Geothermal smartphones when?
That puts real meaning into the term "landline"
Geothermal may beat batteries for energy storage
101–110 of 293 posts
Re: Geothermal may beat batteries for energy storage
#102Earlier quoted context omitted.
> This article is about storing energy generated using renewables in reservoirs; not about tapping into geothermal energy. I think it’s about both. They plan to create reservoirs that heat water _and_ use them to store warm water. Also for the latter the outside heat source will provide energy. FTA: Enhanced geothermal systems (EGS) get around this geographical limitation by creating artificial reservoirs. Developers…
Yeah that last line is key — they’re not creating heat with the excess energy, they’re pumping water. The article doesn’t have much specifics but the implication is they’re achieving much higher efficiency than if they were doing electricity → heat → electricity
It’s not clear from the article, but I think they’re aiming to do both: create new geothermal sources by drilling (running, I guess, some of the risks of fracking) _and_ storing excess energy as heat in those sources.
Re: Geothermal may beat batteries for energy storage
#103The the ratio of area A to volume V for a sphere of radius R is 3/R. The larger the sphere, the less surface area to volume. A corollary of this is that a sufficiently large thermal tank has little in the way of heat loss to its surroundings in relation to its heat capacity.
At large enough scale, it's probably the most efficient way to store energy for general heating purposes. Simple water has significant thermal capacity. 1 tonne (roughly 1 kilolitre, 1000 litres) of water at 80 °C holds ~50 kWh of useful heat relative to normal indoor temperatures. Enough to heat a Canadian home overnight on a bad winter day and then some. 1 tonne of water isn't really that big; a typical car's interior volume would hold several tonnes of water. Home hot water storage, for heating over several days or a week, is quite viable with a large basement tank, and commercially available. Used with intermittent heat sources, and sometimes to save money when heat costs more at different times, like with electric time of use.
A standard Olympic swimming pool holds several thousand tonnes, the largest indoor swimming pools tens of thousands of tonnes. 20,000 tonnes of water at 80 °C = about 1 gigawatt-hour of usable energy storage. Assuming no losses, That could heat many dozens of typical Canadian suburban homes all winter. What about bigger? Some lakes are so large their thermal capacity causes their temperature to significantly lag behind the seasonal changes, moderating the local climate. The largest fully artificial reservoirs are measured in cubic kilometres. That's billions of tonnes. 1 cubic kilometre of hot water would have 30 terawatt-hours or so. That's in the range of the yearly energy consumption of small cities. And at that scale, even a lightly insulated tank would lose an insignificant fraction of its heat, even over a timescale of months.
Getting into less conventional territory, with much higher temperatures (perhaps a molten metal instead of water) and some real big tankers, it might be feasible to literally ship heat. This rarely made sense in the past except in some edge cases like using industrial waste heat. Fossil fuels were almost always the source of the heat to begin with. Just ship the fossil fuels. Far more energy dense and no conversion losses. But the economics are changing.
(As an aside, the effect of the ratio of area to volume is just not intuitive to me, for some reason. But it's a very powerful scaling force in nature. It is why a bucket of water takes days to evaporate while tiny droplets of mist take seconds. Area for evaporation relative to volume. It even limits the maximum size of a terrestrial animal. Elephants push that limit. About a kilowatt just for base metabolism. In a thickly-walled airtight tank. A really big tank. They'd cook from the inside out without active cooling in a matter of hours. Their hearts are heat pumps and their ears are radiators.)
Re: Geothermal may beat batteries for energy storage
#104Earlier quoted context omitted.
Big fan of gravity well storage, it seems simple and elegant. https://energyskeptic.com/2019/gravity-energy-storage/ The above link has some numbers (2019 had it bookmarked so maybe it has improved)
That website is full of deranged ramblings which are largely disconnected from reality. Case in point: > MY NOTE: well whoop-dee-doo. China generates 16.2 trillion terawatt-hours (TWh) a day. That’s 64 billion times more than all of the open-cast mines can provide. Better start digging more holes! 16.2 trillion terawatt hours a day is ~4 million times the total global insolation or 35 billion times total global energ…
Thank you for letting me know! Did a bit of checking and deleting this from my bookmarks!
Re: Geothermal may beat batteries for energy storage
#105Interesting 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…
Pumped thermal storage, where a reversible device is used to generate heat (and cold), then generate power from the heat (and the cold), can have efficiencies of up to 75%.
https://aip.scitation.org/doi/10.1063/1.4994054
"Insofar as the numbers I have presented in this paper are correct, they demonstrate that energy storage is a problem of 19th century science. No future laboratory breakthroughs or discoveries are required for solving it. All that is needed is fine engineering and assiduous attention to detail. Said poetically, this is 21st century rocket science."
Even resistive heat can give efficiencies > 50% if the storage temperature is sufficiently high. For example, the ENDURING system from NREL (now being commercialized by Babcock & Wilcox) has a projected round trip efficiency of 53%, using sand heated to 1200 C to store the heat. Heat transfer from sand to the working gas is via a fluidized bed heat exchanger, a nicely compact system with very large heat transfer area.
https://arpa-e.energy.gov/sites/default/files/2021-03/07%20D...
Re: Geothermal may beat batteries for energy storage
#106Earlier 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 highly dependent on your local electricity and gas prices. A quick google search tells me residential electricity in Germany costs about 2-3x what it does where I live in the northwest US. We're on mostly government owned hydro power and electric prices have been stable for a long time, meanwhile gas keeps going up.
EDIT: Did some quick math using my last power bill, at current prices a heat pump just needs to be about 2.9 average COP to beat gas in cost for me, if gas keeps going up that'll keep dropping!
Re: Geothermal may beat batteries for energy storage
#107Earlier 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.
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.
Re: Geothermal may beat batteries for energy storage
#108Many 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…
> 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.
Re: Geothermal may beat batteries for energy storage
#109Earlier quoted context omitted.
That website is full of deranged ramblings which are largely disconnected from reality. Case in point: > MY NOTE: well whoop-dee-doo. China generates 16.2 trillion terawatt-hours (TWh) a day. That’s 64 billion times more than all of the open-cast mines can provide. Better start digging more holes! 16.2 trillion terawatt hours a day is ~4 million times the total global insolation or 35 billion times total global energ…
Thank you for letting me know! Did a bit of checking and deleting this from my bookmarks!
I find it's a useful barometer of what crazy disinformation is going to be spread next because it has been SEO'd so well.
It also often covers interesting topics, and many of the stories are actually about something important or useful.
Additionally many of the things it 'debunks' are actually terrible ideas, and some of the arguments it uses are valid.
For gravity storage the costs and inefficiencies are a bit prohibitive for the use case of an unsubsidized high capacity (more than 1 day) option, and it's not really competitive with batteries for less (and is highly power limited).
Re: Geothermal may beat batteries for energy storage
#110Earlier quoted context omitted.
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.
And Massachusetts.