Barbouchi, Sami

Dejardins, Gilles

Horber, Bernard

Roland, Didier

English

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Purdue UniversityPurdue e-PubsInternational Refrigeration and Air ConditioningConference School of Mechanical Engineering2010HSPF determination with field-test resultsSami BarbouchiEDFGilles DejardinsEDFDidier RolandEDFBernard HorberEDFFollow this and additional works at: http://docs.lib.purdue.edu/iraccThis document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu foradditional information.Complete proceedings may be acquired in print and on CD-ROM directly from the Ray W. Herrick Laboratories at https://engineering.purdue.edu/Herrick/Events/orderlit.htmlBarbouchi, Sami; Dejardins, Gilles; Roland, Didier; and Horber, Bernard, "HSPF determination with field-test results" (2010).International Refrigeration and Air Conditioning Conference. Paper 1060.http://docs.lib.purdue.edu/iracc/10602228  Page 1 International Refrigeration and Air Conditioning Conference at Purdue, July 12-15, 2010 Sami Barbouchi1, Gilles Dejardins1, Didier Roland1, Bernard Horber11EDF R&D, "Energy in Buildings and Territories" Department, 77818 Moret-sur-Loing, France, (sami.barbouchi@edf.fr). ABSTRACTIn existing houses equipped with hydronic networks and radiators, the supply water temperature can exceed 65°C the coldest days to ensure required comfort conditions. So to replace old boilers by heat pumps, it is necessary that the heat pumps produce water at high temperature the coldest days. In order to analyze their behavior and measure their performances, field-test has been carried out in France on air to water heat pump designed to replace fuel boilers. The results of the field-test has allowed expressing the thermal energy produced and the electrical energy consumed by the heat pump as a function of the average daily outdoor air temperature. So it is possible with weather data of different climate areas to calculate the thermal and electrical energies and so estimate the Heating Seasonal Performance Factor. Keywords: air to water heat pump, heat seasonal performance factor, field-test. 1. INTRODUCTION In Europe, heat pumps are tested and their performances are evaluated according the standards EN 14511-2 and EN 14511-3 (2009). These tests are performed under steady state conditions. They are relevant and give an idea of heat pump performances and allow the comparison between different heat pumps on the market. However, for end-users, who want to reduce energy costs, and also for institutions interested in promoting energy saving, it should be able to measure or estimate with an acceptable uncertainty, the heating seasonal performance (HSPF) of heat pumps. The purpose of this study is to show how it is possible to highlight correlations between different parameters and thus to characterize the heat pump. We also show how it is possible to calculate the HSPF with these correlations and then to apply this method to different climate areas in France and see how HSPF changes. 2. HSPF definition HSPF is defined as the ratio between the thermal energy supplied and the electrical energy absorbed by the heat pump over the heating season, which extends in France from October 1 to May 20. =seasonheatinginputseasonheatingthermalWQHSPF   (1) HSPF involves a measure of the thermal energy supplied and the electrical energy absorbed by the heat pump. The thermal energy is measured directly at the output of the heat pump with a heat meter. The heat meter can measure a temperature difference between 3 and 90 K for a flow rate of 1.5 m3/h. To calculate the thermal energy, it takes into account the variation of the thermal capacity of water, pcρ , which is function of the average water temperature between inlet and outlet of the heat pump. ( )outwaterinwaterpthermal TTcVQ ,, −= ρ   (2) The relative uncertainty of the heat meter is a function of the temperature difference. The manufacturer announced values between 2 and 6%; to calculate the HSPF relative uncertainty, a mean value of 4% will be used. An electric meter measures the electrical energy with an uncertainty of about 3%. The measurement of electric energy meter includes the energy consumed by the heat pump and the water pump. For the calculation of HSPF, the electrical consumption of the water pump will be deducted in order to approach test conditions of EN 14511. Thus: pumpwatertotalPumpHeat WWW −=   (3) HSPF DETERMINATION WITH FIELD-TEST RESULTS,International Refrigeration and Air Conditioning Conference at Purdue, July 12-15, 2010 As the HSPF is the ratio between the thermal energy delivered and the electrical energy consumed, the HSPF relative uncertainty is simply the square root of the sum of relative uncertainties of energy squared.( ) ( )( ) ( )( )22 electricalrthermalrr WuQuHSPFu +=  (4) The HSPF relative uncertainty is then 5% and if the HSPF is 3, the absolute uncertainty is 0.15. 