[HN Gopher] 'Freeze-thaw battery' stores electricity long-term f...
       ___________________________________________________________________
        
       'Freeze-thaw battery' stores electricity long-term for seasonal
       release
        
       Author : OJFord
       Score  : 95 points
       Date   : 2022-04-05 13:15 UTC (9 hours ago)
        
 (HTM) web link (eandt.theiet.org)
 (TXT) w3m dump (eandt.theiet.org)
        
       | seltzered_ wrote:
       | "The freeze-thaw phenomenon is possible because the battery's
       | electrolyte is molten salt - a molecular cousin of ordinary table
       | salt. The material is liquid at higher temperatures but solid at
       | room temperature. The freeze-thaw battery was shown to retain 92
       | per cent of its capacity over 12 weeks."
       | 
       | Any relation between this and 'sodium-ion' battery companies like
       | the recently acquired Faradion? (see
       | https://www.youtube.com/watch?v=W2PmRT3akGk )
        
         | maxerickson wrote:
         | The electrolyte is sodium aluminum and chlorine, which sounds
         | pretty different than sodium-ion.
         | 
         | https://www.sciencedirect.com/science/article/pii/S266638642...
         | 
         | The PNNL article is somewhat better than the current link.
         | 
         | https://www.pnnl.gov/news-media/freeze-thaw-battery-adept-pr...
        
         | cupofpython wrote:
         | molten salt is a form of long term energy storage being used by
         | some companies. One example is below
         | 
         | https://www.maltainc.com/our-solution
         | 
         | Some alternative methods and related companies:
         | 
         | https://www.greenbiz.com/article/big-money-flows-long-durati...
        
       | KennyBlanken wrote:
       | Iron flow batteries already exist commercially, are even more
       | non-toxic/safe, and they don't require heating up (and keeping
       | hot, while using) the battery.
       | 
       | https://essinc.com/iron-flow-chemistry/
       | 
       | The utility industry isn't really that interested in storing
       | power for an entire season. Very little ROI compared to a system
       | that allows them to balance minute-to-minute or day/night...or
       | transmission infrastructure improvements. Got excess generating
       | capacity? Send it somewhere that doesn't.
       | 
       | I hope that some day in the near future we see home-scale or
       | neighborhood-scale iron flow battery systems so that homeowners,
       | apartment buildings, and small neighborhoods can go off-grid.
        
         | pjc50 wrote:
         | I've never really seen the advantage in going off grid _per se_
         | , since it increases the amount of wasted capacity in both
         | generation and storage, and running a few wires is cheap enough
         | in urban environments. The most efficient arrangement might be
         | a global grid.
        
           | projektfu wrote:
           | I am not off grid, but the thing that would draw me to it is
           | as an individual sustainability goal. Perhaps it would be
           | more expensive to initially set up and run, but it should be
           | sustainable for 20-40 years. There is the side benefit of
           | reducing the demand on energy to acheive this sustainably.
           | Spending less on technology and energy means working less. In
           | other words, we pay in our own time for the time technology
           | saves us.
           | 
           | To quote Thoreau: 'One says to me, "I wonder that you do not
           | lay up money; you love to travel; you might take the cars and
           | go to Fitchburg to-day and see the country." But I am wiser
           | than that. I have learned that the swiftest traveller is he
           | that goes afoot. I say to my friend, Suppose we try who will
           | get there first. The distance is thirty miles; the fare
           | ninety cents. That is almost a day's wages. I remember when
           | wages were sixty cents a day for laborers on this very road.
           | Well, I start now on foot, and get there before night; I have
           | travelled at that rate by the week together. You will in the
           | mean while have earned your fare, and arrive there some time
           | to-morrow, or possibly this evening, if you are lucky enough
           | to get a job in season. Instead of going to Fitchburg, you
           | will be working here the greater part of the day. And so, if
           | the railroad reached round the world, I think that I should
           | keep ahead of you; and as for seeing the country and getting
           | experience of that kind, I should have to cut your
           | acquaintance altogether.' _Walden_ , chapter 1, Economy.
        
