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A sand battery could transform clean energy
- yboris 4y agoAn 11-min video on channel Undecided with Matt Ferrell about this tech: https://www.youtube.com/watch?v=G6ZrM-IZlTE https://www.youtube.com/watch?v=G6ZrM-IZlTE
- dimenoz 4y agoFrom "Just Have a Think" (another excellent channel similar to Undecided): https://www.youtube.com/watch?v=sol9FOaKTr0 https://www.youtube.com/watch?v=sol9FOaKTr0
- VBprogrammer 4y agoI'm really starting to grow tired of this format of video. Lots of stock footage and little information, definitely no attempt to bring balance into the discussion. Every innovation is a breakthrough with no downsides at all. This is probably a bit harsh to Matt Ferrel it's probably copycats I've got more of a problem with.
- giarc 4y agoThanks for sharing that. He did a great job simplifying the tech and explaining the pro's and cons.
- jandrese 4y agoUndecided always seems just a bit under-researched and a little too credulous of company claims IMHO. They've got some videos of outright investor scams reported with a straight face.
- kitd 4y agoI appreciate the focus on technological simplicity, cost-effectiveness and environmental cost. Yes, the battery itself isn't as efficient (per m^3) as a chemical one, but the basic engineering and well-established supply chains behind setting one up will reap gains in themselves and means scaling up will be much less challenging. Even the turbine add-on is well understood engineering at this stage. I imagine these could be used to buffer the output from wind turbines or solar plants?
- rob74 4y agoEr, this is probably a good heat storage system, but I wouldn't call it a "battery". A battery is something that you charge with electricity and then provides electricity when you discharge it. Or, otherwise said, a pumped-storage plant is closer to the definition of a "battery" than this thing...
- adamdusty 4y ago> The battery is charged overnight when the electricity prices are lower. Sounds like the battery is charged via electricity.
- automatic6131 4y agoBut missing the crucial second half, releases electricity on discharge.
- tomrod 4y agoIt's not a chemical battery, which releases energy as electricity, but electricity can certainly be generated using heat stored in heated/molten sand. Ultimately its about energy transfer, efficiency, and storage.
- tuatoru 4y agoIt's an accumulator for a district heating system, which are apparently common in Nordic countries. Traditionally district heating systems use waste heat from thermal generation of electricity, which heat is free.
- mdaEyebot 4y ago"Mechanical batteries" are a thing, like flywheels or hydroelectric reservoirs. Batteries store energy, the electricity that flows in and out is just one way to manifest that energy. You could measure it in Joules rather than Watt-hours. At the end of the day, a chemical battery is a reusable bomb that is designed to go off very, very slowly.
- ck2 4y agoBut heat based power always leaks energy? Why not lift something REALLY heavy and let gravity spin a gearbox on the way down? Like say lift a silo of sand? Up the side of an existing hill on a rail/track? Alternately pump water uphill but in cold/hot climates that would be a problem and microbes, etc. Gravity isn't going to leak or fail. And enough of an angle that weight is always coming down regardless of weather.
- elil17 4y agoYou're balancing the cost of energy leaking vs. the difference in capex vs. other inefficiencies of the gravity based system (e.g. heat loss due to friction)
- burkaman 4y agoThose methods are good and already in use, and this is one more additional energy storage method for places where those are expensive or impractical. This method also has the additional benefit of directly providing heat, so if you need heat more than you need power then this seems like a great choice.
- rjmunro 4y agoThis unit stores 8MWh of energy with 100 tonnes of sand. Gravity is about 9.8m/s*2. If you put the calculation into google "8MWh / 9.8m/s*2 / 100 tonnes", it tells you that you need lift those 100 tonnes 29.39km up, which is over 3 times the height of Everest. And the mechanics of the system are much more complicated, more expensive to build and maintain. However, pumping water uphill is done in many places, and is more practical because a lake of water can easily weigh millions of tonnes. The problem is finding places with suitable hill top lakes. Also, if you are using it for district heating output, storing it as heat is convenient. There might scope to increase efficiency by using some sort of heat pump, but getting a heat pump to go up to 600°C is quite hard.
- kwhitefoot 4y ago> The problem is finding places with suitable hill top lakes. And a similar capacity lake at the bottom of the station to hold the water that you are going to pump up to the top.
- Simulacra 4y agoIs there a central location of these "x could transform y" discoveries? Energy storage is vital and it seems every week something new is coming out. Most it seems never make it off the theoretical paper.