3. Results over the field-test period The measurement period extends from November 27, 2008 to May 20, 2009 (Figure 1). It is possible to draw the evolution of the daily COP according to the daily average outdoor air temperature (Figure 2). By superimposing test points, the COP values obtained in laboratory and field-tests are close, except for high outdoor air temperatures. In addition to the outdoor air temperature, water temperature has an important influence on the COP. By plotting the average value of these two variables, it is possible to identify an average heat curve both on the flow and on return (Figure 3). -10-505101520251-oct-0811-oct-0821-oct-0831-oct-0810-nov-0820-nov-0830-nov-0810-déc-0820-déc-0830-déc-089-janv-0919-janv-0929-janv-098-févr-0918-févr-0928-févr-0910-mars-0920-mars-0930-mars-099-avr-0919-avr-0929-avr-099-mai-0919-mai-09TimeAverage daily outdoor air temperature (°C)Figure 1: Average daily outdoor air temperature evolution over measurement period. 0.00.51.01.52.02.53.03.54.04.55.0-20 -15 -10 -5 0 5 10 15 20Average daily outdoor air temperature (°C)Daily COPCOPTest point A-15W65Test point A-7W55Test point A2W45Test point A10W35Figure 2: Daily COP as a function of the average daily outdoor air temperature. 2228  Page 2,International Refrigeration and Air Conditioning Conference at Purdue, July 12-15, 2010 y = -x + 41y = -x + 48010203040506070-15 -10 -5 0 5 10 15 20Average daily outdoor air temperature (°C)Average daily water temperature (°C)Average daily return temperature (°C)Average daily flow temperature (°C)Test point A-15W65Test point A-7W55Test point A2W45Test point A10W35Figure 3: Average daily flow temperature and return temperature as a function of the average daily outdoor air temperature. 2228  Page  , 3International Refrigeration and Air Conditioning Conference at Purdue, July 12-15, 2010 4. Determination of correlations for thermal and electrical energies By drawing the heat energy and the electrical energy per day as a function of the average daily outdoor air temperature days, it is possible to identify correlations between energies and the average daily outdoor air temperature. To fit the energies, a quadratic polynomial function has been chosen; coefficients of determination are 97.5% for the thermal energy (Figure 4) and 98.7% for the electrical energy (Figure 5). Comparing the results of tests and the results obtained by the correlations, the differences don’t exceed 1% (Table 1). Table 1: Comparison measurement and correlation results.  Measurement results Correlation results DifferenceThermal energy (MWh) 12.17 12.20 -0.2% Electrical energy (MWh) 4.25 4.29 -0.9% COP 2.86 2.84 0.7% y = -0.008x2 - 7.859x + 145.919R2 = 0.975020406080100120140160180200-10 -5 0 5 10 15 20 25Average daily outdoor air temperature (°C)Thermal energy per days (kWh)Thermal energy (kWh)Polynomial (Thermal energy (kWh))Figure 4: Daily thermal energy supplied as a function of the average daily outdoor air temperature. y = 0.091x2 - 5.036x + 60.482R2 = 0.9870102030405060708090100-10 -5 0 5 10 15 20 25Average daily outdoor air temperature (°C)Electrical energy per days (kWh)Electrical energy (kWh)Polynomial (Electrical energy (kWh))Figure 5: Daily electrical energy as a function of the average daily outdoor air temperature. 5. Calculation over the heating season To get an estimation of performances over the heating season, weather data collected from a site near the house, where field-tests were conducted, were used. Figure 6 shows the difference between the data from both sites. It was possible from the weather data and with correlations (Figure 4 and Figure 5) to calculate the consumption of the heat pump and its performance over the heating season. The thermal energy supplied is 21.22 MWh, the electrical energy consumed, 7.63 MWh and the HSPF, 2.78. By adding the electrical consumption of the water pump (500 kWh over the heating season), the HSPF is 2.61. Thus, the electrical consumption of the water pump 2228  Page  , 4International Refrigeration and Air Conditioning Conference at Purdue, July 12-15, 2010 leads to a decrease of 6% of the HSPF. This shows the interest in using water pumps with DC brushless electrical motor, which have a better efficiency. -10-505101520251-oct-0811-oct-0821-oct-0831-oct-0810-nov-0820-nov-0830-nov-0810-déc-0820-déc-0830-déc-089-janv-0919-janv-0929-janv-098-févr-0918-févr-0928-févr-0910-mars-0920-mars-0930-mars-099-avr-0919-avr-0929-avr-099-mai-0919-mai-09TimeAverage daily outdoor air temperature (°C)measured by a sensor temperature of the heat pumpmeasured by a weather station nearby010 012 2 256131111179151511191710129141573230 0051015202530-10-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20Average daily outdoor air temperature (°C)Number of daysNormal distributionSize 232 daysMean 6.9°CStandard deviation 5.4°CDD 2434 K.daysFigure 6: Evolution of the average daily outdoor air temperature over the heating season and distribution of the average daily outdoor air temperature from the 1st October to the 20th May 2009. 