12 ms·

> However, because it is physically not possible to charge and discharge the battery at the same time, such trades have to be prevented. The authors are observ

• fluorinerocket 1y ago
  Find area near shore, stick two big electrodes in water a mile apart, energize circuit when price is negative, profit!
  • idiotsecant 1y ago
    I am in the power generation industry and I have honestly wondered why nobody does this. I figure getting the interconnect big enough to make meaningful money is both prohibitively expensive and a lengthy delay.
    • CoastalCoder 1y ago
      Or put them closer together and generate all of the chlorine gas, H2, and O2 a girl could want!
• triceratops 1y ago
  If you have free energy the obvious thing to use it for is carbon capture.
  • bee_rider 1y ago
    I wonder if desalination would be another good use. But, yeah, it is probably just a matter of how fast the processes can absorb extra power.
    • cogman10 1y ago
      District heating and cooling would be an excellent sink for the power. Water needs a lot of energy to cool or heat, concentrated at a district, you could easily absorb a lot of energy at negative prices.
      • XorNot 1y ago
        Electric heating elements aren't free nor infinite in capacity. You'd pay a lot of money for a rarely used asset that has to be replaced by something else most of the time because people want their heating to be reliable.
        • nasmorn 1y ago
          But it is not horrible. A lot of people have resistive water heating for their solar setup because grid sell prices are super low and a 2kw water heater cost basically nothing.
          • XorNot 1y ago
            Which they use all the time. If you did this at a district heating level, you'd just be running an electric district heating system, resistively, which you run all the time - it wouldn't be a dump load, it would just be the load and a very inefficient one at that (compared to a heat pump). The point is all this stuff costs money to build, money to maintain, so if you don't use it most of the time the time you do needs to be incredibly valuable.
            • nasmorn 1y ago
              A 10kw heating element costs 250 euros, lets double that to make it able to switch off by the smart meter. Now if you used it 1% of the year and saved 5ct per kWh you would gain 43 eur a year. Not a super convincing ROI but compared to your 10kw peak solar array a very small investment. If you used it just 2% of the year it would already be pretty good and the switch might become very cheap in the future if most houses use load steering for all kinds of things
• looofooo0 1y ago
  Good luck trying to get rid of such an amount of heat anyway near your batteries.
  • doener 1y ago
    Well in times of negative energy prices wouldn't it even be good if the air conditioning ran at full capacity?
    • Energiekomin 1y ago
      In summer? If its not getting to cold for you. In winter yes also if its not getting to warm for you, but also heating water is easy enough. But you don't need that much hot water Potentially also cooling down your fridge more and your freezer. But that is not that much energy. While that works, it would still be quite a waste. It would be a lot better to save it and discarge it later
    • WJW 1y ago
      Depending on how powerful your air conditioner is, it would rapidly start cooling down the building to a temperature which is too low to still be comfortable. You could maybe buffer this with more thermal mass, but then you are back in the game of storing energy and might as well just get extra batteries.
      • sib 1y ago
        Why not place the air conditioner next to a large electric space heater?
      • amluto 1y ago
        Many heat pumps already have a mechanism for deliberately wasting energy for defrosting the coils. I bet that the same hardware with a different control algorithm could be convinced to heat out the outdoors without much net change in indoor temperature. (The solution involving the smallest amount of extra hardware is to run the system in reverse periodically. There are other solutions.) Whether the negative energy price is enough to balance wear on the system and potential noise is a different question.
• jordz 1y ago
  I work in the industry making hardware and software for large scale commercial and grid scale storage. There are several challenges with this, safety, thermal runaway, and life cycle of the asset which has a limited amount of cycles. Also the architecture of the system for the AC inverters and the DC side can come from very different places in the supply chain and aren’t as vertically integrated leaving you in a position where you can’t actually make this work without compromising something in the supply chain. That being said we are talking about a LOT of energy in these systems and to dissipate that much heat you’d need a load bank.
• raphaelj 1y ago
  Couldn't the battery just do, as an example, 1 minute long charge then discharge cycles? For example, if the electricity price is -28€/MWh (like today in Germany), and your battery efficacy is 80%, you could get paid 28€/MWh charging, then only pay back 22€ discharging, generating a 6€/MWh profit.
  • 7thaccount 1y ago
    The wholesale energy markets don't have sub 5-minute granularity anywhere that I'm aware of. In the US, 1-hour is standard in the day-ahead markets and 5-minutes is standard for the spot markets. There is also the problem that your battery would likely degrade fast depending on the technology.
• 4gotunameagain 1y ago
  The solution is actually what's called a "dummy load". Get paid to waste energy and heat up the planet a tiny bit more, gotta love it.
  • thebruce87m 1y ago
    Can’t we power a big laser and point it at space or something instead? Anyone got a dumber idea?
