Field-testing of hybrid and plug-in hybrid cars in Nordic climate conditions

Use of hybrid powertrain is gaining popularity among new passenger cars for increased fuel economy. Furthermore, manufacturers are introducing also variants that have larger battery capacity and possibility to charge the batteries with off-board grid electricity. This will bring in the option to use electricity in short daily commutes, and avoid even more local pollution and greenhouse gas emissions. In order to get a more truthful picture of the fuel economy and energy use of HEV and PHEV configurations VTT is conducting on-road testing with two MY 2009 Toyota Prius cars. The other one is factory standard, but the other has been converted to a PHEV using an add-on lithium-ion battery pack and charging hardware. Capacity of the add-on battery is about 5 kWh. The cars are used in real-world driving by several users with variable commuting distances and driving habits. Testing entails all-year-round weather conditions in southern part of Finland. Apart from ambient temperature, type of route, traffic conditions and number of occupants are recorded for each trip. Naturally, fuel refills as well as the electric energy uptake of the PHEV variant are also recorded. Over the 30 months period now covered, the use of an add-on battery with plug-in capability for grid electricity uptake has been successful. Both urban type of driving and longer-distance extra urban commuting were analysed. Overall, fuel savings were some 30 % for the long-distance commuters and about 40 % for the short-distance group. The adverse effect of cold ambient temperature was also demonstrated, as in other similar exercises. The field test will continue still for one more 6 month period to complete the 36 month schedule