Hydraulic hybrid promises better fuel efficiency - even on the motorway

A Scottish engineering firm has trialled a hybrid car that it claims can cut carbon emissions by 30 per cent and is better suited to highway driving than conventional hybrids such as the Toyota Prius.

Artemis Intelligent Power's system works much like a conventional hybrid, capturing energy when the car brakes and feeding it back to the engine as it accelerates. But instead of storing the energy in a battery, the system captures it in a hydraulic accumulator.

The hydraulic system is more fuel-efficient because it is only a third of the size and weight of an electric hybrid, according to the company.

Independent tests of the technology fitted to a BMW530i prototype car found that it doubled fuel efficiency and cut carbon emissions by a third compared to conventional engine technologies.

Win Rampen, managing director of Artemis, said that the compressed-gas hydraulic system was also more efficient at capturing and delivering energy than battery alternatives.

"It's hard to store energy quickly in batteries," explained Rampen, adding that because the hydraulic accumulator could be charged and discharged very rapidly it was also better at capturing energy during highway driving.

Conventional hybrids require frequent braking to capture significant levels of energy and have disappointed some drivers with limited fuel efficiency improvements outside of urban areas.

Rampen said that because the hybrid component was made of steel, aluminium and rubber it was also cheaper to manufacture and raised fewer disposal issues than conventional alternatives.

The technology has been licensed to components and system supplier giant Bosch Rexroth, and an unnamed firm has bought the rights to install the technology in off-road agricultural and construction machinery.

"With market introduction, it's Bosch's territory and commercially sensitive, but we will be initially targeting commercial vehicles, " said Rampen.

Artemis said it was also in talks with two wind turbine manufacturers who are looking at the technology to replace turbine gear boxes.

Mechanical gearbox failures account for nearly a third of wind turbine downtime, and Artemis believes a hydraulic alternative will prove more reliable, lowering maintenance costs for wind farm operators.