Hydraulic Hybrids

Energy savings and rapid payback – without subsidies.

Saving up to 27 percent of fuel consumed

Working with Lothian Buses on a project supported by Innovate UK, Artemis collected data on three Edinburgh bus routes seeking opportunities to reduce fuel consumption (and hence emissions) by hybridisation.  We found that 32-35 percent of the energy delivered by the engine was wasted as heat in the brakes; additionally that engine accessories such a cooling fans wasted a further 25 percent.

Using Artemis’ innovative Digital Displacement® hydraulic technology, the parallel hybrid system employs a highly efficient hydraulic pump/motor to capture braking energy and store it in a hydraulic accumulator.  The system is compact, with the pump/motor fitted alongside the engine and the accumulator fitted underneath the floor of the vehicle.  Based on the Millbrook London Transport Bus (MLTB) test cycle, the system offers fuel savings of up to 27%, providing bus operators with a 2-3 year payback without subsidies

Using this data, our study found that a relatively low-cost Digital Displacement hydraulic hybrid system could save 27 percent of the fuel consumed, for a modest additional cost, paying back the original investment in two to three years on fuel cost savings.  By contrast, electric hybrid systems do not offer an attractive payback period without subsidies.