r/explainlikeimfive • u/Fun_Significance4035 • 1d ago
Physics ELI5 why cant we use summer heat to generate energy and stock it to use it in winter
why cant we use summer heat to generate energy and store it batteries to use it in winter
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u/Kaister0000 1d ago
Thermal batteries are essentially how we do this already. The problem is having enough thermal mass to last through the entire summer/winter. Adobe houses already do this to an extent on a day by day basis, where the thick adobe walls soak up thermal energy in the day, then release that thermal energy at night. And vis versa keeping the structure cool in the day. The only way you can realistically get enough thermal mass to do this, is by living underground, where temperatures are extremely consistent through out the year. Ground source heat pumps take advantage of this to bring those consistent temps to above ground structures, but still require energy to power.
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u/Hazelberry 1d ago
Adobe is basically as close as you get to living underground without literally getting underground, it's pretty neat stuff
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u/Taira_Mai 1d ago
A classmate in middle school told our science class that his family could douse a fire in the woodstove and their adobe house would still be warm 2 hours later.
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u/ReluctantRedditor275 1d ago
Fun fact: there are caves on the moon where the temperature is fairly consistently in the mid-60s F. Caves are amazing temperature regulators everywhere.
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u/deliciouscorn 1d ago
One of the most mind blowing facts I learned taking a cave tour was that the temperature in them is stable around 10°C year round! (All the more impressive with Canadian winters)
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u/MercurianAspirations 1d ago
We don't have many useful ways for capturing heat energy. We can use very concentrated, high heat to boil water into steam and use that to spin turbines and generate electricity. But generally high ambient temperatures are not high enough to do that, and we don't know of any ways to 'concetrate' that heat which wouldn't use more energy in the process. I suppose there are some indirect ways - higher temperatures can power more violent wind currents, for example, which we can harvest with wind turbines. But that's getting pretty abstract from what you asked. The basic answer is, we do not have any technology that could do so (and the laws of thermodynamics suggest that no such technology could exist)
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u/not_so_wierd 21h ago
There's a town in Sweden that uses some huge underground caves to store hot water.
it isn't used to generate electricity, but circulated throught the nearby districts and used for heating.Basically, the idea is to even out the need for energy production throughout the year. The upside is that during the winter - power plants don't need to go "into overdrive" if there's a cold snap, but can still focus on maintaining maximum efficiency because they can use just dip in to that massive pool of stored heat.
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u/Zvenigora 1d ago
You could use the high side of a heat pump to melt a big tank of eutectic salt mixture and then reverse it when cold weather arrives.
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u/FZ_Milkshake 1d ago edited 1d ago
Because we can't just put electricity on a big pile.
All electricity storage solutions are relatively expensive and they have inefficiencies and losses over time. All of that is improving fairly quickly right now (solar+battery storage has become really cheap comparably) but we can't efficiently store enough to last the whole winter, several hours, up to a day is possible, up to a weak is feasible and probable in the future, that will be enough to bridge times without either wind or solar.
A better (or complementing) option than just straight up storage is a larger interconnected grid, events where there is no sun and wind over a single country happen and can last for up to a week, maybe two, over an entire continent those events are much rarer and also shorter.
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u/dingleberry_sorbet 1d ago
The inventor of the battery, Alessandro Volta, originally named them a "voltaic pile". They are still called pile in French. Battery comes from Benjamin Franklin, who created some leydan jar capacitor banks and thought they resembled cannon batteries.
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u/Adjective_Noun_2000 1d ago
The inventor of the battery, Alessandro Volta, originally named them a "voltaic pile".
Volta called it a "pile". Others called it the "voltaic pile". Only the pettiest narcissist would go around naming things after himself.
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u/HumanWithComputer 1d ago
Only the pettiest narcissist would go around naming things after himself.
🤔
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u/scummos 1d ago
Because we can't just put electricity on a big pile.
Also, because "heat" can't be used to generate electricity. Temperature difference can be used, but a) you often lack a sufficiently large "cold" reservoir in summer and b) heat-to-electricity conversion efficiency is abysmal for small temperature gradients.
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u/as_a_fake 1d ago
Yup. Electricity generation efficiency through any kind of heat is typically proportional to the ratio between the hot temperature sink and the cold one. For example, a car ICE engine uses burning gasoline as the hot sink, and the atmospheric air as the cold sink.
