Lightcell: An engine that uses light to make electricity

I find the bandgap tuned cell interesting. It reminds me of a TPV https://www.nature.com/articles/s41586-022-04473-y which is tuned for infrared instead of yellow light.

less moving parts means it could work in contexts where moving parts demand lubrication, maintenance.

I felt it was a bit light on putting the system energy efficiency/losses up front. I am sure they're stated but it was hard to work out how it compared to normal PV efficiency, or steam turbine efficiency.

Heat exchangers are applicable to lots of things. I am skeptical that this is significant because almost any heat energy process does reclaim and preheat, and so the size of the thermal mass and efficiency here would be exceptionally well studied and if they have made improvements, they may be as, or more valuable as IPR overall. So while it looks amazing, unless they are spinning it out into wider industry it will be a small increment over things in deployment.

I read their statement of 40% efficiency would be compared to the currently available photovoltaics were generally 20% efficiency is normal.

Amazing idea. BTW, following Danielle on X, very insightful and bright minded person.

Bottom line: 40% efficiency, which is better than I expected but the competition is batteries at 80+% efficiency. It's a hard sell, especially as continual improvements in battery storage will continue to eat away at their niche.

5,000 W/kg sounds great on paper compared to 150 W/kg for batteries and is even in the same ballpark as gasoline at 12,000 W/kg, but I think that's just the figure for the fuel. I don't think it includes storage, the solar panels, the burner, etc... The cost is an open ended question as well. Maybe this will pan out for aircraft?

The energy densities listed are flagged as approximate, so grains of salt etc, but the numbers on the page aren't entirely consistent.

The stated energy density is "> 500 watthours/liter".

But higher on the page we see a relative-energy-density bar graph shows lightcell at 5x the energy density of lithium batteries, and (38/5 =) 7.6x less dense then petrol. This implies an energy density for lightcell of 1250 Wh/liter, as (according to Google) petrol clocks in just under 9500 Wh/liter, and (again according to Google) lithium batteries can reach 300 Wh/liter so let's call it 250 for the math to work out.

I'm curious which number is closer to truth: 500Wh/liter, or 1250? Is 1250 the theoretical max and 500 the current output in a test rig?

If that is 40% efficient as in 40% of the theoretical energy input comes out as electricity then it's quite incredible but I find that hard to believe. It would put it in the same range as diesel engines.

I believe the bar graph is showing relative energy densities of the raw energy sources so the 5x bar is just the energy density of hydrogen as H2. Your 1250 Wh/L number is right for compressed gaseous hydrogen so The 500Wh/L lines up with burning H2 at 40% efficiency. The "use fuel for extended duration" implies that they believe they can achieve a much higher Wh/L with other fuels.

The 40% figure is supposed to be "wire-to-wire", but they do list that as the "target efficiency" which suggests it may be somewhat aspirational. It presumably doesn't include the energy needed to extract and refine the oil into whatever kind of burnable fuel you are using, nor the energy necessary to extract and then blend in the sodium additive.

forbes to prison pipeline?

The better comparison is Fuel Cells and vehicle based electrical generators. So you could put this in a vehicle or remote location, run it off hydrogen or natural gas, and get better efficiency. Potentially this could be a much better option for longer term storage in remote areas as well, where excess solar/wind could be used to crack hydrogen which then gets stored and later burned in one of these instead of a much much larger battery installation.

I would think the energy density varies with that of the fuel they put in. They mention hydrogen, natural gas, gasoline, ammonia, butane, propane, alcohols, syngas…. That’s about anything that is or can easily be turned into a gas that burns.

also, “/liter”, for gases such as hydrogen, can be made larger by using higher pressures in your tank.

On the other hand, they also say “target efficiency: ≥ 40% wire to wire”, and 40% of 1250 is 500, so it may be that.

You still need to truck in the sodium additive even if you're cracking water on site to store the H2. Dunno if you need a couple of mg/kg or if it is like 5% of the fuel to make it burn at the right color.

The solar panel conversion of sunlight to usable energy to around 20%, with a theoretical max of 30%. So it's better than that.

The gasoline vs H2 ballpark is a little wider because storage is not trivial for H2 -- you need to carry around a cryogenic and/or high pressure vessel instead of a plastic box -- which will detract from your p/w ratio. It also wants to leak out, so H2 is maybe better for fleet vehicle applications where they can refill daily. Granted, anything is better than burning more hydrocarbons!

