A new heat engine with no moving parts is as efficient as a steam turbine
news.mit.edu
news.mit.edu
A turbine system would have much better efficiency than 40% if its heat was available at that temperature. For example a closed Brayton cycle gas turbine + steam turbine system. Certainly complex and expensive, but could get much better than 40% efficiency.
Think of the steam turbine as a baseline. Like rating a vehicle in horse power.
On the topic of heat pumps, you could also use a TPV for geothermal power. Since there are no moving parts and presumably no huge steam engine installation, it would be more feasible to have one of these in your back yard. The grid powers a heat pump, you compress the fluid till it hits 2000°C, and your TPV extracts power. The heat pump itself is >100% efficient, so overall you can steal a fair bit of electricity from the ground. Right?
The facts have already been stated that refute your what if. Whether you missed it or not, you're arguing for a perpetual motion machine.
The Layman's version of the 3 Laws of Thermodynamics are:
1) You can't win
2) You can't cheat
3) You can't even choose not to playFor instance, take a Brayton thermodynamic cycle. It's motor cycle, but you can literally just reverse the arrows on this cycle, it becomes a reversed Brayton cycle, which corresponds to a heat pump (or a refrigeration machine, depending on which inlet of the machine you're interested in). In practice, the reversing of the arrow means the reversing of the fluid flow, which means compression processes are now expansion processes and vice versa.
Carnot theory does still apply. The COP (Coefficient Of Performance) of a Carnot heat pump is 1/n, where n is the usual Carnot efficiency of a heat engine.
With n=1/3, you get a COP of 1/1/3 = 3 = 300%
Carnot efficiencies consider ideal machines. So ideal Carnot batteries have a n * 1/n = 100% efficiencies. It means you can't increase the efficiency of a heat engine by putting a heat pump in front of it. In an ideal case (ignoring all losses and inefficiencies), you would get the same efficiency. In practice, you can only be worse.
Are you sure you aren't confusing the coefficient of performance with the efficiency? If a heat pump was >100% efficient, I could cool my house by leaving my refrigerator door open.
"Evaluated herein is one E-TES concept, called Firebrick Resistance-Heated Energy Storage (FIRES), that stores electricity as sensible high-temperature heat (1000–1700 °C) in ceramic firebrick, and discharges it as a hot airstream to either (1) heat industrial plants in place of fossil fuels, or (2) regenerate electricity in a power plant. … We report that systems of 100–1000 s MWh may be cycled daily, and discharged at a constant heat rate typically for 70–90% of the storage capacity. Traditional insulation can reasonably limit heat leakage to less than 3% per day. Preliminary cost estimates indicate a system cost near $10/kWh, substantially less expensive than batteries."
The waste heat from the gas turbine would power the steam turbine. Something like a combined cycle gas turbine, but with a closed loop for the gas turbine (say, helium) rather than combustion.
Steam turbines alone can be operated at higher temperatures by using mercury instead of water. Some plants using this approach were built in the 1920/30s.
I did not understand why that's not fair. Are you implying it is harder to achieve and maintain a 2000 C system?
Based on "They exposed the cell to a high-temperature lamp and concentrated the light onto the cell. "
I would guess this could be valuable for solar concentrators?
Is that wrong?
It's like if I compared the top speed of your Porsche on a perfectly straight road, clear weather, no wind, to the top speed of my sedan, but I've got it pointed toward a very high cliff and I'm claiming a top speed of 400 mph (straight down). It's not a fair comparison, because I am cheating by exploiting a greater 'height'.
If we actually compared the same thing, yours would still be at least 50mph faster than mine (at a slight angle from straight down)
That said, we don't really know what this new design can take in practice, so it's probably a comparison drawn too soon.
With the technology at the time they weren't able to get the efficiency to be competitive with an internal combustion engine, but something like this probably could've made it competitive. I'm not sure if there's any need for it with today's battery performance/price, but maybe as a range extender or something.
https://vri.wwu.edu/viking-series-cars-history/ (scroll down to Viking 29)
https://www.sae.org/publications/technical-papers/content/97... (technical paper)
What I don't understand about the Viking 29 article is how an 8 KW generator is going to power a 75 KW motor, is there something I'm missing?
