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Power

MIT Engineers Design Engine That Converts Heat To Electricity With Over 40% Efficiency (technologyreview.com) 117

Posted by BeauHD from the better-than-the-industry-standard dept.
Engineers at MIT and the National Renewable Energy Laboratory (NREL) have designed a heat engine with no moving parts. It converts heat to electricity with over 40% efficiency -- making it more efficient than steam turbines, the industrial standard. MIT Technology Review reports: The invention 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. It can generate electricity from sources that reach 1,900 to 2,400C -- too hot for turbines, with their moving parts. The previous record efficiency for a TPV cell was 32%, but the team improved this performance by using materials that are able to convert higher-temperature, higher-energy photons. The researchers plan to incorporate the TPV cells into a grid-scale thermal battery. The system would absorb excess energy from renewable sources such as the sun and store that energy in heavily insulated banks of hot graphite. Cells would convert the heat into electricity and dispatch it to a power grid when needed.

The researchers have now successfully demonstrated the main parts of the system in small-scale experiments; the experimental TPV cells are about a centimeter square. They are working to integrate the parts to demonstrate a fully operational system. From there, they hope to scale up the system to replace fossil-fuel plants on the power grid. Coauthor Asegun Henry, a professor of mechanical engineering, envisions TPV cells about 10,000 feet square and operating in climate-controlled warehouses to draw power from huge banks of stored solar energy.
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MIT Engineers Design Engine That Converts Heat To Electricity With Over 40% Efficiency More

MIT Engineers Design Engine That Converts Heat To Electricity With Over 40% Efficiency

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  • Really? (Score:4, Informative)

    by gillbates ( 106458 ) on Thursday June 30, 2022 @10:27PM (#62664540) Homepage Journal

    By way of comparison, 40% is the thermal efficiency of a diesel engine.

    While the MIT review claims that 40% efficiency is more than a steam turbine, this site [lambdageeks.com] says otherwise. And this one [wikipedia.org] also claims steam turbines can reach 50% efficiency as well.

    And should I mention GE sells gas turbines for power generation with 64 percent efficiencies [ge.com]?

    • The problem of disposing the radioactive waste from conventional nuclear power installations is that the stuff creates heat that must be controlled to prevent disasters, Since this conversion system produces usable energy from heat alone with no machinery that requires sustenance. can it be useful as an electrical energy source source buried safely away in isolation from causing disasters?

      • Re:Really? (Score:4, Insightful)

        by huiac ( 912723 ) on Thursday June 30, 2022 @10:52PM (#62664568) Homepage

        Short answer - no.

        This scheme is designed to work with a source at 1900-2400C; that's practical in a purpose-built solar thermal plant, say, but if your radioactive waste gets that hot the neighbours will definitely complain.

        • Re:Really? (Score:5, Funny)

          by ShanghaiBill ( 739463 ) on Thursday June 30, 2022 @11:50PM (#62664662)

          If your waste gets that hot, then it isn't waste. It is still fuel.

          • Re: (Score:2)

            by Kremmy ( 793693 )
            Would be cool if this made it possible to build cheaper radioisotope thermoelectric generators.

          • That is silly and not funny.
            Fission products after a Uranium atom got split: are waste. And not fuel, and they are the ones that produce the dangerous heat. Most of the "waste" is not fuel anyway but unfissionable inert Uranium.

            • Re: (Score:2)

              by jabuzz ( 182671 )

              Fuel is just something that can produce useful energy. So if your "waste" is getting to 2000 Kelvin then it is actually still "fuel" in the broader sense, because 2000 Kelvin is most definitely at the point where you can easily turn that heat into useful energy.

              • Re: (Score:2)

                by dfghjk ( 711126 )

                "Fuel is just something that can produce useful energy" ... by burning it. Fuel is not simply anything that produces "useful energy" nor is it clear why "useful" is in your definition.

                Is Lava "fuel"? Does it not "produce useful energy" according to your definition?

                • Re: (Score:2)

                  by HiThere ( 15173 )

                  Hot lava is fuel if you have a thing in place that can take that heat and convert it to something useful.

                  Fuel is something (anything) that the method you're using can accept an convert into something useful.

