One of the more significant obstacles to automotive start-stop systems is how to keep the car comfy with the engine off. Saving fuel is great, but not if the infotainment system, HVAC et al were to shut down at every red light.
At the SAE World Congress in Detroit last week, Delphi Automotive introduced a Phase Change Material (PCM) Evaporator that it said will keep start/stop vehicle cabins cooler longer and also extend the electric range of hybrid/electric vehicles.
Delphi Thermal Systems president James Bertrand says the PCM Evaporator is less complex and less expensive than an electric air conditioning compressor, but also more efficient.
Delphi’s system integrates a reservoir of paraffin-based phase change material within the air-conditioning evaporator. During normal operation, thermal energy is removed from the material, which solidifies or freezes. When the air conditioning system is stopped, the material gradually liquefies or melts, drawing heat from the air to keep passengers comfortable. The system can typically maintain target air temperature for one to two minutes – long enough to keep occupants comfy during the “stop” portions of start/stop driving.
Besides the PCM, Delphi introduced an HPAC (heat pump air conditioner) and an EGHX (exhaust gas heat exchanger). The HPAC, which integrates a refrigerant heat pump and a coolant distribution system, draws heat from ambient air and “scavenges” waste heat for the cabin. It’s said to reduce battery drain and thus extend the range of hybrid and electric vehicles. The EGHX recovers heat normally lost in the exhaust system. Hybrid vehicles typically run their engines longer in cold weather to keep the cabin warm, but recovering heat from the exhaust system could allow engines to operate in electric mode sooner, reducing CO2 emissions, improving fuel economy, and reducing the need for electric heating, which protects the battery charge.