F2010A049
Fuel Economy and Energy Consumption of Hybrid and Plug-in Hybrid Cars in Nordic Climate Conditions
Use of hybrid powertrain is gaining popularity among new passenger cars while low fuel consumption is becoming increasingly important. 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.
Total energy use of a car is not just function of the total efficiency of the powerplant and driveline. It is also dependent on energy consumption - i.e. net energy requirements to make the car move and keep the conditions in passenger compartment such that the driver and the passenger feel comfortable. This conditioning can absorb quite a share, especially in hot, but also in cold climate, such as the one in Northern Scandinavia. None of these adverse climate conditions are included in the standard evaluation of fuel consumption of passenger cars, as the testing is always conducted in temperatures that do not call the use of air conditioning or cabin heater. (In United States some special testing with the use of A/C is stipulated, though.) Therefore, real-world fuel economy and energy use may substantially differ from the official figures, if the car is used in climate that requires either cooling or heating.
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 HyMotionTM conversion kit by A123 Systems including an add-on lithium-ion battery pack and charging hardware. Capacity of the add-on battery is about 5 kWh, and it is configured to "charge" the original battery of the car during driving until fully depleted.
The cars will run real-world driving by a group of users (about 10 people) with variable commuting distances and driving habits. Testing will entail summer, fall and winter conditions prevailing 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 refill as well as the electric energy uptake of the PHEV variant is recorded.
The cars are also subjected to laboratory testing using the procedures of the ECE Regulation No. 101, to determine their performance in normative conditions. Supplement to the "official" conditions and driving cycles, a few more realistic duty-cycles are also used, as well as ambient temperature taken down to sub-zero levels that should adversely affect both the energy need of the car, as well as degrade the powertrains total efficiency, as more energy is use to heat up the IC engine and cabin interior. Furthermore, battery capacity is expected to decrease with falling ambient temperatures yielding to a shorter electric range.
The paper will present the results of this testing, initiated in April 2009, until February, 2010, or later, if paper submission deadline allows.
This abstract is supplemented by a PDF, which can be viewed here.
Session: Alternative Drivelines