Let's call them "thermal batteries", so people won't think they compete with electrical batteries.

14:00 pro tip. you don't have to just go up LOL you can also go down with it! 10 stories underground 3 stories above ground AND less wall support issues and collapse problems. so the acerage is way less than shown here by a huge amount! also you build a 50 storey building they go down like 20 stories in the basement to anchor it etc. well you can build your sand silo and bury it right next to the foundation and heat it from there forever. run electric in heat and hot water comes out

What I don't get is when people say that the round trip efficiency of Sand is low compared to Li Batteries. My take is WHO CARES?! If you lose 30%-50% of generated renewable power storing it in Sand that's STILL 50%-70% power you would otherwise have lost because you don't have storage. And if Sand is MUCH cheaper than Li batteries and not subject to the scalability issues of batteries then it's better than nothing.

You mentioned a "cold battery". Check out Ice Bear by Thule Energy Storage. This is daily thermal energy storage (DTES). Before refrigeration was invented people would harvest winter time ice from a lake and store it in an "ice house" so they would have ice in the summer time. This is seasonal thermal energy storage (STES). For winter home heat I use PV-direct to heat water in an uninsulated tank when the sun shines that at night heats the house (DTES). I am still trying do decide between sand or water or other for (STES). Thank you for a most informative video.

I think DIYers will build sand batteries. You could probably build some rudimentry heating system using nothing but reclaimed bits and pieces and some tinkering

That heat could be used for saunas even in the summer, or heating swimming pools.

Passive buildings sometimes use thermal mass such as winter sun hitting walls or floors of which cement to heat up during the day and release that heat at night. This works at residental scale

Correction...( 3:16) 1100 degrees Fahrenheit.... 660 Celsius ( at least according to your own text, on-screen)

A dual phase sand tank with separate cold and hot sides sounds kind of brilliant. You'd be able to do all kinds of amazing things with having both a chilled battery and a heat battery. Throw in some heat exchangers and suddenly your steel plants are powering your industrial freezers. The concrete plant down the street can cool the freezer of every local restaurant. If we think in terms of districts and communal sourcing rather than individualized solutions, economy of scale works in *everybody's* favor. It makes little sense for an individual house to power it's own hot water tanks when it would cost orders of magnitude less overall to do so for an entire city, plus there would never be any chance of running out of hot water.

using geothermal to heat and cool your house you basically are using the ground as a cold battery in the summer

I have contemplated creating a sand battery for personal home heating, using Sun tracking mirrors to heat the battery. Thank you for the video

Another great video with fantastic informative points like the energy -> heat ration vs the heat -> energy ratio where I had no idea. This and many other reasons is why I love the channel 🎦🎦

Pretty good video, thanks for the details on the subject of sand batteries. It's great that low quality and can be used for this instead of beach/ocean sand etc

Idk if you slowed down your speech, but this was a lot more understandable than usual 😅 You're awesome. Thanks for everything!

Well done!!

I am a big believer in thermal energy. This was true even before I knew anything. I had a house that utilized a wood burning enclosed burn chamber in our mud room that burned wood very efficiently and heated a ceramic tile wall in the house. There was a ceiling fan near by to aid in distribution of the heat and that wall would stay warm for days. Think if you had something similar that heated sand with excess solar electricity then circulated air through steel piping in the sand to heat the wall. I feel too many people discount ideas such as these with arguments about efficiency. Once installed there is virtually no maintenance. This can be built with off the shelf equipment that would make repairs such as a blower motor easy to do. This type of system could last the entire lifespan of the home and could be self powered by the same solar system. Upfront costs, yes, but after that, you could have supplemental heat for life. The cost for this is not too much compared to the propane cost reduction it could provide. If I could reduce my propane by 30%, that’s like $500 a year, every year, forever!

It could be use to store excess heat from data centers to improve the efficency.

Outstanding video! I've got 5120 watt-hours of LiFePO4 storage, and many hours of wasted solar energy each day. I'm thinking of building a sand battery, using it as a solar dump load. Yours is the best video on this topic so far. Absolutely brilliant and thanks for sharing.

I love the idea. Undecided with Matt did a good video about sand batteries not long ago, for more information.

great keep us posted on new dewelopmens in sand batterys

Great idea! Reminds me of Drake Landing Solar Community in Alberta, Canada, a neighborhood which stores so much energy in the summer that they can use it to heat all winter.

