The design allows the electric motor to be more efficient in powering the car’s wheels, while its integrated compressor uses less power due to synergy between the engine and the compressor, which can also draw on energy regenerated directly from the car’s brakes.

Design concept of the integrated A/C compressor-traction motor unit. Hybrids and EVs use regenerative braking to capture kinetic energy and store it; this requires the conversion of the kinetic energy first into electricity to transport to the battery, resulting in extra energy conversion steps. The integrated compressor with drive motor, however, uses the recuperated energy immediately through the clutch connecting it to the traction motor. Coaxial shafts eliminate any interference that might occur between the two drives, while providing independent speed control during normal operations. Click to enlarge.

The biggest challenge with electric cars in tropical megacities is the range that they can travel on a full-charge, because their batteries are needed to power both the engine and the air-conditioning. In tropical countries like Singapore, up to half the battery’s capacity is used to power the air-conditioning system.

—Prof Subodh Mhaisalkar, Executive Director of the Energy Research Institute at NTU

The development of the machine took place in the course of an exchange program between the DLR and the NTU, with Singaporean PhD student N. Satheesh Kumar working on the project with the support of his German DLR-supervisor Dr. Michael Schier. (The cooperation between DLR and NTU has existed since 2012 and emphasizes electric mobility, energy storage, air conditioning systems, and hybrid lightweight construction as well as multifunctional materials.)

For electric vehicles, the air conditioning uses a lot of electrical energy, thereby cutting down the range of electric cars by up to 50%. To increase the energy efficiency and therefore the range of electric cars, the thermal management and the integration of additional functions into existing powertrain components play a major role.

By integrating the refrigerant compressor directly into the electric motor, we save components, weight and cost. Simultaneously, the more regenerative braking part of the kinetic energy is passed directly to the refrigerant compressor and thus the efficiency is further increased.

—Dr. Michael Schier, DLR’s Institute of Vehicle Concepts

With the potential boost in range through the efficient use of energy, the joint invention recently won the Best Originality Award in the TECO Green Tech International Contest held in Taiwan. (TECO, a Taiwan-based company, is one of the largest manufacturers of electrical drive technology.)

The competition saw 19 entries from top universities including Boston University, University of California (UCLA), Waseda University, and universities from China and Russia.

NTU’s partner DLR will conduct further tests and improvements to the new engine with the aim of eventual commercialisation. The team is applying for a Proof-Of-Concept (POC) grant in Singapore. After the development of the prototype, test bedding and refinements will be done at DLR’s facilities in Germany.

Prof Mhaisalkar said this innovation will pave the way for extending the range of electric cars, as the integrated design combines the two of the most important parts of an electric car, thus reducing its complexity into one highly efficient solution.

For the automobile manufacturers, the new electric motor will also cost less to produce, as it requires less material than its counterparts. Both the weight and size of the electric motor are reduced, creating more space for other components such as an auxiliary battery source.

Resources

• Integrated Air-Conditioning Compressor with Drive Motor for Electric Vehicles (TECO contest poster)