212: Sand Batteries – It’s Getting Hot


Matt and Sean talk about using sand to cut down on energy storage costs.  Thermal energy storage is getting really hot now, but will it work for homes as well?

Watch the Undecided with Matt Ferrell episode, How a Sand Battery Could Revolutionize Home Energy Storage https://youtu.be/KVqHYNE2QwE?list=PLnTSM-ORSgi4dFnLD9622FK77atWtQVv7

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On today’s episode of Still To Be Determined, we’re going to talk about how the movie Dune is really about desert power. Actually, that’s probably far closer to the truth than any of us want to recognize. Welcome everybody to Still to be Determined, where we follow up on discussions that start in Undecided with Matt Ferrell.

I’m Sean Ferrell. I’m a writer. I’m a, I write some sci fi. I write some stuff for kids and I’m just generally curious about technology. And with me as always is my brother, Matt, who is that Matt. From Undecided with Matt Ferrell. Matt, how are you doing today?

The spice must flow, Sean. The spice must flow.


We’ll get into that in a bit. I actually just saw that movie. My son and I went and saw it. And I would have been perfectly happy if it was eight hours long.

I felt the same way. I was like,

I was like, give me more. I was like, I was like, let’s just keep going. Does everybody want more? Let’s just keep going with this.

I thought it was fantastic. Um, not just visually, but sound design, like The subtlety of the acting, I loved everything about it. And when the movie was over, uh, my son, Had this look on his face and I said, you know, a lot of people don’t like long movies, but I really, really like them. And he was like, yeah, I like them too.

So the two of us kind of had a religious experience. What we’re going to talk about today, uh, in just a few minutes is we’re going to talk about Matt’s most recent episode, which talks about sand batteries. That explains all the Dune references. Ah, that explains it all. Before we get into that though, we always like to revisit comments from our previous episodes.

So with that, let me share some thoughts from our earlier episode. This is from last week in which we had our conversation around solar panels versus Tesla panels. And there was this from Bradley Ford, Australia, who wrote in to say, Matt, you really need to look at the Western Australia grid. The grid operator has been deliberately pulling down long distance power distribution lines and deliberately establishing micro grids across the state.

In some cases, They are giving farmers solar systems as it is cheaper for the grid to give this than to support the distribution. That’s exactly the kinds of changing model that we’ve been talking about now for several years. Uh, and so a tip from Bradley to take a look at Australia. I have a feeling you’ve been planning on taking a deeper look at Australia.

What do you have to say about that?

I, I’m always keeping a keen eye on it and like one of my patrons sends me tons. He lives in Australia, sends me tons of news articles about what’s going on in Australia with renewable energy, everything from hydrogen to the solar rollouts, all that kind of stuff. And it’s fascinating is absolutely fascinating to me because what they’re doing is, uh, you have the policymakers kind of dragging their feet in one way, and then you just have the industry and people just doing their own thing, going another way and pushing things forward.

And it’s really cool to see like a utility like this kind of rolling with the punches and adapting and changing how they’re doing things because it’s proving to be very effective. Um, I’m definitely looking at Australia.

There was also this comment from Scott who came in to say, I have a funny story like Paul.

Paul Braren was our guest last week talking about his experience with Tesla’s solar roof, as opposed to Matt’s more modular system. And Scott had this to share. When I had my solar installed, the installer just left it on after testing it. When the inspector came a few weeks later to inspect it, he said it wasn’t supposed to be on until after he inspected it.

We both shrugged our shoulders. Oh, well, I had a few extra weeks of solar energy. So it’s, it’s funny to have something installed in your home that you don’t even know you have. working in the background. So that, that also

illustrates that this stuff is kind of weird. It’s like when they install it, it it’s technically working, but based on permitting, you’re not supposed to turn it on.

My, I, my installation experience was my installer got most of the way through installing stuff. And then the inspector came out and was like, Whoa, I was supposed to do an inspection of the wiring that’s under the panels before you put the panels on. So they had to come back out, take the panels off so they can look at all the wiring.

So it’s, it varies based on your location, but it’s pretty funny that, uh, that he got a few weeks of, uh, I guess free, you know, extra energy that he normally would not

have had. But I wouldn’t say it was free, but it was unexpected.

No, it was definitely not free.

There was also in the comments of our last episode, there was a lot of discussion around one of the things we talked about in our conversation with Paul.

If you can get 50 percent instead of 100% But that’s better than zero percent. Why not go for the 50? Like the idea of, is it better to take an option that is a step in the right direction as opposed to the whole trip versus waiting until you do the whole trip? Because there’s this. Background noise from people who say, well, if you can’t replace your energy use completely with a sustainable source, why bother?

And a part of that conversation deviated into the idea of sustainable energy production, having environmental impacts from a production standpoint, the idea that Producing solar panels has an impact on the environment itself. And people were weighing into the comments to say, going solar is actually harmful to the environment because the things that are being put into the environment by solar production are bad.