More details: http://fennetic.net/pub/viking_29_thermophotovoltaic_electri...
Sadly, F1 is just a money-pissing contest.
There are numerous examples of tech developed for F1 that ended up in road cars.
https://www.carshop.co.uk/latest-news/formula-1-rule-changes...
I'm looking at Dragonfly, specifically, where an RTG provides the electricity and heat to keep everything alive. Imagine what 10x longer flights would do for that mission.
Oh well, I was briefly excited but there's a big enough gap that it probably won't work as is
(Note the reason given for this limit is to guarantee that, if this capsule accidentally falls to Earth, the cladding has the mechanical performance to stay intact on impact. If iridium gets too hot, its strength is permanently degraded (so it says). I suspect if you voided this requirement -- if you created a separate of class of spacecraft "no longer capable of impacting earth" -- the limit could be raised much higher).
[0, pdf] https://ntrs.nasa.gov/api/citations/19910015359/downloads/19... (2.2 "Temperature Constraints")
Cooling things in space turns out to be hard. There's no convection or conduction, so all cooling occurs via radiation. I believe the ISS radiators are rated at about 1 watt per m^2, which means that you can calculate the radiator area (and mass) given your power budget.
To a first approximation, the ISS radiators are about the same size as its solar panels.
This is a factor missing from virtually all sci-fi representations of space ships. I had this realisation a few years back talking about 2001 --- the Discovery should have had a huge set of radiator fins given its nuclear propulsion (ion drive I believe, in the story universe). Wikipedia states that there were radiators in the book, though I don't recall that element.
MMRTG [0] dissipates 2,000 W, in a package that only has several m^2 of radiator fins. That's >100x more efficient than the ISS (1 W/m^2). ISS' radiators have to operate below room temperature; MMRTG fins [1] are in the 100 °C - 200 °C range. Higher temperature -> higher heat dissipation per fin area.
(By the way, the comment we're replying to asks about nuclear quadcopters on Titan [2], which is in dense atmosphere not a vacuum!)
[0] https://en.wikipedia.org/wiki/Multi-mission_radioisotope_the...
And yes, Titan / cold atmosphere would make for highly-efficient thermal gradients.
I hate to throw water on the situation but we constantly read articles about tech that will be a game changer only to never be seen again mainly because it can't be scaled to the size needed and provide the advantages we need.
Yes, it sounds good. But what we need now is a proof of concept rather than theories on how much of a miracle the tech is. My question is, "How can we help to move it forward to a point where we can see actual advantages?"
This particular one requires around 2000C, which appears to be above the critical temperature of most RTGs (though not all!):
https://www.researchgate.net/figure/Critical-temperatures-to...
I wonder if those RTGs also have any disadvantages or are simply more substantial.
[edit]
Corrected cooling requirements as pointed out by the8472 in another comment.
I wondered whether 'critical temperature' meant a temperature above which the junction fails to generate an EMF - which would not be an issue here, even if this were the case, as we know this material works at 2000C - but the article seems to use the term to mean certain temperatures that have engineering relevance, with regard to the design of the device, as opposed to fundamental physical limits to feasibility.
If you had a pit huge enough and hot enough, seems plausible to me.
How does one lose this heat in space?
Silicon's band gap (1.11 eV) corresponds to 1110 nm (NIR), and any photons with more than 3 eV energy (413 nm) are lost (and all the excess energy in photons in between is lost as heat). Newer cells are around 0.6-0.7 eV, but I don't know their maximum capture energy. That's all the violet light and UV. There's a startup that makes a polymer film that can create two lower energy photons in the band gap from a high-energy photon to capture some of that wasted light. This would seem to be a cell that could capture it directly. Very very cool; that's a lot more energy captured per photon.
What I'm unclear on is why you need to heat it up so much to get to those efficiency levels, and it wouldn't just work as an ordinary solar cell.
The TPV is distinct from a solar cell because the TPV is meant to reflect energy back to the source. A solar cell also reflects some energy back to the sun, but that energy is effectively lost. In the TPV case, the reflected power helps keeping the source hot, thus effectively recycling photons in a feedback loop involving the source and the TPV.