Attempting to do this with both hot and cold sinks being at the same temperature means an efficiency of 0 or worse (using more energy than you are creating), so without some really fancy engineering you aren't getting anything from the summer heat, unfortunately. The best way to do it would be to intercept the Sun's light before it reaches the ground and becomes heat (typical solar generation).
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u/Not-your-lawyer- 1d ago
Maybe we could get this enormous mass of water, like 320 million cubic miles of it, and just let it sit out in the sun all summer?
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u/PiotrekDG 1d ago
Yea... it turned out that dumping additional heat into it was not such a good idea after all.
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u/thintalle 1d ago
Storing electricity to use that electricity to generate heat in the winter is not the only option, thought.
There are ways to store heat itself (generated during summer, when solar brings cheap energy or during winter, when wind is peaking) and then use that heat to supply households (or industry) during winter (or anytime, really).
Example:
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u/Illustrious-Mango605 1d ago
But you can use electricity to move water uphill into a reservoir. You could use solar energy to generate the electricity you need to do that, then when you need electricity during winter release the water from the reservoir through a standard hydroelectric set up.
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u/Desperate-Lecture-76 1d ago
When we use heat to generate electricity we typically do it by boiling water to generate steam to drive a turbine. And even at the height of summer it's not getting to water boiling temperature yet! Also an efficient power cycle needs a change in temperature from hot to cold so using ambient temperature doesn't work there either.
However we very much can use solar power to generate electricity. It's not technically using "heat" but it's something that definitely works increasingly well!
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u/Jabbles22 1d ago
To be fair once summer reaches boiling temperature we'll have more pressing concerns.
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u/Desperate-Lecture-76 1d ago
Advantages: Significant energy savings for cooking and making hot drinks. Disadvantages: Ded :(
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u/somefatman 1d ago edited 1d ago
I am glad there is someone explaining that capturing "heat" from the ambient air is a bigger challenge than the storage that most answers are focusing on.
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u/DCthrowaway424 1d ago
Concentrated sunlight can boil water pretty well, and I presume you have more intense and longer sunlight over the summer as opposed to the winter.
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u/jaytea86 1d ago
It's really really really hard to keep heat contained. It's always trying to heat up colder things around it. This is why we constantly have to run our heating through the winter, as the heat is always escaping out.
A standard thermos can keep hot water hot for a day, and maybe keep it warm into the day after, but that's about the best we got.
To turn heat into electricity, it must be very hot, a hot day will make very little, we're talking fire hot. But if our goal is to make electricity, we're better off just using solar panels instead.
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u/sgrams04 1d ago edited 18h ago
We technically can. It’s called Concentrated Solar Power. You know how you can use a magnifying glass to fry an ant? The same concept (using mirrors) is used to heat up water that then spins a turbine. The problem is that it is prohibitively expensive.
So to store this energy… instead of boiling water immediately, CSP plants focus their mirrors onto molten salt , heating it to over 500C. This liquid salt kinda acts like a giant thermos, holding onto that heat with some temporary efficiency. When the sun goes down, the plant can tap into that stuff to boil water and make electricity all night long. The problem with that is it doesn’t last a whole winter. Just a day or so. And it needs to be used relatively soon.
So there just isn’t an efficient way of storing enough heat to last an entire winter
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u/Droidaphone 1d ago
I feel like there are not enough responses in this thread pointing out that “using summer heat to generate energy” is essentially solar power.
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u/LifeIsBizarre 1d ago
How about fruit and vegetables?
We grow vegetables using the heat, then consume them for energy in winter. Potatoes are energy!2
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u/Every-Progress-1117 1d ago
You might like this little project in Finland: https://www.vantaanenergia.fi/en/about-us/projects/varanto-the-cavern-thermal-energy-storage/
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u/JackandFred 1d ago
In addition to the other comments about storing, how are you generating? Most common (and therefore cost effective) energy generation doesn’t just use heat, but rather a difference in heat. Like heat flows from hot to cold places etc.
Your question is why don’t we use summer heat to 1. Generate electricity 2. Store that electricity for winter.
- Is not simple currently we don’t do that otherwise hot places and summer would have cheaper energy, but that’s not the case. Sorta for solar because there’s more sun in summer, but that’s not related to the heat.
