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It makes less sense on a diesel engine because their heat sources are lower temp. Fuel cells produce much more useful heat for a heat engine to capture. And no

It makes less sense on a diesel engine because their heat sources are lower temp. Fuel cells produce much more useful heat for a heat engine to capture. And no, the complexity of heat recovery isn't high at all. The costs pay themselves off almost immediately. They're orders of magnitude less complex than an ICE, last almost forever, and require almost no maintenance apart from cleaning after tens of thousands of hours. If a modern heat recovery turbine is too complex, then so is an electric motor.

SigmundA 5y ago
Diesel exhaust temps are around 600c SOFC operate 600c-1000c. Heat recovery turbines use either organic Rankine cycle (steam turbine) or Brayton where the fuel cell replaces or is along side the combustion chamber in a gas turbine. Comparing the complexity of a Heat recovery turbine to an electric motor is absurd. Let me know when a SOFC with recovery turbine is in a truck.
- darksaints 5y ago
  It's a turbine. It spins inside a housing. It has an input and an output. Modern turbines don't even have oil...they use ceramic air bearings that might need to be replaced sometime after you die.
  - SigmundA 5y ago
    A turbine does nothing by itself again an absurd statement. A heat recovery turbine has a host of support systems to actually recover heat including a generator which is essentially an electric motor to capture electrical energy. I don't see a lot of gas turbines in various use around me, and the ones that are are quite expensive to fix. I do however see electric motors everywhere and they are extremely reliable and cheap.
    - darksaints 5y ago
      Lol, there is no need to speculate about the practicality of heat recovery turbines in vehicles. They're already in use by millions of cars and trucks. Nearly every semi truck on the road has one...sometimes they have two! They're called turbochargers. More specifically, the heat recovery turbine is the exhaust-connected half of the turbocharger. Most car turbos drive air compressors to increase ICE efficiency (surplus electric power isn't so useful for ICE cars), but you can literally chop the turbocharger in half and attach an electric motor to the turbine shaft, and voila, now you have an electric heat recovery turbine. Were you actually thinking I was proposing attaching a steam turbine to a fuel cell? Lol. Can I subscribe to the Cult of Elon's Version of Facts? This is hilarious.
      - SigmundA 5y ago
        Turbo chargers are not heat recovery turbines they will not increase and engine thermal efficiency by any significant amount, diesels use turbo charging to increase power they are just as thermally efficient without them. In order to utilize the increased air mass that forced induction creates more fuel must be injected, this should be obvious. Most turbo chargers do not engage under light throttle. Turbo charger also adds significant cost and are not inexpensive to repair. An actual useful heat recovery turbine is much larger and more complicated, all of the examples of one attached to diesels or fuel cell are either steam turbines as is the case with the Freightliner SuperTruck [1] or full gas turbines as is the case with some fuel cell implementations and some of those also have a secondary steam turbine [2]. The Freightliner still has a turbo charger like any diesel along with a recovery steam turbine, much of the effective heat recovery comes from capturing heat from the engine block itself not just hot exhaust gas. Again your claim that a full heat recovery turbine is a simple as a electric motor is ABSURD. 1. https://www.ccjdigital.com/business/article/14931733/waste-heat-recovery-an-old-theory-finds-new-life-but-will-it-work-for-every-trucking-application https://www.ccjdigital.com/business/article/14931733/waste-h... 2. https://www.ee.co.za/article/co-generation-hybrid-fuel-cell-gas-turbine-systems.html https://www.ee.co.za/article/co-generation-hybrid-fuel-cell-...
        darksaints 5y ago
        > Turbo chargers are not heat recovery turbines they will not increase and engine thermal efficiency by any significant amount, diesels use turbo charging to increase power they are just as thermally efficient without them. This is 100% false, and trivially easy to google. But it also misses the point: turbochargers are heat engines: they convert heat to work. The fact that they use waste heat from exhaust means that they recover energy that is normally lost, which means it is a heat recovery engine. That work can be used any number of ways, but if it is used, you have increased the thermal efficiency of the engine. > The Freightliner still has a turbo charger like any diesel along with a recovery steam turbine, much of the effective heat recovery comes from capturing heat from the engine block itself not just hot exhaust gas. Those are both heat recovery engines. One is rankine cycle (the steam turbine), and the other is brayton cycle (the turbocharger). The only other difference is the source of heat. And again, to drive the point home: https://www.sciencedirect.com/science/article/pii/S1876610214014076/pdf?md5=81032aa431f1a3baea977a5b8820409a&pid=1-s2.0-S1876610214014076-main.pdf https://www.sciencedirect.com/science/article/pii/S187661021...

