version of this. They have either dark barrels of water in the greenhouse with the windows facing south to the sun, or a thin metal wall filled with clay and pipes acting as a sun-heat-battery. They pump the water through the barrels or clay battery into pipes that are under ground to store the heat. In winter time they extract the heat from the ground…

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 house heating, this would be better than nothing and the problem of not having consistent electricity to run the air source heat pump all times would be alleviated somehow by using solar water.

is that crazy?

Re: Geothermal may beat batteries for energy storage

#88

Post by londons_explore »

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.

It would make even more sense to sell that power back to the grid, and then spend the $$$ earned on gas, which would work out cheaper overall.

Obviously in many parts of the world, market distortion means the buy price and sell price for electricity is very different, and in that case a heat pump might make sense to combine with PV.

Re: Geothermal may beat batteries for energy storage

#89

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.

Exactly. Also, the top commenter noted that only electricity was available and currently was relying on massively inefficient baseboard heaters. Solar panels and heat pumps also have great rebate programs and eventually gas will be phased out. Some US cities are now banning gas on new construction in the near future.

The point is that custom solar/geothermal installs seem neat and efficient —- waste not, want not — but probably have a hard time competing with the economies of scale and low maintenance of PV panels and air source heat pumps.

Re: Geothermal may beat batteries for energy storage

#90

Post by merely-unlikely »

cookiengineer wrote: post #68
LinuxBender wrote: post #67

Many of the greenhouse Youtube channels I watch do a smaller DIY version of this. They have either dark barrels of water in the greenhouse with the windows facing south to the sun, or a thin metal wall filled with clay and pipes acting as a sun-heat-battery. They pump the water through the barrels or clay battery into pipes that are under ground to store the heat. In winter time they extract the heat from the ground…

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] https://en.wikipedia.org/wiki/List_of_pumped-storage_hydroel...

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