I don't think they are claiming an efficiency breakthrough on their heat exchanger, just that they've made a competitive heat exchanger that also blocks light very effectively.

I've periodically seen lightcell and danielle fong in various news / reddit /forums over the last few years and it always seems to be steeped in controversy.

I know next to nothing about the field / tech, but a portion of folks seem to be like "incredible visionary etc. etc." and the another portion like "fringe science / complete bullshit / this is as realistic as cold fusion" kind of thing.

Very interested to hear from folks more in the know of like, high level long term viability / what the implications are etc.

My initial thought about this was that it's using fuel to make electricity, right? Rather than using sunlight/hydro/etc -- kinda like a generator, but without the mechanical aspect?

And at the bottom they seem to indicate they are still in the "proving feasibility" stage.

I read this all as: "this is a POC we have, and if we can get it to 40% efficiency than it might make sense (otherwise who cares, just use a conventional generator)"

That can't be true. The current record for non-concentrating cells is 39.5% efficiency using triple junction cells [1]

Concentrating cells are at 47.6% [2]

[1] https://www.cell.com/joule/fulltext/S2542-4351(22)00191-X

[2] https://publica-rest.fraunhofer.de/server/api/core/bitstream...

the 40% efficiency is a claim about how much energy contained in the fuel can be converted into electricity*. It would make the most sense to compare this against either combustion engines or hydrogen fuel cells. Compared to those 40% is not breaking any records but could be extremely useful given the size, flexibility, weight, power output, etc.

Basically big if true, but this thing's 40% and photovoltaics' 20% aren't comparable efficiency numbers.

* They say wire to wire, IDK exactly what that means, but if it includes the losses from green hydrogen production then it seems like pretty wild efficiency. This doesn't line up with the numbers though, as H2 with 1250Wh/L * 0.4 = 500 Wh/L claimed density.

Often I imagine storing light as fuel. Compared to hydrogen, it doesn't weigh much at all, and you can fit a lot in the same space.

(Yes, I know where the halfbakery is.)

To my limited understanding yes, that's what they claim.

Basically burning fuel (any fuel, really) with added sodium to create very bright monochromatic light that can then be converted into electricity using very high efficiency solar cells.

But sunlight is wide spectrum, and a lot of the reasons why the efficiency of regular solar panels is low, is that they don’t absorb all of the spectrum equally well. That’s why there’s all this talk of tandem solar cells with perovskites these days. The two solar cells can be tuned to extract energy from different wavelengths of light.

Since the light they’re making is nearly monochromatic, it’s a lot easier to get higher efficiency. That’s kind of the whole point of the invention.

Do you mean watts or watt-hours?

this was done by a company in Alberta,late 90's early 2000's, except burning diesel, same idea of tuned photovoltaics outside a quarts cylinder,where a flame was buring @ one specific coulor temperature, they were marketing an initial model for sailboats, and had working devices in service. published efficiencies wrre also 40%+ lost track of them and could not find again this effort uses excited sodium,though there will be a number of other possibilities

That's not really relevant. They have a light source that runs on a fuel and are putting multiple PV cells around it. The efficiency they care about is the fuel in to electricity out. If you can put more cells around the light, the system efficiency goes up.

It's a very good idea that is worth pursuing, they are pursuing it. There are many many many problems that need solving between here and "this is a better way to make energy from heat at scale than turning water into steam and spinning a turbine". The science is fundamentally sound but we're nowhere near economic viability.

Isn’t that for sunlight though? I imagine if you have a source that only radiates a single wavelength, you could make a collector for that specific wavelength that’s more efficient than some general case one. Could be wrong though.

My understanding of fuel cells is they are rather sensitive to the purity of the fuel and oxygen. I wonder if this system is less sensitive such that, say, piped hydrogen can be used.

Just be careful or you might make a Kugelblitz

Two questions I have:

1. How much of the fuel's energy is released as heat? They have a heat recapture device, but that's only used to preheat air/fuel, and not used to generate electricity. Is the energy in the heat simply discarded?

2. Can this be made to work without the process of burning? i.e. can it function purely from heat? If it can, it might be able to replace steam turbines in, for example, nuclear plants or CSP plants. That could be hugely beneficial.

