IEA HPP Annex 28 Calculation method Workshop IEA HPP Annex 28 8 th International Heat Pump Conference, Las Vegas, 30 May 2005 Carsten Wemhöner, Operating Agent IEA HPP Annex 28 Institute of Energy, University of Applied Sciences Basel

2 Outline of the presentation  Objectives  Extension to combined systems  Simplifications, calculations steps and input data  Principle of the calculation

3 Objectives of the calculation method  Transparent  no correction factors as far as possible  Easy-to-use  “hand calculation”, no extensive computer application or simulation  suited for standards  Based on publicly available data  standard testing results  component characteristics from technical data sheets  Applicable to the majority of systems on the market

4 Calculation method – basic situation  Output capacity and efficiency (COP) strongly dependent on source and sink temperature and changes over the operation range  Output capacity and efficiency (COP) are known at defined testing points (from standard component testing)  Meteorological data available for evaluation of the source temperature  Controller settings available for the characterisation of the sink temperature  Annual energy requirement for space heating and domestic hot water are known from standard calculations (building regulations)

5 Principle of the calculation method  Annual frequency of the ambient dry bulb air temperature ambient dry bulb temperature [°C]  Cumulative annual frequency of the ambient dry bulb air temperature Meteo data processing

6 33 Principle of the calculation method ambient dry bulb temperature [°C] Bin distribution  Operation conditions at the operating points valid for the entire bin  Bins should have connection to available information on the heat pump characteristic  Conclusion:  Operating point in the centre of the bin  Bin limits between operating points Design indoor temperature OP 1 OP 3 OP 2 design outdoor temperature  3, upper  3, lower Upper ambient temperature for heating

7 Performance factor at operating point  Efficiency values from standard testing valid for the whole bin  COP interpolated for the conditions at the operating point  Further system losses  Storage losses  Additional electrical auxiliary expense  heat pump auxiliaries not considered in the COP boundary (e.g. brine source pump)  Circulation pumps  Control only in times when heat pumps is not running PF i = Q net,i + Q loss,i COP i Q net,i + E aux,i Q net,i COP i Q net,i

8 Principle of the calculation method  Measure for the energy requirement: Heating degree hours (HDH) Energy requirement  Heating degree hours =  Energy requirement in the bin corresponds to difference of cumulative heating degree hours at bin limit  Area of the bin (area between cumulative frequency and indoor design temperature) corresponds to energy requirement  Relative energy requirement in the bin corresponds to ratio of bin areas (weighting factor)  Operation conditions at operating point valid for the entire bin 33 ambient dry bulb temperature [°C] Design indoor temperature OP 1 OP 3 OP 2 design outdoor temperature  3, upper  3, lower Upper ambient temperature for heating  ID aa dt HP 2 HP 1 HP 3

9 Seasonal performance factor of heat pump  Seasonal performance by summation over all bins  Electricity input can be expressed with performance factor SPF hp =  i Q net,i ii PF i iEiiEi  Ratio between bin heat requirement and total heat requirement can be expressed by weighting factor Q net 1 ·Q net wiwi Q net,i

10 Principle of the calculation method Back-up energy ambient dry bulb temperature [°C] Design indoor temperature OP 1 OP 3 OP 2 design outdoor temperature Upper ambient temperature for heating HP 2 HP 1 HP 3  Mixed operation mode heat pump is switched- off at low temperature cut-out BU HP 1 BU Balance point temperature  Alternate operation mode heat pump is switched- off at balance point  Operation of the back-up heating defined by  Operation mode  Balance point temperature  Low temperature cut- out  Parallel operation mode heat pump runs through low temperature cut-out

11 Seasonal performance factor of heating mode  Overall performance of heat pump and back-up heating by weighting with delivered energy fractions SPF h = Q hp SPF hp E hp Q hp + Q bu + E bu + Q bu  bu Q net

12 W3W3 Principle of the calculation method ambient dry bulb temperature [°C] OP 2 OP 1 Upper ambient temperature for heating BU OP 3 design outdoor temperature Balance point temperature HP W2W2 W1W1 Design indoor temperature Domestic hot water  Combination of different operation modes by weighting with the respective energy fractions  Approach: Daily tapping profile  Hot water energy dependent on bin time  Back-up energy of domestic hot water mode is determined by temperature level (operation limit heat pump)  Evaluation of heat pump characterstic based on DHW-testing W4W4 OP 4

13 Extension to combined systems Alternate combined operating systems (heat pump switched):  Calculation of space heating and domestic hot water part  Superposition of single operation modes with weighting of energy fractions  Result from testing: characteristic does not change significantly

14 Extension to combined systems Simultaneous combined operating systems (heat extraction):  Characteristic in simultaneous operation changes significantly!  Three operation modes have to be considered:  Single space heating (e.g. winter operation, DHW storage entirely loaded)  Single domestic hot water (e.g. summer operation)  Simultaneous space heating and domestic hot water (SH and DHW demand)  Fraction of operation in each operation mode by evaluating the running time

15 Extension to combined systems  Running time t: produced heat/output capacity  Maximum running time in combined operation  If t SH > t DHW => t combi = t DHW => DHW operation limiting factor for simultaneous operation  If t DHW > t SH => t combi = t SH => SH operation limiting factor for simultaneous operation  Either space heating (intermediate season) or DHW (winter) could be the limiting factor for combined operation  Maximum value may not be reached due to control effects and not necessarily simultaneous load requirement

16 Overall seasonal performance factor  As in the alternate case the overall seasonal performance of simultaneous operation is calculated  Weighting of the performance factors of the operation modes SPF = QhQh QhQh SPF h + Q DHW SPF DHW Q DHW SPF combi Q combi + +  with the respective energy fraction

17 Assumptions/Simplifications  Main impact on space heating is outside temperature  Effects of intermittent heating included in the calculation of energy requirement (EN ISO 13790)  defrosting considered in the heat pump characteristic (e.g. EN 14511)  Domestic hot water requirement constant over the year (daily consumption)  Control effect cannot entirely be described but is reflected by standard situations

18 Calculation steps  Determination of energy requirement per bin  Determination of fraction by back-up energy (bivalent operation)  Interpolation of output capacity and COP for source and sink temperature  Correction for part load operation  Evaluation of running time in different operation modes  Calculation of auxiliary energy  Calculation of generator losses (recoverable/recovered)  Calculation of total energy input, system seasonal performance

19 Input data  Data of the site  Meteorological data (i.e. hourly values of the outside temperature, irradiation)  Source temperature (e.g. outside air, ground, ground water etc.)  Energy Requirements  Space heating energy requirement  Domestic hot water energy requirement  Heat pump  Type of the heat pump (e.g. brine-to-water, outside-air-to-water etc.)  Heat pump characteristic (standard testing, e.g. EN 14511, ASHRAE 116 etc.)  Operation limits

20 Input data  System design  Controller settings (heating characteristic curve, upper temperature limit for heating)  Balance point (input or based on design heat load)  System components characteristics  Installed storages (heating buffer, domestic hot water)  Back-up generators (electrical, fossil)  Domestic hot water operation (independent/alternate/combined)  Nominal power of auxiliaries (pumps, fans, control…)

21 Thank you for your attention!