CyberMart A Whole-Building Simulation Model for Supermarkets

Transcription

1 CyberMart A Whole-Building Simulation Model for Supermarkets Div. of Applied Thermodynamics and Refrigeration

2 Contents 1.- Introduction. 2.- CyberMart, Systems and Models. 3.- CyberMart. 4.- Evaluation of CyberMart. 5.- Conclusions.

3 1.- Introduction. Energy-saving technologies as heat recovery, floating condensing temperature, energy efficient lighting, energy efficient display cases have been implemented in several supermarkets. The supermarket branch has more and less used the trial and error approach to implement and evaluate new ideas and concepts. A systems model is necessary to be implemented in order to predict and evaluate the introduction of new concepts and ideas in supermarkets.

4 1.- Introduction. The main objective of the project was to create a user-friendly computer program for simulation of indoor climate in different supermarkets, where the influences from cabinets, lighting, people, heat recovery, air conditioning and outdoor climate are simulated.

5 The Supermarket System System Boundaries Electricity District heating District cooling Refrigeration System Ambient conditions HVAC System Heat Cabinet System Indoor conditions t = 22C, HR = 65%

6 Main Program System design LCC TEWI Outdoor Climate Building Heat Rec. Indoor Climate A.C. Cabinets Cold Rooms Defrost Pipes and pumps Brine Compressor Evaporator Chiller Condenser Expansion Valve Pipes and pumps Dry Cooler Fluid Dry Cooler

7 Building Model Heat Balance room air Heat gains to room air Heat losses from room air = 0 Q con H v * (T s T r ) H w * (T r T o ) H c * (T r T s ) Q g =0 where Q con = Q sol. + Q p. + Q eq. + Q l. - Q cabcon H w : Specific loss from room air to outside W/K H V : Specific loss from room air to ventilation air W/K H c : Specific loss from room air to room surfaces W/K

8 Heat Balance room surfaces Heat gains to room surfaces Heat losses from room surfaces = 0 Q rad + H c * (T r T s ) H ac * (T s T ac ) = 0 where Q rad = Q sol. + Q p. + Q eq. + Q l. - Q cabrad H ac : Specific loss from room surfaces to structure W/K H c : Specific loss from room air to room surfaces W/K

9 Heat Balance building structure Heat gains to structure - Heat losses from structure = Accumulated heat in structure H ac *(T s T ac ) H out *(T ac T o ) = C A *dt S /dt where C A : Total heat capacity of the room Wh/ K dt S : Variation of structure temperature C dt : time period h H ac : Specific loss from room surfaces to structure W/K H out : Specific loss structure to outside W/K

10 The equivalent outdoor temperature T e = T out + (I sol α sol + (T sky T out ) *α r )/ α e Where: T out : Outdoor temperature T sky : Sky temperature α sol : Absorptivity for solar radiation α r : Radiative heat transfer coefficient α e : Effective heat transfer coefficient α e = α r + α c

11 HVAC Model mfresh T1 RHEX T2 T3 T4 AC HR AH T5 T6 Tsup msup Outdoor X1 X2 X3 X4 Re-circulation X5 X6 Xsup Supermarket mrecir T7 mout X7 mret

12 Air massflow Outdoor Temperature Air Cooled Condenser UAcond. Discharge Line Compressor Liquid Line Compressor Power Suction Line Expansion device Evaporator Cabinet Cold Storage Evaporator UAevap. UAevap.

13 Completely Indirect System Outdoor Temperature Dry Cooler UAdrycooler Coolant fluid Pump UAcond. Compressor Power Chiller UAevap. Pump Secondary refrigerant UAcabinet Cabinet Indoor Temperature

14 Qlighting Qheatingwires Qinfiltration Qradiation Qwall Q& Q& Q& Q& Q& Q& wall inf rad ligh fheat def = 7.3% = 65.7% = 8.6% = 10.8% = 7.6% = 0% Qfan Qdefrost Qload

15 Qwall Qheatingwires Qradiation Qinfiltration Qwall Q& Q& Q& Q& Q& Q& wall inf rad ligh fheat def = 9.2% = 16.4% = 46.6% = 0% = 16.5% = 11.3% Qdefrost Qfan Qload

16 Life Cycle Cost Present value of single cost SCp n SC [ 1+ ( i p) ] n Present value of annually recurrent cost RCp n = = RC n 1 n [ ( ) ] n 1+ i p ( i p) Life Cycle Cost LCC = Inv + LCC + LCC + LCC + TOTAL ENERGY OM &R Environment LCC others

17 Total Equivalent Warming Impact (TEWI) TEWI calculation TEWI = M losses N GWP ref + RC E N M losses : Refrigerant leak in [kg/year] N : equipment operation time [year] GWP ref : Global Warming Potential of Refrigerant in [kg CO 2 /kg refrigerant] RC : Regional Conversion Factor is the emission of CO 2 per unit of energy delivered in [kg CO 2 /kwh]. E : Annual energy consumption of the equipment [kwh/year]

18 3.- CyberMart

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29 4.- Evaluation of CyberMart. The DSA method was used to consider the sensitivity of the program. 36 parameters were analysed. The total sensitivity analysis of the program is 5.6%.

30 Energy Usage MWh / year Measurement CyberMart Sala Electricity District Heating Hjo Electricity District Heating 80 49

31 Lambohov Simulation from CyberMart No HR or FC HR and FC Ventilation [MWh/year] Lightings [MWh/year] Equipments [MWh/year] Heating [MWh/year] Refrigeration System [MWh/year] Total Energy Usage [MWh/year] Energy Cost [US$/year]

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34 Lambohov Total Energy Usage 2006 Measurement CyberMart January ,7% February ,3% Mars ,2% April ,5% May ,0% June ,8% July ,7% August ,3% September ,2% Total ,9%

35 Lambohov Total Electricity Usage Out.Temp Tot.El.Meas. Tot.El.Cyb. Tot.Comp.Meas. Tot.Comp.Cyb. 80 Temp[ C], Power[kW] Time[day]

36 5.- Conclusions There is a great potential for improvement of energy systems in supermarkets. The system approach and the interconnection between the different subsystem implemented in the program predict and evaluate the introduction of new concepts and ideas in supermarkets. A particular energy efficient solution for each supermarket is possible to achieve only when there is a balance between LCC, TEWI and performance

37 5.- Conclusions. The implementation of new energy saving technologies in supermarkets requires an extensive analyse of energy performances. This analysis should be done during a long period to evaluate and compare the real energy performance with the theoretical values calculated.