Some of the energy incident to the TPV is transformed into electricity, some is reflected, and some is dissipated as heat in the TPV. The 40% efficiency is measured as (electricity+reflected)/incident. Thus, it is not true that the TPV converts 40% of its input into electricity. Instead, the TPV converts some fraction, reflects (40%-fraction) to be recycled later, and dissipates 60% into heat. Using the TPV as a solar cell would reduce the efficiency because the reflected energy is wasted. Part of the magic of the TPV is to design a really good mirror that reflects energy back to the source, which is not a concern for solar cells.
The current design operates best for a blackbody source around 2000K and there is probably no point in using it at 5600K.
Cool stuff.
1 - Tc/Th = 1 - 295k/2000k
https://www.nrel.gov/news/features/2021/new-projects-move-th...
(some of the same people involved in this paper at NREL seem to also be collaborating with Antra, which is great to see)
Heating graphite based thermal batteries to >1900C using the Sun for long term storage? I'm not sure why the article is refraining from being explicit, but i'm guessing the intended application here is to replace the steam turbine usually found at the centre of high temperature solar thermal collectors.
I wonder how feasible and cost effective it is to insulate a battery well enough to maintain over 2000C for multi day periods without substantial loss? The heat storage strategies used for steam turbines doesn't require such high temperatures.
One of the difficulties is keeping the semiconductors cool. They definitely don't operate at 2000 degrees. One envisions a solar power tower[1] with this technology, but with more graphite mass at the collector.
So, not much progress in 40 years.
There's a basalt based thermal storage system in the Netherlands that is used for seasonal storage. It's heated up over the summer using solar energy and during the winter they pump water through it for heating. It's Basalt in a metal box surrounded by wool and it stays warm through the winter. The temperatures for this system are much lower (500 degrees) but the principle is about the same. https://materialdistrict.com/article/battery-natural-stone/
So, if you can heat the mass to the desired temperature, keeping it there is relatively easy. It would slowly cool over time but not at a rate that is problematic and only very slowly. A large enough system might store heat for months/years.
It’s obviously possible. The question is whether it’s cost effective.
While cool (1,900 to 2,400 degrees C cool) the Carnot effiencies should be closer to 86%.
The idea that heat engines get more efficient as you increase delta T has been around for a while. The problem is constructing a delta work extraction loop that doesn't have more losses as a result of the delta T increase, ie the practicalities of extracting work energy.
Warning: I am assuming they are working with an approximately room temperature cold side, as article doesn't say. The practicalities of allowing for the delta-t is usually where the efficiency losses are made.
source: I am an electrical / chemical engineer.
[0] https://en.wikipedia.org/wiki/Steam_turbine#Thermodynamics_o...
Is the comparison fair? Well it's tricky but I'd say yes, the generation of just heat from fuel is normally highly efficient so electricity/heat should be similar to electricity/fuel in the second case. However in a turbine generating plant it's not plain heat but it needs to be converted to steam and moved around, so there are many more loses.
That paragraph in [1] is referring to: "Isentropic steam turbine efficiency refers to the ratio of power actually generated from the turbine to what would be generated by a perfect turbine with no internal flowpath losses using steam at the same inlet conditions and discharging to the same downstream pressure."
It specifically says not to confuse them: "Turbine efficiency is not to be confused with electrical generating efficiency, which is the ratio of net power generated to total fuel input to the cycle."
[1] https://www.epa.gov/sites/default/files/2015-07/documents/ca...
Nuclear powered spacecraft have been hard to develop because of the need for moving parts. NASA's cancelled Advanced Stirling Radioisotope Generator, which was supposed to be a more efficient radioisotope powered generator than the thermoelectric generators previously used, had trouble because the moving part based generator wasn't very reliable.[0]
In addition to eliminating moving parts this is also interesting for nuclear powered spacecraft because it may be possible to pass light through a radiation shield to prevent damage to the converter. The problem is that the reactor would need operate at extremely high temperatures. While this probably isn't high enough to melt the fuel, the fuel might not be structurally stable. Although liquid uranium nuclear rockets are being considered[1].
[0]https://en.wikipedia.org/wiki/Advanced_Stirling_radioisotope...