The innovation here is you have a system that emits monochromatic light, and you have solar cells tuned specifically for that bandgap, plus the system is also "naturally" concentrating because the light output is incredibly bright. 3000 suns vs 500-1000 suns in typical CPV, plus they also do waste heat recycling. End-to-end efficiency of 40% is definitely feasible as advertised.

This seems like a hydrogen fuel cell with extra steps.

1. The countercurrent heat exchanger achieves exactly that: exhaust gases are cooled while the inflowing fuel mixture is heated up.

2. Thermophotovoltaics in general can operate with any heat source, though this device is clearly optimized for combustion. However, the efficiency is far too low to compete in the large-scale power generation segment. This is almost certainly aimed at light aviation, heavy drones, military applications, etc., where there are not a lot of alternatives that combine small size, high power density and good efficiency.

It's not like cold fusion, the lightcell is based on well-understood physics. The author may be too optimistic with efficiency claim, but those are relatively easy to verify independently.

It's only true for a single junction. https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limi...

Multi-junction cells beat that limit, but they're still horribly expensive to manufacture which confines them to niche uses like spacecraft.

It's a different way to capture energy stored in fuel.

Normally to produce electricity from fuel you would spin a turbine, either with a mechanical engine or using vapour. But here the energy is captured through a photo cell, and the author claims that mixing sodium into certain fuels leads to a very significant part of fuel energy going into light at specific wavelength.

It probably doesn't help that the website looks like an American Science & Surplus catalog

I suppose for aviation at least this is no less efficient than a gas turbine or a piston, and it's certainly a good deal quieter, has fewer moving parts, and requires less precision engineering than a jet engine. This feels tailor-made for attritable low->medium performance aviation, aka loitering munitions and drones. Strip away the "green" talk, and you're left with something that can burn just about anything (including hydrocarbons like avgas) without the complexity of a turbine.

This seems possibly not crazy. If you can have one of these powered by natural gas and scale it to 20 kW then you have a nice home generator that is "whisper quiet" according to TFA and also: simple, easy to maintain, with few moving parts, perhaps even durable. The hydrogen aspect of this is not as interesting as the other fuels, though it'd be nice to know the efficiency numbers for different fuel types. That said, having to supply sodium might be a problem.

1. It's hard to capture all the waste heat. If you could run this indoors (but vent outdoors if the fuel is anything other than H2, naturally) then you could use some of the waste heat to heat a building.

2. There are thermovoltaic generators, but they're limited by the need to cool one side of the material. These are typically used in deep space probes that use Pu 240 to power them. To my knowledge thermovoltaic generation is not scalable or practical on Earth at this time.

It might not be a hard sell compared to home generators. Forget hydrogen. Think natgas.

Rechargeables/battery packs have inefficiencies due to the grid and/or solar cells though, in terms of where to measure inefficiency?

I suspect this needs some moving parts to function - without a turbine's suction, you need some sort of a fan to pump air into the thing, and also a fuel pump. Most things with internal combustion require some kind of active cooling as well.

From the "wire-to-wire" mention it seems that they're proposing using electric power to generate and store hydrogen till it's needed, then burn it to get electric power back.

But they say other fuels work, in which case it wouldn't be "wire-to-wire", and then it'd be more appropriate to compare this to a power generator fueled by natural gas or gasoline. A generator with no pistons or turbines, just a fuel pump, sounds fantastic, if they can make it work. But you'd have to supply sodium.

What does "wire to wire" even mean? The input isn't a wire! (Do they mean they think they can synthesize fuel and burn it at 40% overall efficiency? If so, that's pretty good.)

If using compressed natural gas you might not need a fuel pump at all.

This burns fuel at very high temperature, and I wonder how they plan to deal with NOx production. They could attempt to burn the fuel in pure-ish oxygen (with an oxygen concentrator?), but that would increase the complexity of the design and compromise the "quiet" part.

I agree that 40% "wire-to-wire" seems wild. But if it was 40% nat gas to wire that'd be quite nice considering how simple such a generator would be, and it might be more efficient (perhaps significantly more) than traditional internal combustion generators. I.e., if you ignore the green aspects of this it sounds quite nice. Though you have to supply sodium. Hmmm.

A couple video interviews with the inventor:

https://www.youtube.com/watch?v=aMQYAqIxK1s

https://www.youtube.com/watch?v=1U_KbgF-sAc

In context, an important innovation. Perhaps this technology can retrofit into hot gas heat exchangers like in steel works, but they use the thermal energy directly so it may be robbing Peter to pay Paul.

