US Government funds pilot project for heated sand energy storage • Hacker News Board

Re: US Government funds pilot project for heated sand energy storage

#121

Post by iamthemonster » Fri, Apr 05, 2024, 7:15 AM UTC

smallmancontrov wrote: post #4

bell-cot wrote: post #2

> The sand used in the thermal energy storage (TES) system could be heated to the range of 1,100 C using low-cost renewable power. [...] when electricity is needed, the system will feed hot sand by gravity into a heat exchanger, which heats a working fluid, which drives a combined-cycle generator. So this is definitely not a "bury your heating coils in a sand dune, then connect..." technology. Quartz melts (per Wikip…

Huh, it intuitively seems like piping working fluid to the sand ought to be easier than moving the sand to the working fluid. Is the moving-sand approach fundamentally desirable thing (I can't imagine why) or is it just a simplification for the proof of concept?

Nah it's nuts to mobilise the sand as a working fluid. The more mature design option seems to be refractory brick for heat energy storage, with piping running through it where you can raise steam. Running a steam turbine generator is generally seen as uneconomic due to the very low round-trip efficiency, and heat storage usually follows the principle of "if you store it as heat, use it as heat".

Re: US Government funds pilot project for heated sand energy storage

#122

Post by regularfry » Fri, Apr 05, 2024, 9:07 AM UTC

zdragnar wrote: post #115

regularfry wrote: post #8

Earlier quoted context omitted.

The thought occurs that if that is indeed the problem, you could attack it by mixing a metal in with the sand. You'd still get the thermal mass, but conductivity would no longer be a problem as long as it had been in a liquid phase at least once.

The problem isn't so much the sand, it's all the air gaps between the grains of sand. Adding metal won't help any- once it gets to a liquid phase, it'll sink down, or if it doesn't stay liquid long enough, will just trap most of the air in it. Edit: you'll also want to keep oxygen out of the environment in the liquid phase. Depending on the metal you use and the exact makeup of the sand, you'll wind up with some mate…

That's what I was getting at. Fill the air gaps with metal.

Re: US Government funds pilot project for heated sand energy storage

#123

Post by ZeroGravitas » Fri, Apr 05, 2024, 1:08 PM UTC

I'm dubious about all long duration energy storage systems (LDES).

I feel their addressable market gets squashed between a) simply building more renewables and short term battery storage, both of which are reducing in cost due to massive buildout, b) making chemicals from renewable energy (i.e. green hydrogen, that then gets used as a building block for Ammonia or hydrocarbons).

As long as the former is able to cheaply eat marketshare then you can just use the fossil fuels it displaces in the hard to decarbonise markets and still come out ahead financially and in terms of carbon.

The latter can be used in jumbo jets or whatever, but also in fairly standard turbines for electricity production if needed, but emphasis on "if" because if you need it just as insurance against unpredictable demand/weather, then it's a plus point if you can just sell it to farmers, airlines or factories once you get to spring, and the physical storage already exists on a large scale for those purposes.

I think this already makes pumped hydro financially dubious, never mind more theoretical ideas.

The timeshifting of electrical heat demand for industry is another market nibbling away at this, and might be another use for the fluidized bed and sand storage part though.

Re: US Government funds pilot project for heated sand energy storage

#124

Post by pfdietz » Fri, Apr 05, 2024, 1:08 PM UTC

ndonnellan wrote: post #50

HPsquared wrote: post #3

Thermal storage works nicely with solar thermal plants. Not so good for direct electricity storage though.

I was going to chime in to second this. In a former life I worked on power towers and we had designs for air receivers that would potentially work really well with this type of system: - High temperatures - Intermittent solar input not a problem - tall central structure (?? maybe a plus given the paper's tall storage vessels) But high temperature air receivers have their own problems, mostly around receiver material…

And highly concentrating mirrors only work with direct sunlight, while PV works with diffuse sunlight scattered off clouds, dust, or the air itself. Bifacial PV cells even capture light hitting the back of the panel.

Re: US Government funds pilot project for heated sand energy storage

#125

Post by pfdietz » Fri, Apr 05, 2024, 1:10 PM UTC

leecarraher wrote: post #62

it seems the primary benefit for sand over water, is a 1:10 operating temp vs. 5:1 specific heat. So it depends on whether the added complexity of working with a hotter, solid is worth not having to build a facility that is 2x bigger. Are there other benefits I'm missing, or is this concrete block gravity storage vs pumped water storage, all over again?