[1]https://www.uah.edu/news/items/bubble-through-nuclear-engine...
https://en.wikipedia.org/wiki/Radioisotope_thermoelectric_ge...
This means you have to dissipate more than 10 times more energy as heat than the energy you actually want to use as electricity.
Dissipating heat in space is not easy because unlike earth there is no surrounding fluid to dissipate heat into through convection. This means you have to spend precious mass budget on huge (compared to your energy budget) direct heat radiation systems that cannot leverage convection efficiencies.
Thus, a significant energy efficiency increase would be a big deal for RTG powered spacecraft design. It is curious that the article above does not consider this.
Bonus thought: consider what this lack of convection problem means for "Hyperloop" type vehicle systems that operate in a vacuum tunnel, as most conventional trains dissipate excess braking energy through convection from resistive heating elements atop the roof.
However the thermoelectric converter used in those RTGs exploit a different effect, and appear to have quite different properties as a result... What I can tell from a quick dig:
- Thermocouples ("Seebeck effect") operate on a temperature difference, and are more commonly used as temperature sensors. They have the advantage of working at a larger range of temperatures, but the disadvantage of needing to maintain a temperature gradient for power production... Any inherent efficiency is likely negated by the requirement for constant cooling. [0]
- Themal Diodes ("Thermophotovoltaic") is more like a solar panel for a different wavelength (infrared). The principle they operate on suggests no temperature gradient is required, not sure about cooling for other reasons though, but the clear disadvantage is the requirement for a high operating temperature for effective use in power production. [1]
Historically thermal diodes don't appear to have been particularly efficient compared to thermocouples either, obviously this particular one changes that.
[0] https://en.wikipedia.org/wiki/Thermocouple#Power_production
A temperature gradient is absolutely required. Ignoring materials problems (such as melting) a photovoltaic cell ultimately does work off a temperature differential because it has to absorb photons. It cannot do that if its temperature is the same as the black body temperature of the lightsource illuminating it, otherwise they would be at an emission/absorption equilibrium.
This is also why PV cells could theoretically work in reverse mode at night, emitting IR into space. They'd just do that paltry power ratings because ΔT(earth, cosmic background) is much smaller than ΔT(photosphere, earth). And they'd have to be made of a material with a much smaller bandgap.
Which would make the cooling requirements of this TVP lower (relative to input) due to it's higher efficiency? but still substantial.
[0] https://www.sciencedirect.com/topics/engineering/concentrate...
However, extracting exergy (electricity is pure exergy) from a flow of energy is the tricky part and will always be associated with efficiencies way below unity, based on fundamental principles.
Also, you don't need Vantablack, a regular cavity absorber would be fine.)
But maybe not, the glowing comes from black body radiation, so the vantablack material would presumably glow as well (ironically). As long as the heatsink coupling did not block the visible "white" light produced, or glowed itself, then at least the photons from the back would get used. I expect that getting a heatsink paste rated for 2200 C is ... challenging, but, conveniently, you'd do better if you just skipped the paste.
Liquid metal is some of the best performing thermal paste around. In computer applications that's normally an alloy made from Gallium, Indium and Tin, but at 2200C the majority of metals should work. Maybe Gold to reduce oxidation.
Such multi-junction photovoltaic cells, but optimized for the higher temperature of the Sun, have existed for many years and efficiencies over 45% are well known.
So there is no point in heating anything, the concentrated solar light must be directed to an appropriate multi-junction photovoltaic cell, for the best efficiency.
Despite their very high efficiency, the multi-junction photovoltaic cells are seldom used for solar energy, because they are expensive, so they can only be used together with light-concentrating mirrors, to achieve a reasonable cost.
Even with mirrors, the price is still much higher than for normal solar panels, so they might be chosen only when space constraints would prohibit the use of a larger area with solar panels.
I can't seem to find any place that sells these with a brief search, so I'm thinking 1000x.
Having more efficient cells would give you a few more miles I presume. Not too useful for the everyday user, but if you're doing an off grid trip it would be very useful if you camp somewhere and let your car charge for a few days. I guess might as well roll out some proper panels in that case though.
