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									                                                                                                                           Experimental Analysis on Performance of Solar Cooling System in UAE Conditions

 CSEM UAE Innovation Center LLC
                                                                                                                                                                                                                        Experimental and
                                                                                                                                                                                                                        simulation studies
 Experimental Analysis on Performance of Solar Cooling System 
                                                                                                                                                                                                                           Ras Al Khaimah
 in UAE Conditions                                                                                                                                                                                                       (25.68˚N, 55.78˚E)

 Manoj K. Pokhrel, Gaurav P. Raval, Sujata Dahal 
 January 28th,2014
                                                                                                                    Simulation and
                                                                                                                    comparison to RAK
 Second Southern African Solar Energy Conference‐SASEC 2014
                                                                                                                        Cape Town
                                                                                                                     (33.93˚S, 18.60˚E)

                                             SASEC-2014       Experimental Analysis on SC | Gaurav Raval | Page 0                                                                                 Experimental Analysis on SC | Gaurav Raval | Page 1

 Experimental Analysis on Performance of Solar Cooling System in UAE Conditions                                            Introduction

 Overview at glance                                                                                                        Why Solar Cooling ?
  Introduction                                                                                                      Renewable is an alternative to fossil fuels                In GCC; Solar irradiation is abundant
              Why solar cooling ?
              Why experimental analysis is needed ?
              Description of Installed system in RAK-UAE
              Environmental parameters in UAE and South Africa
              System Modeling
              Simulation Results                                                                                   In residence: cooling has major electricity share “Zero Energy” building has to consider cooling
  Experimental     (RAK-UAE)
              Collector-Storage performance
              System Performance
              Discussion
  Comparison (experimental v/s simulation)
              Energy                                                                                               Conventional cooling today creates major environmental problems
              COP & Temperatures
  Performance of solar cooling system                                                                                                          CO2 and Ozone depletion
              Projected Outlook for South African Conditions
                                                              Experimental Analysis on SC | Gaurav Raval | Page 2                                                                                 Experimental Analysis on SC | Gaurav Raval | Page 3

 Introduction                                                                                                              Introduction

 Why experimental analysis is needed ?                                                                                     Description of installed system

                                                                                                                                                                    Solar Cooling System at Solar Outdoor LABoratory (RAK-UAE)
 Experiment being needed to check the pertinence of a theory and a simulation

 Most existing studies in this region being based on theory and simulation

           Only the implementation and test of a system will allow the:
                 Confirmation of the theory                                                                                                                      Installed Solar Cooling System at SOLAB
                 Validation of the simulation                                                                                                                    A. Solar Collectors: 32 Evacuated Tube (4 collectors in one series and 8
                                                                                                                                                                     such series in parallel). Aperture area-96m² (SEIDO 1-16)
                 Assessment of the cost
                                                                                                                                                                  B. Absorption Chiller: 10TR single-effect LiBr/H2O (Yazaki WFCSC10)
                 Recommendation to optimize the system by improving its                                                                                          C. Thermal Storage: 1 Stratified tank with spherical heat exchanger
                     Operating conditions                                                                                                                           (980L Capacity for charging) + 2 Buffer tanks (for hot and cold (TISUN)
                     Modeling for simulation
                                                                                                                                                                  D. Cooling Tower: Wet type400G, Induced draft counter-flow, (Liang Chi)
                     Components
                                                                                                                                                                  E. Chilled Water Distribution: at 7-12°C; Distribution by fan coil units
                                                                                                                    Schematic of Installed Solar Cooling System

                                                              Experimental Analysis on SC | Gaurav Raval | Page 4                                                                                 Experimental Analysis on SC | Gaurav Raval | Page 5

            Simulation                                                                                                                                                                Simulation

           Environmental parameters in UAE and South Africa                                                                                                                           System Modeling

                                                                                                                                                                              - Developed on TRNSYS by CSEM-uae

                                                                                                                                                                              - Parameters & controllers mimic facility

                                                                                                                                                                              -The equations considered are:

        Monthly averages for a year in UAE –Ras Al Khaimah (RAK) & South Africa –Cape Town (CT) (Meteonorm)
        Global Radiation Horizontal (GRH): Maximum: May in RAK (~700 W/m²) & December in CT (~700 W/m²)
                                                                  Minimum: December in RAK (~350 W/m²) & June in CT (~250 W/m²)
                                                                  2013 annual average : RAK 538 W/m² & CT 507 W/m² (All similar)
        Ambient temperature (T):  Maximum: July in RAK (38°C) & January in CT (25°C) (Much Higher in RAK)
        Relative Humidity (RH) :  Maximum in January in RAK (~55%) and June in CT (~70%) (Higher in CT)
                                                  Lower in RAK than in CT (All year)                                                                                                                                         TRNSYS generic simulation model (no auxiliary heater)
                                                                                                                        Experimental Analysis on SC | Gaurav Raval | Page 6                                                                                 Experimental Analysis on SC | Gaurav Raval | Page 7

            Simulation                                                                                                                                                                Experimental in RAK‐UAE

            Simulation results¹                                                                                                                                                      Collector ‐ Storage performance

Solar Fraction Cooling (SFC) & Specific Collector Yield (SCY)                                               Thermal COP of the solar cooling system

    The system
          Has a thermal COP in the range of 0.6 to 0.8

          Can meet cooling demand for eight months (SFC≥ 1.0)

          Cannot meet cooling demand in June-September despite higher SCY

    1.   M. Ssembatya, (2012), Performance Evaluation of a solar cooling system in UAE conditions, A MS Thesis project of KTH, Sweden and CSEM-uae                                                 RAK, June 27- 2013: Typical experimental performance
                                                                                                                        Experimental Analysis on SC | Gaurav Raval | Page 8                                                                                 Experimental Analysis on SC | Gaurav Raval | Page 9