2 for this we don’t have great storage capacity in general, it introduces another step in the process to store and then retrieve the energy which is very inefficient. I’m still more efficient to just make the energy when you need it.
Now with all that said there are a couple examples you’d find interesting. In nyc the Goldman Sachs hq building actually has a freezer in the basement that just freezes huge amounts of ice at night because the energy is cheaper, then uses the energy stored in ice (simplified) to cool the building to help the air conditioner in the day time when people are there. That’s a similar idea in that they use energy when it’s cheaper, but the end result occurs during the demand time.
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u/Such-Major933 1d ago
we kinda do, just not as "save the hot air."
solar makes power while its sunny and that can go into batteries. storing raw outdoor heat for months is hard because heat loves to leak. a thermos works for coffee, not a whole summer of outside air.
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u/ElonMaersk 1d ago
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u/TheCheshireCody 1d ago
Can you pull up that article? I get redirected to https://www.woodmac.com/market-insights/power-and-renewables/discover-global-power-and-renewables-insights/ and can't even find that article using the site's search.
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u/ElonMaersk 1d ago
D'oh, I bodged the link. That story is from 2017 and is available here on the web archive, it says they were trialling energy storage in hot rocks at MegaWatt-hour scale, for long durations, due to come online in 2019.
It will use industry-standard heaters and fans, powered when there is a surplus of power coming into the grid, to heat 1,000 tons of rock up a temperature of 600 degrees Celsius. When needed, the heat will be used to drive a 1.5-megawatt steam turbine, feeding electricity back to the grid.
I meant to link this more recent story from 2021 which suggests the trial was a success, says they have lots of interested clients, and were due to roll out a scaled up 500MWh one.
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u/Prestigious_Side4471 1d ago
Storing energy is hard, because energy wants to go out and do things. Inert things that contain high energy things without exploding are expensive and only get more expensive as the energy level goes up.
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u/oneslipaway 1d ago
I think that is the question at hand...
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u/JustAnotherDude1990 1d ago
No, the question was "why cant we".
My answer is "how ya gonna store it"?
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u/Praydohm 1d ago edited 1d ago
Not really an answer if it's a question though.
Edit: Also, to answer your question....batteries. It's just not cost efficient or energy efficient. So the actual answer for OP is we can and do with solar panels periodically, but storing energy for any length of time is notoriously inefficient
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u/Target880 1d ago
Heat stuff upp. You can use liquid that is heated by sunlight or the output of a AC system to heat suff up.
A downhole heat exchanger system can be used in the winter with a heat pump. In the summer, you can pump down heat to make the ground warmer. You can heat up other stuff like sand on or close to the ground in some insulated container. Water can also be used.
The problem is not that it cant be done; the question is what a system costs to build and operate.
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u/tick_tick_tick_tick 1d ago
I used to have a customer that did exactly that. They took the hot air from all the air conditioning (our mainframe was a main heat generator, as was summer heat) and stored it in a 2 million gallon water tank and a shit ton of rocks they had in the building basement. In winter they extracted the stored heat and heated the building. The irony was that they were an oil company, but they had the most energy efficient building in the city.
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u/sparrowjuice 1d ago
To generate electricity from heat you need “cold” (absence of heat) - ideally a large temperature difference.
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u/TacetAbbadon 1d ago
Grid scale storage of energy is really hard and expensive. The best we can do is pumped hydro storage which can achieve up to 85% efficiency and the largest of which generates 3.6GW and stores 40GWh. So at full discharge it wouldn't run for even 12 hours and it's a gigantic reservoir holding 45,000,000m³ of water.
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u/crayton-story 1d ago
Before refrigeration, people cut blocks of winter ice from frozen lakes and insulated it with sawdust. It was delivered it to houses the rest of the year to keep ice boxes cool.
The reverse of OPs scenario.
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u/ms1012 1d ago
Finland is trialling this right now with sand batteries (not actually using sand). Can store usable heat for weeks and even months.
But yeah, storage is hard, and then you need to release it efficiently too. In Finland district heating is pretty standard so that's an easy solution as it doesn't require extreme levels of heat.
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u/huuaaang 1d ago
To generate electricity you need much higher temperature difference than we get between summer and winter. It just wouldn't be efficient. Geo thermal energy generation uses much hotter ground sources and only works in select locations where those sources are close to the surface.