Just imagine that you have a factory where every machine has a steam engine, but the heat is provided by portable and replaceable sand batteries that's charged at a central heating location. This enables each machine to operate independently for a few hours before their batteries needs to be replaced. The batteries themselves to back to the charging station until they get hot enough again. At the very least, this would make for some very whimsical steampunk setup. It doesn't even have to be that elaborate. It'd be awesome enough to just pull a hot cylinder full of sand from the fireplace, put it in some huge automaton and watch it come to life.

It's good that you mentioned the Northern parts, like Canada or Northern Europe, that's where it can be most useful. I too do not see the use of it much outside the district heating of places in colder climates, because in the Northern places you mentioned we will not get much sun from mid October - start of March, so all we have left of renewables is wind... and we have the MOST need of energy in those winter months when we cannot survive without heating and it is a huge chunk of energy we use. Lithium batteries are not the best storage medium to take in sun in August or September and then store it for December-February when it will be most needed. And even solving winter heating here makes a lot of sense because it is a huge chunk of our energy needs. Probably best options to keep energy gained during summer to the winter month are either convert it to hydrogen or such solutions as the sand batteries for heat.

What goes around comes around! My first home I bought in 1965 was heated in exactly this way - thermal blocks.

I stopped consuming any media concerning the development of battery technologies a decade ago. I'm glad I did. None of them went anywhere

I'm actually planning on building one at my home

One thing to remember when comparing the cost per kwh of a battery vs heat storage is that the electricity from the battery can be used with a heat pump which can have 400 to 500 precent efficiency in converting electricity to heat but also can be used for cooling. But in really cold environments, the sand battery seems like 8t could be a good idea.

I love the concept of a sand battery it's old tech that has been provent o work in small applications so if can use modern tech to refine it the possibilities and environmental benefits are enormous. I can't wait to see where this leads

3:23 insert heat pump comment here

Could be an interesting use for all the unused office space in major cities. I imagine weight would restrict the number of floors able to be used, but buildings could easily have lower floors converted to thermal storage to help reduce heating and cooling cost, while also reducing the required occupancy rate. Especially if the building was able to store more energy than it used and was able to sell excess to surrounding office buildings.

I think it is a fascinating idea to reduce the dependency of Fossilfuel for heating

for a home it is much better to use a huge tank of water right in the middle or your basement and maybe the first floor and constructing the stairway around it. of course you need some insulation around the water tank. due to the fact that an insulation is not perfect anyway some heat always leaks out. however, this "heat loss" is not lost at all, because the tank is in the middle of your house. that means that this thermal leakage is already heating your house a tiny bit. you can also implement two different tube coils inside at the top and bottom and extract and put in the heat very flexible because on the upper end it will always be warmer than at the bottom. this way you can heat the top end up with thermal solar panel to max. 40 degrees C because that is warm enough for your house heating system and then you switch over to put the additional heat at the bottom of the tank. for extraction you could do a similar thing. if the tank is very hot on the top, like 95°C, you take the heat out of the bottom or a mixture out of it to go with the right temperature in your heating. if the whole tank is getting colder, you could extract it only on the top of the tank. this installation lasts practically forever. and while having a basement is expensive, it is still very nice for a big hobby room, fitness room, party room, storage room, etc.

I saw the polar night thing when they first installed it, seemed genius, so i built a small scale one using an approx. 1 cub yard of sand and a small wood stove. it has worked 2 winters now, but i still haven't worked out all the issues yet. i need to move more heat from the wood stove to the sand instead of heating my shop to 80+ degrees. I burn a small fire for approx 5-7 hrs per day, and the heat radiates off the insulated sand box at night and does a good job keeping my 1200 sq ft shop toasty warm all winter. saves a truckload of firewood compared to just the woodstove i had. plan to connect solar panels to it soon!

Cooling provided with heat is actually possible with ´absorption chillers ´ which were generally used in the oil and gas industry where excess gas was burnt to provide heat to run absorption chillers.

I can’t remember the show but instead of sand they froze a like a 4’ square box of water at night when energy was cheap to help the a/c during the day. Pretty sure it was a library or public building and in California

One thing that is really hard to quantify is the cost to downstream users. The beauty of batteries is that users all already are set up to use power. If you want to bring a huge sand battery to share heat then every home or business needs to be set up tp directly use heat. Perhaps that happens in some areas of the world - but none that I know. Also, how much heat would be lost in distribution? How much would it cost to prepare infrastructure to move around that much heat without huge losses? So many more factors to consider! Thanks for the good video and view of something new!

