Absolutely superb. The 'hot bricks in a box' concept of very high temperature thermal energy storage has been really coming into its own with the fall of solar PV costs, and it's quite suitable for industrial consumers of medium temperature heat. There's also a heated granite storage silo in Scandinavia that's recently gone into operation. The rate of heat transfer in the heat storage material is a classic constraint.
I think this niche of 'very long duration, very constant slow rate of discharge' is clever, and it would suit industrial heat consumers but could also suit district heating for buildings in a climate that's predictably in need of heating all winter long (Canada for example).
They seem to have a decent grasp of the fundamentals, both of the technology and how to commercially carve a niche. I wish them well, and thank you for the post.
I have a home in the southwest that is off grid and runs on solar plus lifepo3 batteries. It has been 5+ years now. My cost per kwh is below $0.008 as of today including all capital and maintenance. These numbers get a bit complicated, for example I run the AC much colder than I would if I was paying more for it. I have extra fridges and freezers I probably wouldn't if I had to pay higher per kwh. I "throw away" a lot of power too that I am not counting when the batteries fill up.
I have about 40kwh of storage. The batteries are in steel boxes and there are some basic precautions to take with them but lifepo3 has a very manageable risk profile quite different from lipo. Batteries and solar equipment continue to get cheaper, the same system I have is now 50% cheaper today then when I bought it, including tariffs.
The link really discusses more of a single neighborhood or medium industrial site possible type of technology. Really just a huge very hot pile of sand and steam turbine or propane cell generation. On a kwh basis it is probably not competitive with solar+battery unless your use case involved a lot of direct use of hot water or heating something.
They skipped a few real competitors that'll shrink their market:
1. In places with underground water reservoirs, these can be used for heat storage very similar to this. It's location dependant but I think there's European district heating networks doing this already.
2. Heat pumps for process steam are gaining ground. The temperature at which heat pumps lose competitivness is slowly rising over time. They mention storage at 600C. Heat pumps win under 80C and are up to 160C and aiming for 200C though at those temps cheap gas will probably win for now. Heat pumps can also recycle process heat and cool and heat at the same time.
3. Wind doesn't get mentioned. Wind doesn't pair as neatly with batteries as solar does but in places with seasonal storage issues the batteries can be used for solar and wind during summer and wind plus whatever (biogas/nuclear/hydro) in winter. They need to worry about both centralised big batteries and customer sited ones.
In general I'm supportive of the idea, but similar to the Nordic sand battery, when they start talking about generating electricity from the stored heat I take that as a signal that they've realised the alternatives above combine to really squeeze the market they have left and undermines my faith in the rest of the product.
Yeah, Form Energy exists to basically disprove this:
Batteries will still be too expensive to arbitrage these seasonal differences effectively. Thermal electricity storage is orders of magnitude cheaper for storage, but worse at daily cycling
Form, like the authors, agrees that Lithium-ion is great for intra-day cycling and not suitable for is seasonal storage. Unlike the authors, Form believes it can engineer chemical storage with the requisite properties. Form’s batteries have something like 10 days of capacity relative to the size of their inverters.
Form's basic idea is that low round trip efficiency can work as long as it's cheaper enough.
They've always had $20/KWh as a notional price but there's already talk of Sodium batteries in China getting near that price point, while having nearly double the round trip efficiency.
...if you want to take your chances with cheap junk in a safety-critical application. I watched about 3 minutes of that video and the number of issues that guy ran into was disturbing. You'd have to be nuts to put that thing in your house.
I am in no position to install a battery system, but if I were, I would definitely build a little cinder-block shed to hold the array. Offset that a good distance from standing structures and instant piece of mind.
I'm not knowledgeable enough to know whether or not this will cause a perma-fire in my home. I wouldn't even know where to begin to determine whether this is a death trap or a great deal. I'm leaning towards the former
Please do not give that guy more exposure than he already has, his advice is going to get someone killed one of these days. He knows just enough to be dangerous.
I would strongly disagree. Inexpensive batteries are everywhere now - this is the work of market forces, not some guy on Youtube - and he's one of a handful of people who you can trust to do an honest dissection of a battery. You don't have to be a rocket scientist to check for a handful of basic safety features and characteristics, which is more or less what he does.
Given how many years of experience we have with Will Prowse, it would be helpful if you could elaborate a little on why we should trust your opinion more.
I've done a lot of spreadsheets on this kind of solution, but on a slightly smaller scale: a single family home. While it will work for a while it is not enough to meaningfully offset the seasonal cycle which is the thing that needs solving. Storing energy for a few days up to two weeks is (relatively) easy, storing it cheaply for up to 6 months is very hard unless you are willing to invest massively offsetting much of your savings. The pile of rock required to heat an average home for a couple of weeks handily outweighs the house itself. And that's without a double conversion, it is used and stays as heat, the idea was to moderate the leakage upwards as a source of heat by blowing air in a controlled manner rather than to convert it again.
