Hybrid Car

In 1998, Daimler announced that they will start selling fuel cell automobile within 5 years. This announcement was failed and now hybrid car seems most successful. Mr. Greenwood continued discussion about hybrid car with Mr. Cooper living in Manhattan Beach, and found many interesting points.

Tank-to-wheel efficiency of conventional Otto cycle car is only 16% as illustrated fellow. Here, Otto cycle engine loss is 72%, standby /idle loss is 10% and drive line loss is 2%. Accessories loss, such as air conditioning unit consumes 2% but for comparison purposes, it was assumed 0%.

Tank-to-Wheel Efficiency of Conventional Car

Whereas, tank-to-wheel efficiency of hybrid car using Miller cycle reaches 37% by eliminating standby and idle operation loses and recovering power during braking. as shown below. Following mechanism of Prius was prepared after reviewing the Toyota site  http://www.toyota.com/planetkaizen/ which Mr. Cooper found. If you wish to know in more detail, go to the "Explore" section and type "Hybrid" into the search bar.

Tank-to-Wheel Efficiency of Hybrid car

Mr. Cooper founds different figure of tank-to-wheel efficiency of 32%. But if hybrid runs 60MPG in urban area, and if mileage of conventional Otto cycle car is 26MPG which correspond to tank-to-wheel efficiency of 16%, tank-to-wheel efficiency of hybrid car becomes 37%.

Based on those figures I have guesstimated other type of vehicles.

Vehicle Type

Well-to Tank Efficiency(%)

Tank-to-Wheel Efficiency(%)

Well-to-Wheel Efficiency(%)

Gasoline (town mode) 88 16 14
Gasoline (highway mode) 88 28 x 98 24
Diesel (town mode) 90 20 18
Diesel (highway mode) 90 47 42
Gasoline Hybrid (town mode) 88 37 32
Diesel Hybrid (town mode) 90 46 41
Fuel Cell Vehicle(FCV)(town & highway mode) LNG 91 x Transport 98.5 86 x 44 x 98 33
Compressed Natural Gas(CNG)(town mode) LNG  91 x Transport 98.5 16 14
CNG Hybrid (town mode) LNG 91 x Transport 98.5 37 33
DME Diesel (town mode) 71 20 14
DME Diesel Hybrid (town mode) 71 46 33
Electric Car (town & highway mode) LNG 91 x Transport 98.5 x Combined Cycle 59 x Grid 95 Battery 85 x Motor 98 42

Bush administration launched a new energy policy placing hydrogen fuel from oil and gas. This is idea is based on utilization of fuel cell. But it is unlikely as shown above table. Such scheme may increase carbon emission. According to Mr. Cooper, not only Sierra Club but Cato Institute started criticizing Bush administration.

Rather than converting fuel, direct combustion in engine can achieve higher efficiency. Diesel engine can achieve higher thermal efficiency than gasoline engine. Therefore Diesel Hybrid car can achieve 41-42% Well-to-Wheel Efficiency for highway mode and for town mode. Fuel cell technology might be obsolete as Daimler presented prototype Diesel Hybrid car in Tokyo Motor Show in 2005 and French company, Peugeot announced commercialization of Diesel Hybrid car by 2006.

Mr. Morinaga who was a professor of Nuclear Physics in Univ. of Munich for over 25 years told me a story about Prius. When his wife visited hair dresser in Germany a month ago, she heard a chat among men client about buying Prius for their private use. One of them asked "What if all of us buy Prius, who buys Daimler". Another man replied "Japanese may wish to buy those cars".

November 13, 2003

Rev. February 13, 2010

Latest 10・15mode Well-to-Wheel Efficiency data by Prof. Ishitani are; (Chemical Engineering Vol.71 No.2 2007) .

Vehicle Type Energy Input Carbon Dioxide Emission




Electric Car 0.94


Fuel Cell Hybrid 1.5


Diesel Hybrid 1.2 89.4
Gasoline Hybrid 1.7 123
Diesel 2.0 146
CNG car 2.7 148
Gasoline 2.7 193

Rev. April 1, 2007

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