A cold battery is know as ice storage which has been around for years. They used to be recharged at night when electrical rates were low. Now they are recharged in the day and are depleted at night when there is no cheap solar to power HVAC equipment.

Interesting tech. BTW heat can power refrigeration too, look up propane powered refrigerators

I have been using sand batteries for 4 years in a greenhouse it works responsibly good. I use a solar collector in a circut using pex pipe. I’m considering using solar to run heating elements so I can obtain higher sand temperatures.

I have heard of building techniques that regulate temperature by piping to areas far below surface. It also reminds me of traditional kim chee making where they bury jars of veggies to ferment at a constant temperature underground. This seems like something that could be very useful if integrated into new home construction. Not sure about the safety concerns living over a heat storage but I see potential.

Hot and cold sand batteries? Now you’re getting into some interesting territory here. You’re also going to be able to collect condensation for drinking water in such a system, because you need hot and cold to absorb water from the air. On top of that you’re using excess energy that would have been wasted to get it. Pushing the idea further with more tweaking and you have a steam engine that barely runs out of water and fuel and has the potential to become an engine that runs on the atmosphere around it.

I like your idea about using it to cool as well. It sounds like you are thinking of having more than one temperature bank. You could draw heat from one for your heating needs and sink heat to the other for your cooling needs. Keeping strategic temperature ranges in each would allow you to use passive heat transfer for most applications. At the lower temperature ranges you could also use hydronics for a passive transfer medium, and heat pump for active transfers. It would be interesting to see what the net difference between heat needs and heat waste is in our homes. If we had staged temperature batteries we could capture waste heats and use them to preheat the thermal medium in the higher temp stages so that they require less energy. Heat Needs: Dryers, Stoves, Ovens, Water Heaters, Home Heat - Air, Home Heat - Radiant Floors, Side Walk Snow Melting Coils, Roof Snow Melting Coils, Swimming Pools (maybe not in San Diego, but up hear in the North), Green Houses, Cold Lithium Batteries, etc. Heat Wastes: Fridges, Freezers, Chilled Water Dispensers, Air Conditioning, Freeze Dryers, Green Houses, Hot Lithium Batteries, etc. I'm thinking three to five stages, one really hot, and two at the opposite ends of the useful heat pump temperature spectrum. Perhaps two more, one at the freezing and boiling point of water, since it is probably the best passive medium. That would complicate the waste electrical power side of the equation a little bit more, but I wonder if it is worth it. I think of two exotic waste cases. The fictional Stillsuit worn on Arrakis (I loved that episode by the way), and the intricate thermal management of a real Tesla vehicle. Questions: 1. It sounded like you were saying that they use sand as insulation too, which makes me wonder if we use much better thermal insulation, how long do you think we can we store heat. Can we save passive summer heat and use it in the winter? What about the opposite, save the absence of heat from the winter to sink heat to in the summer? 2. What are your thoughts about using deserts and glaciers to moderate the climate on mega scales? For instance, what if we tugged a huge iceberg from one of the poles to the California coast and moved the ice inland to Death Valley. It could take several years to complete, but the resulting ice melt would be inland where it is desperately needed, while lowering temperatures and not raising the sea level. (I got this idea from the movie: Brewster's Millions) I'm waiting for you and Matt Ferrell to collaborate on an episode. You, him, and Grady Hillhouse produce my favorite channels.

I love the idea. There is also company called Caldera. They were doing 'smaller' sand batteries called WarmStone - sand sealed in a vacuum chamber. 2 tons of sand +500C deg and insulation of that void was so good that you could touch the battery with hand. They wrote that you could use it in your house heating system for even a month. They abandoned this product for homes and shifted to store and deliver heat for brewery and other big companies. The thing is this requieres 2 things. Hight class materials - heating elements, prepared sand without moisture, very good insulation - that vacumm was a sweet spot, but its hard to manufacture alone, so you need to build almost like a new house with ceramic coating and thick insulated walls. Secon is amount of sand - something like 10 tons should be a good starter. Plus good pumps, pipes, sensors etc. Then good plan to take that heat out and plut into waterboiler and floor heating system etc.

This reminds me of Sam Altman's investment in Exowatt (thermal storage). Maybe additional efficiencies can be garnered from heating and cooling. Data centers generate a lot of heat. Cogeneration architecture, dealing with electricity and heat.

