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Power Science

New Heat Engine With No Moving Parts Is As Efficient As Steam Turbine (mit.edu) 79

Posted by BeauHD from the one-step-closer-to-a-decarbonized-power-grid dept.
An anonymous reader quotes a report from MIT News: Engineers at MIT and the National Renewable Energy Laboratory (NREL) have designed a heat engine with no moving parts. Their new demonstrations show that it converts heat to electricity with over 40 percent efficiency -- a performance better than that of traditional steam turbines. 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. The team's design can generate electricity from a heat source of between 1,900 to 2,400 degrees Celsius, or up to about 4,300 degrees Fahrenheit.

The researchers plan to incorporate the TPV cell 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. When the energy is needed, such as on overcast days, TPV cells would convert the heat into electricity, and dispatch the energy to a power grid. With the new TPV cell, the team has now successfully demonstrated the main parts of the system in separate, small-scale experiments. 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-driven power plants and enable a fully decarbonized power grid, supplied entirely by renewable energy. The researchers published their findings in the journal Nature.
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New Heat Engine With No Moving Parts Is As Efficient As Steam Turbine More

New Heat Engine With No Moving Parts Is As Efficient As Steam Turbine

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  • 4,300 degrees Fahrenheit! (Score:1)

    by Anonymous Coward

    4,300 degrees Fahrenheit!

    IF you could store something at such a high temperature without tremendous losses, maybe this could be interesting. But in the real world, you get something that hot, it's going to dissipate energy into the surrounding environment and drop in temperature fairly rapidly.

    I think people would be better served by storing more modest temperatures underground and use geothermal heat pumps to retrieve it later when the heat is needed for your home or office. Far more practical.

    • Sure it would drop in temperature as the surrounding environment increases, but then suddenly the surrounding environment would be the one that's hotter and it would dissipate energy back into the storage area and everything would be good again.

      Boom! Physics is so easy.

    • Re: (Score:2)

      by SirSlud ( 67381 )

      did you just skip over "heavily insulted"?

    • Re:4,300 degrees Fahrenheit! (Score:5, Interesting)

      by K. S. Kyosuke ( 729550 ) on Thursday April 14, 2022 @07:24PM (#62448206)

      4,300 degrees Fahrenheit!

      That's like almost ten sheets of papers burning!

      BTW a traditional heat engine that would work at just 40% efficiency with a 2200K hot end would be considered piss-poor. Natural gas plants are over 60% with around 1500K hot end.

      • Depends on what temperature the cold side is.

        One thing nice is if you use a flash boiler on the cold side of this thing you should be able to get another 35% of the leftover energy into electricity via turbines.

      • Re: (Score:2)

        by ceoyoyo ( 59147 )

        Sure, but your efficiency drops pretty fast when your turbine blades get all wobbly.

      • Being dependent on steam really limits the sources of heat to lower temperatures. Many nuclear designs such as molten salt or pebble reactors work at much higher temperatures.

      • Re: (Score:2)

        by gweihir ( 88907 )

        The main point here was "no moving parts". And that is really impressive at >40% efficiency.

        • The question remains if wasting one third or more of your potential electrical energy output is worth getting rid of moving parts, considering that the energy industry is apparently already more than happy with adding additional moving parts (a steam turbine) to a gas turbine to increase its efficiency by a similar ratio.

          • Re: (Score:2)

            by gweihir ( 88907 )

            Since this has never been done before, nobody knows. However, discounting it at this time would be entirely premature. Also you are comparing it wrongly, because you need to compare it to energy _storage_, not energy creation.

      • A heat engine operates between two thermal reservoirs to flow heat and turn it into mechanical energy. However, this is really not mechanical but a photovoltaic one that converts it to electricity. So it’s not really a heat engine and it’s 40% efficiency in that thermal range is closer to state of the art design.
        • Well I wasn't the one saying that this was a heat engine (of course it's not); rather that we already have better existing technology in form of heat engines with cooler hot end AND higher efficiency to boot.

    • I'm a bit rusty on my thermodynamics, but at that kind of temperature (/delta-T) isn't 40% about the theoretical Carnot cycle efficiency?

    • To put it in perspective, the surface of the sun is 5,500 degrees C (~10,000F). Hot lava is up to 1,200 C (2,190 F). My guess is this might be useful for a nuclear fusion reactor.
    • i mean there is plenty of volcanos where you can probably use it

    • Surround the heat reservoir on all sides with the TPV cells, and pull a vacuum on the chamber. Then the heat has nowhere to go but into the energy-producing cells, which (ideally) reflect back photons that are unused.

    • The transfer rate of heat is entirely dependent on the available transfer mechanisms. Nuclear reactors use water because it's very dense and very fast to transfer heat away.

      a vacuum provides almost no method for transferring heat...you're left with only photon radiation which is very slow in comparison

    • Re: (Score:2)

      by mspohr ( 589790 )

      Also, very hard to capture sunlight and achieve this temperature.