- philipkglass 4y agoThis article is about a pilot scale project that is already built. It is significantly further along than a report about a theoretical energy storage mechanism or one that has only been demonstrated at the laboratory bench scale.
- Moissanite 4y agoResistance heater plus thermal mass as a time-shifting mechanism for heat has existed for decades in the UK - they are referred to as "storage heaters" and have generally been avoided wherever possible because of the high cost of electricity relative to gas. Operating at large scale like this probably helps, but really the main benefit comes from the district heating part.
- jonatron 4y agoStorage heaters might make comeback if gas prices remain high, because intermittent wind power and smart meters make it possible to use electricity when it's windy and cheap.
- bodyfour 4y agoIndeed, they are: https://tepeo.com/thezeb https://tepeo.com/thezeb
- Moissanite 4y agoSlightly different, as this seems to hook in to your existing water pipes for moving the heat out from a central location - but an interesting find. Another I'm watching from a distance is microwave-based heating, essentially replacing the gas burner in a combi boiler with a flow-through microwave heater.
- ZeroGravitas 4y agoHeat pumps feeding into underfloor heating do a very similar thing to this sand battery. They let you feed heat into a thermal mass in order to buffer it. This has the double impact of a) letting you take advantage of cheaper electricity by modulating your load slightly, b) letting your heat pump run continuously at a lower heat output, maximising efficiency as it extracts heat from the continually replenished outside air.
- stormdennis 4y agoIndeed. In our prefab classroom in winter, sitting on the class storage heater before classes started was the prime real estate.
- choeger 4y agoHow does it compare to heatpumps, though? If a large-scale heatpump was used to power a district, it would only need 1/3 or even less of the electricty. From that perspective, does it make sense to store thermal energy or does a chemical battery become attractive again?
- Moissanite 4y agoI think the bigger problem with batteries is capex per kWh, rather than efficiency.
- elil17 4y agoYou have to include the capex cost of the heat pumps. This design uses no equipment at the customer's homes, just pipes of hot fluid. Those pipes already exist in Finland, where district heating is relatively common. The next logical step is pumped thermal energy storage, where you pump heat into the sand using a heat pump - but there is significant capex associated with that.
- hedora 4y agoHeat pump efficiency drops rapidly with temperature differentials. This doesn't matter much when the goal is to heat air to room temperature, but it would matter a lot with a 600C target temperature. It's likely cheaper to use a lithium ion battery to store the electricity, then run a heat pump at the house off that. On top of that, it'll use a tiny fraction as much electricity.
- elil17 4y agoIt's true that heat pumps become less efficient at higher temperature differences. That's why these systems use lower storage temperatures. It's also true that, even then, the storage temperature has to by higher than the typical evaporator condensor for a heat pump, leading them to be less efficient (think 175% efficient vs. 300% efficient). You're looking at LCOS of $0.23 kWh-1 [1], which is higher than Li-ion. However, such a system may offer other advantages (better recyclability, no reliance on lithium, less risk of fire), or such systems may be cheaper in the future, which is why people are researching them. Additionally, these systems work with existing district heating pipes, which is great because it mean's you don't have to expand the grid capacity. In places with district heating, that could make a lot of sense. (I don't think anyone is proposing building new district heating systems, just retrofitting old ones). [1] https://www.sciencedirect.com/science/article/abs/pii/S019689042100248X https://www.sciencedirect.com/science/article/abs/pii/S01968... Also, Carnot efficiency increases without bound as the temperature difference decreases, so lowering the temperature of the room or increasing the temperature of the outdoors make a huge difference. The same applies vice versa for air conditioning which is why people use cooling towers.
- ouid 4y agothe transportation of "heat" is a lot more complicated than the transportation of electricity. I'm not opposed to putting insulated piping everywhere to transport hot water around. It's better than building bridges to nowhere, but i can't help but feel that the losses will scale badly. Pipes have a lot of surface area.
- kitd 4y agoThis is already widely done in Nordic countries and well understood. I went to a geothermal plant about 25km outside Reykjavik. It also supplies much of the communal hot water for the city. Between the plant and the city, in the depths of winter, it loses 1deg C.
- jabl 4y agoThe usual district heating pipes around here have an inner pipe where the actual hot water is pumped, then about 10cm of some yellowish insulation material (polyurethane?), and then an outer pipe to protect the insulation. AFAIU heat losses through the piping aren't considered a huge problem.