                • Re: (Score:2)

                  by nasch ( 598556 )

                  Fuel cells don't burn their fuel.

                  • They do. That is why they are called that way.
                    Typical fuel cells, use either H2 and O2 to create water, burning the H2, or Ethanol (C2H5-OH) with Oxygen. Burning the Ethanol in that process. There are plenty of others. One element gets oxidyzed, with: oxygen. We call that "burning" as laymen :P

              • You could.
                But no one is building a "give us some radioactive waste" and "we make energy from it, reactors."
                That would be an RTG https://en.wikipedia.org/wiki/... [wikipedia.org]
                Not super efficient, not really worth the money and the hassle and the risk.

                • Re: (Score:2)

                  by HiThere ( 15173 )

                  It's not at all clear that RTGs are the only thing that could take radioactive "waste" and extract energy from it. Any heat exchanger could probably do that. Whether it's worthwhile is a separate question.

                  • Of course every heat converter could do that.
                    I was probably mind locked in "nuclear plant" and that is why I picked RTG.

            • I do not think that was meant to be funny or silly. It was actually rather insightful. I think what's pretty incredible is that you completely fail to understand the fundamental truth in that post.

              If a fishing breakdown product is emitting this much heat, it's clearly undergoing further fishing, which makes it a potentially usable source of energy. Provided the reactor setup is appropriate for the sequence, there's no reason to stop using an energy-generating mix, when it is not uranium.

              I have to conclude t

              • Re: Really? (Score:5, Funny)

                by PsychoSlashDot ( 207849 ) on Friday July 01, 2022 @09:20AM (#62665350)

                If a fishing breakdown product is emitting this much heat, it's clearly undergoing further fishing, which makes it a potentially usable source of energy. Provided the reactor setup is appropriate for the sequence, there's no reason to stop using an energy-generating mix, when it is not uranium.

                You're absolutely right. They just need to tuna the reactor a little better and keep the fishing going, for Cod's sake.

              • A fishing breakdown is usually the result of the wrong bait being employed in my experience. Try using live bait and avoid fishing during the heat of the day. Nothing bites then it seems.

              • If a fishing breakdown product is emitting this much heat, it's clearly undergoing further fishing,
                No it is not. It is just radioactive decay. Obviously you can use that. But getting the decaying fission products out of radioactive waste and then use them again in an RTG makes not much sense: hence no one is doing it.

                I have to conclude that either you didn't understand, or you're just trolling against nuclear power.
                I understand it very well. You are the troll. Dumbass.

                Provided the reactor setup is appropri

        • It was just a wild hope. There is possibility that the process performed a mile or two in a subterranean installation under an uninhabitable desert region might disturb a minimum of neighbors.

          • Transporting 2000C radioactive material to the underground bunker might be a problem.

            There's bound to be some neighbors along the way.

            • In general, dealing with radioactive waste has never been well handled, not to speak of satisfactory solutions. Much of it accumulates locally around the power generating sources that produces it awaiting some military clown who decides an ordinary missile strike can cause disasters to satisfy even the worst military sadist, It just disturbs me that somehow that radioactive output of fierce energy cannot somehow be converted into useful purposes..

            • Considering nuclear enrichment plants for nuclear power are not on-site at the power plant already, this is already a solved problem. Storing fuel rods separately shielded keeps the temperature way down until it goes into the reactor and gets near other fuel rods.

      • You still have to have a source of heat. Coal, nuclear, solar, whatever. Once you have that, it just a question of how close to the theoretical thermodynamic efficiency you can get, which depends on the temperatures of your heat source and heat sink. Forty percent sounds pretty good for an electrical generator with no moving parts, but the real question is the lifetime of the equipment and the initial investment cost of the device. That gives you the economic value versus other methods of converting the
      • These cells won't cool anything. If you think that's how they work, you've misunderstood thermodynamics.

      • The problem of disposing the radioactive waste from conventional nuclear power installations is that the stuff creates heat

        True, but unless things go very, very wrong i.e. there is a meltdown that stored waste never reaches the 1,900-2,400C temperatures that this needs to generate power. However, since the system needs these temperatures and works off radiated energy it might be great for extracting power from a future fusion reactor where the temperatures are high and the plasma is magnetically contained in a vacuum vessel.

