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Large-scale ‘sand battery’ goes online in Finland
- jpollock 4y agoAlberta has a neighborhood that stores heat in the summer for winter use: https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community
- LegitShady 4y agoits only ~50 homes
- barbazoo 4y ago> Optimal community size would be 200-300 homes to realize the economies of scale. The number of systems would remain the same; only the number of boreholes would need to increase Decentralized systems like this one are cheaper and faster to build so it makes sense that the number of households served is on the low end. That doesn't mean it's not useful tech.
- Retric 4y agoIt’s interesting. 7 million in support to supply 97% of annual heat for 52 homes isn’t that far off being reasonable for an early R&D project. An 80% price drop at modest scale, say 100 different 300 home subdivisions actually seems achievable. I think it’s largely a question of how dependent this is on local geology.
- deleted 4y ago[deleted]
- O__________O 4y agoRead the Wikipedia page, might be missing something, but seems like the system works in summer and winter, but don’t see anything about summer production being used in the winter.
- bathtub365 4y agoFrom the Wikipedia page: > The borehole thermal energy system (BTES) is located underground to store large quantities of heat collected in the summer to be used in the winter.
- rcv 4y ago> The borehole thermal energy system (BTES) is located underground to store large quantities of heat collected in the summer to be used in the winter. Basically they heat up the soil and rock beneath their park during the summer using hot water/glycol from their solar arrays, and then during the winter they pump cold water through it which soaks that heat back up. What's amazing is that it apparently took 4 years to fully saturate the area with heat energy.
- tsol 4y agoAnd there isn't a massive amount of heat loss with that? It's a cool idea, what surprises me is that it actually works
- ggm 4y agoLondon Underground originally was kept cool because of its thermal mass. Over the last 100 years, it has now turned into a giant heat store, and there is an emerging airconditioning problem. I believe its the resistive heating from the trains passing through, over time, plus the sweaty exhalation of millions of people. TL;DR ground heat is remarkably persisting and takes years to dissipate, if deep enough. Coolth, the absence of heat, is really the same in this regard, because the heat transport through the ground is not rapid. This is also why deep hot rocks need fracking to get thermal energy working unless its happening naturally. Rocks all around the place "down there" are hot. Very hot. A lot of ground water comes out hot. Bath (uk) for instance. its hot. So how come the rest of bath is cold and wet? Because ground heat doesn't move fast.
- O__________O 4y agoFrom Wikipedia, “When the tunnels were built the clay temperature was around 14 °C; this has now risen to 19–26 °C” According to the same page though, the tunnels only add 4% to the heat and humans add 7% — remaining 89% comes from the trains; unless I misunderstood something. https://en.m.wikipedia.org/wiki/London_Underground_cooling https://en.m.wikipedia.org/wiki/London_Underground_cooling
- koreanguy 4y ago
- FastMonkey 4y agoWhat's the round trip efficiency of something like this, and what's the rate of loss to the environment? There's been a couple of these posted in the last few days and I have no feel for these numbers.
- loufe 4y agoThis was the question I came to pose... This is such an exciting field but when the CORE most important variable is missing, I tend to assume the worst - in this case being that the value is atrociously low.
- TheSpiceIsLife 4y agoThe key here is: this isn't a battery. It's electricity powered thermal storage for municipal heating. Which, in my opinion, is a smart idea. Why bother converting the heat back to electric to end up being used to generate heat in homes. You could use this as a heat sink at the home attached to a high efficiency heat pump for 6:1 thermal efficiency. We could do with municipal heating here in Tasmania
- vkou 4y agoThe RTE of turning electricity into heat (or hot water into hot sand into hot water) is pretty good, most of your problem will be environmental losses between the heating station and the end-users. It's not going to be as good as a heat pump, but they don't work very well in very cold climates, and storing electricity (or energy that you turn back into electricity) is expensive/lossy/difficult.
- jpollock 4y agoData from Drake's Landing in Aberta has a COP of 30 (30kw of heat per kw of electricity)? The heat stored is waste heat - otherwise lost to the atmosphere, so storing it until use is should be compared to typical heat pump COP of 2-4. https://www.dlsc.ca/ https://www.dlsc.ca/ https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community
- timbit42 4y agoThe sidebar on this article claims efficiency "up to 99 percent". OK, but what is typical? https://www.dailymail.co.uk/sciencetech/article-10982885/Worlds-working-sand-battery-store-green-power-months-time-installed.html https://www.dailymail.co.uk/sciencetech/article-10982885/Wor...