- jandrese 4y agoCampuses and some municipalities have steam pipes for distribution of heat. However, the economics of moving steam around vs. using the steam to turn a turbine to make electricity to run heat pumps is dubious. The electric solution is much more complicated, but it can also be used to cool the buildings in the summer and run lights, so the tradeoffs can be worth it.
- dontlaugh 4y agoMunicipal heating can be extremely efficient, precisely because it doesn't take that much insulation to make losses a non-issue and heat generation tends to scale up very well.
- mdorazio 4y agoI'm confused... this is basically the same as molten salt, just with sand instead of salt. Molten salt has been around for a very long time and is how solar thermal power plants store energy and continue to generate power after dark. Is there an innovation here that I'm missing?
- zdragnar 4y agoMolten salt is very corrosive, and this only heats to 600C, and sodium chloride doesn't melt until 800C. This is a cheaper, lower maintenance option.
- scythe 4y agoThe molten salt used for energy storage is a sodium nitrate – potassium nitrate eutectic with an operating temperature range of 200-550 C and a much lower corrosion behavior than chloride salts.
- zdragnar 4y agoah, fair enough. The design in the photo is much more vertical than horizontal- maybe they're designing for space constraints? I would imagine 500*C molten salt would be significantly more efficient than sand, so the only charitable thing I can come up with is they're simply putting the cheapest materials they can (discard sand, free electricity) to good use.
- zardo 4y agoDifferent application and price point. This doesn't operate at a high enough temperature to make generating electricity back from it feasible, so it's only good for heating. But, you can build big and cheap for seasonal scale storage, and it can be underground with a secondary land use on the surface.
- michael1999 4y agoNon-electic. Direct heat storage for district heating with zero high-tech involved. Resistive heaters, air ducts, a silo, sand, and some fans -- all established enough for utility use.
- zdragnar 4y agoThis seems rather strange to me, having immersed myself in the rocket mass heater community a bit. Sand is generally the last option to choose for thermal mass, because it is so inefficient at storing heat; the very air between the grains acts as insulation. Instead, clay (or clay mixed with straw to form cob) is the preferred medium for storing heat, as it is a significantly better conductor and stores much more heat energy than the air between the grains of sand. It seems like they are using the air as a medium here- the article states that they blow air through the sand, and the resistive bands heat up the air, which then sheds some of the heat onto the sand (or picks some heat up off the sand, depending on if it is storing or discharging). I guess the cheapness and simplicity of construction makes this a better option at the scale they're operating at, but it's pretty wild to imagine how much more efficient the system could be if it had been designed differently.
- LordHeini 4y agoDon't confuse heat capacity with conductivity. And the air is blown through pipes in the sand, which means you need something which will easily surround the pipes. Solid materials would suffer from thermal expansion problems (like cracking), while liquids evaporate so sand seem to be a reasonable choice. For their application the conductivity does not really matter and the cheap reject sand was chosen because it has the best mass to price ratio. It is heated to 600°C so it would be not the best idea to use clay with straw ;)
- zdragnar 4y agoAh, I missed the pipes bit. Yes, that is exactly how the mass storage heaters I am familiar with work- pipes run through clay, which does need to be fully dried before you heat it to avoid cracking. I did overlook the 600*C bit at first- straw would definitely be a bad idea, lol. I still would guess that the additional cost of clay would be worth it. Clay is both more conductive AND has better capacity- the air between the grains of sand is an insulator, and has significantly lower storage capacity than the grains of sand themselves. Another option some people use if they don't want a permanent installation (or just need occasional portability) is large stones with gravel for fill. It's quite a bit less efficient than clay, but the larger size of the gravel and rocks inside make it a better option than sand. I imagine they have done the math on the cost of the sand and the efficiency they are getting out of it, it just goes against everything I have ever learned about thermal mass storage from the permie / rocket heater mass storage community.
- avanai 4y agoThey compare its cost effectiveness to lithium electrochemical storage batteries, but it seems much more apt to compare it to large-scale flow batteries, which also use relatively cheap, easily available materials. How does it compare to those?
- marcosdumay 4y agoIt's more apt to compare it to phase change heat storage. What somehow doesn't appear anywhere on the article. (I do believe the article's design fares much worse, even on capex alone. I never saw some salt selection that melts at 600°C, but I imagine it would have better results even in a lower temperature.)