And I wanted to give you an opportunity to respond to that. I know how I would respond to that, but I’ll let you start off with your

response first. That’s all myths have a seed of truth, but that seed of truthiness to them where it’s like, okay, yeah, there’s things in there that are not good for the environment, you know, mining and minerals or whatever the thing that’s in there that could theoretically leach into the soil.

And it’s like, okay, that makes sense why people buy into it. But it’s. They’re myths. They have been debunked again and again. One of the ones that comes up a lot is solar panels take way more energy to make than they’ll ever generate over their life span, which is so demonstrably false. Uh, it’s, it’s shocks me that that one’s still out there.

It takes about two to three years of time for a single solar panel to work off the energy impacts that it took to make that panel. And that panel is going to last for 30 years. So just do the math. It is way positive energy wise and production wise for that panel. Um, the impacts on the environment as far as like the toxic materials that are inside of a panel is true, but those are sealed and sandwiched in and do not leach out into the soil.

They do not toxify the soil or whatever you want to call it. It’s fine. Any impacts like that, if a panel’s cracked, it’s minimal. And then if a panel’s cracked like that, it’s probably not performing well and it’s going to be taken down. The idea that solar panels aren’t recycled and they’re just chucked into landfills is true at the moment, but that’s not going to be true forever.

Solar panel recycling is happening and that’s going to help reduce the impact on the environment. It’s going to reduce how much mining you have to do because you can take a dead solar panel and turn it into a new solar panel. So that is actively happening. I have a whole video on that. So the idea that solar panels are doing more harm than good is just flat out wrong.

wrong in every single way. And it’s going to get better over time because we’re getting better at producing it. We’re using better materials. We’re getting recycling kind of locked down and figuring that out. So it’s just going to get better and better and better and better. The other aspect of this is just by living our lives, we impact the environment in bad ways.

It’s just, there’s, it’s unavoidable that we’re going to cause impact on the environment. Um, so we’re just trying to find ways. That are better than what we were currently doing. Like, can we make this better? Every step counts. And so this is another one of those burning fossil fuels is far worse for the environment than making that solar panel and switching to solar panels, which is why I would argue if you can get 50 percent of your use from solar.

Yeah, it’s not the whole enchilada, but guess what? It’s reducing the, the fossil fuel impacts by half because you’ve just gotten half of your energy from something else. So it’s. It’s definitely worth taking those steps. And it’s for, for me, it’s the misinformation that keeps it’s so pervasive because it’s so believable because there are elements of truth to it.

But as soon as you kind of peel back the layers, you see, Oh yeah, that’s kind of a half truth because They didn’t take all these other things into account and didn’t look at the actual data. So it’s like, if you look at how it’s actually working, it’s fine. It’s a big step that we’re taking.

My big pushback against the argument that going sustainable has too much of a negative impact on the environment is simply to say, but not going sustainable is what got us here.

So, how is staying the course the right action? Like we have to look for something. We have to try things. If solar ends up not being a key component of our energy production a hundred years from now, fine, but it can’t be what it’s been for the past hundred years. Like that’s no longer an option. So I’m like, I’m always not necessarily skeptical of the underlying argument.

This has an impact. I’m skeptical of the motivation for even making that argument. It’s, yes, I, you, you are very right in all of your responses, which are very directly responding to the statement. And I find myself more often thinking like, what made you say something like that? Because what’s behind that is either an intentional obtuseness or a lack of understanding of like big goals.

Like what do the goalposts that I see line up with the goalposts this other person sees? Maybe they don’t yet know what our goalposts are. And that goes back to like better public education, better, uh, better encapsulation of the entire goal from, um, start to finish, which may be a certain audience is just not getting.

Maybe they’re mishearing what is being asked. So there’s also

the politicization


absolutely everything today where you, you picked your camp politically and then whatever the ideology is, is what you’re kind of buying into. It steers the response. And it’s like, it’s human nature. I’m not blaming people for having that reaction.

It’s social media amplifies that to a new level. So it’s like, I’m not casting aspersions on anybody. It’s just, I get why people say those things. I just wish they would kind of challenge their own point of view just a little bit. Because as soon as you start to scratch the surface, you start to realize that doesn’t make sense.

So yeah. Challenge your thoughts.

On to our discussion about Matt’s most recent. This is how a sand battery could revolutionize home energy storage. This originally dropped on March 26th, 2024. So a big component of this is land usage. There is, there are models of this, which are rather large and obviously people would not want to necessarily add them to a home.

There are models that you talk about that are getting smaller. I’m talking about various, um, forms of use of sand as the heat holding component in what is effectively a battery. A physical thing that the heat being held is energy storage, and it can then be used to in HVAC systems, water systems. Um, so what we end up with are home models that are a combination.

