Issue: Oct 2007


The new 130 grams limit from the EU is likely to change the priorities towards high efficiency syste



Automotive Industries spoke to inventor and industrialist Lennart Stridsberg

by Lenny Case

Lennart Stridsberg’s hybrid vehicle concept the Strigear was for many years dismissed as being completely unrealistic. The claimed fuel consumption was simply too low to be believed. 2005 was a turning point. “Thereafter the simulated performance has been confirmed by some large auto manufacturers.”

The new 130 grams limit from the EU is likely to change the priorities towards high efficiency systems,” says Lennart Stridsberg, inventor and promoter of the Swedish Stridsberg Powertrain AB.

Stridsberg Powertrain develops ultra-efficient hybrid vehicles and high-power density electric motors. Together with the aircraft industry, it is also developing a wide set of proprietary designs to make electromechanical systems in aircraft’s lighter and much more reliable. So reliable, that an aircraft can be permitted to take off even after a single fault has been detected.

According to the company, converting a C-class car to a Strigear Diesel would cut CO2 emissions by 50 to 67%; by 50% for a diesel with manual transmission and up to 67% for a gasoline vehicle with automatic transmission. A Strigear car with car body and total weight similar to the first generation of the Toyota Prius would give 101 mpg in US city traffic, 82 mpg on US highway, 2.58 liter/100 km in the EU, 40 km/liters in Japan and 0 - 100 km/h in 8.6 seconds with unnoticeable gear shifts. This performance is obtained when using as far as possible identical components such as equal power batteries, equal power electric motors and equal power engines.

Highly efficient hybrids have become much more important with the new EU limit of 130 g CO2 per kilometer. Presently, a Volvo V70 emits 231 g/km, far above the EU limit. With a Strigear hybrid powertrain, it would emit 78 g/km, a reduction by two thirds and far below the EU limit. The Volvo example would require the same amount of semiconductors and battery as in the first version of the Toyota Prius, so costs should not be prohibitive.

The Strigear uses two electric motors, an internal combustion engine and an actuator
controlled gear box. By using the two electric motors to control the gear shift, gear shifts are performed in some 0.03 to 0.07 seconds. This makes the gear shift unnoticeable for passengers. The Strigear concept claims almost dramatically higher acceleration than competing system even when using almost identical components.

“During acceleration, there are two power sources, the thermal engine and the energy storage such as a battery. In planetary systems such as the Prius or the Dual Mode, part of the power from the thermal engine is absorbed by the first electric motor. To be of use, this power must be used by the second motor. This means that the second motor must be able to absorb both the electric power from the battery and electric power that the first motor has absorbed from the engine. To be able to do that, the second motor must have a power rating above the power of the battery. In the Strigear, the two electric motors work in parallel. As long as the added power rating of the two Strigear motors are at least equal to the power of the battery, the acceleration will be given by the total power of the battery and the thermal engine,” says Lennart Stridsberg.

Automotive Industries spoke to inventor and industrialist Lennart Stridsberg.

AI: What is your vision of how future car engines will evolve?

More optimized to work well on high power and with short on – off duty cycles in hybrid vehicle applications.

AI: What do you think will be the biggest breakthrough in automobiles?

In the very long perspective, electric cars that are driven by computers, not by human drivers. Computer drivers could improve the capacity of the road network dramatically.

AI: What are some of the technologies you are working on for the future?

We have technologies to make electric motor systems much less vulnerable to single faults. We think such systems could be comparable in cost and require less space and mass.

AI: What, in your opinion, are the biggest challenge facing automotive manufacturers today and how can they circumvent them?

Obviously, to participate in the reduction of total CO2 emissions. The primary goal should be to reduce the total energy consumption of vehicles. Using alternative fuels could be part of the solution, but that is far from evident. There is no enormous amount of biomass available, so biomass based fuels will not solve more than a fraction of the whole problem. The biomass that can be obtained does often eliminate more CO2 emission if it is quite simple burned in a power plant. Solar panels could hopefully become an important energy source. But it seems initially more sensible to use that energy to reduce the use of say natural gas to generate power in power plants. The saved gas can power a hybrid vehicle. This would certainly be much more efficient than to convert the solar generated electricity to hydrogen that feeds a vehicle fuel cell.

To reduce the total energy consumption of cars by half or two thirds as by the Strigear hybrid can be implemented rapidly and does not require any new battery technology or any new fuel supply infrastructure.

AI: How close is the automotive industry as a whole to becoming less dependent on fossil fuels?

I think we should concentrate on making the total economy less dependent on fossil fuels. Cars made today will be in use for some 15 years. During that period it seems likely that all energy that can be obtained from wind, wave, solar and nuclear can be used to replace fossil fuel in power plants and furnaces. It might be more efficient to put the investments in that field. For the coming ten years or so, the production of aircraft and road vehicles should probably stay on liquid fuels and natural gas. But of course, they should be built to make a very efficient use or their fuels.


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