If the goal is conversion back to electrical energy, the high temperature is a huge advantage.

Re: US Government funds pilot project for heated sand energy storage

#126

Post by pfdietz » Fri, Apr 05, 2024, 1:11 PM UTC

throwitaway222 wrote: post #49

Seems to me that direct battery storage research is a much much much MUCH better use of government research funding. Sure if you want to use sand heat holders for heating houses, fine.. but for conversion to electricity? bleh

Batteries are likely better for diurnal storage, but the per-energy capital cost of the sand silos ($2/kWh(th))) would be really hard to beat with batteries, so for longer periods this could be superior.

Re: US Government funds pilot project for heated sand energy storage

#127

Post by smallmancontrov » Fri, Apr 05, 2024, 2:49 PM UTC

bumby wrote: post #90

smallmancontrov wrote: post #86

Earlier quoted context omitted.

If I had exact figures, I wouldn't need to ask for anyone's intuition. Thankfully, ChatGPT was willing to work with me, and I will summarize the results here. Typical refrigeration COP (Coefficients of Performance): Absorption refrigerator: 0.6-1.2 Compressor refrigerator: 1.5-4.0 Estimated TES economic advantage: 1.1-2.5x Conclusion: yes, absorption refrigeration is probably inefficient enough to make it a long shot…

The temperature in TFA are outside the range of most commercial absorption chillers, so this is more about making cheap electricity. I would imagine absorption would be more applicable if the same tech was used to generate lower-quality heat that's not suitable for a combined-cycle generator.

> outside the range of most commercial absorption chillers

"Off the shelf" isn't a constraint here, sort of the opposite: I'm trying to imagine the space of things that are physically possible but not yet commercially mature. Theoretically, higher temperatures mean more possible efficiency. That's the one ray of hope in otherwise dismal efficiency figures that are currently only viable, as you point out, if the heat is ~free.

Re: US Government funds pilot project for heated sand energy storage

#128

Post by quickthrowman » Fri, Apr 05, 2024, 5:53 PM UTC

autoexecbat wrote: post #96

adrian_b wrote: post #91

Earlier quoted context omitted.

Heat can be used directly not only for heating, but also for cooling. There are air conditioning systems that are powered by heat, not by electricity. There are places where the power plants use the residual heat from the generation of electricity not only for heating during the winter, but also for cooling during the summer, by producing chilled water.

> There are air conditioning systems that are powered by heat, not by electricity. How does that work?

Either absorption refrigeration or a steam turbine that compresses the working fluid.

Re: US Government funds pilot project for heated sand energy storage

#129

Post by Tagbert » Fri, Apr 05, 2024, 7:59 PM UTC

pimlottc wrote: post #106

Tagbert wrote: post #105

Earlier quoted context omitted.

The Pernell with heat compared to electricity is portability. It is easy and efficient to transmit electricity but heat is not

> The Pernell with heat Did you mean to type "problem"?

yes, but somehow it got "corrected" to Pernell. I'm not sure who Pernell is or why they would be relevant to the discussion. :-)

Re: US Government funds pilot project for heated sand energy storage

#130

Post by bumby » Fri, Apr 05, 2024, 11:45 PM UTC

smallmancontrov wrote: post #127

bumby wrote: post #90

Earlier quoted context omitted.

The temperature in TFA are outside the range of most commercial absorption chillers, so this is more about making cheap electricity. I would imagine absorption would be more applicable if the same tech was used to generate lower-quality heat that's not suitable for a combined-cycle generator.

> outside the range of most commercial absorption chillers "Off the shelf" isn't a constraint here, sort of the opposite: I'm trying to imagine the space of things that are physically possible but not yet commercially mature. Theoretically, higher temperatures mean more possible efficiency. That's the one ray of hope in otherwise dismal efficiency figures that are currently only viable, as you point out, if the heat…

>Theoretically, higher temperatures mean more possible efficiency.

I think you might be conflating a few things here. For a cycle to produce electricity, that's correct. But the mechanism of absorption chillers is fundamentally different. The chemistry of the materials and their phase change temperatures are definitely a constraining factor. Could you, in theory, develop some other absorbent/refrigerant that works at those higher temperatures? I suppose, but I would suspect there are much easier ways to get efficiency gains.