روش آزمون مصرف انرژی HVAC اتوبوس بر اساس رفتار واحد HVAC

This paper presents a test method for determination of energy consumption of bus HVAC unit. The energy consumption corresponds to a bus engine fuel consumption increase during the HVAC unit operation period. The HVAC unit energy consumption is determined from the unit input power, which is measured under several levels of bus engine speeds and at different levels of testing heat load in the laboratory environment. Since the bus engine fuel consumption is incrementally induced by powering an HVAC unit, the results are subsequently recalculated to the unit fuel consumption under the defined road cycles in terms of standardized diesel engine. The method is likewise applicable either for classic or electric HVAC units with a main consumer (compressor or high voltage alternator) mechanically driven directly from the bus engine and also for electric HVAC units supplied from an alternative electric energy source in case of hybrid or fully electric buses.

Mobile HVAC systems in vehicles are important energy consumers. The influence of HVAC operation on the fuel consumption and emissions of passenger cars (M1 vehicles comprising no more than eight seats in addition to the driver's seat) has been discussed rather thoroughly during the last 10 years, see for example Benouali et al. (2003), Vermeulen et al. (2005), Weilenmann et al. (2005), Weilenmann et al. (2010), EU Commission Consultation Paper (2003), or Shecco Technology (2007). Nevertheless, literature review about related publications shows that commensurate attention is missing in case of bus air conditioning systems. We try to fill this gap by this paper. The cooling capacity measurement of HVAC units is a common evaluation method, which is specified for example in ASHRAE 37 Standard (2009). HVAC unit cooling capacity at maximum compressor speed is typically used in order to compare the performance of bus or rail HVAC units. Air-conditioned buses are typically equipped with HVAC units that are powered by the variable speed bus engine and therefore the maximum cooling capacity is not practical for the recalculation of bus engine fuel consumption increase. The variable speed bus engine is usually operating at high speed for very short time, so it does not represent realistic operation conditions. HVAC unit main consumer, compressor or dedicated alternator, is usually driven from the bus engine using a belt or by an electric or hydraulic power transmission and the compressor speed can either follow the bus engine speed or it can be practically independent on engine speed. Hence Ryska et al. (2000) introduced a comparison method for cooling performance evaluation of transport refrigeration and HVAC units during a vehicle operation with respect to different engine speeds.

The new test method and examples of the test results focused on energy consumption, or furthermore on fuel consumption determination during the operation period of vehicle powered bus HVAC units were introduced in this article. The principle of fuel consumption test mainly consists in the HVAC unit input power measurement at various speeds of the main consumer (compressor or high voltage alternator) and at the testing heat loads corresponding to the real bus operation. The tested HVAC unit runs in automatic temperature control mode with adjusted setpoint temperature at controlled ambient temperature for a test period from reaching the requested setpoint. The test results are recalculated to the HVAC unit energy consumption under defined road cycles and consequently to the fuel consumption for certain types of HVAC units, where the vehicle diesel engine is used as primary source of energy. The test system is based on simulation of real bus HVAC units operating conditions in the laboratory environment in order to get comparable test data for various kinds of bus HVAC units. Therefore, the method is planned to be discussed with International Association of Public Transport UITP for the next phase of the ‘SORT’ project (Standardized On-Road Tests cycles) as a draft of the standardized test procedure. Additionally, in order to express and compare energy requirements together with road transport emissions of buses equipped with various brands of HVAC units, the fuel consumption test data can be used for calculations of the operational lifetime costs as requested by European Directive 2009/33/EC.