TRNSYS SIMULATION OF SOLAR ENERGY SUPPLY TO A MILK PROCESSING PLANT

Transcription

1 TRNSYS SIMULATION OF SOLAR ENERGY SUPPLY TO A MILK PROCESSING PLANT Joana Tarrés, Detta Schaefer, Alaia Sola, Laura Sisó and Jaume Salom IREC, Catalonia Institute for Energy Research Xavier Felipe and Marta Garrón IRTA, Research & Technology Food & Agriculture CONTEXT OF THE PRESENT STUDY Saving water and energy for resource efficient food processing Integration of solar heat into dairy industry processes will be demonstrated by IRTA The research work associated with the solar system design and sizing was developed by IREC Pilot facility: Combination of experimental solar system + experimental milk treatment system 1

2 Challenges OBJECTIVES OF THE STUDY To optimize the system configuration in order to increase solar thermal contribution (or solar fraction) To show that it is possible to achieve with conventional direct streamed Sidney vacuum tube solar collectors a middle temperature range of 150ºC for experimental UHT applications in a southern European country Outputs from TRNSYS simulations Size of storage tank and solar field Outcome of possible system configurations to define optimal installation and control schemes Assessment of duration of periods with 100% solar operation to feed-in the storage tank and UHT process SCHEME OF THE PILOT FACILITY T 2 Primary circuit Secondary circuit Energy distribution network Processes and equipments T 1 Steam boiler Heat treatment equipment Homogenizer Superheated water V1 Sanitary steam Direct steam injection T 9 B1 Q 1 T 4 T 5 T 7 T 6 Q2 V6 n.c. V5 T 11 T 21 V2 n.c. T 12 Superheated water Phase 3 UHT T.150ºC Phase 2 UHT T.100ºC B2 n.c. T 8 B3 Q3 Phase 1 UHT T.97ºC Fill up circuit Heatsink Q4 T 16 T 15 Air T 17 T 14 ATOMIZER equipment B4 V4 T 20 T 13 T 22 Sanitary Water T 19 T18 Sanitary Hot Water System B5 B6 V3 2

3 Primary circuit TRNSYS SOLAR THERMAL SYSTEM MODEL Secondary circuit Energy distribution network Processes and equipments T=150ºC TRNSYS SOLAR THERMAL SYSTEM MODEL Working fluid Solar field Storage tank Superheated water at 150ºC Hydraulic system pressure 8.5 bar Direct-flow evacuated tube solar collector Model: Buderus - LOGASOL SKR12.1 Collector absorber area = 2.57m 2 Number of collectors in series = 5 Total number of collectors = 40; 30; 20 Volume = L, L, L; L Hydraulic system pressure 8.5 bar 3

4 Solar fraction (1) INTRODUCTION OF STRATIFICATION VALVE V2 (2) NUMBER OF SOLAR COLLECTORS AND TANK SIZE (3) INTRODUCTION OF STRATIFICATION VALVE V5 INTRODUCTION OF STRATIFICATION VALVE V2 Fixed tank size (5 000 L) SF = Q UHT Q boiler Q UHT Better stratification in the tank 45% 40% 35% 30% 25% 20% 15% 40 collectors 35 collectors 30 collectors Lower boiler usage 10% 5% Higher solar energy 0% Valve V2 not included Valve V2 included 4

5 Solar fraction NUMBER OF SOLAR COLLECTORS AND TANK SIZE The larger the tank, the larger the solar fraction obtained. The configuration with 30 collectors gives a larger solar fraction. 45% 40% 35% 30% 25% 20% 15% 10% 5% 0% l l l l Tank volume 40 collectors 35 collectors 30 collectors RESULTS - TANK TEMPERATURES AND SOLAR ENERGY Legend: T1 T5 = Tank nodes temperatures Load_UHT = Heat load in UHT 40 solar collectors L tank SELECTION: Solar field of 30 collectors Tank volume of L Qsolar_intank = Heat provided by solar system to tank 30 solar collectors L tank 5

6 Temperature (ºC) INTRODUCTION OF STRATIFICATION VALVE V5 Valve V5 Time when Tin_UHT 150ºC Nr. of days when complete UHT process experiment is exclusively supplied by solar energy Hours / year Days / year Not included Included UHT 1 UHT 2 UHT 3 UHT Heat transfer rate (kw) Tout_UHT Tin_UHT T_setpoint Load_UHT Hour of the year CONCLUSIONS Solar fraction is enhanced by installing 30 collectors in front of 35 or 40 collectors in the present system Introduction of stratification valve V2 in the cold return from UHT process leads to an increase of the annual solar fraction of 10% Introduction of stratification valves V2 and V5 100% solar fraction is accomplished during few days per year with continuous 150ºC water supply to the experimental milk treatment process Size of the facility to reach a maximum annual solar fraction of 39.6% assessed using TRNSYS: Solar field: 77 m 2, 30 ETC, 2.57 m 2 /u (absorber area) Storage tank: L 6

7 Sponsors: Financed by: 7