Planes do have a reasonably large wing surface area that could be panelled up if they're not too heavy (you can make quite large RC planes fly perpetually in the sun even with regular monocrystalline panels) so there would definitely be some fuel savings from it if you had like a hydrogen powered jet that already uses electric propulsion.
They have been used for solar panels in satellites or space probes, where maximum efficiency is more important than the price, and in experimental solar plants with movable mirrors that concentrate the solar light from a very large area onto a small photovoltaic cell.
In both applications, the complete systems are very expensive and the cost of the photovoltaic cells is a very small part of the total.
The article mentions a mirror layer as part of the cell, for retaining the energy of out of band photons. Would that be the "off" solution, just bounce them back when they are not needed? Cell moved out of the path? Somehow that triggers "too simple to be true" heuristics in me, but on the other hand... yeah, mirrors (or just very white surfaces, precise direction is not needed) can be quite capable of not getting heated by incoming photons, and that must mean bouncing them back.
When you want to generate energy, you open the insulation and let heat out to hit this chip.
It’s like opening an oven door to let some hot air out.
https://en.wikipedia.org/wiki/Pressurized_water_reactor#Cool...
You need a completely different sort of materials and need to consider new types of risks for a reactor that's supposed to operate at such temperatures.
Can’t it just heat something else than water? E.g. something that’s liquid at 2000C?
The example that springs to mind for me is a steel mill. The temperatures required there easily meet and exceed what is required to generate and store energy with this device.
An example where this idea works is a condensing boiler where the burned gases heat is used to increase efficiency by 10-30%.
This website is very well made. Snappy, nice design, good discoverability and information architecture.
There aren't many web (-designs) I really like. Most of them feel off in some way or another. Another good one would be MDN.
Does anyone with design competency know what it is I like about the design? Are there some known principles at hand here that I can learn more about?
Beyond that, it does have good fundamental design. Hierarchy of typography is simple and clear, they font used for the article copy is legible and sized nicely. And, because of he lack of advertisements and attempts to pull you further into the site, there's enough white space to give it a more relaxed feeling.
If you want to learn the fundamentals of design, pick up the Non-Designers Design Book. Quick read with great explanations of the core principles of good information design.
I found this amusing bio on the Amazon author's page:
Robin Williams spent twenty-five years writing computer and design books and was one of the top three best-selling computer book authors in the world. But the world changed and no one bought computer books anymore, so she went to London and formalized her long study of Shakespeare with an M.A. and Ph.D. in Shakespeare studies.
Would be noisy as hell, but quite a cool project haha
That doesn't means it's useless (it can improve yields for thermodynamic solar) but it means there's a really wide margin of improvement: the theoretical maximum for such temperature is 87%, and if it could be made as effective as a combined cycle[1], you could a yield up to 70-75%.
[1] by that I means being as close as a combined cycle from the Carnot cycle at the same temperature.
The article doesn't provide the efficiency of this insulated hot graphite battery. Given that this device is meant to be paired pretty exclusively with such a battery, it seems like a narrowly applicable solution. Or are there other renewable sources of heat between 1900C and 2400C that could be used for this purpose?
I suppose that if the TPV devices are closely coupled with the white-hot source this should be minimal but it's not clear from the article whether there is an intermediary step, or how they plan to control the TPV's exposure to the heat source to discharge the battery.
Given that this works via radiation (vs convection like a traditional heat engine), the path between the heat source and the TPV would have to be fairly direct, and not lose much heat to any adjacent non-TPV material.
Maybe they have some kind of massively insulated opening/closing heat shield that they can use in a manner similar to the gates used to control water in hydroelectric plants.
It's clearly not ready for production yet, but storing energy as concentrated heat seems like one of the plausible proposed grid-scale storage solutions to me. I'm interested to see where this goes.
For example, low temperature floor heating is very efficient.
You don’t want high temperature deltas because of the associated exergy losses.
What am I missing?
Just guessing, but a heat pump that can actually output at least 1900°C of heat?