        • Several possibly functional fusion projects are in the works but the extreme demands of controlled sustainable fusion environments are still not satisfactorily solved,
      • Or onboard a satellite orbiting mars or some other asteroid. Like a better version of voyager 1.
        • The ideal source of energy for propulsion over interplanetary or even interstellar transportation would be a small powerful source of energy that can utilize extreme power to accelerate the rocket fuel at maximum force and all those advantages have possibilities in a nuclear engine. But that has been avoided since an accident at launch could devastate large sectors of this planet as rocket technology remains insecure . The same dangers lay with radioactive materials merely as cargo on a rocket launch.

          • Re: (Score:2)

            by shmlco ( 594907 )

            Umm... we've been launching radioactive material in space for some time now. IIRC, we launched a radioisotope thermoelectric generator into space on a satellite all the way back in 1961.

          • Re: (Score:2)

            by e3m4n ( 947977 )
            this has nothing to do with propulsion... see Voyager1 and Voyager2. Newtons first law, an object in motion remains in motion. The point of the thermocouple is to power everything from the radio, to the motherboard, to the cameras, etc.
            • But velocity has a great deal to do with applied energy. To attain arrival time quickly or slowly does depend on applied energy and an atomic source of continuous energy can do more for velocity than an initial expenditure of propulsive force as in current rocketry.,

              • Re: (Score:2)

                by e3m4n ( 947977 )
                you are old enough to remember voyager 1 and voyager 2 right? voyager 2 launched in 1977 and is just now right outside the oort cloud. It barely makes course adjustments. I remember when it passed Neptune in 1989. Im not talking startrek stuff here. I am talking voyager technology with new thermocouples to power much more powerful circuitry, cameras, radios, etc. if you want to take core samples from something outside the asteroid belt solar is going to a weakness. Pu-238 stays hot for a very long time.
                • There is a discussion about this at https://physics.stackexchange.... [stackexchange.com] When I was discharged from The US Army Air Force in 1946 there were many articles about space possibilities but Von Braun published one in The Saturday Evening Post speculating on spinning space stations to simulate gravity that looked like the one in the film 2001. As an avid reader of Astounding SF. as a kid I followed all rocketry developments closely,

                • Actually, the half life of Pu-238 isn't all that long. Several Voyager (can't recall which or both) instruments have been shut down, some just last month, because the power production has dwindled and is insufficient to keep them going.

                  • Re: (Score:2)

                    by e3m4n ( 947977 )
                    thats over 40yrs ya know lol. waaaay longer than Li-ION and solar panels. by the time you get to jupiter the sunlight energy is just shit.

      • It is basically a photovoltaic cell that needs to absorb photons in that "heat spectrum": so no.

    • That 64% is combined cycle efficiency, it is not a single engine, and engine efficiency is temperature dependent. At the stated temperatures, this TPVs maximum equivalent efficiency is approximately 1 - 300 Kelvin / 2900 Kelvin = 90%

      • It's going to lose at round trip efficiency relative to a thermal storage system using a combine cycle power plant, that's all that really matters.

    • And should I mention GE sells gas turbines for power generation with 64 percent efficiencies [ge.com]?

      That is about the efficiency of a fuel cell and double the efficiency of some older generators.

      So why aren't these deployed more widely?

      These turbines may be a much wiser and faster investment to reduce CO2 than wind and solar since they could be deployed at scale at much lower cost.

      • Re: (Score:2)

        by jaa101 ( 627731 )

        These turbines may be a much wiser and faster investment to reduce CO2 than wind and solar since they could be deployed at scale at much lower cost.

        The problem is the pay-back period for these investments tends to be decades. There's some risk in a business model that relies on burning fossil fuels in the 2040s and beyond.

        • Re: (Score:2)

          by kenh ( 9056 )

          The risk is political - politicians letting "the perfect" get in the way of the "good enough".

      • Re: (Score:2)

        by jabuzz ( 182671 )

        They are. It's the reason that coal has been on the slide since fracked gas became a thing in the USA. Even if you got rid of all the environmental restrictions on coal, it simply cannot compete with a combined cycle gas turbine power station on cost. At that point you either have to subsidise coal or put restrictions on CCGT both of which are "un-american". The result is that coal power plants close for cheaper to run natural gas power CCGT power plants.

