Unregulated emissions from light-duty hybrid electric vehicles

- NH3, ethanol and acetaldehyde emissions are in the same range of gasoline vehicles.
- Regulated emissions are in the same range as gasoline vehicles.
- Higher regulated and unregulated emissions were observed at −7 °C than at 23 °C.
- The battery state of charge strongly impacts the plug-in hybrid emissions.

The number of registrations of light duty hybrid electric vehicles has systematically increased over the last years and it is expected to keep growing. Hence, evaluation of their emissions becomes very important in order to be able to anticipate their impact and share in the total emissions from the transport sector. For that reason the emissions from a Euro 5 compliant hybrid electric vehicle (HV2) and a Euro 5 plug-in hybrid electric vehicle (PHV1) were investigated with special interest on exhaust emissions of ammonia, acetaldehyde and ethanol. Vehicles were tested over the World harmonized Light-duty Test Cycle (WLTC) at 23 and −7 °C using two different commercial fuels E5 and E10 (gasoline containing 5% and 10% vol/vol of ethanol, respectively). PHV1 resulted in lower emissions than HV2 due to the pure electric strategy used by the former. PHV1 and HV2 showed lower regulated emissions than conventional Euro 5 gasoline light duty vehicles. However, emissions of ammonia (2-8 and 6-15 mg km−1 at 22 and −7 °C, respectively), ethanol (0.3-0.8 and 2.6-7.2 mg km−1 at 22 and −7 °C, respectively) and acetaldehyde (∼0.2 and 0.8-2.7 mg km−1 at 22 and −7 °C, respectively) were in the same range of those recently reported for conventional gasoline light duty vehicles.