- htk 4y agoThe whole thing seems so inefficient but I am not an expert. Can anyone here expand on this?
- gebruikersnaam 4y agoThey are using waste heat that otherwise would just disappear. 50% efficient is still better than 100% not used.
- wikfwikf 4y agoThey are not using waste heat but low-cost electricity. A system heated to 500C is not running on waste heat.
- UberFly 4y agoThere are lots of websites online that explain it more like: https://www.bbc.com/news/science-environment-61996520 https://www.bbc.com/news/science-environment-61996520
- rightbyte 4y agoYou can sink solar power into it in the summer and use the heat in the winter. With intermittent power like solar and wind you probably want to be able to sink it somewhere useful.
- ars 4y agoIt has 80 hours of storage - that's not enough summer/winter shifting. At most it's day/night.
- epistasis 4y agoIf it discharges continually, it will discharge for 80 hours. 8000kWh / 100kW, capacity divided by discharge rate This is a different number than the amount of energy lost when it is not discharging. However I would suspect that this particular unit is not designed to store heat for six months. However there are plenty of underground systems designed for seasonal storage, and the storage capacity is relatively cheap. The problem is getting enough neighbors together to meet the minimum scale.
- pyrolistical 4y agoStrange they heat the sand instead of moving it around like a pumped battery
- mikewarot 4y agoMoving sand (an abrasive grit) around is challenging at room temperate, doing it at 1000°F (500-600°C) seems impossible. It makes far more sense not to subject things to that kind of abrasion, and just flow air or water/steam through it.
- pfdietz 4y agoIt's possible. NREL's ENDURING system does just that. https://arpa-e.energy.gov/sites/default/files/2021-03/07%20Day1-Zhiwen%20Ma_NREL.pdf https://arpa-e.energy.gov/sites/default/files/2021-03/07%20D... Quick stats: stores heat in sand at 1200 C, round trip power->power efficiency of 54%, LCOS of $0.05/kWh for 100 hour storage. Heat is transferred from the sand to the gas for a Brayton cycle by direct contact in a fluidized bed heat exchanger. Babcock and Wilcox is expanding this now to the pilot stage under an exclusive license.
- mikewarot 4y agoThat is a very elegant work around. {They never convey the particles while hot, only after they've given up their heat, or before they get heated and then fall into hot storage} I'd be happy with 54% round trip efficiency, it's way better than losing renewable power by not being able to store it.
- nonrandomstring 4y agoA thermal battery is useful in concert with a heat pump.
- dghlsakjg 4y agoFrom this article it seems like they are using the sand to store heat that would otherwise go to waste due to temps too low to otherwise turn it into other forms of energy. At least that’s what it seems like. They aren’t very specific, but it explains why they aren’t using something more akin to pumped water energy storage.
- pavon 4y agoAs an American it completely breaks my expectations that district heating not only works can be more efficient that decentralized heating. The amount of heat lost just moving water from the water heater on one side of the house to the shower on the other is ridiculously high in houses here. The idea that you can insulate well enough to efficiently move heat across a city is amazing to me.
- deleted 4y ago[deleted]
- Swizec 4y agoMy hometown has a power plant in city center. During winter it uses the entire downtown area as a heat sink. It's great. Power plant gets cooling for its hot water, city residents get cheap heating for their homes. Best part is you don't even care about heat loss because you're trying to get rid of all that heat anyway. This scheme has been inplace since the 60's. https://en.wikipedia.org/wiki/Ljubljana_Power_Station https://en.wikipedia.org/wiki/Ljubljana_Power_Station District Heating is quite popular in much of the world. USA built the first such system back in 1853. https://en.wikipedia.org/wiki/District_heating https://en.wikipedia.org/wiki/District_heating
- teruakohatu 4y agoGiven how much health problems are caused by coal power plants, not sure it is that great to live near one. But if you have to have coal, it makes good sense to harvest the energy rather than wastefully pumping the steam into cooling towers.
- Swizec 4y agoI mean it’s already there and has been for 60 years. I’m sure its polution pales in comparison to the 200,000+ cars driving in the area daily. Back when the coal power plant was built it was pretty normal to live near coal burning things.