           | KennyBlanken wrote:
           | Utilities around the US are working in numerous states to get
           | favorable legislation letting them pay a fraction of what
           | they do now for solar and wind energy fed back into the grid
           | by residential and commercial customers. Once you even out
           | your meter and reach net generation, any further generation
           | into the grid you'll soon be getting bupkus for. Sorry, but I
           | got better things to do than line the pockets of my state's
           | for-profit utility company.
           | 
           | In rural areas, getting connected can mean tens of thousands
           | of dollars...if they even offer it to you at all.
           | 
           | No matter where you are, you have to pay a monthly connection
           | fee. It really adds up, and given how cheap solar and wind
           | are now, you don't really get anything for it. Battery
           | storage systems a couple years ago were very expensive, but
           | prices are crashing and safer tech like lithium iron
           | phosphate are becoming more commonplace. Heatpump systems
           | have gotten so efficient that I'm pretty sure my next furnace
           | isn't going to be a furnace, but an electric heatpump.
           | 
           | In my area, we lose electricity for a day or so in the
           | winter, 1-3x a season. A year or two ago we were without
           | power for 3 days. Everyone has generators; expensive,
           | noisy/annoying (especially given they conduct a weekly
           | "exercise"), wasteful, polluting, and expensive to maintain.
           | 
           | Having at least a large battery backup would mean I don't
           | freeze, I can cook, take a hot shower, do my laundry, and my
           | food doesn't spoil. And I don't need to pay the electric
           | company for a product that just isn't very reliable and is
           | increasingly irrelevant.
        
             | PaulDavisThe1st wrote:
             | > Battery storage systems a couple years ago were very
             | expensive, but prices are crashing and safer tech like
             | lithium iron phosphate are becoming more commonplace.
             | 
             | Unless you live in a mild climate and/or have a full
             | Passivhaus-level construction and/or live in a very small
             | building, there are no current batteries that will get you
             | through a winter of heating.
             | 
             | I live in New Mexico, have some of the best insolation
             | numbers around (outside of Arizona), generate around 93% of
             | my annual electricity use, including heating (air source
             | heat pumps) from a 6.6kW PV array. A battery system large
             | enough to store my winter needs built with any currently
             | available technology would be completely untenable, both in
             | terms of cost and size.
             | 
             | I pay $7.71 as a monthly connection fee, and I get back my
             | excess summer production as "free kW" during the winter, an
             | arrangement I much prefer to being paid directly. The "free
             | kW" are a 1:1 match for my over-production.
        
       | credit_guy wrote:
       | Sorry to be a killjoy, but $6/kwh is at least 20x too expensive.
       | In 2021, the average price of electricity in the US was 14
       | cents/kwh. Assuming you charge with free electricity, your
       | charge-discharge efficiency is 100%, there is no capacity loss
       | over the years, and your cost of capital is zero, you need more
       | than 40 years to break even at that price. All the 4 assumptions
       | above and a few others (zero installation and maintenance cost,
       | zero insurance, zero cost of disposal) are super unrealistic.
        
         | mechagodzilla wrote:
         | I think you misunderstood the article - they're talking about
         | the capacity of the battery in terms of kilowatt-hours, not its
         | cost relative to round-trip efficiency. If the cost were
         | $6/kwh, you could build a 100kwh battery for $600, and
         | charge/discharge that many times. I think this is supposed to
         | be interesting both for its relatively cheap materials (and
         | useful level of energy density), and its ability to be 'frozen'
         | in a room-temperature charged state for long periods of time
         | without much loss of charge.
        
           | credit_guy wrote:
           | Seasonal storage means you charge in the summer and discharge
           | in the winter. One cycle per year. You need 40 years to sell
           | electricity 40 times.
        
         | AtlasBarfed wrote:
         | "Exploring the use of Iron" "Limited by Nickel"
         | 
         | "Limited by Nickel": This is just lithium ion battery storage,
         | it is plainly obvious.
         | 
         | "Exploring the use of Iron": using LFP (which will be 200-230
         | wh/kg in production later this year)
         | 
         | "Added some sulphur": great, but you're wayyyy behind the
         | current state of the art research in Li-S.
         | 
         | That cost is appropriate for maybe a day or two of storage.
         | Months between seasons? That's ridiculous, even if we had a
         | dirt-cheap 200 wh/kg sodium ion battery which COULD probably
         | hit 6$/kg, unlike their unnamed/unspecified techs they are
         | "looking into". Likely it is since every other battery buzzword
         | was notched in this article.
         | 
         | The use case, providing more energy in the summer, is covered
         | with solar + couple day grid storage and existing nuclear or
         | gas turbine for load leveling.
         | 
         | What we need is to install as much wind and solar as possible
         | to immediately eliminate coal, then add storage and more
         | wind/solar as needed to start eating away at gas turbine.
         | Nuclear should stick around for long-term load levelling until
         | batteries become dirt dirt dirt cheap.
         | 
         | This article is so poorly written that it might as well be
         | unintentional FUD.
        
