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US startup begins producing 40%-efficient thermophotovoltaic cells

pv-magazine.com

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Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#21

Post by mnw21cam »

RobLach wrote: post #6
_hypx_ wrote: post #3

> This cell achieved an efficiency of 41.1% operating at a power density of 2.39 W cm–2 and an emitter temperature of 2,400 C. At those temperatures, this is not very impressive.

For those of us unfamiliar with the properties of these materials, what would be considered impressive? Are there examples that are better?

If you have a heat source with a temperature of 2500C, then the theoretical maximum efficiency of conversion is around 89% assuming you have a heat sink available that can stay below 30C. (1.0 - (30+273)/(2500+273) = 0.89). All heat engines will be worse than this because of practicalities, but a real steam turbine system can be around 47% efficient and a combined cycle can be 60% efficient, using a cooler "hot" end than 2500C.

https://en.wikipedia.org/wiki/Thermal_efficiency

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#22

Post by 20after4 »

rkagerer wrote: post #20
svantana wrote: post #16

Could this be used to create a nuclear power generator without moving parts? Some radioactive material in the center, some coating to absorb the radiation, and a shell of these cells to generate electricity.

Are there already solid state ones that use the heat from radioactive decay and the Peltier principle? I assume your idea, if feasible, might be more efficient?

Yes they exist, though I don't think they are Peltier devices: https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#23

Post by 20after4 »

Animats wrote: post #7
glenngillen wrote: post #5

Earlier quoted context omitted.

Could you elaborate on your last sentence? My naïve assumption was that theoretically the closer to 100% you could get the better, though for some applications you might take a cheaper and lower efficiency panel if it could consistently provide more than the required energy needs. With a storage system, you can just keep adding more storage to soak up higher conversion efficiencies. What am I missing? Why does 40% ma…

Because utility-scale batteries are around 86% round trip efficiency. Pumped storage is around 79%. 40% as a conversion efficiency alone isn't good. That's not a round-trip value; heat loss in storage has to be considered, too.

In a heat-based system couldn't you use more cells to absorb remaining heat?

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#24

Post by zo1 »

throwbadubadu wrote: post #14
oblio wrote: post #13

Earlier quoted context omitted.

> Why the moon, and what does that have to do with regular photovoltaic efficiency? Presumably to produce energy at night and avoid the need for storage. Seems like a moonshot, though.

But not with these cells? Not getting it :( Or why does (any) storage thing become only interesting then?

They, like me, read the title as "Photovoltaic", which are solar cells. And the comment was around that presumably. I was also reading the headline and the first comments entirely confused until I read the article and it elaborate that these are "ThermoPhotoVoltaic" cells, which involves heat and ties in to the article's comments about this being used for energy storage.

All around, confusing. I didn't even know we had such a thing.

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#26

Post by brucethemoose2 »

20after4 wrote: post #22
rkagerer wrote: post #20

Earlier quoted context omitted.

Are there already solid state ones that use the heat from radioactive decay and the Peltier principle? I assume your idea, if feasible, might be more efficient?

Yes they exist, though I don't think they are Peltier devices: https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...

If you want a "zero moving part reactor," what you are really looking for is: https://en.m.wikipedia.org/wiki/Fission_fragment_reactor

And its spaceflight cousin: https://www.projectrho.com/public_html/rocket/enginelist2.ph...

Though they are not peltier devices either.

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#27

Post by fsh »

svantana wrote: post #16

Could this be used to create a nuclear power generator without moving parts? Some radioactive material in the center, some coating to absorb the radiation, and a shell of these cells to generate electricity.

There are betavoltaic generators [1] that directly produce electricity from decay electrons using p-n junctions (similar to photovoltaic cells). However, in the vast majority of applications, they get outperformed by modern lithium batteries (i.e. coin cells).

[1] https://en.m.wikipedia.org/wiki/Betavoltaic_device

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#28

Post by magicalhippo »

mnw21cam wrote: post #21
RobLach wrote: post #6

Earlier quoted context omitted.

For those of us unfamiliar with the properties of these materials, what would be considered impressive? Are there examples that are better?

If you have a heat source with a temperature of 2500C, then the theoretical maximum efficiency of conversion is around 89% assuming you have a heat sink available that can stay below 30C. (1.0 - (30+273)/(2500+273) = 0.89). All heat engines will be worse than this because of practicalities, but a real steam turbine system can be around 47% efficient and a combined cycle can be 60% efficient, using a cooler "hot" end…

For photovoltaic cells there are other factors which limits this further. For a single p-n junction the limit is around 33% for normal sunlight[1], though it's too early in the morning for me to calculate it at the proposed ~2700K temperature. By stacking junctions you can get higher but then other things kick in[2].

[1]: https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limi...

[2]: https://en.wikipedia.org/wiki/Solar-cell_efficiency#Factors_...

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#29

Post by vlovich123 »

20after4 wrote: post #23
Animats wrote: post #7

Earlier quoted context omitted.

Because utility-scale batteries are around 86% round trip efficiency. Pumped storage is around 79%. 40% as a conversion efficiency alone isn't good. That's not a round-trip value; heat loss in storage has to be considered, too.

In a heat-based system couldn't you use more cells to absorb remaining heat?

Adding more cells won’t help for two reason. Let’s say the extra cells would help absorb, they can only capture 40% which means you’ve got exponentially increasing costs chasing after all the heat you didn’t absorb (+ physical location of where to put the cells). The real reason though is physics, namely the 2nd law of thermodynamics. If you could keep adding cells to capture the heat other cells couldn’t, you’d basically get really really close to a perpetual motion machine which we know is impossible. That’s because a good chunk of the unabsorbed heat is either reflected from the cells or not absorbable from the source.

TLDR: Adding more cells won’t help due to economics, geometry, and fundamental laws of physics.

Re: US startup begins producing 40%-efficient thermophotovoltaic cells

#30

Post by jddj »

bestouff wrote: post #11
konstantinua00 wrote: post #9

Earlier quoted context omitted.

it's the temperature of light emitter, not of the panel it's pretty much saying "efficient (for a photovoltaic) electricity from powerful infrared" Sun is 6000 degrees, so most of its emergy is in different frequency Instead, this panel is planned to be used in thermal batteries, I think the article says. I guess main competition is steam turbine or smth?

FWIW when we say "a light at 6000 K" it means "a light with the same color as a black body heated to 6000 Kelvin", so it has nothing to do with temperature, it's only a (veery rough) way of characterizing color.

And we also say that it's a "cooler" colour temperature than a black body only heated to 3500K.

Go figure.

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