        • Re: (Score:2)

          by kenh ( 9056 )

          The coal plant you own is cheaper than the gas turbine plant you have to buy/build.

      • Re: (Score:2)

        by nojayuk ( 567177 )

        Combined-cycle gas turbine generators ARE being built and deployed widely. They burn gas and emit CO2 and add to climate change. They're the anonymous grey buildings with a funny-looking exhaust stack close to a grid interconnector that keeps the lights on when the Green wind turbines and solar panels that get all the public attention don't generate much electricity (which is a lot of the time).

        There are modern coal-fired power plants that can manage up to 46% efficiency, so-called ultra-supercritical boile

        • Combined-cycle gas generators are not used to "back" renewable energy projects. Commercial-scale wind/solar are usually combined with "peaker" plants, not combined-cycle gas. Installing wind/solar and selling on the spot market isn't a great business. Power producers prefer to sell part of their production on longer-term contracts. In order to do that, they agree to sell a certain amount at a certain rate. The buyer doesn't really care how the electricity is produced. In order to meet contractual obli

          • Re: (Score:2)

            by nojayuk ( 567177 )

            CCGT plants aren't used to "back" renewables, they're one of several methods of generating electricity to meet demand and in many places the principal method.

            Thermal efficiency of CCGT plants is around 60% once they're up to temperature -- the hot exhaust gases from the ca. 45-50% efficient turbine are used to raise steam to drive a small steam turbine to generate "extra" electricity. That's a lot better efficiency than the best coal-fired plants.

            it's easy to pipe gas from producer plants direct to a CCGT

            • I think this is what I said although there was another poster disagreeing so maybe I did not write my post well. CCGT used to be *very* popular. Back when I owned AEP shares and paid more attention, the CEO of AEP talked about a concern that CCGT would get over-built and cause gas prices to skyrocket thus taking away the cost advantages. I don't think that ever happened.

              I don't design power infrastructure so I have to defer to my friends who do this for a living. When he designs a wind/solar installa

              • Re: (Score:2)

                by nojayuk ( 567177 )

                That's odd. Here in the UK the few open-cycle gas plants left in service only get run for a few hours a year, to test them and keep them operational just in case they're needed because of grid trips or loss of other generating plant. In contrast to open-cycle generators we've got about 32GW of CCGT capacity with some more being built. Some times in winter when electricity demand is at its highest, as much as 30GW of that CCGT capacity can be online at one time.

                Open-cycle generators produce less electricity

      • Because it is not the turbine that has 64%, but a combined cycle gas plant that has 64%.
        The turbine is around 42% - just like any other turbine on the planet.

    • I dont know what the previous efficiency of a thermocouple is, but this discovery is significant for deep space satellites that use heat from radioactive material to power their onboard functions. More efficiency means more available power for more functions. The further from the sun the more worthless solar panels are. Its an inverse square rule.

      • The radioactive material (Plutonium) in those deep space satellites is nowhere near hot enough for this technology.

    • Re:Really? (Score:5, Informative)

      by drinkypoo ( 153816 ) <drink@hyperlogos.org> on Friday July 01, 2022 @08:16AM (#62665222) Homepage Journal

      By way of comparison, 40% is the thermal efficiency of a diesel engine.

      40% is the peak theoretical efficiency of a fully modern road-going diesel engine at peak efficiency, which is only ever achieved while cruising in the "sweet spot [fleetequipmentmag.com]". And you can consistently do that only while cruising on flat ground.

      In actual practice a diesel is more commonly at around 20% efficiency, which is why electric motors just slaughter them (at 95%+ efficiency for all current EV motors, even while regenerating.)

      The most efficient-while-cruising diesel engines reach 50% efficiency or thereabouts, but they are in container ships. You can't make a small diesel that efficient.

    • It's 43.3% simple cycle.

      64% is combined cycle after waste heat is shunted through a steam turbine. Good engineering will account for this but let's compare just oranges.

      https://www.ge.com/gas-power/p... [ge.com]

    • That is not the efficiency of the gas turbine. A gas turbine is around 42%, just like a steam turbine. It is a

      "&gt64%
      Net combined-cycle efficiency

      That means it is used in "combined cycle" gas plant where the first stage is a gas turbine (or several) and the exhaust (and potentially additional gas burned) is used to heat a steam turbine.