            Experimental in RAK‐UAE                                                                                                                                                   Experimental

            System performance                                                                                                                                                       Discussion
                                                                                                                                                                                Region A
                                                                                                                                                                                         Gradual Increase in Collector Efficiency
                                                                                                                                                                                         High heating up period. Good Stratification observed
                                                                                                                                                                                         Period can be reduced for early start-up of chiller in 2 ways:
                                                                                                                                                                                           •   Alternative heating system in parallel to solar heating
                                                                                                                                                                                           •   Reducing Storage tank volume
                                                                                                                                                                                Region B
                                                                                                                                                                                         Destruction of stratification in storage tank
                                                                                                                                                                                           •   Sudden exertion of cooling load & unsteady behavior of chiller at start-up
                                                                                                                                                                                           •   High Chilled p
                                                                                                                                                                                                 g                             p                          g
                                                                                                                                                                                                             power consumption due to accumulated cooling load in distribution
                                                                                                                                                                                           •   Mixing due to direct circulation of hot water to chiller
                                                                                                                                                                                Region C
                                                                                                                                                                                         Fluctuations in Thermal COP despite constant hot water inlet at 80°C
                                                                                                                                                                                           •    Humidity Fluctuations causes fluctuations in cooling water inlet temperature
                                                                                                                                                                                           •    Humidity fluctuations also causing cooling load variations
                                                                                                                                                                                         Highest Thermal Energy gain
                                                                                                                                                                                Region D
                                                                                                                                                                                         Gradual decrease in incident radiation and cooling load requiring less chilled energy
                                                                                                                                                                                         Improvement in Collector Efficiency
                                                                                                                                                                                           •   Lower operation temperature of collector field
                                                                                                                                                                                           •   Non requirement for pipe & thermal mass heating-up energy
                                                                                                                                                                                           System can be operated for at least 7hours per day  11:30 to 17:30 hours except in peak
                               RAK, June 27- 2013: Typical experimental performance                                                                                                         summer to maintain comfort conditions in given space without using auxiliary heating source

                                                                                                                       Experimental Analysis on SC | Gaurav Raval | Page 10                                                                                Experimental Analysis on SC | Gaurav Raval | Page 11

      Comparison of experimental to simulation in RAK‐UAE                                                                              Comparison of experimental to simulation in RAK‐UAE

      Energy (1 autumn day)                                                                                                            Energy (1 day for each season)

                                                                                                                                                    Fig. 8 Experimental results with respect to simulation results for performance comparison
                                                                                                                                    Rejected Energy                Simulation : Rejected Energy = Heating Energy + Chilled Energy
                                                                                                                                                                    Experiment: Rejected Energy = Heating Energy + Chilled Energy + (10-15%)
                                                                                                                                    Gross Collector Efficiency  50-55% in winter and autumn while 45-50% in summer.

                           RAK, November 28- 2012: Energy comparison                                                                Peak demand (summer)           Degradation of performance due to high temperatures & high relative humidity

                                                                          Experimental Analysis on SC | Gaurav Raval | Page 12                                                                                               Experimental Analysis on SC | Gaurav Raval | Page 13

      Comparison of experimental to simulation in RAK‐UAE                                                                              Performance of Solar Cooling System

      COP and Temperatures                                                                                                             Projected outlook for South African conditions

                                                                                                                                     Global Radiation Horizontal                       Ambient Temperature                                      Relative Humidity
                                                                                                                                            (UAE & SA)                                    (UAE & SA)                                              (UAE & SA)

                                                                                                                                    Weather Data for simulation for both locations is taken from Meteonorm database (9:00 -17:00 daily hours)

                  RAK, April 27 -2013: COP and temperatures comparisons                                                             Global Radiation Horizontal (GRH)  Similar in UAE & South Africa  Similar thermal energy gain

   Global Radiation Horizontal data are from CSEM-uae data base                                                                    Ambient temperature(T)  Lower in South Africa  Moderate cooling demand in South Africa
   Coefficient Of Performance (Thermal)  Experiment: 0.46 - 0.67
                                                                                                                                    Relative Humidity(RH)  Higher in South Africa (often >40%)
                                         Simulation: ~ 0.7
                                                                                                                                    Wet and Dry Cooling Tower both are possible to install in South Africa due to better ambient temperatures
   Inlet Temperatures to chiller        Mismatching between simulation and experiment
    Correction in System Modeling is required, Losses and In-steady behavior of chiller at start-up to consider                       Environmental parameters more favorable for South Africa  Better performance are expected in SA

                                                                          Experimental Analysis on SC | Gaurav Raval | Page 14                                                                                               Experimental Analysis on SC | Gaurav Raval | Page 15

      Experimental Analysis on Performance of Solar Cooling System in UAE Conditions


        Technical Potential of Solar Cooling in UAE?  YES

        Experimental results indicate fluctuations in Thermal COP varying from 0.46-0.67.

        Worst performance in peak summer months [July-September].
                                                                                                                                        Thank you for your attention.
        Sustained operation of chiller in evenings possible-Collector Efficiency improves later in the day.

        Key Aspect for longer operation :
              Optimized Design and Selection of Hot Water Storage Tank

     Stratification maintenance throughout operation required for maximum benefit from system

        System Modeling needs improvement.

        Location of Cooling Loads should be closest to the system

        Weather Conditions of South Africa also favors Solar Cooling System adaptation

        Economic Aspect has to be studied deeply for commercial viability in both UAE and South Africa

                                                                          Experimental Analysis on SC | Gaurav Raval | Page 16                                                                 SASEC-2014                    Experimental Analysis on SC | Gaurav Raval | Page 17


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