    • beAbU 1y ago
      There are so many things that are energy intensive and not really economically viable: co2 capture, crypto mining, "green" hydrogen, we could see a world soon where a large scale BESS would have an on-site dummy load that does something useful with that electricity
      • Analemma_ 1y ago
        The problem with all those things is that they are ridiculously capital intensive to set up, and then they sit idle 80% of the time Worse, the whole point of negative electricity prices is that they're an inefficiency in the market which ideally will eventually be optimized away. Then what do you do with your billion-dollar plant that can only run with negative prices that no longer exist?
        • adgjlsfhk1 1y ago
          You're assuming the way they get optimized away isn't by these sorts of plants.
    • karmakurtisaani 1y ago
      I guess the problem with building a pure energy waster is that it could only operate every now and then, and it's not guaranteed to see negative prices in a few years from now. So, might not be all that profitable.
    • 1y ago
• ZeroGravitas 1y ago
  Not sure if it's discussed in the paper but apparently in Australia there have already been recorded instances of batteries charging with negative price electricity and then selling back that electricity at a still negative but closer to zero price and so profiting. When I first heard it, it seemed wild that they couldn't hold on for the price to go back above zero, but I guess if we're talking high frequency trading it makes more sense. They might have bought and sold many times while the price is different levels of negative before switching to charging up in preparation for the later price rises. And the round trip inefficiency helps too.
  • petertodd 1y ago
    That's not as ridiculous as it sounds! As you know, negative electricity prices mean that someone is willing to pay you to dispose of electricity they need to generate for some reason. For example, a conventional steam-turbine-based electricity plant might prefer to just keep running for a brief period of time when demand is low, rather than subject their equipment to a power cycle, which increases their maintenance costs. There's other, dumber, examples based on stupid contracts and badly designed solar... but this example is a reasonable one that exists for good engineering reasons. The battery provider in this circumstance is profiting from their ability to accept power when demand to dispose of electricity is particularly high. When that need goes down, they can reasonably profit by dumping that energy on someone else who is also able to dispose of the electricity. But at a lower cost. E.g. imagine an big industrial refrigerated storage facility that can consume some excess energy by supercooling their refrigerators. But they can't consume unlimited excess energy, because at some point their warehouse just gets too cold, and they don't have unlimited refrigeration capacity anyway. So in this simplified example, the battery storage service is getting paid a lot of money to quickly absorb a lot of energy, which they then dump more slowly to the refrigerated warehouse (and similar providers) as the surplus diminishes, in anticipation of another surplus in the near future.
    • kurthr 1y ago
      If it was so profitable, why wouldn't the electricity utility do it themselves? Certainly, they have the scale, infrastructure, and pricing power to do it. Oh, that's right. This is supposed to be wealth transfer.
• _trampeltier 1y ago
  I know a country, the national train company turns lots of outside lights on (daytime), if the price is negative.
  • _Algernon_ 1y ago
    Great for the local insect population.
  • cyri 1y ago
    Yes that is the SBB in Switzerland but they do not turn the lights, instead they turn on the heaters for the track switches. Not sure if that is all rumours.
• hwillis 1y ago
  > Surely the power electronics or even just the control algorithms in a BESS could be slightly modified to consume power, get warm, and not transfer any current to or from the battery cells, effectively taking advantage of the BESS’s heat sink to sink excess power and sell that service. Unless you specifically design for it (specifically, with a dummy load), the efficiency of the system is inversely proportional to its ability to do this. You need a secondary system. The power system can connect the battery terminal to in or to out, so if you switch both on at once you effectively bypass the battery. It's called shoot-through current and is generally considered a destructive process. If you can switch on and off fast enough you could limit it to a non-destructive level, but in practice most systems will not switch fast enough. They are designed to operate with the battery load, which is at minimum ~10x higher resistance than the transistor itself. In practice it is often 100s of times higher. That's where the efficiency comes into it. If a power system is 98% efficient (pretty normal- this does not include power lost to heat in the battery itself), that means the electronics can only burn 1/50th as much power as normally passes through the system. Worse, when you put the switch into shorted position it will try to pass 50x its rated current. You need to switch much faster -certainly more than 50x faster- and that will probably put it outside its operating region. It is relatively easy to just have a large resistor, but it is not very well suited to use battery power systems. Batteries are very low impedance, and the power system exists to transform to a lower voltage and higher current. Resistors are cheaper when they are higher voltage, so the power system is a hacky kludge. The overall solution is just more batteries. Oversupply is a transient problem and always will be.
  • ACCount36 1y ago
    > Unless you specifically design for it (specifically, with a dummy load), the efficiency of the system is inversely proportional to its ability to do this. You need a secondary system. Many multicell BMS already have this kind of "power shedding" capability. They use it for cell balancing - to equalize voltage between cells with slightly different characteristics. This is desirable despite the power waste, because it reduces wear, increases charging efficiency and allows battery packs to last longer. Some battery packs are also designed to be able to dump enough power into heat to be able to keep the batteries warm during extreme cold.
