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Steam-powered prius

Discussion in 'Fred's House of Pancakes' started by Priipriii, Jul 27, 2024 at 11:43 PM.

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  1. Priipriii

    Priipriii Member

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    Had this idea pop up in my mind the other night. So you know how engines are only 20% to 40% energy efficient, and the majority of the rest is wasted as heat to the coolant or exhaust.

    What if we were able to harness that to increase the thermal efficiency and possibly get the prius to 100mpg or more?

    I would build a steam-powered rotary valve system to rotate a third generator MG3 that would generate additional electricity to keep the prius in EV mode longer. This would work by rerouting the coolant to go through it first before the radiator. The exhaust would be trickier, but it could be done through convection. Perhaps snaking the exhaust hose to create as much surface area for the heat to transfer over to the coolant.

    What do you guys think? Is it too complex to be worth it, or will my idea in practice fail to give any meaningful results? Maybe its all a pipe dream (no pun intended), but i sincerely think there is potential to capture some of the energy thats wasted from ICE.
     
    #1 Priipriii, Jul 27, 2024 at 11:43 PM
  2. fuzzy1

    fuzzy1 Senior Member

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    With a stationary system, you certainly could get some gain. The best combined-cycle steam power plants, burning natural gas, are now in the 62-64% efficiency range.

    But in a mobile system, the extra efficiency needs to offset the energy cost of carrying along the additional weight. That will be difficult, especially considering that the Prius's exhaust ought to be cooler than the exhaust of a traditional ICE engine, thus any energy scavenging will have both less energy to work with, and can't reach the same thermal conversion efficiency.

    The Prius engine is already at about 40%, and should be spending far more of its operating time somewhat near its peak efficiency than any traditional non-hybrid propulsion power plant.
     
    #2 fuzzy1, Jul 28, 2024 at 12:39 AM
  3. bisco

    bisco cookie crumbler

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    gen 5 probably could have achieved 75mpg if they had put efficiency ahead of power and big wheels. but would it sell?
     
    #3 bisco, Jul 28, 2024 at 9:02 PM
  4. Priipriii

    Priipriii Member

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    75mpg would definitely sell. The ideal vehicle would be one that gets the most mpg, and when needed, a switch to power mode to also get a lot of ponies while sacrificing mpg. Preferably AWD with two back motors in the rear wheels for maximum traction control at turns or in bad weather. Large wheel base for offroad capabilities. Extremely durable to last around 400k miles. And lots of inside space with a hatchback.

    Would you buy anything else if such a vehicle existed?
     
    #4 Priipriii, Jul 28, 2024 at 9:10 PM
  5. fuzzy1

    fuzzy1 Senior Member

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    I don't believe that will ever exist as a gasoline vehicle. By the time the tech advances to the point of achieving it, the EV mandates will have already removed fossil fuel vehicles from the new car market. Some instead of talking about 75 mpg, you'll be talking about 500+ miles of battery range.
     
    #5 fuzzy1, Jul 28, 2024 at 10:50 PM
  6. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    How do you boil water to make steam when your proposed heat source is cooler than the boiling point of water? I mean, there are ways... but they all cost additional energy and it may be enough to spoil the results.

    You might not want to steal the heat from the coolant anyway. A gasoline engine gets its best fuel efficiency when 'hot,' and the only time the coolant in a Prius has a real surplus of heat is during continuous high-speed drives in summer weather.

    Given all that, I'd concentrate on using the exhaust system as the heat source for this project. A Prius exhaust already runs much cooler than most cars due to Toyota's use of the Atkinson cycle- they are already directly recovering a lot of that waste heat (as pressure) directly into the crankshaft.

    You could recover still-more heat out of the Prius exhaust, but again that only has surplus heat during extended highway driving.

    During an extended freeway drive you aren't exactly in EV mode, and your battery is still small so you can't exactly save that energy for later any better than you could before.

    So if your setup only works during sustained freeway travel in warm weather, you'd have to work out whether these part-time gains were worth the cost, weight & reliability concerns of adding the extra hardware.
     
    #6 Leadfoot J. McCoalroller, Jul 29, 2024 at 1:11 AM
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