       | phh wrote:
       | It doesn't sound like the improvement of cost is enough the
       | justify using it only for few cycles a year as the title says
       | rather than every other day. That said, I see nothing in this
       | article saying why it would be limited to seasonal release, I'm
       | guessing it just has a lower self-discharge.
       | 
       | The title made me thought of an idea my father had, for which I'm
       | still totally ambivalent:
       | 
       | Freeze water in the cellar (speaking of like 30m^3) using thermal
       | pomp during winter to heat house and when electricity costs
       | little, and use that ice in summer to cool down the house. I
       | didn't run the numbers, but I'd guess that if it was even
       | remotely not a pure energy loss some other people would have
       | already proposed such things.
        
         | brtkdotse wrote:
         | Congratulations, you just invented geothermal heat pumps. :)
         | They've been the preferred way of hearing single family houses
         | in the Nordics since the 90s.
        
         | Haplo wrote:
         | Similar systems are actually being build, but with a bigger
         | scale (like big office buildings). There is no freezing
         | involved, just heating the office space with warm water in the
         | winter (cooling the water to ~10degC) and cooling it in the
         | summer (heating the water to about 40degC).
        
           | mnahkies wrote:
           | During the rebuild of Christchurch, NZ they used this
           | technique for a number of buildings, basically pumping out
           | water with one well, then re-injecting it with another as I
           | understand.
           | 
           | Essentially exploits the ground water remaining a constant
           | temperature year around, warmer than the surface in winter
           | and colder in summer
        
         | KennyBlanken wrote:
         | > some other people would have already proposed such things.
         | 
         | Geothermal heat pumps. Been around for decades. Expensive to
         | install due to drilling the well or laying the field, but very
         | efficient.
        
           | mschuster91 wrote:
           | Geothermal energy is risky AF though. Even with shallow
           | drilling depths, you risk hitting anhydrite and, in
           | combination with water, massive damage like in Staufen [1].
           | 
           | [1] https://de.wikipedia.org/wiki/Hebungsrisse_in_Staufen_im_
           | Bre...
        
             | brtkdotse wrote:
             | The large portion of single family homes in Sweden are
             | heated (and cooled) using geothermal heat pumps. The drill
             | holes are 100-150m deep.
        
             | ClumsyPilot wrote:
             | Geothermal energy for power generation and heat pumps for
             | heating homes are totally different systems. It's like
             | comparing a fireplace in your house to a nuclear power
             | plant.
        
         | Gasp0de wrote:
         | This exists and is actually used in Germany, it is called
         | "Eisspeicher" (ice storage). It is utilizing the effect that it
         | takes a huge amount of energy for the water to go from solid to
         | fluid, about the equivalent of heating water from 1 to 81
         | degrees.
        
         | ZeroGravitas wrote:
         | There's a few large building air conditioning units that do
         | exactly this. Ice Bear was one brand name I think.
        
         | mabbo wrote:
         | > Freeze water in the cellar (speaking of like 30m^3) using
         | thermal pomp during winter to heat house and when electricity
         | costs little, and use that ice in summer to cool down the
         | house.
         | 
         | Unless I misunderstood, the Toronto Zoo has or had such a
         | system setup for one or more of the food pavilions.
         | 
         | What's interesting about this is that the storage grows with
         | the volume (n^3), but the heat/cold loss grows with the surface
         | area (n^2). So you're ability to 'store cold' gets better as
         | you get bigger.
         | 
         | Just the same, you could also use it backwards in the winter
         | time. On hot, sunny days at the end of the summer, warm up the
         | water stored.
        
           | [deleted]
        
           | treeman79 wrote:
           | How does this compare to hauling ice down from a local
           | mountain lake?
           | 
           | Feels like 0-18th century tech. Doesn't mean it's bad though.
        