Thanks for a clarification which makes sense.

She seems like someone with an eye for a clever solution to an existing problem, an eye for funding (her compressed air "LightSail" thing raised over $70 million), and maybe a somewhat shaky relationship with practicality.

Reminds me of the TimeCube page…

hey! this is the inventor, danielle fong.

thanks to curl-up who posted this, whoever you are.

since it came up, "wire-to-wire" efficiency is what I intended to coin a synonym for electrical to electrical efficiency, with hydrogen storage. for example, an 80% electrical to hydrogen efficiency, and a 50% hydrogen to electrical efficiency, would yield a 40% wire to wire (electrical to electrical) efficiency. of course, people are working on 95% electric to hydrogen efficiency, and 50% fuel to electrical efficiency is a target.

here's an illustrative energy flow diagram for us trying to hit 60% -- even more aggressive. https://x.com/DanielleFong/status/1775595848887677138

we'll have to fire the web dev (me)

I wonder if they recover the sodium and run it back through the process.

For that matter, could you maybe put sodium in a sealed container and then heat the whole container? Like a sodium vapor lamp but causing it to glow by throwing heat at it instead of passing electricity through it.

it can work purely from heat, however our process requires high temperature heat for power density.

maybe so. i don't know about attritable for the first applications though. may long range or duration oversight. a large % of the cost is these specialty cells which have not been scaled up to mass production. in the denominator is the intensity of light we can produce, which is based on how high a temperature we can drive, there's a very nonlinear brightness vs temperature. but at 100 suns or so we can get near to $1/W on the cells at startup scale

we think it will be, it's a good bet

correct

indeed yes; the sodium is added as sodium chloride. in molten form, it wicks along sapphire and alumina surfaces, similar to a candle. it reforms into sodium chloride as the temperature drops below its boiling point -- 1400 C.

we're exploring fully sealed experiments, but, you have to get the heat into the sealed cell somehow.

https://patents.google.com/patent/US12136898B2/en?oq=US12136...

oh god

come on guys

correct

we're bootstrapping off the multijunction production while using just a single junction that matches the sodium D light well

thanks!

let me know if you can remember the name or a reference, thanks!

fuel cells have trouble being cheap, lightweight, high efficiency, and long lasting, all at the same time. I think this could have better scaling on all those dimensions, plus could use natural gas or propane or other fuels for when you don't have hydrogen

Does the tube become less transparent because of contaminants? Over what time scale? Is this issue exacerbated before the system is operating at full temperature (e.g., coking)? Is the sodium vapor kept in the closed cavity or is it a consumable? If a consumable how much is needed? How is it stored and dispensed?

you need at least valves/regulators, but for self pressurized fuels like propane, butane, or even natural gas (CNG or LNG) you can probably get away with only that, and fans for air intake and cell cooling.

we're not aiming to break records with the absolute heat exchanger efficiency, which can get into the high 90s (%) if you're willing to devote a lot of space and mass, but we are innovating in the heat exchanger area. to capture more of the waste heat up to a higher temperature, and preheat the incoming air and possible fuel to a higher temperature, we have to exceed 1000 C and want to drive towards the 1600-1800C maximum working temperature of the high alumina 3d printed material we're using. Thankfully Formlabs has already done some of the preliminary development on the material, but it's bleeding edge both as a material and in use in heat exchangers.

that's correct. the mass of the power related systems are a moving target based on what we're developing. but we are aiming for a medium term target of > 1 kW / kg for e.g. DC power to a drone or a hybrid drone power system

and better than small diesels / turbines / internal combustion engines, at closer to 20%

Why would I use this instead of a fuel cell?

we don't see any degradation in sapphire tubes, though quartz, which is more convenient to work with because it almost completely resists thermoshock, does degrade slowly. there is a layer of salt on the tube which becomes transparent when melted, above 800 C. sodium vapor is provided to the reaction tube via direct evaporation -- melted sodium has a high surface tension and surface affinity for alumina, and wicks into the chamber. after combustion as it cools, it reforms into sodium chloride. for all fuels we've explored, sodium-chlorine is the maximum bond energy, but you can have some swaps if you have for some reaction alkali or fluorine in your fuel (don't!), the sodium chloride condenses from 800-1400C in the heat exchanger, and then wicks itself back along the surface to where it is evaporating. We hope to drive this process to some number of 99.99..% recovery, and just add granular salt (or could be a solution) to replenish. There is only a few % of salt needed in the flame, and if you recover 99.9% of the salt then you would have hundreds of total refuelings before you need to replenish a salt vessel of about 1%.

