Issue: Apr 2007

High-performance hybrid

Stridsberg’s parallel hybrid vehicle systems use both the advantage of a serial hybrid vehicle system and a parallel hybrid vehicle system.

by AI Staff

Swedish company Stridsberg Powertrain AB 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 more reliable. The invention is the brainchild of Lennart Stridsberg. The company currently markets a hybrid vehicle concept called Strigear.
A Strigear car with the body and weight of a Toyota Prius would be able to do 101 mpg in US city traffic, 82 mpg on US highways, and is able to achieve 100 kilometres on 2.58 litres of fuel in the European Union, plus 40 kilometres per litre of fuel in Japan.
The Strigear uses two electric motors, an internal combustion engine and an actuator controlled gear box. Gear shifts are performed in 0.03 to 0.07 seconds. Stridsberg’s patented parallel hybrid vehicle systems use both the advantage of a serial hybrid vehicle system and a parallel hybrid vehicle system.
Automotive Industries spoke to Lennart Stridsberg.
Automotive Industries (AI): Is the Strigear concept engine more fuel-efficient than alternatives? If so, why?
Stridsberg: Its hardware design eliminates the losses inherent in the electrically variable transmissions based on two motors and one or more planetary gear systems. The gear box permits the optimizing algorithm to select between, for example, five different topologies by selecting a suitable gear. The patented optimization algorithm gives better component utilization.
AI: What are Strigear’s commercial implications? Which companies have evinced an interest in the system?
Stridsberg: Interest has been limited so far. Initially the performance we described seemed unrealistic. Thereafter the simulated performance has been confirmed by large auto manufacturers. Most developers are already engaged in heavy development programs regarding other solutions also using two electric motors and one thermal engine. What they require is a single motor hybrid system able to cut high costs. The new 130 grams limit from the EU is likely to change the priorities towards high efficiency systems.
AI: The Strigear concept claims almost dramatically higher acceleration than a competing system, even when using almost identical components. Why?
Stridsberg: During acceleration, there are two power sources - the thermal engine and the energy storage. In planetary systems, 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 - the second motor must be able to absorb the electric power from the battery and electric power that the first motor has absorbed from the engine. Thus the second motor must have a power rating above the power of the battery. In the Strigear, the two electric motors work in parallel.
AI: What are some of the challenges facing a concept like the Strigear?
Stridsberg: We are confident in our technology, simulations and knowledge. Our challenge is to find an industrial partner that, together with us, is prepared to develop the technology into industrial components and bring those to the market either as licensees or suppliers of components.
AI: What is the future of the hybrid power trains?
Stridsberg: When politicians start implementing regulations that can affect the CO2 emissions, there are not many alternatives to efficient hybrids using internal combustion engines. The IEA estimates that biofuels could cover between 4 to 8 % of the fuels used in the road transport sector in 2030. The future of efficient hybrids is bright if there are regulations to significantly reduce the consumption of fossil fuels.
AI: What are some of the other concepts you are developing for the automotive market?
Stridsberg: We are working on air cooled electric motors for hybrids and on highly reliable electric motors for hybrids. The focus is on a highly efficient hybrid system.

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