This also solves the spillage issue, and doesn't have the potential to poison local soils because the stuff is solid. Although, you have to wonder what benefits sand has over local earth given that you don't need to excavate anything to do traditional, residential geothermal storage.

Water ingress is a huge issue for below-ground-level structures, so it really isn't as straight-forward as one might think.

Going up is cheaper than going down.

I get your point and it does have merit. But by the same logic, the efficiency of the renewable power source wouldn't matter either. Looking at it in reverse, a lower round-trip efficiency means lost power that you wouldn't lose if you used a Li-ion battery, improving your energy independence.

@@ipp_tutor Yes, but With Sand batteries you don't have to Ramp up production on Li, Cobalt, Manganese, and every other substance we would need to electrify everything and keep pumping out Batteries. The cost of mining, transport, pollution, discard, recycle of any Chemical battery (even if we switch the Na instead of Li) will Always be more than building a Big insulated tank and filling it with sand.

Better than nothing is often the wrong way to go. Also t here are far superior media than sand, and quite inexpensive as well.

​@@jonjohns8145Why not just convert excess supply into hydrogen injected into existing natural gas system with a capped limit where safety wouldn't be an issue.

Exactly

They have been called "heat stores" for decades. Some people in hot climates pump the hot air from their roof spaces during the day into a bed of rocks under their houses to use as heat during the night. Pumping air is very cheap, and rocks are excellent thermal stores. Others use 'trombe walls' to the same effect either storing energy in the wall, or a rock bed underneath. Trombe walls can also cool houses!

Battery? Do these stores electricity?🤔🤨

People do but it is harder than it looks. One can use a water-heater's thermal element (electric backup element) for heating it up, but getting the heat out of the sand battery is actually not entirely trivial. Basically you need something that can tolerate the heat and you need airflow to get the heat out again. An open-ended steel pipe with a fan on one end to push air through, and then some fins (like a piece of a radiator) to disperse the heat in the air because you don't want a blast of hot air at 500C. Regulating the output is the hard part. You can't just duct it to the house (not at 500C). One mistake and the whole house burns down.

On most videos you'll see on the subject, there's usually a lot of physical effort involved, and it doesn't really last past half a day. They work, but there's a human in the loop, and it's not a small part. An electrically-heated sand battery might require less effort, but there's usually not a reason to do that unless the electricity isn't coming from the grid, otherwise, you might as well turn on your normal electric heater. So far, I haven't seen anyone do anything beyond a proof of concept or proof that it works for the room they intend to heat. Also, almost none of them do any sort of heat regulation, but that's usually because they're trying to heat a large room as quickly as possible. I've never seen one try to do a hot water system.

We have water batteries here in Germany. It´s just a huge insulated water tanks placed underground with a coil in it and some plumbing. Solar energy during the summer is being stored all the way up to the winter. It´s overall efficiency is better than with Li-ion batteries and it´s cheaper. Doesn´t get as hot as with Sand but is cheap and works.

I live in the desert southwest of the US, and that would be a wonderful application for our region. PLENTY of sun here, even in the winter. Such a system wouldn't have to be huge (as Ricky stated home systems would need to be) as our heating requirements are modest through the winter months. Even so, we do *have* heating requirements, as well as the need for hot water (of course). I would love to have a system like that for our home.

This is already being done here in Germany with water heat storing tanks. Also good thinking on your part. It´s efficiency is fantastic because sun energy is abundant in the summer and it´s used in the winter.

Most uses with the heat pump are indoor-outdoor, but if you create heat-cold storages, then it might be more effective when the indoor-outdoor temperatures are less extreme. Also, if you have solar panels on the roof, you might want to cool them by bleeding the heat off and directly into your storage system.

Cold batteries are already in use. There is one under Helsinki, a huge pool of cold water, and it's a part of a pretty extensive district cooling system. They have also district heating but the cooling system is also quite widespread and has been there for 20 years.

I've also seen an old ice house design from somewhere in the middle east, where they can't just store the ice. It used the expansion of air descending through a chimney into a larger chamber to make ice. My father used to work at a historic cliff dwelling in New Mexico where that mechanism occurred naturally, keeping the caves at about 65 F even when the temp outside was in the hundreds.

Actually yoy can get cold from heat since fridge works on heating and gasifing things.

@@Nurk0m0rath For the cooling chimney, what's the process which does the cooling and is that cooler air just becoming the ambient air for their living area? It's not stored anywhere of course.

@@markhathaway9456 I'm no physicist but I understand the cooling effect is created by reverse compression. When the air is drawn into the chimney (or cracks in the cliff) and compressed, then hits a larger chamber, it slows and expands, becoming colder. I'm none too clear on the details of how it works though. I've been trying to remember where I saw that design and the closest I can think of is that it might have been in one of those features about ancient advanced technologies.