fuel cells have trouble being cheap, lightweight, high efficiency, and long lasting, all at the same time. I think this could have better scaling on all those dimensions, plus could use natural gas or propane or other fuels for when you don't have hydrogen

https://news.ycombinator.com/item?id=42745109

People use the thermoelectric effect for various "energy harvesting" applications, see

https://www.tegmart.com/wood-stove-thermoelectric-generators...

It's an area where you hear about progress from time to time because the technology could improve if people find materials that have a better ratio of electrical conductivity/thermal conductivity.

If you electrolyse water with electricity into h2 and o2 then you have tour first wire.

When you reform the electrons via this engine and the photovoltaic cell you have your second wire.

i'll take it

For what it's worth, I wish you luck on this.

our patent is here. https://patents.google.com/patent/US12136898B2/en?oq=18%2f51...

thanks!

oxygen works and might be worth it for a stationary application like a powerplant for an AI data center. but NOx breaks down exothermically. so our approach if you hold the flame at >1300 C for less than a second or so you can destroy most of the NOx. This doesn't happen in a Diesel because the pulse stays that hot for only a short time, locking in the NOX that is produced. this is a matter of sizing the heat exchanger / flow rates correctly. we have to validate all this though. good question

well observed

Thanks

Wouldn't it generate more heat than is needed to heat the fuel mixture?

The end goal isn't to preheat the fuel, it's to keep the heat from escaping, because you want all the heat to go into the sodium.

The heat is being used to generate electricity.

> fuel cells have trouble being cheap, lightweight, high efficiency, and long lasting, all at the same time.

Flow batteries?

Not light weight (for stationary batteries, does that matter) but tick the rest of the boxes

Hey Dani, do you have any videos of prototypes in operation?

1.6mb, mostly images. A reasonable and to-the-point use of resources. Very few "modern" sites achieve this page weight.

Did you also consider a thermionic setup before settling for thermovoltaics? I assume it would be trickier to design and run.

How much sodium is used? In what form is the sodium stored?

Hey, thanks for jumping into the thread! I stumbled upon Lightcell a couple of days ago after seeing the episode of First Principles [1] podcast, and found it really interesting, so decided to share what you're doing with HN.

[1] https://www.youtube.com/watch?v=1U_KbgF-sAc

Money laundering continues

500 MW GE turbines claim 64% efficiency, and one can use the wasted heat for district heating. If we have to burn something then using these turbines seems to be the best option, running 2-3 electric cars for the emissions of one. And probably 3000 e-bikes. Shouldn't you compete in this range of efficiency?

Isn't "hot" sodium: Super corrosive,

Highly reactive (goes booooom with water or oxygen)

Expands incredibly when heated

For those efficiencies i would recon you'd need temperature in excess of 1500k right?

That does not sound like anything that is easily "safe" or "reliable"

Correct me if I'm wrong, but I don't see this being viable even if you reach your target efficiency.

The problem with hydrogen is the storage cost. Improving wire to to wire efficiency can help only so much. Have you calculated the electricity cost with those efficiency rates when you include the cost of storage? "Overall cost of renewable hydrogen in 2030 varies from €2.80–15.65/kgH2." improves with scale. https://www.sciencedirect.com/science/article/pii/S036031992...

Quick and dirty math, may contain errors:

Lightcell target is 0.5 kWh/L. Hydrogen weighs 0.09kg/L.

-> storage cost alone: ~ €0.5/kWh in large scale, €2.5/kWh in small scale.

Average electricity cost in the EU has been €0.289 per kWh.

aha, i was wondering how that worked. Creating pure sodium using the Downs process requires a lot of electricity and I doubt this engine would be economic if that was required. But it looks really promising, >= 40% efficiency is a great goal.

Battery densities are going towards > 500 wh/kg. There's some talk of batteries of several kw/kg long term. And since we're talking technology that is very much in the early stages of development (see the helpful image in the article), that would be an apples to apples comparison. 500wh/kg is basically a done deal. Several battery companies have announced products that are shipping in the next 2-3 years. From there to 1kw/kg seems very feasible. Several companies have hinted at that being a goal for them.