           | SECProto wrote:
           | > On hot, sunny days at the end of the summer, warm up the
           | water stored.
           | 
           | Phase change stores/requires much more energy than simple
           | temperature change. 0degC Ice to 0degC water transition is
           | 334J/g, 0C water to 100C water is ~400J/g (ie 4J/g per degree
           | C), 100C water to 100C steam is 2260J/g.
           | 
           | To store heat from the summer for winter warming (say best
           | case 40C summer temp) you'd be looking at least 3x as much
           | material for heat storage vs ice storage for summer cooling
           | (at say -10C)
        
             | xvedejas wrote:
             | This is a useful thing: storing energy in a phase change
             | makes it easier to keep the energy stored for a longer
             | period of time compared to if there was no phase change.
             | The difficult part is that steam is much farther from
             | ambient temperatures than ice is (and also that it is far
             | less compact). Newton's law of cooling means that the
             | larger the temperature difference, the faster the heat
             | loss, so steam would require much more insulation than ice
             | would.
        
               | sacrosancty wrote:
               | Besides insulation, there's no hope of storing thermal
               | energy as steam because the density is 1000 times lower
               | than ice or water while the specific heat is similar, so
               | the heat capacity per unit volume is about 1000 times
               | lower.
        
               | SECProto wrote:
               | Storing heat as steam is actually very good and efficient
               | - as long as you're storing the heat for location
               | shifting, not temporal shifting. It's regularly used in
               | combined heat + power plants
               | 
               | (Yeah, I know I'm being both pedantic and off topic,
               | since the discussion here is specifically about seasonal
               | storage)
        
           | bombcar wrote:
           | The cube/square law also applies in the opposite direction,
           | this is why it takes longer for lakes to freeze and why the
           | Great Lakes never do.
           | 
           | I believe at least one university on the Great Lakes does
           | heating and cooling with pipes deep under the lake.
        
             | frosted-flakes wrote:
             | The Great Lakes do occasionally freeze over significantly,
             | though never completely. 2013-2014 was one such winter,
             | when ice coverage reached 92% across all five lakes. That's
             | quite unusual though.
             | 
             | And the city of Toronto uses lake water for cooling. Heat
             | from a downtown cooling loop is dumped into the city's
             | drinking water supply, bringing the temperature up to
             | around 13deg from 6deg (if I remember correctly).
        
               | mabbo wrote:
               | Not just drinking water. The cool water is pumped into
               | buildings to work as the air conditioner for a lot of the
               | big buildings.
        
         | jewel wrote:
         | Your father's idea is a good one. Here is a thermal heat pit
         | which is being used to store heat for the winter:
         | 
         | https://stateofgreen.com/en/partners/ramboll/solutions/world...
        
         | gwbas1c wrote:
         | Don't forget that, until the invention of refrigeration, people
         | used to harvest ice in northern climates. They would store it
         | in hay, and then sell it throughout the year.
         | 
         | Ice was even shipped internationally.
         | 
         | (And, if you're a fan of Disney's Frozen, this is exactly what
         | Sven did.)
        
       | gwbas1c wrote:
       | > The battery's theoretical energy density is 260 watt-hours per
       | kilogram
       | 
       | Makes me wonder how big a battery would need to be to handle all
       | of the overwinter energy demands of some densely-populated US
       | states.
        
         | KaiserPro wrote:
         | Massive. But I don't think thats the point of this.
         | 
         | I imagine you'd pair this with an energy source(say solar), so
         | that you are able to smooth out/absorb excess energy and
         | release when its needed. You could use it as an energy supply
         | of last resort.
        
         | mfringel wrote:
         | Just to put some numbers around that...
         | 
         | Density of ice at 0 degC is 0.92 kg/L. So, 1 kg of ice =~ 1087
         | cubic centimeters of space, or a cube ~4.25 inches on a side.
         | 
         | Rounding that down to 4 inches for the moment, you get 27 of
         | those per cubic foot, or (260 Wh * 27) = 7.02 kWh, and then
         | round _that_ down to give the extra quarter-inch back, you get
         | ~6.5 kWh /ft3 theoretical capacity.
         | 
         | A typical household in the US uses 10,715 kWh/year[0], so
         | (10715/6.5) = 1648.46 ft3 for a household's worth of freeze-
         | thaw battery storage, or a cube 11.81 feet on a side.
         | 
         | Yes, of course it's more complicated than that, but the scale
         | is pretty interesting.
         | 
         | ---
         | 
         | [0] https://www.eia.gov/tools/faqs/faq.php?id=97&t=3
        
       | jessriedel wrote:
       | For more on the general problem of storing thermal (rather than
       | electrical) energy on a seasonal basis see
       | 
       | https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storag...
       | 
       | I was especially surprised to learn that serious attempts at
       | storing heat in _soil_ and _rock_ have been made
       | 
       | https://en.wikipedia.org/wiki/Seasonal_thermal_energy_storag...
       | https://en.wikipedia.org/wiki/Drake_Landing_Solar_Community
       | 
       | which in the winter is able recover >40% of the energy stored in
       | the ground through boreholes in the summer ("BTES Efficiency")
       | 
       | https://www.dlsc.ca/reports/swc2017-0033-Mesquita.pdf
        
         | nikanj wrote:
         | Furthermore, we have a real problem with the soil storing heat:
         | https://citymonitor.ai/transport/londons-tube-has-been-runni...
        
