Plug-in hybrid electric vehicles (such as the Toyota Prius Plug-in, pictured) are already noted for their environmental advantages and fuel savings – but now a new breakthrough technology could mean their fuel economy is boosted by a further seven per cent.
The improvement has been discovered by the University of Stuttgart working in partnership with Ohio State University. They have created a simple organic rankine cycle waste heat recovery system that has the potential to recover up to 10 per cent of engine waste heat and deliver a fuel consumption reduction of seven per cent.
Their analysis, which was presented as part of the ASME Internal Combustion Engine Division 2012 Fall Technical Conference, took a student prototype plug-in hybrid electric vehicle and looked at the potential for engine waste heat recovery taking into account a number of driving cycles. From there, the researchers designed a quasi-static thermodynamic model that was optimised for the prototype and evaluated the amount of energy that could be recovered using the waste heat recovery system: in both urban and highway driving conditions.
According to the researchers, around 35 per cent of the energy developed by fuel combustion is usually dissipated in exhaust gases: so its recovery and conversion into mechanical power could be hugely significant in boosting engine efficiency and reducing CO2 emissions. They believe that organic rankine cycles offer the highest potential for engine waste heat recovery among all of the methods they have tested.
The authors highlighted that a number of additional studies show that there could be fuel efficiency improvements as high as 10 per cent using a Rankine cycle – but that there is a need to balance the heat rejection rate with packaging and costs.
According to their simulations, the organic rankine cycle is able to produce up to 1.9kW of electric power in highway driving conditions: and this corresponds to a fuel efficiency improvement of seven per cent. The researchers even looked into the effects on fuel economy of adding the extra weight to the vehicle, and found them to be minimal.
Paul is a freelance writer with a background in everything from motoring to finance; and holidays to women's undergarments he just writes about them, honestly! He has now sadly crept into his early 30s and seems to have forgotten everything learned at school Still, he's a green car fanatic and isn't that what counts?
Alex Kovnat
The problem with an organic Rankine cycle heat recovery system is, where are you going to put it? This is going to be a problem especially with small cars.
I get the impression that everybody is standing in line outside the office of their legislative representative, to lobby for regulations mandating their particular pet idea or invention on everybody else's cars.
Unfortunately it is becoming increasingly difficult to find room to accomodate and package everybody's pet ideas, especially with small cars where you don't have much room.
October 12, 2012