- Schroedingersat 4y agoVanadium flow batteries are about half but will not stay that way if scaled (vanadium production is too limited). Iron flow is currently 'it will be dirt cheap later we swear, ask us about a demo project'. So probably substantially more expensive. No compelling reason not to believe them though.
- Schroedingersat 4y agoThis was wrong. Vanadium electrolyte is only 1-2 molar. Vanadium production on the order of current generation can support ~100GWh/yr
- scythe 4y ago>The battery stores 8 MWh of thermal energy when full. When energy demand rises, the battery discharges about 200 kW of power through the heat-exchange pipes: that's enough to provide heating and hot water for about 100 homes Cool, so we just need three million of these to take care of Europe. If you look up Kankanpää on a map, you will find that it is a very small town in the middle of nowhere. And I haven't looked this up, but I'm suspecting it's got abundant sand production/shipping nearby from the Baltic. In those conditions, this sand-thermal storage might work well. But for most of the world, the space requirement, low energy efficiency, and costs associated with building large projects (and digging deep holes) in places where people actually, you know, live, will basically rule this out.
- naavis 4y agoAre you implying it shouldn't be developed if it doesn't cover 100% of all use cases all over the world?
- saalweachter 4y agoI wonder what the threshold is for a niche solution. You don't want to be, like, the only person with a sand-heat-battery. Well, you might, as an individual, if you like to tinker, but as a municipality it's a pain. All of your problems are unique, you can't just hire a repairman to come in and swap out a standard part for another, you don't have a standard payscale for your Sand Management Technician, etc etc. How many installations do you need before it becomes a good idea? 1% of the total? 50 total in a service area?
- scythe 4y agoNo, I'm implying that the headline claim "transform clean energy" is overstated. It mostly applies for far-flung, low-density areas. This is still useful, but not transformative for most of us.
- jandrese 4y agoThis feels like one of those technologies that dead ends because the costs of PV solar cells/wind turbines and batteries is dropping so fast that by the time it's ready for the mass market it is no longer competitive, especially when you add in the complexity of engineering the solution to match your problem and being a first mover on a new technology. I note that even the figure provided in the article ($2,000/MWh) is out of date, and current prices are closer to $500/MWh and still dropping. I'd expect this to be a nice niche solution for them but have tepid uptake elsewhere.
- SamBam 4y agoI'm confused by your comparison to PV solar cells, although I'm probably not just not understanding your comment. This is an energy storage device, not an energy generator. Its purpose is to smooth out the peaks and troughs of non-steady renewable energy flow.
- mcbishop 4y agoThere's an option of overbuilding PV to fully accommodate cloudy days or the winter season (with extra PV going to waste on sunnier days). ...Versus making up the difference with stored energy.
- rjvs 4y agoThat doesn't help at night, storage is still necessary.
- onceiwasthere 4y agoNot if you keep overbuilding for star and moonlight!
- tzs 4y agoYou'd still need something to handle the nights around new moon, so you'd have to overbuild enough to be sufficient when all you have is starlight. A bit of Googling suggests that the combined energy per second that reaches Earth from all the visible stars other than the Sun is around 0.0000002% of the amount from the Sun. I recall reading that the area needed with current solar panel technology to power the entire US would be 10000 square miles. With starlight being 0.0000002% of sunlight, that suggests we'd need 5 trillion square miles of panels to get the same amount of energy at night. The surface area of the earth is a little under 200 million square miles. That suggests that it isn't possible to overbuild enough to work off of starlight. It would be even worse on cloudy nights. On cloudy days you still get a significant amount of sunlight coming through, because the Sun is giving us so much more than we need. Not so with stars.
- Havoc 4y agoCan it use desert sand? That stuff is useless for construction but might still be good for this?
- ben_bai 4y agoAs it is only a heat storage device, yes. The cheapest sand will do.
- Schroedingersat 4y agoThe principle works with anything that won't catch fire. Or anything that will catch fire and then still be big and heavy once it's done burning.
- WalterBright 4y agoI've proposed on HN multiple times that home HVAC systems could have a "battery" that consisted of an insulated box of rocks. It could be heated or cooled during periods when renewable energy is cheap, and used as a heat source/sink the rest of the time. This idea was regularly ridiculed. I'm glad to see someone thinks it isn't so stupid :-)
- bilsbie 4y agoThere’s low hanging fruit like that everywhere. In this case I think new home builders are really conservative with trying new things due to the high price of houses and strict building codes. And even though it’s a simple idea it’s the kind of thing HVAC companies would be happy to Charge you 20K for. Just like geothermal.