6. Calculation for different climate areas in France Weather conditions greatly influence HSPF, and from a climate area to another, the weather can vary greatly. The French thermal regulation (DGUHC, 2005) defines 8 climate areas. For each climate area, HSPF will be calculated. To do this, weather data from the software Simbad (CSTB, 2004) were used, these data represent decennial weather data in different French cities and each city represents a climate area. Figure 7 shows the distribution of the average daily outdoor air temperatures at Trappes, which is one of the representative cities. Trappes is located in the suburb of Paris. Using these weather data and correlations previously defined (Figure 4 and Figure 5), it is possible to calculate the thermal energy supplied and the HSPF for each climate area (Table 2). Thus we see the difference between HSPF from a climate zone to another. The minimum HSPF is equal to 2.71 in Nancy and the maximum is equal to 3.50 in Nice. The HSPF values are also shown on the map in Figure 8, where it is possible to distinguish each climate area. 0 0 0 0 0 0 01 1519161427261927191516101363 310 0 0 0051015202530-10-9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20Average daily outdoor air temperature (°C)Number of daysNormal distributionSize 232 daysMean 6.5°CStandard deviation 3.7°CDD 2692 K.daysFigure 7: Daily average outdoor air temperature distribution for the city of Trappes (decennial weather data). Table 2: HSPF calculation with the correlations for different climate areas in France. Climate area H2c H2d H2b H1c H1b H3 H2a H1a City Agen Carpentras La Rochelle Macon Nancy Nice Rennes TrappesDD 2227 2132 2095 2609 2986 1525 2313 2692 Thermal energy supplied (MWh) 18.37 17.53 16.96 21.28 24.14 12.92 18.68 21.87 HSPF 3.02 3.04 3.15 2.88 2.71 3.50 3.06 2.88 2228  Page , 5International Refrigeration and Air Conditioning Conference at Purdue, July 12-15, 2010 Figure 8: France map with the HSPF for each climate area. 7. Heat pump compared to gas and fuel boilers After determining the HSPF and the thermal energy supplied over the heating season, it is interesting to compare the heat pump with existing heating systems. For the calculation, the HSPF is taken equal to 2.78 and the thermal energy supplied to 21.22 MWh. Table 3 shows that by comparing existing gas boilers with a heat pump, the energy consumption can be divided by 3.5, the energy bill by 1.5 and CO2 emissions by 5. This shows the interest in France to substitute old boilers with a high efficiency solution such as heat pumps. Table 3: Comparison of the energy consumption, the energy bill and CO2 emissions between a heat pump and conventional boilers. Efficiency Heating system consumption (MWh)Energy price €/kWh Energy bill k€ CO2 emission per g/kWh CO2 emission in ton Fuel 70% 30 (x4.0) 0.060 1.8 (x2) 333 10.1 (x7) Gas 80% 27 (x3.5) 0.043 1.2 (x1.5) 250 6.6 (x5) Electricity with heat pump 2.78 8 0.110 0.9 180 1.4 8. CONCLUSION This study has allowed the characterization of an air to water heat pump with field-test results. It was possible to find correlations between the average daily outdoor air temperatures and the thermal energy supplied and the electrical energy consumed. Therefore, by incorporating weather data of 2008/2009 heating season, it was possible to calculate the HSPF (2.78) and the thermal energy supplied (21.22 MWh) over the heating season. It was also shown that by comparing existing gas boilers with a heat pump, the energy consumption is divided by 3.5, the energy bill by 1.5, and CO2 emissions by 5. The characterization of the heat pump was performed for a given heat curve. In following works, the goal is to analyze data from different sites with different heat curves and thus highlight the influence of the heat curve, in addition to the average daily outdoor air temperature. 2228  Page , 6International Refrigeration and Air Conditioning Conference at Purdue, July 12-15, 2010 NOMENCLATURE cp  thermal capacity    (kJ/kg/K) Q  thermal energy    (J) T  temperature    (°C) W  work     (J) ρ  specific volume    (kg/m3) COP  coefficient of performance DD  annual degree-days for heating  (K.days) HSPF  heating seasonal performance factor ur  relative uncertainty REFERENCESBarbouchi S., 2006, D. Clodic, J-B. Ritz, HSPF calculation of a system allowing switching between a single-stage to a two-stage compression system, Proceedings, International Refrigeration and Air Conditioning Conference at Purdue. Barbouchi S., 2006, J-B. Ritz, High temperature heat pump for the retrofit market in France, IEA heat pump centre newsletter, retrofit heat pumps for buildings, volume 24, No. 4. CSTB, 2004, SIMBAD Building and HVAC Toolbox, MATLAB/Simulink.DGUHC (Direction générale de l’urbanisme de l’habitat et de la construction), 2005, Réglementation thermique 2005, des bâtiments confortables et performants, URL : www.logement.gouv.fr.EN 14511-3, 2009, Air conditioners, liquid chilling packages and heat pumps with electrical driven compressors for space heating and cooling. Test conditions.EN 14511-3, 2009, Air conditioners, liquid chilling packages and heat pumps with electrical driven compressors for space heating and cooling. Test methods.2228  Page , 7

HSPF determination with field-test results

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HSPF determination with field-test results

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