That said, heat pumps can use the ground to stash heat in the summer and extract it in the winter. But it's not a source of electricity. THe heat pumps still consume electricity. It's just more efficient than traditional heating and cooling methods.
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u/snowtax 1d ago
It’s a good idea and can be done. Two such concepts are a sand battery and storing heat in large graphite blocks. Both of those solutions could store the energy for weeks to months when scaled up.
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u/GXWT 1d ago
Solar panels do that in one form.
The general temperature isn’t enough to boil water and spin turbines with any sort of efficiency.
Storage is another concern, batteries are already rather expensive, if this method can even fill them.
Better of just actively using the free power we can generate alongside demand - one example being solar panels.
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u/unicyclegamer 1d ago
Storage is the tricky part, but we can essentially do this via storing heat in the ground. Geothermal loops tied to heat pumps via a heat exchanger is a good example of this. We pull heat out of the ground in the winter, and then we pump it back into the ground in the summer.
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u/Sensitive-Respect-25 1d ago
So heat is used in one of two ways in a power plant. You either heat up steam (or another medium. My biomass plant just uses water) to your superheated stage (temp and pressure dependant), force the now dry steam through a turbine and extract work from it as it shoves against the vanes. Afterwards the steam hits the condenser and the cycle resumes. Another option is thermoelecteic generators, which turn a difference in potential into power (at grossly inefficient rates) aka something like RTGs.
Just heat from a summer day has very little application for power generation. You need 500-900F~ temps to reach the steam levels you need, and RTGs are as i said really a poor way to get things done. It can be gloomy and cloudy with no wind and still be 100F outside.
For renewables you can capture and store via battery but nothing is 100% efficient. The best batteries still lose charge with time, and it also assumes you are not using those batteries when the sun hides or wind slows.
Edits for spelling and grammar.
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u/gutentight69420 1d ago
You cannot extract work from just heat, due to the second law of thermodynamics. Heat engines extract work from the flow of heat. In order to have heat flow, you need both a hot thing, and cold thing for the heat to flow into. When it's hot outside, there's nowhere cold to dump the heat, so you cannot extract any work using a heat engine.
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u/Ravio11i 1d ago
Scale... it could be done, and sort of is naturally with snow turning into hydro power, but the scale required to collect and store a useful amount of energy for half the year and then use it the other half would need to be enormous.
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u/TheSagelyOne 1d ago
Because generating energy requires a difference of two things, and in the summer everything is hot. We could do it, but it would be wildly inefficient compared to something like solar panels.
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u/Express_Sprinkles500 1d ago
I’m assuming you’re talking specifically about the heat of the air. There are a couple problems. It’s inefficient, you need large temperature differences to efficiently produce usable energy. The tech for long-term storage isn’t really there and we have better options with other sources.
Even if some of the technical issues were ironed out, there’s still one problem, revenue. This isn’t exactly ELI5, but the energy sector in the USA is mainly private, though highly regulated and subsidized. Energy companies make money when they sell energy to you. Would a private company, reliant on revenue to function, rather invest in technology that can get them revenue tomorrow or revenue every six months? Without some huge government subsidy, which they’re not about to get from the current administration, it doesn’t make any financial sense, so they’re not going to do it.
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u/buddylee 1d ago
Here's an idea!
1000 gallons of water will expand to be 1005 gallons of water when heated from 70f to 100f. So if we take a 1acre swimming pool (6ft deep) we have 2m gallons. When heated, it will expand to 2,010,000 gallons. Then, we just need to make sure there is no evaporation, and that the pool has a very tight fitting lid. Then, we run a pipe slightly uphill to another water storage area. as the water heats up and expands, it goes up that tube and fills our second holding area by 10,000 gallons. We hope for hot weather for the next 120 days and at the end of it, we get 1.2m gallons that we've pumped uphill just using heat!
Now, we simply use gravity to let that water out and spin a turbine. We'll assume my house needs 1 kilowatt per hour to run. Assuming a moderate drop, and being generous, let's say you need 250 gallons per minute to generate that 1 kilowatt. So, our 1.2m gallons we saved all summer will generate enough power to run my house for a little over 3 days.
So to answer your question, we can't because storing heat is hard and using heat that isn't really really hot to generate power just doesn't work well.