  • Fix everything with this one weird trick (Score:3, Interesting)

    by RightwingNutjob ( 1302813 ) on Thursday April 14, 2022 @08:15PM (#62448326)

    The radiated power of a hot surface is proportional to T^4.

    The hotter your graphite battery, the more energy comes out in them photons and the harder it is to insulate it. So peak power output is generally going to be inversely related to how long the charge is stored.

    This is true for an electric battery too, of course, but is a less dramatic effect.

    This is in contrast to using intermittent renewable energy to produce synthetic hydrocarbons which can be stockpiled almost indefinitely.

    Or using nuclear fission which produces no emissions and runs 24/7 with proper maintenance.

  • I wonder if these could be used to convert waste heat from large crewed spacecraft into electricity?

  • Is this very similar to this morning's story titled 'Thermal Batteries' Could Efficiently Store Wind, Solar Power In a Renewable Grid ?
    https://hardware.slashdot.org/... [slashdot.org]

    First dupe in a while, not bad. Unfortunately this tech seems overoptimistic, to put it mildly.

    • You know how it is. Scientists are under huge pressure to publish groundbraking research, so they move quickly. So quick in this case that twocpapers were published about this topic in less than 24hs. Otherwise Slashdot would be posting dupes. But that is impossible.
  • If I had a million dollars.... I have a system that I'd build for doing geothermal powered desalinization and energy preservation.... Oh well.

    • If your idea is good, you should be able to get someone reputable interested in it.

      • It's neigh impossible to get anyone's attention with money anymore. That's why there's so many small time inventors publicizing their ideas then disappearing or suddenly dying... Either way, it's a desalinization system that uses a combination of wave power and geothermal energy to use refrigeration to repeatedly freeze and melt sea water to purify it instead of using filters or boiling. Could be completely self contained and then also use geocaching for storing excess heat for energy.

  • Net CO2 emitter? (Score:3)

    by BenBoy ( 615230 ) on Thursday April 14, 2022 @10:49PM (#62448626)
    I'm probably reading this incorrectly, but are we talking about white-hot (well insulated) graphite as a way of reducing atmospheric carbon emissions? Because the failure mode would seem to this naif to be sudden, enthusiastic *release* of CO2. It's no Chernobyl, but it seems like it'd be a start ...
    • You are correct. Of course it's not comparable to Chernobyl, because this burning graphite wouldn't be highly irradiated :P
      However, whether or not the graphite can spontaneously combust is entirely dependent on the presence of oxygen.

      I imagine people who have created ultra-efficient infrared photovoltaics are probably pretty well aware of the danger of hot ass graphite.
      Beyond that, presence of oxygen would only lower the efficiency of the system and reduce the insulation ability.
      I think it's probably p

    • How much graphite do you think is in this thing? Burning it will release as much CO2 as burning an equivalent amount of coal. Unless the device is the size of a small mountain, burning it down is not going to do anything to the atmosphere that your car doesn't do in normal operation.

  • Comment removed based on user account deletion
  • Long term storing of heat over 1900 degree Celsius doesn't sound an efficient design. How about using their heat engine inside nuclear power plant? If they could use it there and eliminate warm waste water discharge, it may be a useful invention.
  • Could be useful in other areas too
  • This is the kind of research that eventually leads to making renewables affordable, efficacious, and thus, viable. So far, they are good at generating power, but not at distributing it to demand. These kinds of things bridge the gap. Certainly there's a lot left to figure out. When we have all the pieces, like off-peak supply, figured out, THEN we can switch away from fossil fuels. (But not before that -- it would be sawing off the branch we are sitting on.) We just need to keep this kind of research co

    • Re: (Score:2)

      by Budenny ( 888916 )

      It does have to last you, maybe not a month, but a couple of weeks. Or something has to last you a couple of weeks. The UK makes detailed information available on wind production, and remember this includes off shore as well as on shore:

      https://gridwatch.co.uk/WIND [gridwatch.co.uk]

      Before its possible to move to intermittent sources of generation you have to provide for continuous power supply at the critical period, December, January and February. In the case of the UK, it is dark at about 4pm - the days are shorter the

      • Short-term storage solutions (a couple of days) like this one would already go a long way towards ensuring that the gas generators only have to run for a few days in a typical year.

  • So you have this material that will absorb the energy from sunlight. My understanding is most of the sunlight that hits earth is reflected back and when it is trapped, one of the reasons is the greenhouse gas effect. So these guys are finding an orders of magnitude more efficient way (than greenhouse gases) to trap the sun's energy and release it back into our environment. And since we don't have 100% effective insulation, that will leak; and the waste heat from work being done. Isn't this just shifting how

    • Re: (Score:2)

      by bws111 ( 1216812 )

      Glass is also 'orders of magnitude more efficient' at trapping solar energy than greenhouse gases are. That does not mean that actual greenhouses are contributing to global warming in any meaningful way. Of course, it the entire globe was enclosed in glass that would be different. But it isn't. Heat that 'leaks out' of a greenhouse can be radiated off into space. Heat trapped by greenhouses gases aren't radiated into space.

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