• andoma 1y ago
  Our house have geothermal heating (heatpump conncted to 160m drilled hole, pretty common in Scandinavia). The heatpump supports having a coolant loop for cooling the house in the summer. Thus the heat pump pretty much exchanges heat from the house to the well (heating it up ever so slightly). It would certainly be possible to insert a resistive dummy load on that loop and just store that heat in the bedrock as well.
  • frabert 1y ago
    This! Or, if you don't have geothermal heating but have an electric water heater, maybe temporarily increase the temperature it goes to: maybe it's normally set to go to 65C, then when you detect that you have negative prices and your batteries are full and your water already hot, maybe heat the water to 70C and store that little bit of extra energy as heat! If you have thermostatic valves in your bathrooms, you won't even notice the difference except by the fact that your water heater now can apparently hold a little bit more water than usual :)
    • cogman10 1y ago
      Assuming regular negatives (more than once a day) you could also tie the heating to the grid prices with maybe an hour buffer around your high water usage times to make sure you are up to temp. Modern water heaters will keep temp for a shockingly long period of time.
    • john61 1y ago
      I have a heat pump for hot water and calculated this with an offered floating energy tariff. It is not economical because the high net tariffs are not floating but fixed per kwH and negative / very low prices are seldom here and only for a short period of time available.
• matthewdgreen 1y ago
  Wouldn't that discharge the battery and hence contribute to battery wear, by wasting a charge cycle?
• borner791 1y ago
  Balancing.. thats probably 1-0.5% of the BESS capacity. The impedance of LFE cells are so high when charged pretty small amounts of energy can slosh around before a protection disconnect, over voltage for example
• adiabatichottub 1y ago
  I don't know why it rankles me to think that generated power should be fed into a dump load just to make the storage owners extra money. Even though it's inefficient at the system level, it shouldn't be harmful releasing energy that would have been eventually dissipated as heat anyways. And yet it still just feel wasteful to me. I had to go search my bookshelf for this one: "There has been an increasing awareness among engineers of the last two decades that machines can perform a useful purpose in many applications, even though their characteristics do not conform to the orthodox standards of goodness. The main objective of the engineer is to make money -- to exploit economically the physical properties of materials. Economic considerations, however, do not stop at the first cost of an article, nor at the running cost, but extend to everything connected with that article in the situation in which it is to be used." Eric R. Laithwaite, Induction Machines for special purposes
  • colechristensen 1y ago
    >I don't know why it rankles me to think that generated power should be fed into a dump load just to make the storage owners extra money. Even though it's inefficient at the system level, it shouldn't be harmful releasing energy that would have been eventually dissipated as heat anyways. And yet it still just feel wasteful to me. This is one of those efficient market things where you need to manage the market in order that wasteful things happen sometimes... but that waste is an opportunity. If you and your competitor are both in the business of dumping energy into heat, you're going to compete with each other for access to that money. Then one of you is going to try to find a way to make _more_ money with that energy and find something quickly scalable with not-too-high idle overhead costs to do with that energy besides just flowing through a resistor. Negative prices are a sign of an inefficient market or just the lag time between a changing landscape of resources and someone to utilize them. If there's a free resource someone's going to figure out how to use it, just let it hang out for a while and the problem fixes itself. Especially with solar energy, this is just going to be a thing. There's a certain balance where overprovisioning is cheaper than storage and so you just do that. Then you wait for industry (or consumers) to figure out how to take advantage of the intermittent cheap energy.
    • 1y ago
• thescriptkiddie 1y ago
  there are no circumstances under which it makes sense for energy prices to actually be negative. it is a sign of a market behaving very badly. propping up prices by intentionally wasting energy only treats the symptom not the cause.
  • AnotherGoodName 1y ago
    It’s only ever brief and essentially a penalty to power generators for not turning off the generation in a reasonable time
    • londons_explore 1y ago
      In most markets, it happens because one player is being given some subsidy - ie. 'we will guarantee all power you sell sells for $X/MWh', or 'You get a contractual green bonus of $$$ if you produce XMWh this year'. Those contracts mean the person producing the power is still incentivised to do it even with negative prices.
      • thescriptkiddie 1y ago
        exactly. all i'm saying is that if you have this problem it makes way more sense to pay the offending party to stop producing excess power (or fine them for not stopping) than it does to pay someone else to intentionally waste it.
• burnt-resistor 1y ago
  Supercapacitors ready to soak up power to charge batteries whenever rates stabilize.
  • XorNot 1y ago
    Supercapacitors are much more expensive then batteries with much shorter lifespans to boot (years, versus decades).
• msgodel 1y ago
  I think they just don't understand how such a market would work. You'd trade futures on the power and if you hold the contracts to maturity you'd be on the hook for delivering/accepting the power. Everything before maturity happens on paper.