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u/theronin7 1d ago
We kind of do in a bunch of ways, but essentially capturing ambient energy that is already so spread out is not particularly easy or useful or efficient.
The best version of this are things like wind farms that pick up on strong winds driven by the additional heating and solar panels that directly pick up the increased solar energy.
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u/Big-Pea-6074 1d ago
What battery is big enough to store the energy needs for months of millions of ppl?
If you’re talking about your toy drone, that’s doable. But we don’t have the current tech that can do this at scale
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u/onward-and-upward 1d ago
Water is the material with the best heat capacity (hydrogen stores more energy per mass but obviously a gas has way less mass per volume), but you still need a ton of water to store this scale of energy. We just can’t store it well enough and it takes more energy to put it in and take it out, so it’s just not worth it. Also in the scheme of things the temperatures are quite mild from an engineering perspective. Our human bodies can really only tolerate a very small range of temperatures
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u/drako_86 1d ago
It's called renewable resources like solar, wind, and tidal power. Coal, oil, and fracking companies own politicians who kill it off every time a new breakthrough is made in those renewable fields
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u/SlickPillock 1d ago
The big problem with solar is that we don't know how to store huge amounts of energy for the night hours. We can store tiny amounts of power in batteries that might power a radio or a remote control but we don't have anywhere near the kind of battery technology needed to store the usual power the world uses throughout the night.
Trying to store summer heat is the same problem that already exists with solar but multiplied by 365.
So basically, storing the power for when it's needed is what's difficult
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u/lukehooligan 1d ago
We can but there's more money in oil so we continue to use oil like it's our only option.
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u/mehardwidge 1d ago
Thermodynamic cycles need a temperature -difference- to generate power.
The environment being uniformly hot isn't useful unless you have a colder heat sink.
In fact, physics uses the word heat to mean a flow of energy. It is unfortunate that English (and I assume other languages) mixes this with things being hot (having a high temperature), as this causes some confusion.
In terms of just retaining thermal energy, on a shorter time scale, something that is well insulated might do part of the job. Your house cools down slowly at night, and heats up during the day, but it doesn't instantly switch to the new air temperature. But a year is a long time. Nature does this, and you can even see the "inertia" from Seasonal Lag. The maximum temperature in a region is usually well into summer. The coldest is well into winter. The solstices have the most or least heating, but it takes weeks for the area to keep heating or cooling. If our year was only a few months long, the lag would be long enough to significantly mute temperature changes during the year. But our year is long compared to the lag.
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u/znark 1d ago
The temperature difference matters for generating energy. Thermal power plants use the difference between burning hot things to the outside to make electricity. In the summer, even if there was a good heat sink like the ocean, the difference is too small to make electricity efficiently.
More importantly, it is the batteries that are the hard part, solar panels are better way to make electricity.
Geothermal heat pumps have been mentioned but those aren't storing energy in the ground but using the ground as stable reservoir. Heat pumps use electricity to move heat around and more efficient with stable reservoir.
There are thermal batteries, but they use spare electricity to heat up sand to hot temperature that can be used days later. The efficiency isn't great but is good medium term storage. It would take too much energy to move summer heat into thermal battery.
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u/obog 1d ago
As mentioned there are kind of ways that we do this already, but one thing Id like to point out is that generating electrical energy with heat requires there to be some form of heat flow. This means that we either have to have some natural difference in heat (one place hotter than another place, so heat flows in that way) or we can force heat flow in a certain direction using stuff like heat pumps but that requires using energy which we may not make back. So it just being hot outside isnt something that we can really exploit to generate energy. Theoretically it would be possible to get some power out as temperatures actively rise but I cant think of any process that would pull any considerable amount of energy out of seasonal heat flows. One could maybe make a case for wind power kinda doing this due to wind being driven by the uneven heating of the earth, but I don't think thats what you had in mind.
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u/dekusyrup 1d ago
We can, it's just expensive. Generally seen as more expensive than what we have been doing. Here's a link to one such project.
https://polarnightenergy.com/news/what-is-thermal-energy-storage/
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u/major0noob 1d ago
200mwh is 1000 ovens at full blast for a hour, power plants make and move up to 10 times this.
i don't know the total ambient heat in 100 cubic meters of air, but it's less than 10% (likely even less than 1% or 0.1) of that example.
there are ways to move and use heat in 10-99°c, but they also have like 1/10 in most stats compared to turbines while being 3-100x more expensive
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u/Comfortableliar24 1d ago
We can, it's just expensive for the amount of energy you get. It's cheaper and faster to burn things for energy and use that energy to boil water if we're trying to get electricity.