Equivalent to the size of maybe a water heater, one of them looked to me like it was a little bit bigger than a water heater. One looks like it’s very much built around the idea of, I actually wonder if the company making it wasn’t thinking like, let’s make something that people would recognize as small enough to fit in their home.

It really did look like this thing looks like a water heater, so you know you’ve got space. But ultimately there is a physicality to this that not everybody will be able to connect to that you would have to have. Either space in the home for some of these, or space in literally under your yard. Which then leads me to my first question, which is, do you see this as being a technology which would fit at all into an urban environment?

Is there an opportunity here for this to have a place in a setting like where I live, where I’m a renter. I live in Brooklyn, New York. Nobody’s digging up any yards here to put in something like this. And. Yet, the technology looks like it is so, first of all, relatively affordable and good for certain cases that might actually mesh with an urban market, you know, like the idea of a large building benefiting from heating and cooling from something like this.

Do you think this is technology that is going to find more of its market? In less urban environments, is this something that is going to be more of an off grid option or a more rural option where there’s just more terrain, more opportunity to put these things underground? Or is there an aspect of this that could find a market in an urban, in an urban setting?

I actually think, I didn’t state this in the video, thermal energy storage systems, I think, are going to make most sense for utility scale uses, industrial uses. And urban settings than home use. And part of the reason for that is like for the sand batteries, they require a lot of volume. They be big. So it’s like if you had a building, let’s say in New York city, a big apartment building, and you were trying to make an efficient system, you might have some kind of geothermal heat pump system that can use extra, extra energy from solar panels in the roof.

That’s pumping extra storing extra heat during the day. Because it has excess energy during the day, so it’s sucking that heat away that it can use overnight and into the next day, um, where you’re kind of time shifting things in an appropriate way. That is going to be much more effective in a large scale setting because You know, like when you go into Costco, you buy in volume, you get a slight discount per unit.

Um, it’s something along those lines where it’s going to be more effective. That’s one of the downsides that we brought up in this video where it’s like, if you’re doing it for a home, you have this huge amount of space. And they’re the cost ratio for like what it costs to put that same battery in the backyard and how much space is required.

It’s going to be kind of a hard nut to crack potentially for a lot of you case use cases. But if you’re talking about like industrial heat storage next to a, like a factory of some kind, it’s like, they’re going to be able to, you know, Pay for that cost. It’s going to be worth it to them in a huge way.

And for maybe large apartment buildings in New York and stuff like that, it could make a lot of use case. So residential heating systems, um, that might make a lot of sense. So I do think so. And one of the companies I brought up in this video, and we made a different video about them is Polar Night Energy, which is doing essentially that like over in Europe, like gigantic, huge silos.

That can do like, uh, district heating systems and be a heat storage device for those. I think that’s where this is probably going to be the most make the most sense and get a foothold. And part of the reason I did this video was because I was curious would it work for homes? And technically, it technically works, it’s just a, Can they get it to a point where you can afford it and a point where it makes financial sense?

I find myself as I was watching the video thinking if only there was a way to use this technology to help cool down the New York City subway system. Because when you go down those stairs into the subway, it is often 85 degrees? Like, confusingly so. It’ll be four degrees outside and you get downstairs and you’re just like, why is it so beastly hot in this subway station?

And it’s because there are probably steam power transfer pipes under New York City. Like we have, like we have in New York City, and I’m sure a lot of urban environments are like this, a strange Frankenstein’s monster of, you know, Eras of technology. We have everything from 100 years. It goes back a hundred years and it’s like, okay, there’s steam pipes and then there’s electrical lines.

And there’s all these things that generate heat. And I found myself, I was always watching this and like, could somebody come in and create some kind of like. Conduits that siphon that heat and then move it somewhere and put it into a storage unit somewhere and use it for something else other than just making everybody super uncomfortable in the city subway


But it’s the same thing in Boston with, I remember Park Street station going down there. Yeah, I remember that. In the middle of summer, it’s, it’s hot and it’s humid outside, like 97 degrees Fahrenheit. And then you go into the parks, the Park Street station, and it would be like, did somebody turn on. Oven on down here, because it’s even hotter and more humid down


Yeah, yeah, yeah. And it’s when you go down there and you feel like you’re watching, like suddenly it feels in some of these stations, like you’re walking past open ovens where there’s shoveling coal directly into it and you’re like, am I in the belly of the Titanic? Where did I, did I turn the wrong way?

What is going ? So there were also in the comments on this one, some interesting. Uh, sharing of stories, and I just wanted to, I wanted to end this episode with some DIY, uh, anecdotes from some of your viewers that I find these fantastic. There was this from Hugh, who said, Living in Maine, I have a bias toward using wood for heating, as it is cheap and renewable.