Based on what you said in your video on a 100-ton sand battery heating 100 homes in Europe, an average home would only need 1 ton of sand to heat that home. One ton of sand equals 22 cubic feet.

This idea can be home make easily !!

One company which produces absorption chillers, which perhaps is still operational is ´Carrier Ibara ´ based in Japan.

This brings up a question for greenhouses in the winter. Would it be better to have a separate sand battery to heat the greenhouse or would it be better to integrate it into the flooring cement the greenhouse? And would it be better just to run pipes within the sand battery to increase the floor heat or would it be better to use a heat exchanger to heat the air?

A cold battery makes a ton of sense. Use a ground source heat pump to cool large sand battery. Run a hydronic loop through the battery to your fan coils using a mixing valve to control the temperature of the water. You would want to cool the battery down as low as can be done efficiently by your heat pump. And size it to last overnight on your hottest night. The hope would be that your solar array would be enough to charge your DC batteries and cool the sand battery far enough to make it overnight. This is made easier by the fact that the hottest nights are generally preceded by the longest sunniest days.

1 huge advantage is that a sand battery, if done right, can hold temperature for many months, you can charge it in the summer and heat your home in winter with it, when solar is at its lowest output.

It's fascinating how sand's ability to retain heat offers a sustainable and scalable option for energy storage. 🔥

I grew up in the 70s in a house in Albuquerque that had a Gravel storage system under the house, for our active solar system on the roof. And then Reaganomics came along and threw out the solar incentives, and we lost all that

Maximizing efficiency is great, but economics still rules. If a sand battery can be built, on a per watt basis, for some fraction of the cost of a Li-On battery, then it is going to have an advantage, even if it only has a 65% roundtrip efficiency. This sand battery technology also would seem to have a big advantage for longer duration electricity production than a Li-On battery, which could prove to be useful for overcoming longer lulls in renewable energy production.

Ammonia cycle refrigeration would work great with this sand battery system.

My only question is this: What kind of sand do the batteries take? For example, does it take rough/course sand that is used in construction and concrete or the fine and smooth sand from oceans and African deserts?" If it’s the latter, could that help reduce brine from our oceans when we desalinate our waters? . I figure this product of theirs would incredibly valuable if it contributes to solving this problem of Brine.

You state that this wouldn't work very well during the summer (other than your "cool battery" you mention later on). However, this would work great in the summer as well for "passive" cooling. Using a large radiator of sorts above the home, create an updraft through the home cooling from conduit that's in the ground. Even if not using it to "directly" cool the home, use this cooler air as the ambient "outside" air for an airconditioner to transfer heat into out of the home, making the aircon far more efficient. The pumping would almost be not needed for this type of loop as convection would keep hot liquid at the top of the draft tower/vent.

Regarding you comment of heating with natural gas at the end of the video. I'd like to clarify for you and (moreso) others who may not realize that the US (i I'm assuming that's where you live. I do) obtained approximately 40% of it's electricity supply from natural gas in '22 and even more in '23 (43%) that's excluding the additional almost 20% from coal. Renewable sources only slightly outpaced that. (21%) I'm 100% with those trying to get us toward renewable energy sources. We've made great progress but we have to be cognizant of where we are right now and the trade offs of the future. It's good to know where we sit.

Have you been to Minnesota in January? I think we get cold too. Can you do a video on how district heating works? Have US communities tried district heat? I feel like the energy and HVAC industries have us convinced that it’s not a good investment.

Sand batteries are a good idea, a simple and cheap method of storing heat in the warmer months for use in the winter months by making use of surplus green energy, this would be ideal for North America/Canada, Northern Europe including Russia, and northern Asia including China to see them through December, January and February. But given the amount of sand required, I would view it as impractical for an individual home, but if you are building a street of 30 houses, it could make sense to scarify one plot for a big sand battery (which could at least have the facia of being another house) and be capable of suppling heat to the other 29 houses. It would definitely make sense for large buildings, like schools, hospitals, office blocks,Apartment block and shopping centres, although it could be argued that in a city there would not be enough space for a large sand battery, but what if the ground floor of any large building was to become the sand battery, and human activity were to start on the first floor, in a similar way the ground and first floor of a multi-story car park could be filled with sand to provide heat to surrounding buildings, alternatively you could bury the sand battery underground, but if a maintenance issue required you to empty it of sand this would be complicated. There might even be a case for sand batteries to be situated next to the junctions of main roads, like crossroads, roundabouts, or sharp bends, anywhere were braking or cornering takes place, a sand battery could provide under road warming for 100 yards either side of a potential hazard point, just enough to prevent ice forming. there is a growing number of places using district hot water systems to provide heating, may be there is the opportunity to combine an underground hot water reservoir heated by surplus green energy as district heating, and supplement that with an above ground sand battery also heat by surplus green energy I am reasoning that a properly insulated sand battery should hold on to its heat much longer Than a water reservoir, and would therefore be used to top up the hot water reservoir right through to the end of winter, with out having to rely on a fossil fuel back up, by thinking on multiple levels, you could get double the heat storage on the same ground area.