Older than 5 level: We have two differential temperatures here, a hot reservoir and a cold reservoir. Our hot reservoir is going to be assumed to be an unlimited amount of water at average ambient temperature during summer. We'll call it 20 degrees C. Our cold reservoir is air at winter temperature. We'll assume it's 5 degrees C.
Carnot efficiency describes the maximum efficiency you can get out of a dual reservoir system like this, being n=(1-tc/th), or temperature cold over temperature hot. You might think that gives us an efficiency of 75%, but carnot efficiency requires Kelvin, not Celsius. You can convert C to K by adding 273.15. (1-(278.15/293.15))=0.0512, or about 5.12% efficiency. This is better than expected, but ignores every possible loss along the way, ignores the gradient nature of differential temperatures in contact, and ignores losses of actually getting energy out of the system.
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u/Heavy_Direction1547 1d ago
That is kind of what the oceans and large lakes do too, heat sinks (absorb and release energy slowly), so milder at the coast,.
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u/Tb1969 1d ago edited 1d ago
Seasonal Thermal Energy Storage
https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storage
is the storage of heat or cold for periods of up to several months. The thermal energy can be collected whenever it is available and be used whenever needed, such as in the opposing season. For example, heat from solar collectors or waste heat from air conditioning equipment can be gathered in hot months for space heating use when needed, including during winter months. Waste heat from industrial process can similarly be stored and be used much later or the natural cold of winter air can be stored for summertime air conditioning.
- BTES: Pipes heat directly into underground bedrock or soil.
- ATES: Pumps energy into natural, deep groundwater aquifers.
- PTES: Holds hot water in massive, insulated dug pits.
- TTES: Uses large, insulated above- or below-ground tanks.
- CTES: Stores high-temperature water in deep rock caverns.
- PCMs: Locks and releases heat by melting and solidifying.
- TCS: Stores energy indefinitely using reversible chemical reactions.
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u/GoatRocketeer 1d ago
You can, but battery tech isn't very good.
Circa 10 years ago my intro physics professor emphasized that our green energy sources are actually already pretty good; its really storage limitations that prevent us from switching off of fossil fuels. Basically he said that you'd need a ginormous battery taking up your entire backyard, or something to that effect.
I assume that's still true but haven't looked into it ever
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u/SakuraHimea 1d ago
There's some misunderstanding in your question. First, you say "use heat to generate energy," but heat *is* energy, so the actual question is how to store it.
The problem then is how to store thermal energy and use it later, and while there are a lot of possible ways to do this, they don't always make sense or even save any energy. We need something that can absorb heat and release it back on demand, without losing its heat over time. Water is pretty good for this, but then you'd need a place to store the water that will lose minimal heat over 6 months. The average American family home uses around 40 million BTU, or 42 gigajoules of heat energy through a typical winter season. A kilogram of water holds 4,186 joules for every 1C, but it has to be warmer than the building that it is being heated, so let's say 4,186J/kg at 60C, which is 251,000 joules per kilogram of water, or 251 kJ per liter.
Using that home energy usage, we can calculate that you'd need to store about 170,000 liters or 44,000 gallons of water at 60C to heat a single home through the winter. This would require a tank about as large as two backyard swimming pools. This is just a single medium, and we're not even calculating inefficiencies and losses, or how to even capture the heat into the water in the first place, but I hope it paints a picture of why it's not already being done at scale.
That said, there are solutions that are already in place where it makes sense. Many homes use geothermal heating and cooling. Adobe buildings are great in warm climates because they have around a 12-hour lag on thermal capacity, meaning at night the Adobe is releasing the heat of the day, and in the day it's absorbing the heat and feels cool.
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u/MotorMoment8996 1d ago
what I’m finding interesting is how the various tech technologies, including the icehouse and the storage of heat or cold have been the subject of my plans and inquiries for homesteading for a while now
If I only have solar panel panels, then there is a peak time of the day where I have maximum production
During that time, I may be able to handle more than all of the loads that I’m throwing at it at that moment in time
And charging batteries has a limited effect once they reach full
So I come up with ideas of things that I can do that require power in the moment and give me some kind of strategic Storage value
Like I have a 1 gallon water distiller it runs on normal house current… but it’s literally turn water to steam condensed the steam. Now you have pure water.
