Staying Warm on the Road!

Steinbeis student designs energy-efficient interior heating system for electric cars

Electric vehicles are still in the starting blocks in Germany – for most people, they’re a technology of tomorrow rather than something that already plays a role in their lives. But in the face of climate change and finite oil reserves, they’re seen as ever more important: continuing global population growth, high demand for mobility, and tightening air pollution restrictions in large urban areas all point to the need for alternative drive technologies in the automotive industry. E-vehicles are key in combatting these problems. As part of her master’s degree in business engineering at the School of Management and Technology at Steinbeis University Berlin, Julia Le Cocq designed a smart interior heating system for Daimler’s Smart electric drive (Smart ed) car.

The German government wants to see at least a million electric and hybrid vehicles on the country’s roads by 2020, with these vehicles making up the majority of urban traffic by 2050. To facilitate this, it founded the National Platform for Electric Vehicles in May 2012 with the aim of paving the way for eco-friendly driving on a broad scale. Although the most obvious advantage of e-vehicles is their lack of emissions, the charging stations that power them still result in local emissions, since they are connected to the national grid – meaning the energy that electric vehicles run on comes from coal, oil and gas power plants. So an e-vehicle can only be truly green it it’s charged with renewable sources like hydroelectric or solar energy.

For her master’s degree project at Daimler, Julia Le Cocq tackled the question of how the interior of Daimler’s Smart ed car can be heated to a comfortable temperature in an energy-efficient way at outside temperatures as low as -7 °C. Her work focused on designing an energyefficient heating system to keep the interior comfortable while increasing the car’s driving range. As the interior heating runs off the same lithium-ion battery that powers propulsion, the driving range is reduced at low temperatures, since much of the energy is used to keep the vehicle warm. The Smart ed’s electric motor also generates much less heat than a combustion engine, so recycling waste heat from the motor is insufficient.

Le Cocq ran several series of tests with people in the car, surveying them on their subjective experience of the interior temperature. Each time, different contact surfaces in the interior, such as the seat and steering wheel, were heated to different temperatures. The test persons were fitted with 7 temperature sensors on different parts of the body. Le Cocq analyzed the results with respect to energy efficiency and battery capacity, with the aim of developing a systematic solution combining thermal comfort and smart energy management that would appeal to end consumers. Based on the results, Le Cocq elaborated a concept for an energy-efficient heating system using heating elements integrated into contact surfaces in the car’s interior. The system can also be used to precondition the car before driving at low and very low temperatures, thereby extending its range. For Daimler, Le Cocq’s work can act as a guide in the future design and development of interior heating models for electric vehicles.

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