That can be a medium for storing heat in a system with a heat pump. Whether something natural like stone would be best for a cold storage isn't known to me, but natural safe materials at temperatures which don't explode, even when water is applied, would be great.

Totally

That's the biggest "gotchya" to this entire discussion...GSHP (ground-source heat pumps) are already better than the best sand batteries. The sun already heats the earth, such that the energy needed can be moved around (through heat pumps) to warm and cool your home, as needed. With that work done, heating water with a heat pump is also very easily done. My home has an air-source heat pump and hot water heater with a heat pump on top of it. My summer vacation place is going to use a ductless mini-split for all the same reasons. The sand battery is going to have limited application for metro areas with existing hot water radiator networks.

I think data centers could give the heat to a local central heating system?

you would need a way to be pulling the heat out of the batteries at least on average at the rate the heat is being put in, since the data center heat output would be fairly steady and it doesnt need any of that heat back. buffering in sand batteries might let the heat be coupled to consumers better.

Data centers already recycle waste heat to some degree. The real problem though is that the "heat" you get out of a data center really isn't all that hot, and it is really really difficult to extract useful work out of something that isn't all that hot.

I'm pretty sure you'd quickly run into huge losses if you try to run very hot or very cold water through long runs of pipe. A city-wide system would (I surmise) have far greater losses than using heat pumps for individual freezers and water heaters. Industrial freezers (and heat pumps generally) are already extremely efficient. With a good modern unit, you get about 3x more cooling than the amount of energy you put in. This is because heat pumps MOVE heat, rather than generating it.

Check out videos on using a Rocket stove to make and direct the heat you want to store.

Agreed!

@jxpat watch this video

This is totally doable, though if you have access to the grid the easier dump is to just throw it onto the grid with a cheap micro-inverter. In your case, however, I would spend the bucks on adding more main battery storage to improve your overnight margin and give you some bad-weather bridging capability first, before worrying about energy dumps. One thing you are going to hit up against is, well, the weather. On hot days we have a ton of excess solar but no real overnight heating needs. On cloudy days or cold winter days we generally do not have enough solar so there isn't any excess to dump in the first place. That's a bit of a problem actually. One has to have excess production during the days or weeks where the dump can actually provides a useful service. -- In anycase, if you are going to do a dump I recommend doing it through a satellite battery instead of directly from the main system. That's what I do. I have a 48V main system (10kWh) and a small 24V satellite battery. I have a DC-to-DC which dumps any excess energy when the main system is full over to the 24V satellite battery. This way I can transfer excess energy at 1000W but my actual "dump" doesn't have to be 1000W, and I can control WHEN I actually dump to the actual dump independent of when the excess energy was being produced (which can be quite important actually). I then have a timer which turns on the actual dump from the 24V satellite battery at an opportune time for when the dump is useful. The actual dump device can be anything. It can be a sand battery, a small A/C or heat pumps, or a cheap little grid-tied micro-inverter if one has access to the grid, it can help the water heater, Etc. -Matt

Exactly It’s not a theory (any longer) but a proven solution that should be highlighted 🎉

And, how do they store it for long-term use ?

@@markhathaway9456 They store a heat in a large underground area all summer, and it stays warm enough to provide heat all winter. You can't easily insulate something this well for a single house, but you can for a neighborhood. (Heat escapes based on the size of the surface area but the total amount of heat/energy stored is based on the size of the volume.)

Even in the SUMMER?? Ok, DUMBBELL.

But the heat could come from concentrated solar which is 95% efficient at catching sun rays instead of 20-25% photovoltaic with also a lot less copper silver silicon etc

It could work, but get a “open-minded” mechanical engineer to do some heat loss heat gain computation, you’d need to ensure it doesn’t overheat ( which is a different problem, even in very cold climates) I did something like that but using earth tubes that were charged/ recharged and it worked fine 👍🏿

Thank you, Kori. I'll see how open-minded of a mechanical engineer I can find :) @@koriifaloju2051

There was one in Texas too, I think

Off hand, additional installation cost and maintenance access would probably be the primary reasons not to put the tank under ground. Digging/excavating a big enough hole can be expensive. If placed underground, you also might have issues with sinking, groundwater infiltration, seismic instability, etc. If there is any issues with the tank, maintenance and repair of the tank would be a lot more expensive and time consuming. Having said all that ... placing it underground might have some advantages, such as the tank being more insulated by the surrounding ground and other advantages.

