5 ms·

Can anyone explain the importance of this to someone with no understanding of physics?

templar_muse 8y ago
Well as you know current power generator technology for the most part uses a heat source (burning coal, nuclear reactor, etc.) to produce steam from water, this pressure difference is used to drive a generator which turns the rotational energy of the turbine into electrical energy. Thermo-electric devices like thermocouples and thermopiles convert heat energy directly into electrical energy.
meta_AU 8y ago
Heat engines generate work (power) through the movement of heat from hot to cold. Conventional systems (steam turbines, Stirling engines, regular thermoelectric generators) require a temperature difference of much higher than 5C between hot and cold, which limits the situations they can be used in. This apparently can work at much lower temperature differences than other systems while generating 'useful' amount of work.
- VBprogrammer 8y ago
  I wonder if this could be used to power an electric recovery generator in a Internal Combustion Engine in hybrid applications. If my back of the envelope calculations are correct a typical 2 litre engine exhausts over 1000 litres of exhaust gasses at ~300c per minute. A fair amount of energy is lost to the atmosphere this way. In combined cycle power plants they use the exhaust gasses of a turbine engine to power a secondary steam power plant. This obviously would work in a car if it weren't for the huge complexity and cost.
  - meta_AU 8y ago
    Sure,but you are judt bolting one heat engine to another (the motor). I'm assuming the efficiency of the motor is better than the TEG (generally the case), so why not just draw power from the motor instead? This technology is probably more applicable to situations where you have a source of low quality heat and you want to extract a tiny bit of power.
    - VBprogrammer 8y ago
      Yeah, checking wikipedia the efficiency of TEGs are ~5-8% so I guess that is why this idea isn't used. It would be hard to justify the cost / weight at that limit.
      - lostlogin 8y ago
        Many applications don’t have a weight limit, things like generators powering remote living locations.
      - dsfyu404ed 8y ago
        There's got to be more to it than that. I would suspect that energy recovered over the service life isn't enough to more than break even. If up front cost and/or weight/packaging were the issue you'd see them employed at least occasionally in marine/rail/off highway/stationary industrial applications where physical trade-offs aren't as big of an issue and the up front cost is can be more easily amortized over the long service life of the equipment it's tacked on to.
    - logfromblammo 8y ago
      An internal combustion engine relies more on the heat from the chemical reaction than the heat of the engine block. And the hot gasses are just blown out the exhaust pipe. It isn't a closed cycle. Bolting a heat engine to the internal combustion means that the excess heat from the engine block and the exhaust gases can do some work before convecting, diffusing, or radiating away. The usual problem is not the additional weight of the heat engine part, but the enormous radiator you would need to maintain a proper cold well. This would likely be a ribbed (finned) aluminum plate covering the entire underside of the car, with scoops and fans to ensure sufficient airflow across it. The combustion engine part could then be redesigned to produce higher temperatures, as the heat engine portion can be actively driven if necessary to cool the engine block--or to warm it, as might be needed for diesel startup.
      - windows_tips 8y ago
        Combustion engines don't rely on heat so much as pressure (can be viewed as the same thing in some models). There's no need to have "excess" heat in an engine.
  - jdietrich 8y ago
    Formula 1 cars use a much simpler method to recover energy from exhaust gases - a generator attached to the turbocharger.
    - VBprogrammer 8y ago
      Aircraft engines had an "simpler solution" to this problem, they geared the output of the turbo charger down to the crankshaft speed and directly recovered the power into mechanical energy. This was known as a turbo compound engine: https://en.wikipedia.org/wiki/Turbo-compound_engine https://en.wikipedia.org/wiki/Turbo-compound_engine These improved fuel efficiency by 15-35%. It's actually the reason my mind jumped to recovering energy from exhaust gasses. Doing this directly from heat would be elegant if it could ever be made cost effective.
someonenice 8y ago
As I see it, this is good for low power iOT devices that are installed in remote / hard to reach areas (say underground etc. ..). A small temperature difference could produce power enough to run the device without any battery. Heart Pacemaker require around 10uWatt and this new power source seems to provide 12uWatt for 1 cm2. If temperature difference could be maintained, then could provide a low weight, low power source that do not require changing battery.
- lostlogin 8y ago
  Thanks. If that energy is stored in a battery or capacitor, how could it bleed off any excess charge (in your example 10 v 12uW). Is this a thing that’s is problem anywhere?
  - pjc50 8y ago
    Getting rid of a few microwatts is never a problem. If these things behave like Peltier elements, they'll simply float their voltage up to a design maximum then stop extracting energy as the electric field balances the energy of the electrons they're trying to extract from.
- windows_tips 8y ago
  Is there a 5C difference anywhere in the body? Skin temperature to blood temperature, maybe?
  - function_seven 8y ago
    That's what I was thinking. 37°C inside vs. up to 32°C (90°F) outside and you still have enough temp gradient to produce the power. All you need to do is install this heatsink on your chest :)
    - crooked-v 8y ago
      And to satisfy precedent, pipe any leftover power after running the pacemaker to a ring of white LEDs.

