Honda investigating 'Rankine Cycle' to power hybrids

Honda is investigating ways of recapturing heat energy lost through a car’s exhaust to help generate electricity and power an electric motor for a new generation of ultra-efficient hybrid cars. Conventional internal combustion engines waste a lot of energy in creating heat, but by applying a ‘Rankine cycle,’ a process where hot exhaust gases are used to heat up a water reservoir and create steam to spin a turbine, electricity can be generated. This electricity can then be used to charge up an array of batteries and help power a hybrid-electric powertrain.

Engineers have been using a Honda Stream as their test vehicle, a compact crossover sold in Japan and parts of Europe powered by 2.0L direct-injection petrol four-cylinder. The car was fitted with a new cylinder head with insulated exhaust ports, an evaporator built into the catalytic converter, a high-pressure water reservoir plus a generator and condenser. Maximum power available from the volumetric expander was as much as 32kW and maximum thermal efficiency of the unit is rated at 13% at 23kW.

Initial tests show that a car travelling at a constant speed of 100km/h and can improve thermal efficiency of the engine by 3.8%. In the U.S. highway cycle, the Rankine cycle system regenerated three times as much energy as current regenerative braking units. At a recent hybrid vehicle press event in San Diego, Honda officials said the design would need to see higher efficiencies achieved if were ever to enter production.

Via: Jalopnik