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US startup begins producing 40%-efficient thermophotovoltaic cells
- Animats 3y agoA possible application of this would be backup power for fuel based heating, so that as long as you have fuel, you can get enough power to run the fans and controls. For an energy storage system, though, 40% makes little sense.
- glenngillen 3y agoCould 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% make little sense?
- Animats 3y agoBecause 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.
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- 20after4 3y agoIn a heat-based system couldn't you use more cells to absorb remaining heat?
- vlovich123 3y agoAdding 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.
- nine_k 3y agoTechnically, perpetual motion is possible: consider a sphere rotating in vacuum. A source of free energy, a "perpetual engine", is indeed impossible.
- vlovich123 3y agoA sphere rotating in a vacuum should still experience black body radiation and gravitational drag. Damn kids and their pesky attempts to violate the 2nd law.
- nine_k 3y agoCooling down would not slow down the sphere, if the radiation is uniform. Gravitational drag, maybe, but only if there is something to drag nearby, and we postulate a vacuum. A sphere is symmetric and thus does not emit gravitational waves. I wonder if an effect akin to black hole evaporation could play a role: if one of the two virtual particles gets accelerated towards the sphere, it may bring some momentum to it. But, assuming that the space is isotropic, statistically such momentums should cancel out.
- vlovich123 3y ago
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- nine_k 3y agoRecuperating 40% of energy you harvested nearly for free (as in opex, not capex) may be strictly better than not harvesting this energy at all. Negative electricity prices that happen sometimes are pure waste.
- _hypx_ 3y ago> 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.
- RobLach 3y agoFor those of us unfamiliar with the properties of these materials, what would be considered impressive? Are there examples that are better?
- mnw21cam 3y agoIf 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 https://en.wikipedia.org/wiki/Thermal_efficiency
- _hypx_ 3y agoWhich is the problem of the idea. Any kind of thermal engine, such as a stirling engine, would beat this idea in efficiency with those kinds of temperatures.
- magicalhippo 3y agoFor 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_limit https://en.wikipedia.org/wiki/Shockley%E2%80%93Queisser_limi... [2]: https://en.wikipedia.org/wiki/Solar-cell_efficiency#Factors_affecting_energy_conversion_efficiency https://en.wikipedia.org/wiki/Solar-cell_efficiency#Factors_...
- fbnbr 3y agoThis just becomes interesting if electricity can be produced from reflected photons by the moon such as at night energy production is possible. Other than that I believe in fusion although the giant fusion reactor does help during the day. Instead of making photovoltaic more efficient they should do this with batteries
- throwbadubadu 3y ago> This just becomes interesting if electricity can be produced from reflected photons by the moon such as at night energy production is possible "referring to thermal energy grid storage (TEGS) consisting of a low-cost, grid-scale energy storage technology that uses TPVs to convert heat to electricity above 2,000 C" You all speak in miracles here, the use case seems to be converting thermal energy and energy storage. Why the moon, and what does that have to do with regular photovoltaic efficiency?
- oblio 3y ago> 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.
- throwbadubadu 3y agoBut not with these cells? Not getting it :( Or why does (any) storage thing become only interesting then?
- zo1 3y agoThey, 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.
- svantana 3y agoCould 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.
- rkagerer 3y agoAre 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?
- 20after4 3y agoYes they exist, though I don't think they are Peltier devices: https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_generator https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...
- brucethemoose2 3y agoIf you want a "zero moving part reactor," what you are really looking for is: https://en.m.wikipedia.org/wiki/Fission_fragment_reactor https://en.m.wikipedia.org/wiki/Fission_fragment_reactor And its spaceflight cousin: https://www.projectrho.com/public_html/rocket/enginelist2.php#id--Nuclear_Thermal--Fission_Fragment_Type https://www.projectrho.com/public_html/rocket/enginelist2.ph... Though they are not peltier devices either.
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- fsh 3y agoThere 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 https://en.m.wikipedia.org/wiki/Betavoltaic_device
- zimbatm 3y agoStupid question: could this be used underground in volcanic areas like Iceland?
- eptcyka 3y agoYes, but you can also use steam there.
- rgmerk 3y agoStupid answer: probably not as far as I can tell. My understanding is that to get those kinds of temperatures from geothermal you need to drill to currently infeasible depths. But you don’t need those kinds of temperatures from a geothermal resource to make it very cost-competitive.