SigmundA 5y ago

Diesel exhaust temps are around 600c SOFC operate 600c-1000c. Heat recovery turbines use either organic Rankine cycle (steam turbine) or Brayton where the fuel cell replaces or is along side the combustion chamber in a gas turbine. Comparing the complexity of a Heat recovery turbine to an electric motor is absurd. Let me know when a SOFC with recovery turbine is in a truck.

darksaints 5y ago
It's a turbine. It spins inside a housing. It has an input and an output. Modern turbines don't even have oil...they use ceramic air bearings that might need to be replaced sometime after you die.
- SigmundA 5y ago
  A turbine does nothing by itself again an absurd statement. A heat recovery turbine has a host of support systems to actually recover heat including a generator which is essentially an electric motor to capture electrical energy. I don't see a lot of gas turbines in various use around me, and the ones that are are quite expensive to fix. I do however see electric motors everywhere and they are extremely reliable and cheap.
  - darksaints 5y ago
    Lol, there is no need to speculate about the practicality of heat recovery turbines in vehicles. They're already in use by millions of cars and trucks. Nearly every semi truck on the road has one...sometimes they have two! They're called turbochargers. More specifically, the heat recovery turbine is the exhaust-connected half of the turbocharger. Most car turbos drive air compressors to increase ICE efficiency (surplus electric power isn't so useful for ICE cars), but you can literally chop the turbocharger in half and attach an electric motor to the turbine shaft, and voila, now you have an electric heat recovery turbine. Were you actually thinking I was proposing attaching a steam turbine to a fuel cell? Lol. Can I subscribe to the Cult of Elon's Version of Facts? This is hilarious.
    - SigmundA 5y ago
      Turbo chargers are not heat recovery turbines they will not increase and engine thermal efficiency by any significant amount, diesels use turbo charging to increase power they are just as thermally efficient without them. In order to utilize the increased air mass that forced induction creates more fuel must be injected, this should be obvious. Most turbo chargers do not engage under light throttle. Turbo charger also adds significant cost and are not inexpensive to repair. An actual useful heat recovery turbine is much larger and more complicated, all of the examples of one attached to diesels or fuel cell are either steam turbines as is the case with the Freightliner SuperTruck [1] or full gas turbines as is the case with some fuel cell implementations and some of those also have a secondary steam turbine [2]. The Freightliner still has a turbo charger like any diesel along with a recovery steam turbine, much of the effective heat recovery comes from capturing heat from the engine block itself not just hot exhaust gas. Again your claim that a full heat recovery turbine is a simple as a electric motor is ABSURD. 1. https://www.ccjdigital.com/business/article/14931733/waste-heat-recovery-an-old-theory-finds-new-life-but-will-it-work-for-every-trucking-application https://www.ccjdigital.com/business/article/14931733/waste-h... 2. https://www.ee.co.za/article/co-generation-hybrid-fuel-cell-gas-turbine-systems.html https://www.ee.co.za/article/co-generation-hybrid-fuel-cell-...
      - darksaints 5y ago
        > Turbo chargers are not heat recovery turbines they will not increase and engine thermal efficiency by any significant amount, diesels use turbo charging to increase power they are just as thermally efficient without them. This is 100% false, and trivially easy to google. But it also misses the point: turbochargers are heat engines: they convert heat to work. The fact that they use waste heat from exhaust means that they recover energy that is normally lost, which means it is a heat recovery engine. That work can be used any number of ways, but if it is used, you have increased the thermal efficiency of the engine. > The Freightliner still has a turbo charger like any diesel along with a recovery steam turbine, much of the effective heat recovery comes from capturing heat from the engine block itself not just hot exhaust gas. Those are both heat recovery engines. One is rankine cycle (the steam turbine), and the other is brayton cycle (the turbocharger). The only other difference is the source of heat. And again, to drive the point home: https://www.sciencedirect.com/science/article/pii/S1876610214014076/pdf?md5=81032aa431f1a3baea977a5b8820409a&pid=1-s2.0-S1876610214014076-main.pdf https://www.sciencedirect.com/science/article/pii/S187661021...