There's only so much district heating that is needed. And mostly only in the winter. You'd actually need more energy for cooling in the summer when nobody wants to heat their place. District heating is a nice creative solution for waste heat. But there's a limit to how much of it you can use and how practical it is to use it. Mostly it's still waste heat that's going to be wasted (blasted straight into the atmosphere and space).

And we don't have to burn stuff. Which is why coal and gas powered electricity generation is a bit under pressure in most markets. There are cheaper and better ways to get energy now.

I think it looks more than good enough. It loads fast, not bloated and mostly to the point. What's lacking in content is some links to more details. (patents etc.)

How do patents work with science actually? I saw upthread that they've patented it, so is independent verification allowed so long as you don't commercially sell it, or give units away at all or so?

Are you also on Mastodon or something similar?

This is a really innovative idea, even more than the previous compressed-air energy storage thing she did, which really seemed like it should have worked.

I hope this one does, and I think the inventor has more than enough smarts to find out. Good luck.

Correct me if I'm wrong but I think this is apples and oranges: storage can be reused, while electricity is consumed.

Has this been put into practical use somewhere in public/commercial domain?

Fuel is burned to head sodium, if you are getting too much heat for your taste you can burn less fuel. It is kinda the goal of the exercise.

But in any case, I believe that the more you heat sodium, the more light it emits, probably there is a practical limit on an incoming heat power after which the thing will go boom, but before that it will follow some roughly linear law: the more heat energy in, the more light comes out. Though I'm not a physicist, so I make be wrong, even if I do not see how I can be wrong.

Since you are talking about electrical to electrical, and you compare to lithium batteries in a chart, do you mean that this thing works like a battery?

Like, coupled to solar power, can charge during the day (making hydrogen using some cycle) and provide electrical power during the night

No contact page?

That's the levelized cost over the lifetime. Hydrogen storage is expensive to both build and maintain.

The issues include hydrogen embrittlement, constant leakage and safety issues. Containers don't last. H2 is the smallest molecule. It gets into the containers and wears them out and leaks away. Casing and seal damage is constant. Pressure vessel storage loses little below 1% leakage per day.Liquid hydrogen storage is about 1-3% leakage per day. Salt cavern storage much less but they have problem of H2S generation by Micro-organisms.

Making hydrogen is extremely energy-expensive and, as result, money-expensive if it is not by-product of crude oil processing. It is why hydrogen cars & Ko is not viable really if we stop to process crude oil (in additional to the problems with storage and transportation).

Hydrogen is greenwashing by big oil companies, only they could provide "cheap" hydrogen, and not some water cracking with electricity from renewable sources.

They use a lithium battery as a base for energy density. The lightcell can use a variety of different fuels to create light in the band they want to capture. They 'lean' towards hydrogen, because it's more 'sustainable', but you can get even higher energy densities if you use petrol.

> Average electricity cost in the EU has been €0.289 per kWh.

I'm curious where you're getting this from, and also what other Europeans on HN currently pay?

I'm in Spain with Octopus (via Spock's collective bargaining), and my effective price for December ended up being 0.131 EUR/kWh, while you claim a price that is 3x what I currently pay. Just wondering if I'm an outlier with the price Spock managed to get us.

Edit:

> The EU average price in the first half of 2024 — a weighted average using the most recent (2022) consumption data for electricity by household consumers — was €0.2889 per KWh.

https://ec.europa.eu/eurostat/statistics-explained/index.php...

Guessing that's your source :) Seems that's specific for home usage though, while your comment seems to be in a different context. Not sure electricity is cheaper/more expensive in industrial contexts.

Schottky solar cells are also a thing although their efficiency isn’t great either

So you’re recycling the waste heat and reducing the operating temperature to normal solar cell levels as opposed to thermoelectrics?

I can see that being a good use, ultra-quiet ISR that can stay aloft for extended times and doesn't require the complexity of a jet turbine? There has to be enormous demand for that.

This would be a great addition to the website. Also, talk about applications, even show a comparison chart vs existing solutions

Or turn it around a bit. If the entire device could operate at high pressure, then one could imagine putting it inside a jet or rocket engine. Feed it compressed fuel/air mix, burn, extract some energy via thermophotovoltaics, and blast the exhaust out a nozzle or use it to spin a turbine to drive a bypass fan.