Well as you know current power generator technology for the most part uses a heat source (burning coal, nuclear reactor, etc.) to produce steam from water, this pressure difference is used to drive a generator which turns the rotational energy of the turbine into electrical energy. Thermo-electric devices like thermocouples and thermopiles convert heat energy directly into electrical energy.

meta_AU 8y ago

Heat engines generate work (power) through the movement of heat from hot to cold. Conventional systems (steam turbines, Stirling engines, regular thermoelectric generators) require a temperature difference of much higher than 5C between hot and cold, which limits the situations they can be used in. This apparently can work at much lower temperature differences than other systems while generating 'useful' amount of work.

VBprogrammer 8y ago
I wonder if this could be used to power an electric recovery generator in a Internal Combustion Engine in hybrid applications. If my back of the envelope calculations are correct a typical 2 litre engine exhausts over 1000 litres of exhaust gasses at ~300c per minute. A fair amount of energy is lost to the atmosphere this way. In combined cycle power plants they use the exhaust gasses of a turbine engine to power a secondary steam power plant. This obviously would work in a car if it weren't for the huge complexity and cost.
- meta_AU 8y ago
  Sure,but you are judt bolting one heat engine to another (the motor). I'm assuming the efficiency of the motor is better than the TEG (generally the case), so why not just draw power from the motor instead? This technology is probably more applicable to situations where you have a source of low quality heat and you want to extract a tiny bit of power.
  - VBprogrammer 8y ago
    Yeah, checking wikipedia the efficiency of TEGs are ~5-8% so I guess that is why this idea isn't used. It would be hard to justify the cost / weight at that limit.
    - lostlogin 8y ago
      Many applications don’t have a weight limit, things like generators powering remote living locations.
    - dsfyu404ed 8y ago
      There's got to be more to it than that. I would suspect that energy recovered over the service life isn't enough to more than break even. If up front cost and/or weight/packaging were the issue you'd see them employed at least occasionally in marine/rail/off highway/stationary industrial applications where physical trade-offs aren't as big of an issue and the up front cost is can be more easily amortized over the long service life of the equipment it's tacked on to.
  - logfromblammo 8y ago
    An internal combustion engine relies more on the heat from the chemical reaction than the heat of the engine block. And the hot gasses are just blown out the exhaust pipe. It isn't a closed cycle. Bolting a heat engine to the internal combustion means that the excess heat from the engine block and the exhaust gases can do some work before convecting, diffusing, or radiating away. The usual problem is not the additional weight of the heat engine part, but the enormous radiator you would need to maintain a proper cold well. This would likely be a ribbed (finned) aluminum plate covering the entire underside of the car, with scoops and fans to ensure sufficient airflow across it. The combustion engine part could then be redesigned to produce higher temperatures, as the heat engine portion can be actively driven if necessary to cool the engine block--or to warm it, as might be needed for diesel startup.
    - windows_tips 8y ago
      Combustion engines don't rely on heat so much as pressure (can be viewed as the same thing in some models). There's no need to have "excess" heat in an engine.
- jdietrich 8y ago
  Formula 1 cars use a much simpler method to recover energy from exhaust gases - a generator attached to the turbocharger.
  - VBprogrammer 8y ago
    Aircraft engines had an "simpler solution" to this problem, they geared the output of the turbo charger down to the crankshaft speed and directly recovered the power into mechanical energy. This was known as a turbo compound engine: https://en.wikipedia.org/wiki/Turbo-compound_engine https://en.wikipedia.org/wiki/Turbo-compound_engine These improved fuel efficiency by 15-35%. It's actually the reason my mind jumped to recovering energy from exhaust gasses. Doing this directly from heat would be elegant if it could ever be made cost effective.

someonenice 8y ago

As I see it, this is good for low power iOT devices that are installed in remote / hard to reach areas (say underground etc. ..). A small temperature difference could produce power enough to run the device without any battery. Heart Pacemaker require around 10uWatt and this new power source seems to provide 12uWatt for 1 cm2. If temperature difference could be maintained, then could provide a low weight, low power source that do not require changing battery.

lostlogin 8y ago
Thanks. If that energy is stored in a battery or capacitor, how could it bleed off any excess charge (in your example 10 v 12uW). Is this a thing that’s is problem anywhere?
- pjc50 8y ago
  Getting rid of a few microwatts is never a problem. If these things behave like Peltier elements, they'll simply float their voltage up to a design maximum then stop extracting energy as the electric field balances the energy of the electrons they're trying to extract from.
windows_tips 8y ago
Is there a 5C difference anywhere in the body? Skin temperature to blood temperature, maybe?
- function_seven 8y ago
  That's what I was thinking. 37°C inside vs. up to 32°C (90°F) outside and you still have enough temp gradient to produce the power. All you need to do is install this heatsink on your chest :)
  - crooked-v 8y ago
    And to satisfy precedent, pipe any leftover power after running the pacemaker to a ring of white LEDs.