So I really hope these guys will succeed where I can't even get it to work on paper, sometimes scale really is a requirement to make something work and this could very well be one of those.
Isn't it cheaper to just buy more panels, enough to meet your winter needs? Then who cares if they sit mostly idle for most of summer; energy not used is harmless.
Then your storage model becomes "a cloudy week" rather than "a whole season", and the storage scale changes significantly.
This is certainly the solution in somewhere like Australia where the winter production is about half of the summer production. It gets more problematic in places further north/south where its 5x or worse and then you need quite a bit of land to produce enough power and battery storage than can go multiple days at least.
The difference between net zero across the year and 95% unlikely to need the grid on solar and batteries is a staggering difference, about 10x the panels and battery storage. But the equation changes drastically depending on local weather patterns and the solar irradiance difference from summer to winter.
No, (1) you need too much space and I'm pretty much maxed out already (50 panels), during the wintermonths (2) the angle is really bad, (3) the days are shorter and (4) you're overcast a lot of the time. So that simply will not work. But in the summer I have so much excess I get penalized for it, which is ridiculous.
In almost all cases you lack the area for doing that. And that's not even considering exposure, as in winter most north facing panels on a roof won't get any direct sun because it's lower on the horizon
Panels are surface area limited. The maximum my house and land can support is the 10kW I already have.
Honestly I'm pretty skeptical of residential rooftop solar - it's not even close to the solution, it's just a cost optimization we shouldn't actually need.
Depending on your case. Where I live (NYC, a barebones Great Depression-era building) my electric bills skyrocket (3-5x) in the summer due to the house being heated by the sunlight. The roof is white, but it helps moderately. Heating in the winter takes much less energy, especially if we factor in all the electric devices inside that also release some heat.
Storing a half-day's worth of electricity, and powering stuff from a solar panel at daytime, would likely let my apartment stop consuming external electric power in the summer.
Assuming my apartment consumes no more than 15 kWh during the hottest days (according to the meter), a moderate 8 kWh battery, and $1000 worth of solar panels, would suffice, given the room and a permission to mount the solar panels somewhere.
> The pile of rock required to heat an average home for a couple of weeks handily outweighs the house itself.
Maybe I'm failing to follow the intended argument here, but I do not see what is expensive about this. Houses are hollow; they do not weigh all that much. Dirt is cheap, especially when sourced locally.
The only place where you could conceivably store this without having another conversion or lossy transport loop is under the house. It's not exactly trivial to excavate that much space under an existing structure without having the whole thing come down. I think I've figured that part out but it would still be legally quite shaky and it might destroy the resale value of the house unless it can be made compact enough that it would fit within a standard basement. Insulation is the key problem to solve here.
I only looked at this from the homeowner perspective as a DIY project, but if I were to look at it from a utility scale commercial perspective I'd say the first thing I'd do would be to compare it to wind power because where I live that is probably one of the most efficient ways to generate renewable energy even if there is no storage option. It nicely dovetails with solar. When I did this at the residential scale in an off-grid house I built I managed to get it - fairly easily - to the point where we did not need a generator at all, even though we had one.
That depends on how hot you are prepared to get your rock.
I’m also off grid, also suffer in the winter (although a spot of hydro power is going to alleviate that somewhat), and have also thought about thermal storage - I actually calculated that a 20ft container filled with sand could give us thousands of kWh, as long as the sand could get up to ~600C.
At that temperature you of course have to think about making really damned sure no water gets in there, but it makes the volume of material more manageable. Would still work with resistive heating, energy out would be trickier but not impossible to engineer something that wouldn’t explode.
Insulation volume was the issue for me. Sand works well enough, the ideal setup would be - as far as I've figured this out - a sinkable construct that has insulation in the bottom and the walls that you can put together in a modular way by slipping one part after another into a basement. Then you sink it in the same way that you sink a well. Indeed, keeping water out of it essential but you can test where the water table is and keep a very healthy margin. The 'instant steam explosion' angle in case of a water leak in the house is one of the reasons I've never actually done it.
Snow load is not mentioned when using horizontal panels. In higher latitudes, solar is relatively uncommon because of the sunlight deficit in winter. Panels that are deployed are usually placed at an incline equal to the latitude (or even vertically) to capitalize on free snow shedding and to regularize/maximize year-round minimum output (i.e. bring up winter by bringing down summer). Mounting solar panels flat is sensible from the standpoint of this technology (no solar output needed in the winter, that's what the storage is for!) but may be breaking a lot of ground (and panels) with horizontal panels in snow country.
Energy storage yes, electricity storage no. Very limited utility and questionable use of solar PV, which has about a 20% conversion efficiency of solar energy to electricity. Seems like a lot of extra steps to make heat.
One of the biggest uses of residential energy is heating/cooling. Especially in winter months where PV generation is significantly lower (I have seen numbers of 2-5x summer generation), having "free" heat could be quite valuable.