An obvious down side is that most jets have very, very high fuel flow and power output, and the area required to extract enough electricity to make this whole exercise worthwhile may be excessive. Also, a lot of military applications are not going to like that sodium illuminant lighting up the exhaust gasses, scattering radar, or otherwise making the plane more visible.

edit: I see that there’s an effort to recirculate the sodium. Maybe that’s enough.

We detached this comment from https://news.ycombinator.com/item?id=42745018.

We detached this subthread from https://news.ycombinator.com/item?id=42745018.

*grain of sodium

Their patent[1] says they use sodium chloride as the source of sodium ions. I don't know how they'll deal with the hot salt corroding stuff. Probably ceramics, superalloys, and/or special coatings. Like other types of engines, there are tradeoffs between unit cost, maintenance cost, and unit lifetime. Some applications will prefer a high unit cost with a long lifetime and low maintenance (generators at construction or mining sites). Others will prefer cheaper engines that require more maintenance (drones). And others will prefer very cheap engines that only need to work for a few hours (cruise missiles).

If I had to bet, I'd say this idea is not likely to succeed. But the upside of success is so high that it's worth pursuing.

1. https://patents.google.com/patent/US12136898B2/en?oq=US12136...

Sourcing hydrogen from electricity means splitting water and compressing the hydrogen. The electrolysis step is around 50% efficient, and compressing the hydrogen for storage takes some energy as well. If the light cell is 50% efficient at converting hydrogen to electricity, then your "battery" efficiency is around 25%. A typical lithium battery is 80-90% efficient round trip.

This setup does have the advantage that the cost of increasing storage capacity is relatively cheap. You only need to increase the size of the hydrogen tank. But power output would be limited by the size of the lightcell.

There are other disadvantages besides the poor efficiency. People can't see or smell hydrogen, so you'd also need sensors to detect hydrogen leaks. Depending on how quickly the hydrogen is consumed, you might also have to deal with cold temperatures in some parts of the setup (as ideal gas law means the temperature will decrease as hydrogen flows out of the tank). And hydrogen is a very pernicious molecule. It will leak through metal tanks and pipes. It also tends to make metals brittle. And its flame is almost invisible. Lastly, the lightcell consumes salt, but I'm not sure how much so I don't know how big a reservoir would be or how often it would need to be refilled.

If such a generator were powered by nat gas rather than being a battery of sorts, then even being a bit less efficient than an ICE would be attractive if the generator were simpler and had a lower TCO than the ICE equivalent.

I’m with Octopus in the UK (so not EU any more), on the Agile plan so it changes depending on wholesale prices. My average last month was £0.2061/kWh. Fixed tariffs are closer to £0.25/kWh.

It's useful for grid storage. Very large amounts of hydrogen are already stored in salt domes[0]. Current salt domes have volumes in the range of hundreds of cubic kilometers and can support pressures around 50-150 bar, translating into storage of thousands of tons of hydrogen. Along the texas gulf coast, there are hydrogen storage facilities that each store enough hydrogen to translate to around 100 GWh chemical energy. Being able to convert that chemical energy with 40% end to end efficiency means one site could store 40 GWh. In comparison, in 2023 the entire world had only around 56-200 GWh of battery storage capacity[1] installed.

[0]https://energnet.eu/wp-content/uploads/2021/02/3-Hevin-Under... [1]https://www.rethinkx.com/blog/where-is-all-the-battery-stora...

> That's the levelized cost over the lifetime.

I don't see how you can compute that cost if you don't know anything about the amount of energy that goes into and out of the container, and how often that happens.

The article I'm quoting gives a range.

Larger for small storage, and longer term. Smaller for others.

> meta name="keywords" content="Downtown Café, coffee, Fitzroy, tea"

wot?

Patents don't prevent non-commercial use.

I am skeptical. Sounds like this has dubious practicality, perhaps more of a marketing stunt by the inventor than a real product. Maybe more likely he'll be the next Elizabeth Holmes?

Electricity prices for non-household consumers https://ec.europa.eu/eurostat/statistics-explained/index.php...

> The EU average price in the first half of 2024 was €0.1867 per KWh

How is efficiency for say, propane? No need to worry about hydrogen embrittlement or invisible flames around residential areas.

eventually we would hope to get there, but, we are trying to have an edge somewhere that isn't the literal most refined and large capex part of the market first. if we can have a 10x edge

oops. it's a template