12 ms·
(I do some research in this space) There are lots of cheap ways of storing heat... The capacity cost of thermal storage has not been the bottleneck for commerc
by chris_va 5y ago
(I do some research in this space)
There are lots of cheap ways of storing heat... The capacity cost of thermal storage has not been the bottleneck for commercialization, but rather the round trip efficiency. This seems academically interesting, but I doubt it will be much more than that.
To a first order approximation, the cost of power from a storage system is going to be $/kWh_source_power/efficiency+ammortized cost of capital. No matter how cheap the second term is (and it can't be that cheap unless someone invents a 10x cheaper turbine), the first term tends to make storage uneconomical unless your RTE is above ~80%. This will get ~60% at best.
(of course, I could always be wrong)
- new_realist 5y agoDoes this hold true for spilled wind and solar? Does the efficiency matter at all if it would otherwise be wasted?
- chris_va 5y agoCurtailed renewables might make this economical in the short term, but also provides the same benefit for competitive storage technologies (e.g. LiFePO4 batteries). You'd have to compare the LCOE for each over the lifetime of the installation, and I don't think thermal would stack up well.
- KennyBlanken 5y agoThoughts about the iron flow batteries from ESS? They're using an iron flow chemistry that doesn't require exotic stuff. Looks like they've been testing for a while at a bunch of sites, and brought their first 'real' non-test customer online this fall. On paper to a layman, they look perfect for at least some applications. Very cheap and easy to build the "stacks", almost completely nontoxic/safe, and relatively easy to scale (I think they don't scale indefinitely with liquid tank size...that the plate surface area also matters?)
- pjc50 5y ago> scale indefinitely with liquid tank size...that the plate surface area also matters?) For flow batteries, the plate area controls the charge/discharge rate and the tank size controls the capacity. In theory you can scale the capacity as far as you can build tanks; I don't know whether there are practical considerations of "self-discharge" or electrolyte degradation.
- KennyBlanken 5y agoNot for ESS batteries. Please do your homework before you speak.
- Xylakant 5y agoRenewable energy has pushed the spot market prices for electricity into the negative last year in germany and UK. Soaking up that energy and reselling it later may be viable at low efficiency.
- pfdietz 5y agoThe round trip efficiency would be a problem for diurnal storage. For long duration storage, capital cost is much more important than round trip efficiency.
- deleted 5y ago[deleted]
- ggm 5y agoI think you're right to the losses, but didn't consider the surplus energy side of things. We now have an oversupply/underdemand problem for sufficiently periods of the day that time shifting motives by the energy producer outweigh the otherwise brutal economics: they can't send the energy anywhere else because of transmission system constraints. Then need cheap ways to store the energy and loss is probably acceptable for the right outcome: better if you can avoid it, but acceptable. Arguably batteries are ideal for the problem. However thermal storage systems like this one have good scaling to storage side of things: insulation is cheap, adding tanks is cheap. The basic turbine cost can supply wallplate stated power, the tankage gives duration and you can add as many tanks as you have room for. Alongside simply supplying the energy, batteries are great for maintenance of supply frequency but I don't understand how they do reactive power. Turbine based systems do reactive power really well because of the rotational torque (I think) so represent a distinct role in electricity supply stability. (Its entirely possible batteries can do this too) Finally, repurposing of steam turbine based generation sites means they have transmission systems, turbines on site and to hand: the capex component can be less.
- ok_dad 5y agoYou can do reactive power with some batteries since they are all behind inverters that can be designed to do that. The Tesla grid batteries (the big ones, don't know about power walls) can certainly do it via API commands (you can specify real and reactive power components, and frequency control, I'm not sure if they can all 3 be run at once though). I'm not sure if all battery companies have this feature though. I used to control several dozen sites with Tesla batteries via their battery control API, though we never used reactive power or frequency control. We still need storage solutions like this for long term storage, though, as batteries are mainly used for load shifting and short term arbitrage right now, at 6 hours of discharge and less.
- ggm 5y agoThat's good. Condensers and like appeal to my steampunk sensibility but they aren't magic or instant. If batteries can do reactive quickly and as well as they do FCAS then it's a huge plus. Getting more than 6 hours is a good point too. I'm sure battery tech is going to include scaling to meet that, this kind of heat storage might just be about time to market.
- trailbits 5y agoWhy would the RTE of this salt solution be so much lower than the molten salts demonstrated in the DOE Solar Two project? According to the technical report at https://www.osti.gov/biblio/791898 https://www.osti.gov/biblio/791898 they achieved round-trip energy storage efficiencies of 97%.
- thereisnospork 5y agoThat is probably quoting it on a heat-basis. Only 3% of heat might be lost from storage, but from the 97% remaining you can only ever convert ~60%[0] of that thermal energy into useful electricity. [0]Rough #. Carnot efficiency would define your max theoretical for a heat-engine process.
- londons_explore 5y agoI think you might be misunderstanding Carnot... The heat engine is reversible with 100% (theoretical) efficiency...
- The_rationalist 5y agoHow? (without a demon's maxwell)
- thereisnospork 5y agoI was presuming resistive heating - a heat pump does make more sense. That said a practical heat pump with even a 1-way efficiency of 97% seems unlikely.