           | alexchamberlain wrote:
           | Stupid question: can we harness this 100 year old heat to
           | power something today?
        
             | vikingerik wrote:
             | You can't exactly harness heat; what can be harnessed is a
             | temperature _differential_ , to convert into some form of
             | mechanical motion or electrical potential. You'd need some
             | apparatus that connects the hot mass and some cold sink
             | with thermocouples. Whether that's possible or feasible on
             | the scale of the London Tube, I don't know.
             | 
             | https://en.wikipedia.org/wiki/Thermoelectric_effect
             | 
             | Instead of that, probably a more feasible way to make use
             | of heat is just as heat, by some way of circulating it into
             | buildings in the winter. One interesting angle of looking
             | at this would be that it's really an artificially created
             | geothermal source.
        
             | thescriptkiddie wrote:
             | Yes
             | 
             | https://www.newcivilengineer.com/innovative-
             | thinking/harness...
        
       | lbriner wrote:
       | This is pretty sweet!
       | 
       | There isn't enough information about larger/heavier but greener
       | battery technology that would be suitable for grid/home storage
       | without the environmental costs associated with the rare earth
       | stuff needed for transportation.
        
       | a9h74j wrote:
       | Tangent, but in the seasonal storage context.
       | 
       | Apparently, according to a reported simulation, if you (1) take a
       | ca 15m x 15m house thermally in contact with the ground, (2)
       | insulate the ground outside to a radius of ca 40m, and (3) heat
       | the interior to say 25C, then (4) evenually (50years?) the ground
       | itself under the house will come up to a steady temperature
       | consistent with that.
       | 
       | Even if the simulation was correct, I can only see this being
       | sustainable with solar gain being used for heating, but it makes
       | for an interesting long-term-oriented picture.
       | 
       | One imaginable scale of application could be for a cluster of
       | houses in a larger agricultural setting.
        
         | snewman wrote:
         | Gradual heating of the ground is definitely a thing; over the
         | decades, certain London Tube lines have drifted from pleasantly
         | cool to sweltering: https://www.wired.co.uk/article/central-
         | line-temperature-lon...
        
           | ClumsyPilot wrote:
           | Yes, people are literally dying in the heat from heart
           | attacks because city planning won't allow TFL to knoxk down a
           | house sp they cam build a ventillation shaft
        
             | jdmichal wrote:
             | Do the tubes never cross a road? Why knock down a building
             | instead of taking a vent to a street?
        
         | gnorme wrote:
         | I'd love to read more about this simulation, have any links?
        
           | a9h74j wrote:
           | I am unable to find a link, and IIRC this was reported 10
           | years ago or so. I recall an attribution to German designers
           | or architects. I cannot remember where exactly it was
           | reported, but I remember it as moderately plausible
           | reporting, although not in a journal.
           | 
           | A quick estimate with soil:
           | 
           | Take a specific gravity of 2.7 gm/cm^3, a specific heat of
           | 0.2 cal/gm-K, and 1 cal ~ 4.2J ~ 4.2 W-sec. For a cube 25 m
           | (2500cm) on a side, if I am not mistaken this suggests a
           | thermal inertia of about 3.5E10 W-sec/K.
           | 
           | Now take a thermal conductivy of 1 W/m-K. For a slab of 25m x
           | 25m, also with a thickness of 25m, we get a net conductivity
           | of 25 W/K .
           | 
           | Then 3.5E10 W-sec/K divided by 25 W/K gives 1.4E9 sec . Given
           | 3E7 sec/year, that suggests about 47 years.
           | 
           | Aka a 50 year time scale.
           | 
           | Of course this assumes a low water table.
        
