[HN Gopher] Lightcell: An engine that uses light to make electri...
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Lightcell: An engine that uses light to make electricity
Author : curl-up
Score : 67 points
Date : 2025-01-14 13:36 UTC (3 days ago)
(HTM) web link (www.lightcellenergy.com)
(TXT) w3m dump (www.lightcellenergy.com)
| megaman821 wrote:
| 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.
| ggm wrote:
| 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.
| detourdog wrote:
| I read their statement of 40% efficiency would be compared to
| the currently available photovoltaics were generally 20%
| efficiency is normal.
| enragedcacti wrote:
| 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.
| enragedcacti wrote:
| 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.
| larodi wrote:
| Amazing idea. BTW, following Danielle on X, very insightful and
| bright minded person.
| jandrese wrote:
| 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?
| VBprogrammer wrote:
| 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.
| jandrese wrote:
| 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.
| kube-system wrote:
| 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)"
| datadrivenangel wrote:
| 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.
| jandrese wrote:
| 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.
| hgomersall wrote:
| 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.
| imglorp wrote:
| 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!
| Tade0 wrote:
| Do you mean watts or watt-hours?
| finnh wrote:
| 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?
| enragedcacti wrote:
| 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.
| Someone wrote:
| 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.
| tekno45 wrote:
| forbes to prison pipeline?
| bnetd wrote:
| More likely than you think.
| josefritzishere wrote:
| The solar panel conversion of sunlight to usable energy to around
| 20%, with a theoretical max of 30%. So it's better than that.
| qayxc wrote:
| 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...
| sroussey wrote:
| 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.
| choilive wrote:
| 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.
| MalbertKerman wrote:
| It's only true for a single junction. https://en.wikipedia.or
| g/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.
| audunw wrote:
| 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.
| mhb wrote:
| 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.
| jasonjmcghee wrote:
| 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.
| thot_experiment wrote:
| 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.
| sesm wrote:
| 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.
| randomcatuser wrote:
| 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?
| qayxc wrote:
| 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.
| card_zero wrote:
| 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.)
| waveBidder wrote:
| Just be careful or you might make a Kugelblitz
| metalman wrote:
| 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
| nialv7 wrote:
| 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.
| mppm wrote:
| 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.
| idiotsecant wrote:
| This seems like a hydrogen fuel cell with extra steps.
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