- londons_explore 3y ago> emitter temperature of 2,400 C GE's combined cycle turbines can get system level efficiency of around 63% from these sorts of temperatures. (For those not familiar with them: They're basically aircraft jet engines followed by steam turbines using the hot exhaust. They are in widespread use to generate electricity from gas, but they can also run off any other liquid fuel, or simply off anything that gets very hot.)
- 15457345234 3y agoThere are a looooot of moving parts in a CCGT generating station, multiple oil loops, multiple coolant loops, many consumables, a complex control flow. Being able to replace the combined turbine/alternator assembly with a 'when it gets hot, voltage comes out' unit would give you significant reliability gains and lower operating costs.
- pbmonster 3y agoWell, you still have to cool those cells. It's still a heat engine, after all. And you can't just let radiation do the job for you, no way the semiconductor likes getting anywhere close to this hot.
- fnordpiglet 3y agoLiquid cooling with a heat exchanger can be pretty low profile.
- fnordpiglet 3y agoYeah came here to say this. A complex turbine setup is large and complex. A panel setup with liquid cooling and a heat exchanger isn’t. I feel like these sorts of things should be useful in situations where there’s a lot of excess heat in some other process that’s typically wasted. Smelters, incinerators, high temperature chemical reactions, etc. Because they are presumably not large you can clad and enclose the high temperature area in these sorts of panels and capture 40% of the wasted energy and divert it back into the process. That would have compounding effects.
- pbmonster 3y agoI don't get why they go for storage with this. Storing a block of carbon or tungsten at 2000°C for hours or days does not sound like something that will ever be economical. A battery leaking energy this quickly (and it will leak₎ will need to be incredibly cheap to ever make sense. I wonder if you could use this with parabolic mirrors, though. Build a large mirror array, focus sunlight onto a big carbon sphere (maybe coat it with one of those new materials that are transparent for visible light but pretty reflective for IR), cover the top of the sphere in those new panels. They are more efficient than practically all solar cells and get much more power out the same area than solar cells. This should beat a photovoltaic parabolic mirror setup, right?
- kolinko 3y agoCarbon or tungsten I don't know, but sand as a thermal energy storage medium can be quite economical. Energy loss scales with the surface area (^2), energy stored with volume (^3). With grid scale, above certain dimensions, you can store energy for months while maintaining economic viability. Even for single days or weeks it makes sense. You need hot water in your home 24/7, but sun doesn't shine every day in most regions.
- londons_explore 3y agoIs the sand flowing or stationary? Flowing sand has issues with blockages and erosion. Stationary sand has pretty low conductivity, so getting all the energy out of your 200 yard cube of hot sand might be a challenge.
- benj111 3y agoJust have rods similar to nuclear (well the opposite) You can progressively sink them in as the sand cools/ you want more energy out.
- Cymrukicks 3y agoStationary, this has already been done. It does require a heat exchanger aswell rather than getting a direct current out.
- benj111 3y agoSo what are the trade offs between these and peltier devices? They're much more efficient, I assume much more expensive?
- nine_k 3y agoExpense is usually a function of scale. Everything new and custom is expensive. Electronic chips with incredibly complex structure of some rare materials inside them are priced in cents.
- benj111 3y agoWhat I was getting at is I think I might be missing a gotcha. There's a fair amount of niche applications where peltiers are currently used even though they aren't very good. But no one's mentioning them as an alternative to peltiers.
- Simulacra 3y agoSo is this essentially using waste heat?
- whycome 3y agohttps://commons.wikimedia.org/wiki/File:NREL_PV_Cell_Record_Efficiency_Chart.png#/media/File:NREL_PV_Cell_Record_Efficiency_Chart.png https://commons.wikimedia.org/wiki/File:NREL_PV_Cell_Record_... This graphic of photovoltaic cell efficiency (non-thermo) is super interesting: it shows the progression from 1976 and current capabilities (and not necessarily commercially viable or available). The panels you'll get for your home are probably around 20% efficient in ideal conditions.
- buovjaga 3y agoLinked article is from January. Latest coverage: https://www.fastcompany.com/90951247/these-giant-glowing-carbon-blocks-bring-clean-energy-to-factories https://www.fastcompany.com/90951247/these-giant-glowing-car... They launched a pilot in the summer.
- 8bitsrule 3y agoI was new to this idea, and found this explanation useful: https://www.youtube.com/watch?v=Gn7pfYKB7DA https://www.youtube.com/watch?v=Gn7pfYKB7DA
- m463 3y agoSo does this function as a cooler? In other words - does it remove heat from something at high temperature? I know there are situations where you can't get rid of heat - would this help by removing it electrically?