       | jillesvangurp wrote:
       | Seasonal storage and thermal batteries are pretty easy and cheap
       | to construct. The materials tend to be cheap commodities. All you
       | need is space to construct them and a way to produce the heat you
       | use to charge them.
       | 
       | For example, I know of an experimental setup in the Netherlands
       | called CESAR (https://materialdistrict.com/article/battery-
       | natural-stone/) that uses basalt rock. The basalt is heated up
       | using solar energy in the summer. It is stored in an a metal box
       | insulated with wool that apparently retains heat for
       | months/years. Long enough to last the winter. You 'discharge' by
       | pumping cold water through it. Warm water comes out. Very simple.
       | It has been running for a few years and it seems to be cheap and
       | work as advertised. Relative to burning gas, this looks like a
       | nice idea.
       | 
       | Converting heat to electricity is more tricky and the
       | efficiencies tend to be not great. Of course if the storage is
       | cheap enough that might not be that big of a deal. Efficiencies
       | are also a challenge with geothermal energy. But it's a great
       | solution for heating buildings. This particular solution seems to
       | work around this using molten salt which allows for a relatively
       | large temperature gradient. But without having to drill
       | kilometers into the earth's crust.
       | 
       | Probably over time, cost will decide which solutions end up
       | getting used where and how. A good insight here is that different
       | storage solutions serve very different purposes. You don't use
       | lithium ion for seasonal storage. It's way too expensive for
       | that. But it's great for short term grid balancing needs and
       | seems to be popular for that. Vice versa, thermal mass would be
       | probably bad for balancing the grid it's great for storing lots
       | of energy that you use up slowly during the winter.
       | 
       | It's a tradeoff between how much energy you need stored, how much
       | space you have for storing it, and how quickly you want to
       | charge/discharge. It's telling a lot that a relatively expensive
       | solution like lithium ion batteries are actually cost competitive
       | with things like gas peaker plants. We can do probably do better
       | long term. There is no shortage of good & already validated ideas
       | in this space. All we need is good old engineering and
       | manufacturing to prove products in the market at scale.
        
         | mlatu wrote:
         | the article is about an _electrical_ battery that is seasonally
         | heated up for usage and cooled down for the long term storage
         | of the charge contained in it...
         | 
         | i had only heard of molten salt batteries which need to stay
         | hot long term, so they are heavily insulated
         | 
         | maybe this article is talking about a primary battery (i.e.
         | electrically not rechargable), which would make more sense
        
       | Gasp0de wrote:
       | This doesn't seem cost efficient at all, my (medium sized) house
       | in Germany consumes about 3000kWh of electricity during winter.
       | This does not include heating, which consumes another 15.000kWh
       | (of heat energy from oil, so around 5000kWh electrical energy
       | with a heat pump).
       | 
       | If I were to use this battery I would need to get 3000(8000)kWh
       | of energy storage at 23$ per kWh which would amount to
       | 69000(184000)$. There are better hydrogen-based solutions for
       | that cost. Also, did I read correctly that I have to keep the
       | battery heated to 180degC during discharge? This is going to
       | waste a lot of energy in winter.
        
         | harg wrote:
         | You're assuming that the battery needs to store the total
         | energy requirements of a house for the entire year. Much of the
         | time the energy needs can be met by conventional energy
         | generation (wind turbines, solar, hydro, etc) and the battery
         | is only called upon when there's a shortfall. So you'd only
         | need a fraction of the annual consumption to make it useful.
         | The whole idea is to make renewables more effective by storing
         | the excess. Grid storage will be an important part of the
         | transition to renewables.
         | 
         | But yes, it is expensive, but it's only at the R&D stage. I'm
         | sure could be made cheaper, and the article mentions reducing
         | the cost to $6/kWh.
        
           | t0mas88 wrote:
           | If you use solar power in a climate like Germany you will get
           | that kind of math.
           | 
           | Let's say you use 8000 kwh per year, and you have the solar
           | capacity to create 8000 kwh per year. Assume you already have
           | a normal home battery of ~14kwh so day/night is not an issue,
           | the solar production during daytime charges the battery and
           | all night time power comes from the battery.
           | 
           | Now your big problem is that 70% of the 8000 kwh solar per
           | year is produced from May to September. You need 670 kwh per
           | month for usage, so in those four months you have just under
           | 3000 kwh too much. Then in April and October the panels
           | roughly produce what you use. And November to March you have
           | a total shortfall of 3000 kwh.
           | 
           | So you need seasonal storage capacity of about 3000 kwh to be
           | able to run an 8000 kwh yearly usage on solar in this
           | climate.
           | 
           | The other option is to buy much more solar panel capacity
           | than you need, then you can use a smaller battery which in
           | total could be cheaper since solar panels aren't that
           | expensive anymore.
        