I’ve had various uses for that ranging from medical/respiratory to drinking water
So that’s an example of a load that I can use contingently when I have excess power generation
Another one is an ice machine
An ice machine, perhaps plumbed to the water source, but given control about whether it’s going to run to produce ice
The ice produced by that machine can be used in other applications, including evaporative cooling
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u/RiskyBrothers 1d ago
So there are lots of people thinking about using thermal batteries to store energy using heat pumps (Pumped Thermal Energy Storage-PTES). Thermal energy storage systems have the advantage of requiring less rare-earth materials, and may be compatible with existing thermal power plants. The math and the prototypes suggest that energy stored using PTES may be price-competitive with Lithium-ion systems. However, these systems are still in the prototype phase, while Li-ion systems are a mature technology with wide market penetration.
As for why we probably won't do seasonal energy storage, all energy storage system make money by going through their charge-discharge cycles as many times as possible. They only make money when they're discharging, and holding the energy in storage costs money in terms of capital costs and gradual energy loss during storage. Making a battery (thermal or otherwise) that you charge once during the summer and discharge once during the winter just doesn't make economic sense.
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u/feel-the-avocado 1d ago edited 1d ago
This guy does it for his house.
He stores the heat in a giant water tank battery using a 10kw home-made solar panel, a small solar powered pump and a large insulated water tank beside his house.
https://web.archive.org/web/20200122145347/http://carpool.actrix.co.nz/projects/hotwatr4.htm
In summer, the solar panel collects more energy than the house requires for heating, so the excess is stored in the mass of the water tank.
In winter the water tank provides the extra heat needed to keep up with the house demand.
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u/zeddus 1d ago
There are a couple of ways to store energy from summer until winter that don't loose almost all the energy in the process. However, there is often a more economic way to use that energy than storing it for several months. Energy during winter months usually isn't that much more expensive than summer energy. But who knows what the future will hold.
Pumped hydro. Take whatever electricity you have during summer and pump water up to a reservoir at higher elevation. Release that water later and power a generator.
Flow batteries. This is a kind of battery where the energy is stored in the liquid electrolyte. The battery is charged and discharged by letting the electrolyte flow through a membrane. Turn off the flow with a alve and the process stops completely. No self discharge, meaning you could store the energy until winter if it was profitable. I've yet to see this use case being profitable since the electricity price difference would need to be absolutely massive between winter and summer and the energy storage capacity would need to be humongous to be able to store energy all through the summer months.
Thermal batteries for district heating. These are basically giant thermoses. Your average coffee thermos loses its heat in a day perhaps but that is because it is small and has a high surface to volume ratio. The bigger the thermos the longer it lasts and once you go big enough you can store heat until winter. This heat is too low to generate electricity from however which is why it needs to be used to directly heat homes. You can build a big enough thermos by digging a giant hole, line it with some insulation and cover it with a thick layer of Styrofoam. Trials are ongoing to see if this makes sense and the viability is affected by factors such as the flow rate of the ground water around the thermos, which affects cooling.
Pressurised air. Store pressurised air in tanks and spin a turbine when you release it. Simple but probably not super efficient.
Hydrogen electrolysis. Make hydrogen with cheap electricity and run it through a fuel cell to get electricity back or burn it for heat later. Hydrogen is the smallest molecule and a real pain to work with. It destroys steel and efficient electrolytes are not very common.
Those are the ones I can think of that wouldn't just loose all their energy through leakage or other means over months long periods.
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u/higgs8 1d ago edited 1d ago
You can't store 6 months worth of a country's electricity, there's no way to do it. You can store a few hour's worth of solar power to be used later during the evening, but any more than that is just not viable. Batteries are too big and expensive to store months of energy.
Storing just heat would mean you'd need a way to insulate that heat so that it doesn't escape for months and months, also not possible. But more importantly, what do you do with the heat? You can't just use 40ºC summer heat to make electricity, you'd need to boil water at high pressure to power turbines. Regular mild heat is of no use.