- crazygringo 4y agoJudging from other comments here, it seems like that's not an economic solution for storing electricity -- only for storing heat. And I suppose it's really not so different from simply having a hot water heater like so many homes do? That you could program to only add more water to when electricity is cheapest? (And in-floor heating uses hot water pipes.) But hot water tanks are very safe, they're only 60°C. I would think that 600°C sand (or rocks) is the kind of thing that's not particularly safe to have inside your home. That's really, really hot. Have you done the math and figured out how many rocks a home would need, how much insulation, and so whether it's even viable in theory, setting aside practical engineering/safety concerns?
- WalterBright 4y agoIt's for storing heat (and cold). > Have you done the math and figured out how many rocks a home would need, how much insulation, and so whether it's even viable in theory, setting aside practical engineering/safety concerns? No. But why wouldn't it be viable? And what could be cheaper than a box of rocks? No moving parts, other than a fan your HVAC system has anyway.
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- lastofthemojito 4y ago> The answer nestling in Vatajankoski power plant, 270 km (168 miles) north-west of Finland's capital, Helsinki, is remarkably simple, abundant and cheap: sand. Wait, I thought there was a sand shortage? https://www.bbc.com/future/article/20191108-why-the-world-is-running-out-of-sand https://www.bbc.com/future/article/20191108-why-the-world-is... https://www.reuters.com/business/environment/sand-crisis-looms-world-population-surges-un-warns-2022-04-26/ https://www.reuters.com/business/environment/sand-crisis-loo... I guess there are different types of sand though?
- swores 4y agoFrom the article: > "The company uses cheap, low-quality sand that's been rejected by builders instead of high quality river-sand which is used in vast quantities for construction, leading to a global shortage."
- cjtrowbridge 4y agoThe article goes into detail answering these questions, in case you haven't read past the first paragraph before sharing your opinions; "The company uses cheap, low-quality sand that's been rejected by builders instead of high quality river-sand which is used in vast quantities for construction, leading to a global shortage."
- breischl 4y agoIt's a cool idea. The big advantage might be in being cheap, simple, and non-toxic, so that it can be easily deployed in less-prosperous areas and with less expertise. It seems probably even simpler than the "concrete stacking battery" whose name I forget. But... >with currently available technology the process of converting heat back into electricity only has an efficiency rate of 30% Yes they're recovering heat as well, which is great when it works. But in general 30% is not great. This probably only makes sense to use when you have huge amounts of nearly-free power. Like if you massively overbuilt solar/wind (which could be a plausible thing to do!) or nuclear.
- unwind 4y agoI thought heat output was the main effect, thus the talk about "district heating pipes" in the list of components. With nuclear power generation I thought there was no need to store energy, since it can generate at all times and ramp up/down pretty quickly.
- breischl 4y agoI'd say the marketing on at least this article is more geared at the electric energy. Heat is a form of energy for sure, but not a big enough one that it could "transform clean energy". Nuclear can be ramped, but typically is not. I haven't dug into why, but I get the impression it's partially economic - the plants are very expensive to build and the marginal cost of a few hours of fuel is so low that they prefer to just run all the damn time. I think there may be some technical reasons as well. In general if you look at how utilities operate, they will ramp down literally everything else before the nuclear plants. That probably applies less to the Small Modular Reactors people keep talking about, but those are still not really a factor.
- Schroedingersat 4y ago30% of that noon day summer sun looks pretty good on a cloudy day mid winter. In some places where mid-winter PV output is 1/4 of summer, it *already* makes sense to overbuild by a factor of 4. Keeping 30% of the summer energy would double the winter output. Of course this only makes sense if the electricity extracting bit is much cheaper than wind.
- smt88 4y agoThis is a stupid idea, and there are some great YouTube videos that explain why[1]. tl;dr We already move enormous amounts of drinking water, and reservoirs are much better (and cheaper) candidates for batteries than sand/cement/etc. 1. https://www.youtube.com/watch?v=iGGOjD_OtAM https://www.youtube.com/watch?v=iGGOjD_OtAM
- Schroedingersat 4y agoThis is for storing low grade heat, not work. And it doesn't use gravity.
- sergiomattei 4y agoOr just use pumped-storage hydroelectricity
- sedivy94 4y agoMy initial thought is… why bother? There are so many vectors for energy loss from source to destination. If the sand is heated by coils, why not install on-demand heating on-site?