VDI 4650 BLATT 1
Calculation of the seasonal coefficient of performance of heat pumps - Electric heat pumps for space heating and domestic hot water
|Publication Date:||1 March 2019|
|ICS Code (Heat pumps):||27.080|
|ICS Code (Central heating systems):||91.140.10|
Government institutions and other institutions granting assistance want to be clear on the environmentally relevant results that can be expected. Naturally, the energy consumption is also of interest to users, potential users and operators of heat pump systems. This standard provides them with information on the efficiency of their systems under standardized conditions. As the energy demand depends on the specific building, the weather and the user behaviour, no statements can be made in this regard. Likewise, it is not possible to make any statements about the heating costs because these depend not only on the consumption but also on the energy prices.
The energy efficiency of heat pumps is determined by quite a number of factors relating particularly to the boundary conditions of operation. In addition to the heat source temperature, the supply temperature of the heating system and the variations of these quantities during the heating season, the energy consumptions for the auxiliary drives of the heat source system and the difference between the supply and return temperatures of the heating system are also relevant.
Laboratory measurements of the appliances can only yield accurate information on the energetic benefit if they are related to the design parameters of the entire heat pump system. Measurements of systems yield actual consumptions despite measurement uncertainty, but these results only apply to existing systems which are already in operation with designs that may deviate from planning and perhaps the user's operation of heat pump that is disadvantageous for the system. Larger deviations are difficult to explain and, in most cases, cannot be improved subsequently. Easyto- handle data for the correct assessment of the entire heat pump system, that is of the appliance and the associated peripherals, is therefore particularly important to provide guidance to all those working in this trade.
The seasonal performance coefficients calculated on the basis of this standard reflect the performance that can realistically be achieved in practice with wellfunctioning systems. This standard is not meant to replace detailed simulation calculations; it does not correlate the heat generator with the building, and thus cannot serve as an instruction for dimensioning. Due to the varying, and quite influential, user behaviour, being a significant problem as already mentioned above, a comparison of the calculated seasonal coefficient of performance with the measured values of the seasonal performance factor can only be made with reservations.
This standard applies to electrically driven heat pump systems for space heating and domestic hot water heating in residential buildings. Heat sources considered are groundwater, ground source (borehole heat exchangers and horizontal ground heat exchangers) and air. The heat is delivered to a water-based central heating system or to a hot water tank.