Submitted by lughnasadh t3_yw53j1 in Futurology
That’s sounds super inefficient. How much energy does the whole process use? Does it use as much as it can store?
>>That’s sounds super inefficient.
They claim the opposite.
In a research paper here they speak of an RTE (Radiative Transfer Efficiency) of 77%, and say the system's simplicity contributes to its efficiency, as it has only only two thermodynamic transformations: one compression and one expansion.
77% isn't great for batteries (For example Tesla's Powerwalls are 90% round trip efficient (you get 90% useable A/C power for the 100% you put in (includes all the AC->DC->AC steps, plus battery losses)
Of course if these are 40% cheaper, than that's what really matters for some power sources. Especially as we super saturate with solar and other.
cost per KwH is really the king for grid scale storage.
We don't necessarily need 1 single type of battery for the entirety of the world to focus on, though.
Perhaps this replaces a large number of lithium battery uses, but if it doesn't make sense for bigger things like an electric car then we can still use the old tech. If it's made how they claim, it should be drastically better environmentally even if only a portion of the world's lithium ion battery uses are met.
The fact these don't need the exotic elements to function, coupled with not needing major tech breakthroughs makes these incredibly viable.
Agreed.
I would point out that my understanding is the Powerwall neglects transmission and other losses to consumers. These would likely be more proximal to where the power comes in and thus big picture may be more competitive than 77% vs 90% (though grid scale would likely have that in common and the price basis you mentioned would still drive choice). Also batteries degrade and would likely have more significant maintenance/replacement costs. I know Powerwall can do larger installations, but believe they are more suited for end user demand whereas this is more grid scale.
Yeah, but if you can store solar or wind power that nobody can use at that moment it‘s not a 23% loss but a 77% win. If that power replaces fossil fuel power you would have to produce at night or in winter, it would be a huge win.
Yes, agree. But for a system such as this I think that would be common against all alternatives, the difference might be that the CO2 could allow for more capacity, or a reduced initial cost (making it more widely feasible) and potentially having additional future scalability benefits.
True, they make a "megapack" or something that is being installed grid scale. I own two powerwalls and Solar (bought before Elon went off the deepend, but I think the economics are still about the best for Tesla Solar). So my generation is on the roof (I never charge from the grid, except for an impending storm). My current reading match up about with the spec sheet (for Month to date in Nov : 287kWhr in and 250kWhr out (and battery 87% charged as of noon, it normally charges to 100% by about 1pm if I'm not doing a lot of high energy items at home)
Oh, RTE means "Round Trip Efficiency". The paper's abstract doesn't make clear if this is a theoretical number from their numerical model (aka best case), or measured efficiency (real world). And ya, 77% is terrible compared to batteries, but possibly still useful in cases where you have so much overproduction at zero cost (really only solar) that it's still useful to throw out 1/4 of the energy.
You have to be careful with efficiencies though the only important metric is really cost usually because I mean keep in mind like a solar panel is only 20% efficient but it's super cheap so who cares.
Efficiency is very important for batteries.
It's important in context as well.
If I have the same energy source and in storage and retrieval I lose 50% then yes that's horrible.
But if I'm grounding wind and solar in the day because I just make so much that I don't need it. And at night burn coal because the sun goes away. Storing energy, even at a 50% loss is a huge win.
Efficiency is important as it relates to cost.
A battery that's 98% efficient at a cost of $350 per kWh is less cost-effective at scale than a battery that has 70% efficiency at a cost of $50 per kWh.
You also have to consider real world factors unrelated to direct efficiency such as scalability, supply chain, and complexity of manufacturing.
An extremely efficient battery that requires the most advanced manufacturing facilities in the world, using materials from a dozen different mines spread across 3 continents, is going to be much more difficult to scale than an average efficiency energy storage solution that uses (relative to industrial projects) ubiquitous off the shelf components.
In our current situation perfect is very much the enemy of good enough.
Also efficiency is largely irrelevant if system cost is low and we are talking about storing renewable energy. Pumped hydro is considered viable and it’s far less efficient than 70% but it uses already existing technology and can use existing infrastructure as well (pumping water uphill into a reservoir to later be put through an already existing hydro plant for example).
Right but of the battery is 70% then you are actually only getting 70% of 20% not even including the wasted power that the user has. Every step is a chance for more and more to be lost so we want to minimize that loss as much as possible.
Just to be contraion, but when the spot price of electricity is negative (which happens often in Australia) it actually pays to be inefficient.
Wait they pay you to waste electricity in Australia sometimes?
Yes. The coal plants fight wind and solar for the right to not turn off and make it up for when the sun goes down. However they can't pay rooftop to turn off, so they are month by month losing the war. In Aus we install 200MW every month of rooftop. If everyone had rooftop as cheap as us they could do the same.
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