  • Let me guess... (Score:2, Informative)

    by Bodhammer ( 559311 )
    Commercial applications are 5-10 years away. Whatever.

    • Re: (Score:2)

      by Z80a ( 971949 )

      It's when you least expect it, with little to no media fanfarre, such as with everything that was developed during your lifetime, including the blue leds behind your screen and the several improvements to materials used in your everything.

  • Why not just use it as a solar panel? It's substantially more efficient than current photovoltaics and gets better, rather than worse, as it gets hotter.

    • It's substantially more efficient than current photovoltaics and gets better, rather than worse, as it gets hotter.
      a) t's substantially more efficient than current photovoltaics actually it is not. Efficiency in this context means: how much of the input do you get out as useable output. As this "thermo-photovoltaic" is only using a small spectrum - albeit with 40% efficiency - it produces less power than a "normal-photovoltaic" cell, that uses a different spectrum, with 25% efficiency.
      b) it does not get bet

      • a) t's substantially more efficient than current photovoltaics .

        actually it is not. Efficiency in this context means: how much of the input do you get out as useable output. As this "thermo-photovoltaic" is only using a small spectrum - albeit with 40% efficiency - it produces less power than a "normal-photovoltaic" cell, that uses a different spectrum, with 25% efficiency.

        Not so, as I read it. They start with a surface that is heated by the incoming infrared. But this surface is paved with a structure of

  • Glorious Soviet technology developed Ural truck, converting fuel to heat with 100% efficiency!

  • Might be interesting for RTGs (Score:4, Interesting)

    by hackertourist ( 2202674 ) on Friday July 01, 2022 @02:22AM (#62664876)

    Current RTGs use Peltier elements with a conversion efficiency of about 5%.
    The MIT article lists 40%, at a temperature of 2400 C, up from a previous record of 32% at a lower temperature. As far as I know, the junction temperature in the Voyager RTGs is 1000 C.
    Wikipedia [wikipedia.org] quotes 35% at 1770 K, which works out to 25% at 1270 K/1000 C.

  • Lifetime, materials, difficulty to make? (Score:3)

    by gweihir ( 88907 ) on Friday July 01, 2022 @05:52AM (#62665070)

    All suspiciously absent. Other than that, pretty cool research. Probably nothing will come from it, but that is not absolutely certain.

  • Tldr; Wondered if you could put these in a steel foundry but the melting point of most metals is below 1900C. White hot radiation starts at 1315C though. I'm wondering how they keep the things from melting! They need to be near a white hot energy source.
    https://en.wikipedia.org/wiki/... [wikipedia.org]

  • "TPV cells about 10,000 feet square and operating in climate-controlled warehouses to draw power from huge banks of stored solar energy."

    Climate controlled how, to match Mercury's? These cells are optimized for temperatures between "1,900 and 2,400 C"! And why store solar heat if there is a heating problem? Wouldn't it make more sense to wrap very hot things in these cells, like furnaces at steel mills (which still aren't hot enough)? How about using it to reduce the heat we generate by 40% instead o

    • Also the stuff about 'high energy photons' is ridiculous. They are 2k photons FFS.

    • Re: (Score:2)

      by HiThere ( 15173 )

      Reduce the difference in temperature between the heat source and the heat sink, and you're guaranteed to reduce efficiency.

  • I dream of a cell like that that works with temperatures in the 27Â C and higher and generates energy while cooling that air a couple of degrees. The generated electricity moves a fan, and bum! Free air conditioning. Always hoping.

  • So, it works at small scale. Why automatically make the jump to grid scale when you could probably make the jump to house-size scale much faster and easier? Or are they worried that nobody will buy it?

  • That's some pretty warm graphite. I got to wondering a few things.

    First, what does the black body radiation curve look like at 2,000 degrees? Specifically, what frequency is most of the energy radiated at? I never took thermo or that level of physics so I don't know how to figure it out.

    Second, I sure hope the chip doesn't have to be at that temperature. That would take some seriously exciting solder joints.

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