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Comment by mcbishop | Hacker News Reader

An increasingly-viable alternative to global transmission interconnectivity is distributed energy resources (behind the meter, on utility-customer sites).

The latter offers better resiliency and lower transmission / distribution losses.

A well-insulated building and its hot-water tank are both (thermal) energy storage systems, that are more durable (and more affordable) than electrochemical batteries. A building can be pre-cooled or pre-heated when on-site solar is plentiful, to the end of the occupant's comfort range. This means a smaller on-site battery bank is needed to achieve year-around grid independence (for a conditioned / comfortable building).

It seems that we're just getting started with on-site flexible-load control, and building energy automation generally. The higher electric rates in some markets make it financially viable for end users today.

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I live in a 200 year old house in Mexico. The walls are half a meter thick. At night we open the windows, which are oriented toward the prevailing winds, and the house cools down. Mid-morning we close it all up and it stays cool all day. Meanwhile people with modern houses have to run their air conditioning to keep cool.

I saw exactly this in 2000 year old homes in Morocco where the temps are regularly 120F+ in the summer and below freezing at night in the winter.

Without need of electricity there absolutely zero issues with heat or cold.

I have had arguments with Americans who are absolutely convinced that wasting energy in an AC is good and something to be proud of, while opening windows is primitive, and bad. It was funny.

I somewhat suspect that you are being a bit uncharitable towards their position here.

They are adults. Them being wrong is their problem, not mine.

I am saying that they probably didn't say what you said they did.

Doesn't matter. I don't know these people.

Passive solar design is such a beautiful elegant thing. A fun book here is Let it Shine by John Perlin. He shares examples from around the world, over the last 6,000 years.

Technology Connections has an interesting video about pre-cooling:

https://www.youtube.com/watch?v=0f9GpMWdvWI

The author also made a good point that despite wind and solar being intermittent, they are actually fairly predictable a or less day in advance (thanks to weather forecasts).

The video is super articulate.

I like what he did at 6:49:

> So that I can take advantage of these low rates at night, I use a roughly 16kWh battery that I just happen to have lying around. I charge it up over night starting at 10pm on the dot, and it's done charging usually by 3 or 4 in the morning. I keep it topped off until around 7, and then I start using it during the day. And it doesn't need to be charged again until the evening. Now the reason I just happen to have that battery lying around, is because that battery... is my house.

You can see this play out in Texas, at the ERCOT dashboard.

https://mis.ercot.com/public/dashboards

Interestingly, you can see that wind and solar are anticorrelated there: wind tends to die down during the day, and spring back up at night.

I work in the field of distributed energy resources and it’s incredibly cool.

We’re remote first and hiring. https://www.voltus.co

It'd be interesting if you can scale and reach profitability.

It seems like a reboot of EnerNoc and has much of the same team. EnerNoc was burning ~50 million/y on 400 million revenues before it was purchased at a discount by Enel. [0]

[0]https://www.greentechmedia.com/articles/read/enel-to-buy-ene...

Yep, much of the same team, with a different strategy (more tech-focused and participation in more energy market programs). Regulation of DERs largely killed EnerNoc, now Enel X, and the like. Voltus' CEO helped repeal the order[1], ensuring DERs make parity with conventional generators.

> if you can scale and reach profitability

I don't know what I can actually reveal, but scaling is our focus right now.

[1] https://www.ferc.gov/sites/default/files/2020-06/Order-745.p...

That was a win!

In power markets, it's really hard scaling around each market/state's idiosyncracies almost like it's not a technology problem and more regulatory/financing. Hope you guys figure it out.

100%, well put. Our energy markets team is larger than our engineering team :). But it's also certainly a technology problem in that meeting each market's idiosyncratic requirements requires technology.

Hope you don’t get gobbled up by the energy behemoths that love the centralized grid model.

Do you hire data analysts/ scientists ?

Yep, contact me at leo@voltus.co

One another option is gravity storage- with (exotic idea alarm) a ice piston in isolation material. Basically create a artificial vertical glacier and transport the heat from the cooling into a separate storage "hot well". Then use and abuse accordingly.

https://www.youtube.com/watch?v=ObvQFX6noDw

That's really cool (dad pun intended). I don't understand the ice component though... is the heat capture an ancillary benefit? One web-search result uses a rock mass: https://heindl-energy.com/.