Hmm a cold battery... nice!

Cold battery is an interesting idea. But for that you could use water, the phase change of going to ice would store a massive amount of energy, much more than you could get with an equivalent volume of sand without going to super low temperatures which would kill efficiency.

Check out Batsand for a domestic solution when you come back to this. Also Antora, both for their high temp heat and also their interesting IR PV heat to electricity solution.

Very interesting 🤔

Great topic. There have been many “batteries” like this. Simply a means of storing energy. The real killer app will be the super capacitor. The ability to store massive amounts of energy quickly could change everything. Imagine a super capacitor connected to a sand (heat) battery. Theoretically one could capture lightning instantly and then feed that into the sand battery. Then draw the energy out in a controlled fashion from the battery. It’s only a question of figuring out the materials and methods. Definitely not simple but it is physically possible

yeah sand sounds very lightweight haha at least we could also use them under our doors during floods

Peltier devices would pair nicely with sand storage. Efficiency would be awful but no moving parts for maintenance. Heat one sand battery and cool another during surplus and then reverse for generation

I like geothermal for cooling and heating. Ground is a great medium.

Sand batteries would be great for domestic applications. They could be located under a driveway or garage and provide a hot & cold geothermal sump/source for heat pumps. Heat pump COP could be boosted significantly with this technology. It would be ideal for continental climates - hot days/cold nights. We have to get smarter with pumps and thermal distribution generally.

I live in L.A. and love the idea of storing cold in a sand battery. Couldn't I build it under the foundation of my house?

It is conceivable that the stored heat from a sand battery could be used to generate electicity by means of a stirling engine.

There are cooling systems that work with heat. Refrigerators that work with propane gas and do not have an electric compressor are an example. In summer you can use the heat of the sand to cool Using an air conditioner with technology similar to old gas flame refrigerators

Hello. I w recently learned a lot about the TESLA baseless turbine. I honestly think it is viable, needs 2024 engineering. Some great content online about it and I can see you making a great video about the possibilities.

When are going to do a video on tidal & ocean current power generation?......

2:30 can't we redirect the demand better so it can be used for energy intensive processes? 2:52 i just wondered why there are no Solarpanels on the roof?

Good evening all. I like the cold storage concept and I wondering why one would spend money for a sand storage facility instead of going directly to Geo-thermal storage? One will still need battery storage to run the systems without grid assistance. How big would a sand storage system need to be to to keep 100 square meters of your home, home X in location Y, comfortable throughout the year? I am embarking on a massive home remodel in California, and heating without Gas is starting to look like an excellent idea. Thanks 🦊Riki2Tails

Consider a geothermal heat pump system with a large ground pipe heat loop that works as AC for cooling in the summer hot, or for heat for warming during the cold winter / effectively treating the ground & heat loop as a geothermal battery energy buffer, thermal capacitor if you will //

The large capacity for storing heat comes from the max temperature, which is easy to achieve through resistive heating coils. But on the cool side, it seems to me that you would have to get much colder than freezing to have a similar cooling capacity. Is there technology that can achieve very cold temperatures efficiently with electricity? On the topic of usefullness if used only for heat. I remember a video on this topic that mentioned very northern locations that don't get much sunlight in winter. The heat battery was useful there because they could be heated during the summer, and would hold their heat for months into the winter.

How about using absorption chillers to cool the home during summer?

Wait, why are sand battery silos built upwards and not downwards (into the ground)? Wouldnt that help with thermal insulation?

People have been doing this stuff for decades. Heating their ground with solar energy during the summer and using that energy during autumn and winter. And the opposite during summer. Without heat pumps.

There's companyies like Potters Industries that could help make it cheaper by using Glass Sand.