Now, do the economics shake out for storing heat to deliver in winter? No idea, but the idea is not far fetched. Outside of bitcoin mining, there are few uses which can soak up the increasing glut of midday PV generation. Anything that can seasonally store that (even at terrible efficiencies) is valuable. What is going to be the most economic option? No idea. My personal bet is iron-air batteries, but there are a lot of contenders in the space that are competing for widespread adoption.
Readit News
I think this niche of 'very long duration, very constant slow rate of discharge' is clever, and it would suit industrial heat consumers but could also suit district heating for buildings in a climate that's predictably in need of heating all winter long (Canada for example).
They seem to have a decent grasp of the fundamentals, both of the technology and how to commercially carve a niche. I wish them well, and thank you for the post.
I have about 40kwh of storage. The batteries are in steel boxes and there are some basic precautions to take with them but lifepo3 has a very manageable risk profile quite different from lipo. Batteries and solar equipment continue to get cheaper, the same system I have is now 50% cheaper today then when I bought it, including tariffs.
The link really discusses more of a single neighborhood or medium industrial site possible type of technology. Really just a huge very hot pile of sand and steam turbine or propane cell generation. On a kwh basis it is probably not competitive with solar+battery unless your use case involved a lot of direct use of hot water or heating something.
Dead Comment
1. In places with underground water reservoirs, these can be used for heat storage very similar to this. It's location dependant but I think there's European district heating networks doing this already.
2. Heat pumps for process steam are gaining ground. The temperature at which heat pumps lose competitivness is slowly rising over time. They mention storage at 600C. Heat pumps win under 80C and are up to 160C and aiming for 200C though at those temps cheap gas will probably win for now. Heat pumps can also recycle process heat and cool and heat at the same time.
3. Wind doesn't get mentioned. Wind doesn't pair as neatly with batteries as solar does but in places with seasonal storage issues the batteries can be used for solar and wind during summer and wind plus whatever (biogas/nuclear/hydro) in winter. They need to worry about both centralised big batteries and customer sited ones.
In general I'm supportive of the idea, but similar to the Nordic sand battery, when they start talking about generating electricity from the stored heat I take that as a signal that they've realised the alternatives above combine to really squeeze the market they have left and undermines my faith in the rest of the product.
They've always had $20/KWh as a notional price but there's already talk of Sodium batteries in China getting near that price point, while having nearly double the round trip efficiency.
LiFePO4: safe, unless you crack them and ignite the liquid with a blowtorch, or something.
Deleted Comment
So I really hope these guys will succeed where I can't even get it to work on paper, sometimes scale really is a requirement to make something work and this could very well be one of those.
Then your storage model becomes "a cloudy week" rather than "a whole season", and the storage scale changes significantly.
The difference between net zero across the year and 95% unlikely to need the grid on solar and batteries is a staggering difference, about 10x the panels and battery storage. But the equation changes drastically depending on local weather patterns and the solar irradiance difference from summer to winter.
However the mounting systems, solar charger controllers, and inverters are mostly not.
The bulk of the cost of panels now isn't the panels themselves, but all the supporting infrastructure.
The seasonal variation can be as high as seven to one, so the total install has to be very very cheap to support a 700-1000% over build.
Honestly I'm pretty skeptical of residential rooftop solar - it's not even close to the solution, it's just a cost optimization we shouldn't actually need.
Storing a half-day's worth of electricity, and powering stuff from a solar panel at daytime, would likely let my apartment stop consuming external electric power in the summer.
Assuming my apartment consumes no more than 15 kWh during the hottest days (according to the meter), a moderate 8 kWh battery, and $1000 worth of solar panels, would suffice, given the room and a permission to mount the solar panels somewhere.
Maybe I'm failing to follow the intended argument here, but I do not see what is expensive about this. Houses are hollow; they do not weigh all that much. Dirt is cheap, especially when sourced locally.
As an investor - what RoIC do you want to see when doing initial analysis
(for example, $10M capex per system, with 10,000 systems TAM )
I’m also off grid, also suffer in the winter (although a spot of hydro power is going to alleviate that somewhat), and have also thought about thermal storage - I actually calculated that a 20ft container filled with sand could give us thousands of kWh, as long as the sand could get up to ~600C.
At that temperature you of course have to think about making really damned sure no water gets in there, but it makes the volume of material more manageable. Would still work with resistive heating, energy out would be trickier but not impossible to engineer something that wouldn’t explode.
Now, do the economics shake out for storing heat to deliver in winter? No idea, but the idea is not far fetched. Outside of bitcoin mining, there are few uses which can soak up the increasing glut of midday PV generation. Anything that can seasonally store that (even at terrible efficiencies) is valuable. What is going to be the most economic option? No idea. My personal bet is iron-air batteries, but there are a lot of contenders in the space that are competing for widespread adoption.