             | PaulDavisThe1st wrote:
             | > The other option is to buy much more solar panel capacity
             | than you need,
             | 
             | You need the space to install them also. I have a 6.6kW
             | array, and would need 3x that capacity to heat my home
             | using electrically-powered air source heat pumps during the
             | winter months. Even with 0.75 acres / 0.30 hectares, that
             | would be quite a lot of my property covered by panels, and
             | way more than could ever feasibly fit on the roof (the
             | current array is ground mount).
        
         | [deleted]
        
         | awestroke wrote:
         | You heat you house with oil? I thought Germany was
         | environmentally conscious
        
           | coryrc wrote:
           | It's called "greenwashing". A fair bit of electricity is
           | produced with solar (at a far higher cost than their
           | neighbor's carbon-free electricity) but their gasoline and
           | diesel vehicle manufacturing continues unbounded and their
           | heat primarily comes from fossil fuel.
        
           | llampx wrote:
           | Germany is still mining coal but they are environment
           | conscious so they sell it to Poland to burn and buy
           | electricity from them.
        
         | gwbas1c wrote:
         | Gosh, it's still coming out of academia. It takes awhile before
         | these kinds of things are economically viable.
        
         | pjc50 wrote:
         | The economics is not great as described, but I wouldn't see
         | this at being an individual level solution. The larger it is,
         | the easier it is to insulate.
        
       | [deleted]
        
       | ema wrote:
       | Just realized that with a battery intended for seasonal storage
       | you only get one cycle per year so for the same ROI as a battery
       | that cycles weekly or daily it has to be much cheaper per kwh of
       | capacity. OTOH it only needs to last for like 50 cycles.
        
         | maxerickson wrote:
         | I wonder what the napkin math is vs something like methane
         | synthesis.
        
         | cupofpython wrote:
         | I like to imagine a system with the different geothermal-like
         | technologies working together in maybe a layered like
         | structure.
         | 
         | Extracting from the winter / summer cycle, the day / night
         | cycle, and the consistent deep ground / surface air temp
         | differential.
         | 
         | Granted day / night might not have enough variation to take
         | advantage of in a lot of places - but surely some cool tech has
         | come out of desert areas right?
        
           | jdmichal wrote:
           | Arid locations already enjoy much cheaper cooling via swamp
           | coolers over heat pumps. They're just enough to keep it
           | bearable during the day, then the night comes and clears out
           | all the latent heat.
        
       | wppick wrote:
       | Is there any examples of using something like a server farm to
       | heat a building in the winter? Removing heat from a server farm
       | through heat exchange with a cold building seems like an
       | efficient combination of two interests (building needs heat,
       | servers need to get rid of heat). Of course this becomes a
       | problem in the summer months...
        
         | wongarsu wrote:
         | Stockholm, Sweden has an open district heating network:
         | buildings can not only buy heat from it for heating, like a
         | normal district heating network, they can also sell surplus
         | heat to the network. At least two data centers (Bahnhof Thule
         | and Bahnhof Pionen) sell heat from their heat exchangers to the
         | network.
         | 
         | https://celsiuscity.eu/wp-content/uploads/2020/06/Waste-heat...
         | pages 7-9
        
         | uomo wrote:
         | One of Amazon's buildings in Seattle (Doppler) uses a data
         | center next door to reduce their overall heating costs during
         | the winter.
         | 
         | Source: https://www.aboutamazon.com/news/sustainability/the-
         | super-ef...
        
         | Quindecillion wrote:
         | This is actually one of the use cases that Satoshi Nakamoto
         | spoke about in regards to Bitcoin mining.
         | 
         | The purpose built machines for mining (ASICs) turn electrical
         | energy into heat through performing hashes. If you need
         | electrical heating there's functionally no difference between
         | turning a regular heater on or turning on an ASIC. The benefit
         | of turning an ASIC on instead is you can recoup some of the
         | cost of expending the electricity.
        
         | grenoire wrote:
         | In Amsterdam, the botanical gardens and Hermitage Amsterdam
         | exchange heat in that sort of mutually beneficial way, https://
         | www.cultureelerfgoed.nl/onderwerpen/praktijkvoorbeel....
        
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