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Geothermal may beat batteries for energy storage

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Re: Geothermal may beat batteries for energy storage

#131

Post by PaulHoule »

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…

They are building a lot of them in China

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

Re: Geothermal may beat batteries for energy storage

#132

Post by londons_explore »

mint2 wrote: post #123
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…

Claims like that really aren’t helpful without numbers backing them up the cited paper gives the efficiency of heat pump but we’re missing multiple crucial values to get from there to a comparison of heating costs Edit: https://great-home.co.uk/air-source-heat-pump-running-costs-... At current average British prices of 28p for electricity and 7p for gas, and using averages for both it looks like the commenter was mos…

From that paper, the average COP measured was 3.06 (averaged between 2 and 7 degree outdoor temperatures, typical of the UK).

The UK electricity price is currently fixed at 34p/kwh for electricity and 10.3p for gas.

A new gas boiler has a COP(efficiency) of 1.054 (it can manage efficiency higher than 100% because gas is metered by the 'lower heating value', which assumes the exhaust gas escapes as steam, but the boilers actually condense most of that steam to water, getting additional energy out).

So. Total price is: Gas: 10.3/1.054 = 9.77p/kwh in your home.

Total ASHP price is: 34p/3.06 = 11.1p/kwh in your home.

And this analysis ignores the fact that ASHP's typically have much worse efficiency making hot shower water (which a gas boiler doesn't), and obviously also have considerably higher upfront costs too.

Re: Geothermal may beat batteries for energy storage

#133

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…

Oh, also: an air source water heater would need an external heat source—otherwise you’ve just made a closed system and won’t be able to heat the house beyond what solar thermal provides, plus heat loss of the house.

Re: Geothermal may beat batteries for energy storage

#134

Post by jws »

distances wrote: post #107
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.

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, or just a fixed angle and having surplus energy most months.

In my case, panels were much more expensive when I designed my system, I initially roof mounted them, but when replacing the roof under them I moved them to a pole and went with a tilting mount and manually move the panels twice a year. My load is much higher in the summer, but I still need some power in the winter. And northern winters can be cloudy a lot and have limited sun even on a clear day. At my location there is about a factor of 5 difference in solar energy per square meter per month. So you design for each month and then pick a solution that is best. In my case the summer load is so high that even though I get 5 times the energy, it is still the driving force on sizing the system.

Re: Geothermal may beat batteries for energy storage

#135

Post by jandrese »

londons_explore wrote: post #132
mint2 wrote: post #123

Earlier quoted context omitted.

Claims like that really aren’t helpful without numbers backing them up the cited paper gives the efficiency of heat pump but we’re missing multiple crucial values to get from there to a comparison of heating costs Edit: https://great-home.co.uk/air-source-heat-pump-running-costs-... At current average British prices of 28p for electricity and 7p for gas, and using averages for both it looks like the commenter was mos…

From that paper, the average COP measured was 3.06 (averaged between 2 and 7 degree outdoor temperatures, typical of the UK). The UK electricity price is currently fixed at 34p/kwh for electricity and 10.3p for gas. A new gas boiler has a COP(efficiency) of 1.054 (it can manage efficiency higher than 100% because gas is metered by the 'lower heating value', which assumes the exhaust gas escapes as steam, but the boil…

However, the ASHP can also be used to cool your home in the summer. In the past this has been a dubious benefit for most of northern Europe, but heat waves have been getting stronger, last longer, and happen more frequently as time goes on. This is turning into a serious consideration.

Also, you can theoretically power a ASHP with renewable energy, while there are few if any carbon neutral replacements for natural gas.

Re: Geothermal may beat batteries for energy storage

#136

Post by jandrese »

martin_a wrote: post #11
moffkalast wrote: post #8

Earlier quoted context omitted.

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.

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.

Yeah, pumped hydro is one of those power sources that doesn't scale down at all.

However, home scale conventional hydro is a thing. If you live on a hill with a creek that runs down it you can install a generator that produces a usable amount of consistent power for the cost of a few hundred meters of PVC pipe, a barrel, some connectors, and a small electric turbine. Search for micro-hydro if you want to know more.

Like all hydro solutions it's heavily dependent on the geography and only suitable for well under .1% of the population, but where it is feasible it can be a huge step towards off-grid living. Add in some batteries, maybe supplement with some solar panels, and you've got all of the electricity you need year round at a somewhat affordable price.

Re: Geothermal may beat batteries for energy storage

#137

Post by fy20 »

mnw21cam wrote: post #72
boxed wrote: post #62

Earlier quoted context omitted.

That's just a ground heat pump no? I have the same on my house. It's pretty great. I get cooling in summer and heat in the winter.

If you're in an area that gets hot enough in summer for you to want cooling, then yes you'll be pumping heat into the ground during summer and extracting it in the winter. For those of us who don't get hot enough in summer to want cooling, we're always extracting heat from the ground, and so the ground we're extracting heat from gets cold, which reduces the efficiency of the system. Having a solar powered mechanism f…

Another approach would be to have a longer length of piping. The rate at which the soil temperature drops when you extract heat, and then 'recharges' naturally, will vary greatly if you have 100m vs 1000m of piping. This is why ground source heat pumps use pipes laid out in coils, as it greatly increases the surface area.

Re: Geothermal may beat batteries for energy storage

#138

Post by aidenn0 »

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…

Forget geothermal, I'd love an air-exchange system for the summers where I live. It's not uncommon for the low to be in the 50s, with the high in the 80s. If I could just store some of that overnight cool in water and then run it through the central air system, I almost wouldn't need AC.

Re: Geothermal may beat batteries for energy storage

#139

Post by londons_explore »

jandrese wrote: post #135
londons_explore wrote: post #132

Earlier quoted context omitted.

From that paper, the average COP measured was 3.06 (averaged between 2 and 7 degree outdoor temperatures, typical of the UK). The UK electricity price is currently fixed at 34p/kwh for electricity and 10.3p for gas. A new gas boiler has a COP(efficiency) of 1.054 (it can manage efficiency higher than 100% because gas is metered by the 'lower heating value', which assumes the exhaust gas escapes as steam, but the boil…

However, the ASHP can also be used to cool your home in the summer. In the past this has been a dubious benefit for most of northern Europe, but heat waves have been getting stronger, last longer, and happen more frequently as time goes on. This is turning into a serious consideration. Also, you can theoretically power a ASHP with renewable energy, while there are few if any carbon neutral replacements for natural ga…

Most boilers purchased today allow use with a Hydrogen mix, and some under development allow 100% hydrogen. Before the widespread extraction of natural gas, towns were powered with 'town gas', which is ~50% Hydrogen, so this is very much proven tech.

There are a bunch of potential ways to make green hydrogen too.

So, there very much is a path to green with a gas boiler.

Re: Geothermal may beat batteries for energy storage

#140

Post by fy20 »

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…

That's around the weight of a fully loaded A380.
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