TÜV SÜD: Economical heating adds valuable kilometres

TÜV SÜD: Economical heating adds valuable kilometres 

Power-guzzling heating and air-conditioning systems are a major cause of low range in electric vehicles. Reducing power consumption can add extra kilometres to the range of a vehicle and place its driver at the head of the mobility race. For this reason, the experts at TÜV SÜD Automotive concentrate their attention on individual vehicle components when measuring vehicle range in line with the TÜV SÜD E-Car Cycle (TSECC). Initial results show that power units tailored to the needs of electric vehicles can slash power consumption by up to 15 per cent, adding an average of 15 kilometres to the range of the vehicle. Electric mobility is one of TÜV SÜD's key themes at the IAA, held in Frankfurt am Main from 15 to 25 September 2011.

According to manufacturers' specifications, the average range of today's electric vehicles is approximately 150 kilometres - but this range can be slashed by more than half when temperatures plummet. The reason, in addition to the fact that battery performance declines in below-zero temperatures, is primarily the high power consumption of heating and air-conditioning systems. To counteract this effect, electric vehicles generally use special types of heating systems – electrically or petrol-driven designs which may be with or without air-conditioning. However, these systems may discourage consumers previously used to unrestricted mobility and pleasant temperatures from buying electric cars. This problem has spurred vehicle manufacturers and OEMs to pay special attention to the consumption levels of heating and air-conditioning systems, with the aim of increasing vehicle range. "In electric vehicles, temperature and range are two sides of the same coin", explains David Bordeaux of TÜV SÜD Automotive GmbH. "This is exactly the point where leverage must be applied if electromobility is to be successful. We support our partners by providing robust, traceable measurements of all power consumers within the vehicle. The TSECC standard we have developed extends far beyond statutory requirements."

In designing their measurement procedures, the experts have focused primarily on practical considerations. All procedures apply not only to the statutory consumption measurement methods set forth in ECE-R 100 (measurement according to the New European Driving Cycle or NEDC) as reference values, but also comply with the TSECC Standard, a driving profile more closely aligned to practical conditions and realistic temperature ranges from +30 °C to -7 °C. Under these conditions, measurements of the consumption of heating and cooling systems are especially challenging because the in-car temperature must be maintained at a constant level at all times despite strong fluctuations in external temperatures; this temperature consistency is monitored by an extensive array of measurement points in the vehicle interior. "The in-vehicle temperature naturally plays a central role in the actual consumption of an air-conditioning system, because the car's passengers set the system to heat or cool, impacting on consumption", explains Bordeaux.

Awareness of vehicle energy flows

Important factors in data reproducibility and comparability are not restricted to temperature alone; battery charging levels and rolling resistance must also be taken into consideration. The first stage of all measurements is to charge the battery fully. The TÜV SÜD experts then measure consumption according to the NEDC and TSECC, including 'worst case' measurements at -7 °C and under operation of all additional consumption sources. "Lights, windscreen wipers, rear-windscreen heating, air-conditioning - we can pinpoint consumption levels for each individual element", says David Bordeaux. To do this, power is measured both at the battery and at a wide range of points throughout the vehicle. "This enables us to record precise measurements of the power consumption of individual systems."

Further information on TÜV SÜD's electromobility activities can be found at
www.tuev-sued.de/e-mobility.

Contact: Frank Volk