If we had those kinds of heat pumps I guess we'd use them in all kinds of industrial processes
A heat pump COP of 3.5 or higher or happens only at relatively low delta-T between the source and destination temps of the heat pump [1] - like the delta-T typical for space or water heating. The COP degrades exponentially with increasing delta T as it has to work ever harder to pump heat against an ever higher temperature/pressure (assuming thermal storage with a fixed volume with few losses).
The refrigeration cycle can't raise temperatures even hundreds (much less thousands) of degrees C - otherwise we'd already have heat pump stoves and ovens.
This is coincidentally also one reason why all else equal, heat pump clothes dryers (which are great) take a bit longer than conventional technologies to dry clothes: they only reach about 50C (vs 70C-75C for standard gas or electric resistance dryers).
> Push that back into the heat pump and, violà, 1kW of free heat left over!
Because the COP degrades with the delta-T, it bottoms out at 1 (an electrical resistance heater), and in your scenario, you end up with 1kWH in, and 400Wh out, so a theoretically 40% efficient battery.
Minus the electrical generation, and at much lower temperatures, your scenario with a heat pump + thermal storage does however describe how the new domestic thermal heat batteries can work with heat pumps [2].
1. https://www.engineeringtoolbox.com/heat-pump-efficiency-rati...
P.S.: A heat pump is usually able to "cheat" an "efficiency" (aka Coefficient of Performance) over 100% because (for a refrigerator) it's defined as the inverse of the usual Carnot efficiency.
When you want heating, you artificially get up to +100% to the CoP from the spent "mechanical" power being 100% converted into heat.
EDIT : Ugh, took a while to get this right !
I understand there are other kinds of engine, such as a gaming engine etc, but in this context it seems like there are better descriptors. "Heat to electricity converter"?
https://www.linquip.com/blog/steam-turbine-efficiency-comple...
How would you go about converting the energy stored in a thermal battery to a high enough temp for this to work? Some kind of heat pump? It has never been clear to me how to concentrate heat like that.
1. https://nucleus.iaea.org/sites/graphiteknowledgebase/wiki/Gu....
My guess is a vacuum flask made of tungsten. Tungsten sheet metal is a thing and it has the second highest melting point of currently known elements, which is 3,422C.
Then for the 'battery' you will want to find a material that has a phase change around the temperature required for this heat engine to operate. The energy required for water to go from 100c water to 100c steam is considerably more significant than the energy required to go from 0c water to 100c water.
Graphite will likely come into play because you need to have electrodes to heat the material up to storage temperature. Graphite is a good for this sort of thing. Although gradual erosion will likely limit the life of the battery.
Or just slide the insulation down in front of the thermocouples when they aren't needed. I have to assume these things mostly work on radiant heat at those temperatures.
[edit]
Efficiencies of over 40% in steam turbines with temperatures between 500 and 600C from an article in 2002: https://www.power-eng.com/news/new-benchmarks-for-steam-turb...
tldr: thermoelectric generators don't have great efficiencies, but by cogenerating heat and electricity they can get viable (if you need heat and electricity, make a bit more heat than you need and put a thermoelectric generator, the non-converted heat will just end up as useful heat). This would be adapted to households, which typically need a lot of heating.
“The heat engine is a thermophotovoltaic (TPV) cell, similar to a solar panel’s photovoltaic cells, that passively captures high-energy photons from a white-hot heat source and converts them into electricity.”
One detail is that objects radiate at all temperatures. The trick is to choose the temperature so that you get a lot of emission in the band that matches the best performance of the PV component.
Not enough was invested in nuclear. Fossil fuels received massive funding (and subsidies). Had we deployed more nuclear power for baseline and industry, we would have been in a far better place. The Cold War also messed up things, and caused the reactors that were deployed to be the ones better suited for weapons first, energy second.
Note that our solar panels are similar to computer chips. Investing more money would have sped up the development but not in time for it to be viable in the 80s.
The Manhattan Project cost, adjusted for inflation, $22B. That was just to blow something up. Had the United States and Great Britain not subsequently developed nuclear energy, it is likely it never would have been developed because it would have been impossible due to cost. Only a nation can develop nuclear energy, it is not something that could have been developed privately, again, due to cost.