Or just use the sand that’s already there

which is why it is more interesting to use the heat to generate steam to run a turbine to create electricity

Umm as mentioned in the video it can be used for district heating, so you have a plant that provides hot water in a given area, nothing needs to change in the infrastructure outside of the plant, sure if you're running your own heating that's not gonna help much but it doesn't mean there are no use cases where it doesn't fit in perfectly

Building codes. Most of Europe has district heating. Most of North America doesn't. If cities start planning to add this infrastructure, then you absolutely could see this in the future. Although most systems only change in response to scarcity or drastic disturbance.

In Alaska, they do use radiator/district heat. They also have underfloor piping as well as typical radiators.

Efficiency would be more than awful but I agree on the low maintenance. Efficiency is kinda the crux of the matter, though... if one is over-producing so much that one can still get something useful out of multiple stages of an extremely inefficient dump, its better to do something more direct with that overproduction than stuff it into a sand-battery.

My biggest concern is what do you do with it during summer? It's not going to take all summer to charge it. I live in a part of Africa where energy and electricity overall is very scarce. But it's also very hot here most of the year. Can really say it only gets cold 2 months of the year here. So my question is, what application is there during the other 9-10 months of the year. I'm curious to see how one could use the sand battery as an alternative to air conditioning

@@abarairenji4483 hot running water, no need to ever use a boiler or whatever again. But it's more catered to northern climates, that have 3-6 months of need for heating.

@@nikm3r true, hot running water would be an ideal solution. I was thinking of converting back to electricity. Yes you lose about 50% energy when doing this but considering it's in a region where the grid only powers about 35-40% of residents, I don't think that energy loss is too bad right?

@@abarairenji4483 it would really depend on how cheap solar + regular batteries vs solar + sand battery + turbine to turn the heat back to electricity would be in your area of the world. Do the math! I just saw your name btw, nice!

@@nikm3r hehe, thanks. Appreciate you taking the time to educate me a little. 👍

No reason for thermal coal, start there. Solar is cheaper now. "Natural "gas, which is methane gas was the bridge fuel of the 90s not today. If I had to choose nuclear would be our bridge fuel for electricity generation for now. Natural gas energy plants can be turned off and on for demand, thats one good thing about them. Keep adding local renewables which dont have to be transmitted so far.

LOL That would be a site to see!

I wonder how long a Tesla would go if you swapped the battery pack for an equal mass of hot sand. Interesting question

​@@ipp_tutorI'm an irresponsible stoner but my uneducated guess would be zero miles. > pulls battery out > pours 1000 lbs of scorching hot sand in car > FORGETS device to convert heat to some other form of energy Y'all need to go touch grass and go camping to learn the hard on how to properly think ahead.

65% rountrip efficiency is likely better than Hydrogen, which we should also be pursuing at scale. California already has a glut of renewable electricity during the day.

If the heat is coming from Photovoltaic panels those also have low efficiently. Would it be more economical to us evacuated solar tubes to heat sand, then use it for home heating and electricity?

@@ricza7345 Have you seen the latest hybrid solar PVT? The panels also run tubing for water serving two purposes. Cooling the panels(which dont like extreme heat) and heating water. Ive seen this idea used in Europe.

They are comparing apples to oranges here. The current project has no reelectrification step. You basically pay $60/kwh just for the heat storage capabilities, while the battery system returns electricity at $150/kwh. The system is too expensive for just heat, because you are paying more than just the renewable energy production, like grid fees and taxes. Even if the electricity price was zero because of taking overproduction, you would still pay 10 cents for getting it into the storage. You can turn 1 kwh of electricity into 4 kwh of heat with a heap pump. Here you convert 1 kwh of electricity to maybe 0,85 kwh of heat, after it was moved from the storage through the district heating and into your home.

How were the blocks heated? How long did they hold the heat? What were the blocks made of?

@@markhathaway9456 I can’t remember what I had for breakfast today so don’t rely on my recall from half a century ago but they were a cupboard full of heavy brick sized thermal blocks with electrical elements sandwiched within. Air was blown through holes and came out all toasty through floor grilles.

water is three times better and much cheaper, if you keep it below 100°C

@@stefanweilhartner4415 *if*, and at those temperatures you lose a lot of the efficiency because the greater a temperature difference between two things, the quicker the heat transfer occurs. If you want to have a line of 80 degree air coming out of the tank, it would take significantly faster to get to that temp running through 800 degree sand than 98 degree water.

@@Fenthule but i don't need it quick in the center of the basement of a house.

@@stefanweilhartner4415 Water stores less heat, can corrode the tank or spring a leak. For homes using rooftop solar power to heat the existing hot water tanks works fine already, but we are talking about grid storage here.

@@Fenthule Do you mean to say that the heat transfer is FASTER when the temperature difference is higher ? Or that it's FASTER with certain materials like water ?