- 4y ago
- aaaaaaaaaaab 4y agoWhy sand? - water has 5x the specific heat capacity of sand - water can be pumped around easily - water can be used directly for district heating
- woodruffw 4y agoSand is non-corrosive and doesn't expand significantly at 500C (it takes temperatures ~3x that to get it to melt). That doesn't answer the "why" completely, but those are probably some of the factors. Edit: the article doesn't explain how the "battery" works, but my intuition is that the sand doesn't move. It's likely merely heated and then passively heats whatever actual transportation medium is used (likely water).
- vkou 4y agoPresumably, because sand can be heated to above 100C. Given Newton's law of cooling, it's not entirely clear to me why you want your thermal battery to be heated to above 100C... But I'm not an engineer - I only play one on TV.
- 8bitsrule 4y agoSand (much denser = sinks in water) has low thermal conductivity, and isn't much more expensive. Simply put, in two bodies of equal volume and 'heat capacity', the one that's hotter stores more heat. Sand properties: [https://material-properties.org/sand-density-heat-capacity-thermal-conductivity/ https://material-properties.org/sand-density-heat-capacity-t...]
- tommiegannert 4y agoFrom your link, sand has much worse heat capacity than water at 800 J/kgK vs 4000 for water.
- lazide 4y agoWater also boils at STP at 100C, which limits upper energy storage.
- Animats 4y agoThat's useful. It's storing low-grade heat, which is fine for home heating but not useful for electricity generation.
- jsnell 4y agoFor those looking for the details, I think this is the patent: https://patents.google.com/patent/FI128161B/en https://patents.google.com/patent/FI128161B/en
- excitom 4y ago> It has a particularly strong use case in Finland which sees long and very cold winters, and was recently cut off from Russian gas supplies over a payments dispute. Well I guess that's one way to characterize war-related sanctions and their side effects.
- thematrixturtle 4y agoIt's factual. The gas supplies in question were not covered by sanctions, but Russia tried to unilaterally switch to being paid in roubles and were told to go batter sand (bada bum tssh).
- zmgsabst 4y ago> gas supplies in question were not covered by sanctions, but Russia tried to unilaterally switch to being paid in roubles I don’t think this is a very honest characterization: Russia demanded payment on their terms only after they were kicked out of SWIFT and their reserves frozen by foreign banks. I don’t think I’d describe that change in payment terms in response to bank sanctions as “unilateral” or unrelated to sanctions.
- jelly 4y agoGazprombank is still in SWIFT
- duskwuff 4y agoGiven reports that the Russian military may be paying soldiers through Gazprom, that probably won't last much longer. https://www.rferl.org/a/ukraine-gazprombank-sanctions-funds-russia-war-soldiers-wages/31920143.html https://www.rferl.org/a/ukraine-gazprombank-sanctions-funds-...
- karpierz 4y ago> Russia demanded payment on their terms only after they were kicked out of SWIFT and their reserves frozen by foreign banks. If only there was something Russia could do to stay in SWIFT and not be hit by sanctions....
- aaron695 4y ago
- WalterBright 4y agoI've proposed several times on HN a "box of rocks" at the house level to store heat/cold when electricity is cheap, and release heat/cold when electricity is expensive. It was ridiculed every time. I should have patented it :-)
- tjmc 4y agoHVAC engineer here. At the residential level this is already achievable with hot water storage from either solar thermal and/or heat pumps. Plus you get to use the hot water (assuming you've sized the tank correctly!) Storing heat in rocks or sand doesn't make sense from a thermal efficiency standpoint unless the temperature is high and that isn't economically viable unless you have large volume storage - typically district or precinct level.
- WalterBright 4y agoHow can it not be efficient? The heat to heat a rock is 100% recovered when the rock cools back down. A tank of water works, too, but tanks rust, mildew, and leak.