I built a wood fired, Sand battery to heat a friend’s home. It was simple to build and very efficient. We built it from plants. And this is the part that stood out to me as something I thought you would be interested in for potentially a video of what old designs of renewable or sustainable energy production or storage are out there that people could DIY in this way.

He says, we built it from plans acquired from the University of Maine back in the 70s. Some of the materials used should probably be updated to new or better materials, but I would describe it as we built it. Clear descriptions of how to followed by, and then he goes on to say like how he, he did it all.

It had to do with a concrete floor. There’s then a wood burning stove. It is surrounded by a smaller. Brick, uh, little mini room. And then in the space of the wider room around it is filled entirely with sand. So you have this little wood burning stove inside a little brick chamber and then a layer of sand surrounding that.

And he says, all of this was about 20 feet behind his friend’s house. We dug a trench and insulated the pipes heavily around about four feet underground. These pipes were brought into the basement and attached directly to an existing water boiler, which could be valved off. So you could use either heat source, but with the same circulation equipment, my friend lights a small fire once or twice a day and provides all the heat he needs for his home.

If I was to build this today, I would use PEX pipe and the styrofoam concrete form rather than blocks. I thought that was fantastic, like a 1970s design from the University of Maine, and it only has to light one or two fires in a wood burning stove to heat his home. And as you have said on your channel a number of times, it’s a little counterintuitive given the era we live in to say wood is a renewable resource.

It’s like, you don’t think of it in that way, but yes, there are tree farms and people can get lumber and burn it. And then trees can be grown. Trees are carbon. Trees are carbon capture. So it is a closed loop effectively. Uh, so I found that fascinating. I love that story. There was also

this for that is, yeah, it’s just the ingeniousness of just like, you don’t need cutting edge technologies.

It’s just, it’s heat radiating off an oven. How can I capture that heat and hold on that heat and let it radiate out more slowly? It’s like, okay. Brick walls and sand.

Brick walls, sand, and pipes buried four feet underground. We’re four feet underground. I think it’s, Remarkably, he says, we insulated it carefully, like four feet underground.

You don’t even need to insulate that much because four feet underground, all that hot water going through that pipe at that depth, the ground around it is going to be what? About 60

degrees nonstop. It’s probably gonna be 50 degrees nonstop. Yeah. All the time.

There was also this from C who wrote in to say, I’ve told this story before a friend of mine built one of these himself.

He built a South facing solarium on the back of his house, but underneath the concrete pad, he installed a three foot deep pit and filled it with pea gravel. He used some PVC pipe and some small fans to blow air from the warm solarium. Into the gravel pit during the day, the cool air coming back would help regulate the temperatures in the summer.

In the winter, he could divert the warm air into his house to help lighten the load on his furnace. Colder return air would go back into the pit to be warmed up before going to the furnace. He could let it charge all day, even in the winter, and use the extra warm air at night when heating demand was higher.

That is so clever. Look at the big brains on C’s friend. This is just, this

is, this is not even like him saying like it’s a

South facing, it’s a South facing house with solar panels. Like this is literally just a solarium, just a bunch of windows. Capture all that light and letting sunlight warm up the room and then doing something different with the air.


That’s, well, this is what I love about some of these renewable technologies, is that they’re super accessible. That if you’re a DIYer, you like to do things on your own, you can do this kind of stuff super cheap, and then also have fun doing it because you like to tinker and do your own stuff, but at the same time, then you have companies, they’re trying to modularize this and sell it as kind of like a.

Appliance, where it’s like you pay a certain amount of money, you get this little appliance, it gets installed in your home and you’re done. So it’s like for the rest of us that are not DIYers and don’t want to do that and don’t want to have the maintenance or upkeep or the tinkering to it, it’s like we have an option that’s kind of doubling down on the same thing.

So I love how Versatile this stuff is like solar is the same thing. It’s like if you are know electrical work and you don’t mind crawling up on your roof or building something in your backyard, you can do it dirt cheap. And it’s like, but for those of us that don’t want to be climbing around on our roof, don’t know how to do electrical work, we can hire somebody to do it for ourselves.

It’s just the, the range of ability and accessibility to this stuff is so, so cool. It’s very inspiring to hear that

kind of stuff. Yeah, it’s pretty interesting. So listeners, what do you think about all this? What did you think about sand batteries in general? And what did you think about the DIY suggestions?

Have any of you experienced a DIY situation that you’ve been a part of? Share it in the comments. Don’t forget you can leave a comment, you can leave a review, and don’t forget to subscribe and share with your friends. Those are all super easy ways to support the program. You can also go to StillTBD. fm, or go to YouTube and click the join button there.

Either of those allow you to throw some coins at our heads. We appreciate the welts and it will go directly into making the podcast that you’re currently enjoying. Thank you so much, everybody, for taking the time to watch or listen. We’ll talk to you next time.

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