> … (thermal) energy storage systems, that are more durable (and more affordable) than electrochemical batteries…

Agree, I think for so long the whole renewable build out has ignored storage costs which will really come to bite electrochemical battery dependent systems in the ass (because banks like UBS have long projected that costs will be harder and harder to bring down and ACS has long talked about the difficult to deal with chemistries with all the different batteries out there [and with the inherit degradation of the system over time]).

I think in the long run (well, unless our political challenges with nuclear get solved), on the utility level (potentially even behind the meter for specific high energy applications that have space to construct/"mine" their own solar field), molten salt storage will take the lead (esp as salt mixtures/chemistries get cheaper, have higher thermal operating ranges, storage and transportation gets better).

Thermal storage in hot sand seems superior. Sand is cheaper, capable of operating at high temperature, and allowing heat exchange to the working gas by direct contact in a fluidized bed heat exchanger.

https://arpa-e.energy.gov/sites/default/files/2021-03/07%20D...

I deff would like to see a 100MW sand system built out.

I think the sand direction is deff an improvement over the 300 delta_C systems now with (NaNO3, KNO3, NaNO2) at the 900 delta_C in used in the pdf, but idk if it will win out in the long run with the need for direct contact vs some kind of sCO2 system with higher delta_C mixtures (for example a theoretical mixture CaCl2 + MgCl2 with 1500 delta_C, or even engineered metamaterials[0, i've only seen some specific examples of electromagnetic metameterials when i was in school about a decade ago, this post was about a year after i left] in a mixture to have even higher delta_c).

There's only so much one can do when one limits the materials used for heat capacity to naturally occurring ones (i imagine that compounds in the future could be engineered to be at least a order of magnatude higher in delta_c from natural mixtures).

[0] https://news.brown.edu/articles/2012/10/quantum

One issue with that sand system is that the sand is hot enough to generate too much thermal NOx in an open Brayton cycle (or combined cycle) system. Which is sad, because that kind of system could save a lot of complexity. One could add a selective catalytic reduction stage afterwards but that increases complexity again.

A very interesting possibility, I think, is to replace the sand with some other mineral and make the solid part open cycle. That is, instead of retrieving and recycling cooled sand, a new stream of pulverized minerals would be used. This could be useful if heat treating those minerals does something desirable. A particular case would be heat treatment of serpentinite to make magnesium oxide and silica, which would then be used for CO2 capture/sequestration.

Both the salt and the sand option are exciting.

This isn't a thermal option, but the iron-air chemistry has promise too. It's basically rusting and de-rusting iron. Much more environmentally benign than lithium ion, and likely way less expensive. AFAIK, this company is the frontrunner: https://formenergy.com/technology/battery-technology/

Iron-air are just another kind of metal-air batteries. The problem with all of them is that hydrogen-air batteries have existed for decades and is basically the same thing. If it wasn't for 20 years of marketing propaganda we'd realize this and never bothered with reinvesting the wheel with another chemistry.

I hear you that marketing spin is a factor here. But if Form Energy can achieve the $20/kWh price that they're pursuing... iron-air is quite different from other chemistries on the financial front. https://www.utilitydive.com/news/form-energys-20kwh-100-hour... (I have no affiliation with this company.)

Yes, but hydrogen-air is already cheaper than that. On large scales it is <$1/kWh and easily cheaper than anything can even theoretically attain.

Wow. Okay, thanks. I need to learn.

By hydrogen-air battery do you just mean a water electrolyzer system paired with some kind of hydrogen fuel cell?

If so, the metal-air systems have a major advantage on the discharging side of things by avoiding the need of a fuel cell and being able to harvest electrons directly via galvanic current.

A hydrogen system is basically the two sides of a battery split into separate components. It's fully possible to build device that does both, although as of today this is less efficient.

The galvanic discharge rate is extremely slow and not really suitable as part of a rechargeable battery system. Any practical metal-air will have some way of discharging faster. The problem is that we have basically solved this for hydrogen-air but not for anything else.

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