When factoring the cost of the energy produced by nuclear fission, the cost of that electricity, the cost of the development of nuclear energy is never factored in. If it were, it would be clear there has never been a more expensive way to generate electricity than nuclear fission. Nuclear energy development was a freebee, and the biggest freebee in the history of civilization: nuclear energy development, paid for by tax payers, was given away and the tax payers' investment never had one penny of return. "Electricity too cheap to meter," never materialized, and not even close. The tax payers were bamboozled.
When all is said and done, the treehuggers have the weaker argument. Sure, nuclear energy has some environmental concerns, but these kinds of arguments pale in comparison to the economic argument: nuclear energy has never been and will never be economically viable. There are reasons, but they can be ignored, because we can see the result, no investor will touch nuclear. And complaining about the type of nuclear plants serves no purpose because the fission plants we built are the cheapest designs there are. Seeder reactors would be cool, but, you see, they're even less economically viable than the fission steam turbine plants.
We could invest everything, every dollar earned, every possible value society could produce, into nuclear energy development, but even if we did, nuclear energy would remain economically unviable.
Again, if we could just invest a small portion of what we wasted on nuclear energy development into solar energy development... well jusT look at how cheap solar has gotten in 20 years with private development. Imagine if it was 80 years instead of 20 and included massive, mind-boggling, government subsidies. Forget any government investment in solar, if solar subsidies could merely match nuclear subsidies, dollar for dollar, no one would be talking about nuclear power anymore.
China spends 4 times more than that yearly on solar.
Further posit: they were aware that nukes were more about making Pu than heat. No insurance company back in the day would accept the risk either (thus the 1957 'Price-Anderson Nuclear Industries Indemnity Act').
Anyway, I'll quote a 1951 expert: "t is safe to say ... that atomic power is not the means by which man will for the first time emancipate himself economically.… At present, atomic power presents an exceptionally costly and inconvenient means of obtaining energy which can be extracted much more economically from conventional fuels.… This is expensive power, not cheap power as the public has been led to believe." — C. G. Suits, Director of Research, General Electric, who who was operating the Hanford reactors. [https://www.ieer.org/pubs/atomicmyths.html]
Sure, but those were Gen 1 reactors. We're overwhelmingly using (pressurized water) Gen 2 reactors these days, which, while being downstream of the same processing as the one required for nuclear weapons, and also theoretically capable to be used to make nuclear weapons themselves, are definitely NOT better suited for weapons first !
Jokes aside, this seems impressive, I have no idea what the best applications would be but wikipedia claims that current similar devices have fairly bad efficiency(https://en.wikipedia.org/wiki/Thermoelectric_generator).
> The team’s design can generate electricity from a heat source of between 1,900 to 2,400 degrees Celsius
Pretty high temperature for me, copper melts at 1800C.
The higher the temperature, the higher the share of exergy in the heat flux. At high enough temperatures, it’s no longer a feat to convert to electricity at high efficiencies.
So, it's just an overrating research PR piece, like the ones people like to complain. This thing probably scales just fine, and may be quite useful. The entire problem is that science gets divulged on those insane PR pieces where it's compared to completely different things, or promise completely impossible results.
This is definitely not my area, but is Carnot efficiency directly comparable to the efficiency numbers cited in the article? Or is the "work" in Carnot efficiency the mechanical work, prior to being converted to electricity?
The comparison to steam engines is misleading, but there’s an important distinction. Steam or gas turbines would reach very high efficiencies at these temperatures too, but won’t because of material properties and limitations thereof.
These limitations don’t seem to exist for this new technology. Hence, reaching very high efficiencies becomes possible. In theory… In practice, I don’t see how heat sources with temperatures that high are feasible or could stem from renewable sources. (something with the thermal battery? Wasn’t explained much in the article)
In any case, in comparison to steam turbines, the technology presented here does absolutely nothing in terms of decarbonising the grid, as claimed. It’s just potentially more efficient. But what’s the source for the primary energy?
My first thought was let's use it in fission (and later fusion) reactors.
I got the impression they would heat the graphite with concentrated solar power.
https://www.theverge.com/2022/2/22/22945975/rondo-energy-dec...