Sand battery powered Tesla... coming soooon! Oh yeah 😎

When it comes to heat energy storage, besides cost of the storage medium, volumetric heat capacity is an important consideration. For instance silicon dioxide has a 1.855 J/(cm³*K) But sodium chloride is 9.04 J/(cm³*K). This means sodium chloride can store more than 4.5× as many joules of energy for each degree of temperature rise in a cubic cm. Yet both cubes have the same surface area to lose heat over. In other words, for each joule a cubic cm of silicon dioxide stores, a cubic cm of sodium chloride rises in temperature by less than 1/4.5 that of the silicon dioxide. And how fast heat is lost given the same surface area and insulation is proportional to temperature. Bulk sodium chloride and sand have similar cost so per cubic meter, so its volumetric heat capacity should take on a more important role in consideration.

Solar Roof PV directly into the AC chiller pump fan system means that when the sun shines heating the building the most, the AC working hardest, all the solar PV energy used directly without being stored in batteries, especially with micro-inverters on the PV panels making AC directly in each panel //

Please review BLOOM BOX technology.

As you say, the Norwegian sand battery rose to prominence a couple of years ago in the youtube community so sorry to sound grumpy but this old news. A follow up on that project might have been interesting.

Like the balanced view, heat batteries are just one more tool, in the energy storage war. Simply right tool for the right job. Sand batteries would be great for heating pools in more tepid areas The other major benefit is life span compared to lithium and that really comes down to the quality of piping , heaters and fans, The sand isn't a wearable item in the equation.

So why not use an inverter to boost up the power on either end?

LHTPV batteries have some benefits over sand. For one, it's electric energy in and electric energy out.

When people picture sand spread across idyllic beaches and endless deserts, they understandably think of it as an infinite resource. But as we discuss in a just-published perspective in the journal Science, over-exploitation of global supplies of sand is damaging the environment, endangering communities, causing shortages and promoting violent conflict. Sand is not the answer as it is used in so many everyday projects in economies around the world and numerous countries are already in short supply. The negative consequences of over-exploiting sand are felt in poorer regions where sand is mined. Extensive sand extraction physically alters rivers and coastal ecosystems, increases suspended sediments and causes erosion. I suppose the west could replace it with the garbage they produce to replace the sand; which of course would never be called exploitation of the poor and lead to world wide social unrest.

A good question, if Sand is good at asorbing heat, using a water sand radiator would actually help remove heat from water more efficiently, allowing for computers water cooling system to work more efficiently, this could also be used in Data Centers where the heat from all the computers could be pumped into the sand allowing for cooler computers in the data centers lowering the cost of air conditioning in the building. I might try a small scale water, sand cooling thing for computers to see what would happen, it would most likely be a double radiator, where you take fans and blow the air through the water pipes to that gets blown out through the the air, but instead of the last part of it transfering to air what if you have the water pipes transfer it to sand, and than transfer it to air, which can hold alot more heat than air can.

If you want to store cold, liquid nitrogen would probably be better because of the phase change (14:40). You're also have an absolute limited of 300 degrees of temperature difference because it's impossible to store below absolute zero.

I keep hoping to see a solution that can do "seasonal" energy shifting, not just "daily". California has a surplus of solar power in Spring and Fall, but we have no practical way of saving this for Summer and Winter. Batteries are too expensive. Sand seems the same. Hydrogen generation is very capital intense for such relatively low annual usage. Ideas?

This tech is extremely scalable. Too good to be true.

The best seasonal thermal energy storage is a tree. There grows lots of waste trees where the winter is cold. Then you need an oven or why not sandbattery to store the heat for daily rate. Sand battery is very nice in that it can be extremely hot. It is pity that smaller object will have a higher surface area to volume ratio compared to a larger object with the same shape. But if it is free to heat it to 700C using for example wind turbine could it replace the oven? In some farm environment it would be feasible to build 5 times bigger sand containment structure than a standard oven. But stil oven is super practical.

we've been hearing for years now that the world is running out of sand. It might be everywhere but the one that can be use for construction is quite scarce now and it seems it's the same for this. So we can forget about that advantage, luckily this tech has many others

Maybe there exists some sort of a substance you can add to sand batteries such as brine they extract from water desalination. Is it possible to use some sort of quantum dots to enhance sand batteries?

Some great ideas in these comments

You need some heat in warm climates as well to heat up your warm water, unless you like to have cold showers.

Still, even at a 30% loss when converting the heat into electricity, if the energy you've put into the sand battery would otherwise be energy you've lost because you'd had to stop wind turbines then that is a pretty good start. obviously if you have a local wet heating system and it is easy to hook into that the use that.