- dredmorbius 5y agoSorry, what?
- londons_explore 5y agoIf you have an ideal Carnot heat pump, it is fully reversible. For example, I can use 10 watts of electricity to remove 10 watts of heat from a cold place and add 20 watts of heat to a hot place. Later, I can apply the same in reverse. I can move 20 watts of heat from the same hot place, heating the cold place by 10 watts, while generating 10 watts of electricity. The use of the phrase "efficiency" while discussing ideal heat pumps is misleading - no energy is ever wasted or lost, the law merely limits the ratio of electrical Vs heat energy you get in/out.
- kragen 5y agoWhat do you think of TCES, in particular for low-grade heat and cooling at the household level, where its lack of reservoir insulation matters in a way that it doesn't matter at utility scale? Is there a good review article you'd recommend reading?
- AnthonyMouse 5y ago> The capacity cost of thermal storage has not been the bottleneck for commercialization, but rather the round trip efficiency. Has there been any effort to do this directly at power plants, so there isn't a round trip? You have a heat source that generates the same heat 24/7 (e.g. nuclear reactor). You have solar panels that generate power only during the day. So you put the heat from the heat source into storage while solar is generating, then take it back out after the sun goes down. You're not going from electricity to heat back to electricity, you're just not converting the original heat into electricity until later in the day.
- DennisP 5y agoTerrapower is doing that with their Natrium reactor. https://www.terrapower.com/our-work/natriumpower/ https://www.terrapower.com/our-work/natriumpower/
- londons_explore 5y agoThis is the right way to look at the problem for nuclear. But it doesn't help for gas turbines, coal, etc - it's even cheaper to just leave the gas/coal unburnt till needed. And most renewables don't make heat to make steam to drive a turbine.
- LordDragonfang 5y agoIf we want to avoid the worst effects of global warming, we need to be leaving that gas and oil unburnt anyway.
- DennisP 5y ago> $/kWh_source_power/efficiency+ammortized cost of capital Is there someplace I could read up on this? I could see using and citing it later. Figuring out the cost per kWh of battery storage has been a pain in my neck. Mostly people just say the capital cost.
- chris_va 5y agoNREL has some decent material on LCOE calculations. Amortized capital cost would be a function of upfront cost, lifetime (years), cycles (and per cycle efficiency over time), capacity factor (e.g. average drawdown of the batteries per cycle), and discount rate. If one has a software background, it might be easier to just to simulate 10 years of cycles to figure out how many kWhs come out of the battery bank per year. Adjust by a discount factor (cycles today pay more in real dollars than cycles in 10 years), and divide the upfront cost by that number.
- db65edfc7996 5y agoSay a tank survives for XXX years before corrosion demands the entire thing needs to be scrapped. Wouldn't that still be an economically attractive option for storing surplus solar energy during the day? Or is the daily upkeep of the installation such that there are significant recurring costs that dwarf the initial capital investment?
- BenoitEssiambre 5y agoDo people talk about storing heat in houses in cold climate regions where there would be no efficiency losses? I always wondered if you could store solar panel energy in large cubes of firebricks that you could dissipate to heat your house. There seems to be some commercial systems (eg. by Steffes) but they are expensive, offer just an overnight amount of energy and seem to be usually used to smooth grid consumption. Why isn't there a version of this designed to store solar energy for longer periods in the winter when insolation is low?
- notinty 5y agoInter-seasonal heat storage is a thing, albeit rare. https://hn.algolia.com/?query=dlsc%2Eca&type=comment https://hn.algolia.com/?query=dlsc%2Eca&type=comment
- lstodd 5y agoIn cold climate regions solar power can't heat houses. If talking about individual houses, not condos, most economic solution is a two-stage water heating powered by a wood pellet or gas burner, where the second stage has a 3-5 ton water tank as a heat storage, so that the burner doesn't need to run continiously. This is a proven, simple, maintainable and safe solution. We're talking ~50-150kW thermal power here. Solar can not reach that. Several cubic meters of almost-boiling water is hazardous enough. Keeping a highly corrosive liquid at 700C in your own home.. no, thanks.
- jonstewart 5y agoPassive solar heating requires loads of storage, and often active systems to transfer heat. But there’s a much easier, more economical way to use solar power for heating in cold climates: heat pumps! PV panels give you electricity and then you get 2-3X the power for heating. There are economies of scale in the supply chain, low CapEx, and not a lot of plumbing.
- BenoitEssiambre 5y agoyeah, maybe solar plus geothermal heat pump would be the most advantageous system right now. Although you can't store and there isn't much solar in December and January here.
- neltnerb 5y agoIt sounds like if you could heat things to a higher temperature while keeping costs the same or slightly higher it would probably improve things then? That's useful to know.
- Someone 5y agoI think cases where you use the round-trip losses to heat things could be an exception. That’s also what the article says in its first paragraph: “If you want both heat and power — for a low price — there have been few good options” Say you’re living up north in Norway. Plenty of sun in summer, very little of it in winter plus guaranteed heat and electricity demand in winter.