Basically, in their words, "a large insulated shoebox full of brick". And I could be wrong, but I think you should be able to scale the amount of "brick" up to whatever size and keep the insulation the same thickness, so the storage capacity would increase by the cube of the scale and the amount of insulation would only increase by the square of the scale.
That would allow you to minimize the fluctuation in temperature - i.e. if it takes 10 days to get up to temperature, because it's big, you don't have to cool it all the way back to room temperature when you take an afternoon worth of energy back out.
I understood the claim to be that this would have close to no moving parts. That sounds it's cheaper to mass manufacure and operate?
Not an expert, but reading this a few negatives popped out. Basically they are heating a black body to 2400C and then making electricity from gathering the emitted light in a cell. They get to pick a temperature to match the bandgap of the cell.
The key problem is getting something that hot without using another (lossy) form of power. The Sun's surface is ~5600C so that's enough headroom to get there from solar. That's cool. But are there any fission reactors that get (or could get) that ridiculously hot?
I think most try to keep temperatures under 1000C. I think many FAST reactor designs are looking at 600C operating temps with peak temp reaching maybe 1200C during emergency testing. But my memory might be wrong.
As for available temperatures from fission reactors: https://en.wikipedia.org/wiki/NERVA
"When the reactor was operating at full power, about 1,140 MW, the chamber temperature was 2,272 K (2,000 °C)"
That's way up there. That's well above the melting point of steel. That's above the highest temperature jet engines made for experimental aircraft.[1] Most jet engines try for exhaust gas temperatures around 600C or so, for a long useful life. Typical nuclear reactors, around 300C.
It's not impossible to operate up at those temperatures. Every steel plant does it. There are ceramic and brick materials that can deal with such temperatures.[2] The storage medium would probably be some molten metal.
This seems way too much trouble just to store energy.
Now if this thing worked at 600C or so, there would be more uses.
[1] https://www.nasa.gov/centers/dryden/pdf/88068main_H-1375.pdf
[2] https://www.ceramicsrefractories.saint-gobain.com/refractory...
But all this just to replace a battery?
[1] https://www.comsol.com/model/inductive-liquid-metal-pump-590...
I'm not saying what they describe can't be done, only that getting the photovoltaic part to work isn't the biggest engineering challenge the concept faces.
As to temperature this thing is for very high temperatures: can generate electricity from a heat source of between 1,900 to 2,400 degrees Celsius. At 40% efficient you need a wide temperature difference which would suggest a high energy density.
Now you add hot gas at the bottom and have say 4 layers per m. So a 3mx3mx3m cube would be 4 layers * 2 panels per layer * 3m * 3m * 3m = 216m2 of panels taking up a 3mx3m section of floor. At 2.38w/cm2 * 10000cm2/m2 * 216m2 = 5.14 MW of power.
That's about 25 acres of absorber, and an implied 25 acre surface area of the liquid metal emitter pool.
There is a basic challenge here to the design - the energy storage density for the thermal battery they envision scales as the cube of the characteristic dimension of the plant, but the power density that can be delivered scales only as the square of dimension. Not saying that can't be dealt with in engineering, but it ain't going to make this easier or cheaper.
> 54 metres (177 ft) high and 48 metres (157 ft) wide > more than 2,500 h/year [sunlight] > peak power of 3200 kW > Temperatures above 2,500 °C (4,530 °F)
Sounds like it could be useful as a "default load" inside an otherwise inactive solar furnace at least.
Photovoltaics just turn solar energy into electricity, and don't need the heat engine. This has made them way cheaper to deploy than solar thermal energy. So unless there's something very important about this new TEG, the solar thermal vs photovoltaic calculus doesn't really change.
I assume that means there could be room to significantly improve its efficiency or operating requirements with more investment and research.
Having one example, even if 'useless' or elementary, is key to developing new technology.
1. Multistage (moderate to high pressure ratio) steam turbines have thermodynamic efficiencies that vary from 65 percent for very small (under 1,000 kW) units to over 90 percent for large industrial and utility sized units.
https://www.epa.gov/sites/default/files/2015-07/documents/ca...
But this title would not be correct.
Methane combusts at 1,957 °C, right in the band for this thermal cell, and is a normal heat source for steam power.
The steam doesn't reach this temperature, of course, but nor does it need to.