- olau 4y agoI'm not an engineer, but I've been following the various rock storage projects, like this one https://www.stiesdal.com/storage/ https://www.stiesdal.com/storage/ for some time, and water tanks are simpler. When you set up a water tank, you just pump water into it to get the storage medium, and when you need to extract heat, you can pump out actual storage medium and do the heat exchange directly. With a rock storage, you either need pipes in them or move air through the rocks, which requires a much beefier overall system since it's harder to extract the heat. Does that make sense? Rusting tanks sounds like a problem with either badly engineered mismatched piping, or badly engineered tanks. Ideally, you'd have a well-engineered tank as a closed system with a heat exchange unit next to it. By the way, I live in a town with a wide district heating system, and there's no storage at all in the individual houses here, only a small heat exchange unit. They are building a 200.000 cubic meter water storage system in the other end, though. I don't know about this particular project, but there are other projects where the water storage is large enough and insulated well enough that they actually do store cheap solar heat from the summer through the winter - and it's cheaper than using gas, even before the current price spikes.
- kumarvvr 4y agoCurious, can this be used in reverse, to keep sand cool and use it to cool down houses? Would bring down a lot of AC usage in tropical countries.
- weberer 4y agoNormally they just pump sea water since that's usually below 20 C anyway. https://en.wikipedia.org/wiki/District_cooling https://en.wikipedia.org/wiki/District_cooling
- calaphos 4y agoA major problem would he that the temperature delta for storage will be way smaller. There isn't really space for the same 500C below ambient in that direction :)
- DavidKarlas 4y agoIf someone prefers video format + founders answering questions... https://www.youtube.com/watch?v=tm7spMG0ch8 https://www.youtube.com/watch?v=tm7spMG0ch8
- deleted 4y ago[deleted]
- matthewsinclair 4y agoDupe? https://news.ycombinator.com/item?id=31999241 https://news.ycombinator.com/item?id=31999241 I am really intrigued as to how some posts for the same (or similar) story get to the front page and others don't rate a mention.
- Jistern 4y ago
- zaxpr 4y agoare we not already running out of sand? 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...
- julienreszka 4y agoWe are running out of a special kind of sand. This isn't the one.
- deleted 4y ago[deleted]
- yellow_lead 4y agoWe are running out of angular sand, not desert sand. Angular sand can be used for building materials like concrete but desert sand is smooth so doesn't work well for it. For this battery, I would expect either sand would work (but I didn't see any details in the article)
- punnerud 4y agoThe ‘sand battery’ explained: Insulate a lot of sand and heat it with an electrical element (300-500°C). When you need the energy back, pump air into it and you get hot air to power generators and heat buildings.
- koheripbal 4y agoIt's important to remember with most of these thermal batteries is that they are limited in efficiency by the laws of thermodynamics, both when putting the energy in and then again pulling it back out. The net round trip total power loss is usually well above 50%.
- einpoklum 4y agoI'm no thermodynamicist, so I can only take you at your word about the power loss. But still: * Suppose you can effectively and consistently get 40% of the energy you put into this kind of battery. * Suppose you can make enough sand batteries to cover your overall power consumption (this is a big ask, but for the sake of discussion let's assume we can achieve this). * Suppose that you have an energy source that's non-uniform across the day. For simplicity suppose that it produces 2N MegaWatts for 12 hours and 0 MegaWatts for 12 hours, i.e. N MegaWatts on average. * Assume that electric power consumption, not including the batteries, is uniform across day and night (It isn't; it would actually be lower when power is generated if we're talking about solar). * suppose we want a uniform power source when considering the batteries. ------ Now, let delta be the fraction of our power output which we divert towards batteries, which are only charging during the 12 hours in which that is possible. Solving for uniformity, fraction not diverted to batteries = fraction recovered from batteries (1 - delta) = 40% \* delta 1 = 1.4 \* delta delta = 1/1.4 = 5/7 ~= 0.7143 1-delta ~= 0.285 So, you get a power source that's uniform over the entire day at 0.285 * 2N = 0.55 * N MegaWatt, i.e. over half of your average power output of the unstable source. That's not great, but it's pretty damn good!
- ktzar 4y agoFrom other articles, the key is that, if the energy recovery happens during cold months and the residual energy in heat form is used to feed municipal heating networks, efficiency can be up to 90%.
- bawana 4y agoHow about putting a thermoelectric device in orbit- you know one of those things that generate electricity from a temperature differential- the sun facing side is hundreds of degrees above zero,the shadow side is hundreds of degrees below zero. Beam the energy to earth with a maser
- s1artibartfast 4y agoIt is hard to radiate heat in space and maintain the low temperature side. Also, thermoelectric materials are notoriously dense and heavy