a. already thought of
b. highly impractical
c. physically impossible
For example, I see a lot of energy in the modern internal combustion engine being wasted in one way or another. Awhile ago, I wondered if it was possible to put a little rotor in an exhaust pipe to get some energy back from exhaust gasses leaving the engine. Well, it turns out that that's exactly what a turbocharger is. So then I wondered if it might be more efficient to couple the turbine to a generator and the compressor to an electric motor, rather than having a strict mechanical connection between the two. It turns out somebody has already done that too, and its called a "hybrid turbocharger." Though it's still in development, I think it could be really cool if put into production, as it could theoretically boost the performance and efficiency of normal and hybrid vehicles, while eliminating turbo-lag.
Aaaanyways, I recently had an idea that (hopefully) skips the "a" category, but may well end up in "b," and it is basically this. Modern engines lose most of their waste energy to heat, and an enormous amount of engineering goes into venting away that excess heat in the way of radiators, fans, intercoolers, etc. However, the vast majority of our power plants, the exceptions being hydro and wind, generate electricity by creating heat. They use that heat to boil water, and then shoot the resulting high pressure steam through a steam turbine coupled to an electric generator. Would it be practical or even possible to replace the extensive cooling system of a vehicle with a simple steam turbine? The energy contained in that steam would be converted into electricity, which could be stored and used to extend the range or power of the car via electric motors or an intake compressor.
Thoughts?
The idea has merit. The challenge is conversion of heat (thermal energy) into mechanical then electrical then chemical energy. At each stage of the conversion process, energy is lost due to inefficiencies. Secondly, stationary turbines use high pressure steam at high temperatures to run through the stages of the turbine. Waste heat from vehicle engines is relatively cool in comparison and is at low pressure, so design conditions would differ. Finally, equipment in a vehicle is always being bounced around, so robust packaging, weight reduction, size reduction, and vibration mitigation would be essential.
ReplyDeleteAll of the above challenges need to be met together to obtain a working solution at reasonable cost based on gasoline being readily available and cheap at $3 per gallon US. As fuel prices increase, the economics would improve.
In spite of the challenges, automakers are working on this. One approach is thermodynamic and another is thermoelectric.
BMW and Honda are referenced here. http://www.greencarcongress.com/2009/05/bmw-rankine-20090503.html.
More on BMW is found at http://www.motorauthority.com/blog/1036884_bmw-previews-future-heat-energy-recovery-technology
See http://www1.eere.energy.gov/vehiclesandfuels/pdfs/deer_2009/session5/deer09_obieglo.pdf for a more technical discussion on the BMW turbosteamer and Rankine cycle.
There are perhaps easier solutions to consider. Weight reduction using composites, ultra light weight steels, even lightweight replaceable skins would reduce vehicle weight, allowing smaller vehicles and engines. Why does a car need to weigh 2500 pounds to transport a 200 pound person?