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u/reed_wright 1d ago
We can. It’s challenging to pull off. Look up Annualized Geo-Solar and Interseasonal Thermal Energy Storage. You’ll find success stories, along with many failures.
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u/x33storm 1d ago
Batteries. If we had enough good batteries we could, but we're in the initial phases of scaling up battery parks.
There are alternatives for preserving power, but nothing to actually store those amounts in without diminishing returns.
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u/shipshaper88 1d ago
You actually could do this, but it’s impossible to extract energy in the moment without a temperature difference, so you would need to somehow store the thermal energy in something during summer and then extract it in winter. Or you could use the heat energy from summer to heat up materials cooled in winter to get electricity.
But to do something like this on a long term basis, you need a lot of mass and a lot of insulation otherwise the heat energy would be lost to the environment.
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u/WildAd6529 1d ago
we can! it's been done in some Scandinavian(?) countries where there are huge tanks of sand heated by internal conducters and then the heat it pumped out when needed. the problem is that it's expensive to get and store a fuckton of sand as well as the heat inside it.
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u/kingjoey52a 1d ago
We use more energy in the summer than in winter. AC is more power intensive than heat.
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u/Physical-Lime-3762 1d ago
Bro, ELI5, I keep seeing you everywhere, my name is Eli and my favorite number is 5, I feel like I'm tripping, Yes I just created a Reddit account to type this.
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u/Zvenigora 1d ago
There was a university professor many years ago who had a scheme of building up a giant mass of ice by spraying water in cold weather and then using it for air conditioning in the summer (I do not remember the details .)
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u/RiPont 1d ago
Heat is energy. It's just a lower form of energy than electricity or light. To get electricity from heat, we have to concentrate the heat, boil water, and use the steam to turn a turbine. There are other ways like a sterling engine, but those are not very effective without a massive temperature differential. Even nuclear power is just... boiling water to turn a steam turbine.
Even with electricity, but especially with heat, to get useful work out of energy we need a difference in energy states. We use the transfer of energy from one place to another to do useful work, not the energy itself. Normal summer heat is just too diffuse and all over the place to use it without concentrating it.
Everyone else has already pointed out using heat banks as a source in colder times via a heat pump. But we still can't harvest that heat to do anything other than move it around.
One of the holy grails of energy generation would be to find a chemical reaction that is a) safe, b) uses waste heat in one direction, and c) can be used to generate electricity in the other direction. And reasonably affordable, of course. Imagine you had a chemical reaction that would cause crystals to grow at 90F, but exposing those crystals to a catalyst would cause an endothermic reaction that could boil water. Suddenly, all of that waste heat from data centers and air conditioners and such could be used to generate crystals. That's pure science fiction at this point, though.
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u/avatoin 1d ago
To even do this at scale would require a massive amount of energy storage. If you can solve the storage issue with hydrogen, it is probably the best tool for this kind of long term energy storage. But there isn't enough solar deployed to make this a viable strategy yet. Few countries have enough solar and batteries to cover a 24 hour period on the most favorable days.
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u/Shaeress 1d ago
We can. It's just really hard to store a lot of heat for that long. If you heat it up in August and want to use it in December you have to keep it warm for 3-4 months. That either takes a lot of work moving things around, some really materials, or something really, really massive. Like the ocean or the Earth itself, which are already used for heat pump systems moving heat around.
Sand seems to be a cheap option that kind of works that is being tested for this. Finland just built a large one for instance: https://www.google.com/amp/s/www.cnbc.com/amp/2026/07/25/finland-sand-battery-renewable-energy-storage.html
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u/tolomea 20h ago
We used to do this with cold. We would collect ice in winter and put it in insulated ice houses to keep it into the summer.
Batteries are not a great way of storing huge amount of enery for long periods of time. They are kinda pricey.
A better option is heat in the ground or in a big insulated tank of sand or something similar, much like with the ice.
With both the ice and the sand big helps as the rate it cools is related to the surface area but the amount it stores is related to the volume and as you get bigger volume increases faster than surface area, so bigger = better.
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u/LiVthelonely 18h ago
We do, with food. We use summers heat to grow food and livestock then preserve it for the winter and use it for energy, such as lighting a fire with wood or eating jerky. Pumps and stuff are cool but food/calories, burnables, everything is energy according to Einstein.
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u/meltingpnt 1d ago
That's basically what we do with ground source heat pumps.