Building simulation conference 27 th July 2009 Glasgow

Building simulation conference - 27 th July 2009 - Glasgow Dynamic simulation of a complete solar assisted air-conditioning system in an office building using TRNSYS ID 555 Sébastien Thomas and Philippe André Department of sciences and environmental management, University of Liège 185 Avenue de Longwy, 6700 ARLON, Belgium 1

1 2 Presentation overview 1. Introduction 4 2. Simulation environment overview 3. Building 3 5 4. H&C emission and distribution 5. H&C production and storage 6. Results & Conclusion 6 2

1 2 Presentation overview 1. Introduction 4 2. Simulation environment overview 3. Building 3 5 4. H&C emission and distribution 5. H&C production and storage 6. Results & Conclusion 6 3

Introduction : Solar air-conditioning context Building cooling has an important impact on energy consumption, therefore on CO 2 emissions. Moreover, strong increase in cooling installed capacity has been encountered last years. Assets for solar energy : - It is one of the largest renewable energy ressource - There are many ways to convert solar energy into cooling effect - Sunny locations have more cooling needs Market available solar cooling technologies -Absorption chiller -Adsorption chiller -Desiccant equipment -PV panels with classical vapour compression chiller 4

Introduction : key asset of solar energy - The cooling load of buildings is generally high when solar radiation is high yearly basis Src: (2007). Solar Air-Conditioning, 2 nd International Conference Proceedings. Regensburg, Germany, Ostbayerisches Technologie-Transfer-Institut e. V. . daily basis For an office building in August in Paris 5

Introduction : Market status of Solar air-conditioning Cooling power installed worldwide is 20 MW 1. - It represents 250 to 300 installations, from few k. W cold to 1 MW cold - Absorption is still leading the market - Solar air-conditioning systems are installed in Office buidings (60%) Laboratory, Hostels, Industry, Library, … Solar cooling costs distribution 2 Development closely linked to its economical profitability, thus it is important to evaluate energy savings and their essential parameters … 1. Src: (2009). R. Gartner Sun & wind energy magazine 1/09 2. Src (2008) : A. Preisler ROCOCO project publishable part 6

1 2 Presentation overview 1. Introduction 4 2. Simulation environment overview 3. Building 3 5 4. H&C emission and distribution 5. H&C production and storage 6. Results & Conclusion 6 7

Simulation environment overview Integral approach to evaluate energy savings : Complete simulation environment is presented (TRNSYS is used to do this) Sub-systems implementation : - Building - Hot and Cold distribution and emission - Hot and Cold production and storage - Climate à Combined simulation of these sub-systems à Possibility to substitute components 8

Simulation environment overview TRNSYS implementation of Sub-systems 9

1 2 Presentation overview 1. Introduction 4 2. Simulation environment overview 3. Building 3 5 4. H&C emission and distribution 5. H&C production and storage 6. Results & Conclusion 6 10

Building modelling IEA-ECBCS 48 European typical office building 1 -c Paris Climate Complete building (3 identical floors) modeling including : - 5 thermal zones - Ventilation - External shading modulation* - Light intensity modulation - Occupancy profile for each zone - Internal gains profiles > People > Appliances > Light *External shading modulation : Manual solar protections, shading fraction depends on solar radiation on window surface. Solar protections do not move when no occupancy Stabat P. 2007. IEA 48 – Description of Type 1 c airconditioned office buildings for simulation test, . IEA-ECBCS Annex 48 working document. 11

1 2 Presentation overview 1. Introduction 4 2. Simulation environment overview 3. Building 3 5 4. H&C emission and distribution 5. H&C production and storage 6. Results & Conclusion 6 12

Heating and Cooling emission and distribution This layer is linked with H&C production and building layers When computing heating and cooling load using Type 56, control and distribution losses are not handled : implementation done here takes these losses into account. 13

Fan Coil Units modelling It has been chosen to use a real FCU where manufacturer data is available. To model heating/cooling coil in a FCU, TRNSYS gives some possibilities : - Using one of the numerous available types of heating cooling coil : Effectiveness approach, Bypass approach, … Tuned with one parameter, not accurate for the whole coil range of temperatures, mass flow - Read manufacturer data using type 697 Manufacturer data needs to be post processed to suit to type 697, it can be source of errors - Implement a polynomial approximation of coil behavior based on the whole manufacturer data and integrate it into a TRNSYS equation This last solution is chosen : Heating coil sensible heating energy = f((Twater supply – Troom), Water mass flow) 14

1 2 Presentation overview 1. Introduction 4 2. Simulation environment overview 3. Building 3 5 4. H&C emission and distribution 5. H&C production and storage 6. Results & Conclusion 6 15

Heating and cooling production and storage The picture represents the lowest energy consumption configuration for this layer Mistake in the text : 142, 3 m² 200 m² Sub-system main components (for one floor) : - Evacuated tube collector - Storage tank - Absorption chiller COPnom - Back up boiler - Cooling tower - Backup chiller COPnom 200 m² 7 m³ 105 k. WC 0. 695 150 k. W 263 k. W 105 k. Wc 3. 5 For each component, parameters have been fixed based on market available equipment. 16

Simulation of solar air-conditioning system : chiller control It appears that absorption chiller control has a huge impact on energy consumption 3 strategies have been developed: case A B case A : Gas and sun are the only energy sources B : Storage is not heated by boiler, when tank temperature is not enough to feed ABS, vapour compression chiller (VCC) is used. case storage is not used for building heating C : idem than B but storage is also used for heating Comparison is done with classical A-C (vapour compression chiller – gas boiler) C For Paris climate 17

Absorption chiller new type Existing type 107 : energy balance but no dynamic effect based on external performance data file Read in Data file Fraction of nominal capacity Fraction of design energy input Depends on current conditions : Chilled water set point, Entering cooling water temperature, Inlet hot water temperature, part load ratio (fraction of design load) Cold production and Hot water consumption are computed Things to take care : -Fraction of nominal capacity is limited to 1 Rated power is maximum power - Part load ratio independent of current condition (based on rated capacity only) 18

Absorption chiller new type - Part load ratio independent of current condition (based on rated capacity only) When dealing with classical chiller (e. g. type 655), part load ratio (so called fraction of design load in type 107) is the load met by the chiller divided by the capacity of the chiller at the given conditions. Obviously it is between 0 and 1 In type 107, part load ratio is load met by the chiller divided by the capacity of the chiller at the rated conditions. It implies values larger than 1 and has less sense than previous definition New type 255 = existing type 107 + part load ratio depending on current conditions 19

1 2 Presentation overview 1. Introduction 4 2. Simulation environment overview 3. Building 3 5 4. H&C emission and distribution 5. H&C production and storage 6. Results & Conclusion 6 20

Simulation of complete solar air-conditioning system : results Building Heating and Cooling loads For P aris c lima te 21

For P Simulation of complete solar air-conditioning system : results aris c 22 lima te

Simulation of complete solar air-conditioning system : results H&C and auxiliaries consumptions have been computed H&C For P aris c Auxiliaries lima te Case A For Paris climate 23

Conclusions and next developments A complete office building solar air-conditioning application was presented and divided into three major parts to enhance readability. System control has a huge impact on energy consumption. It appears that VCC chiller as backup is useful for energy savings (but implies cost of new equipment). Savings reach more than 30% ! Solar air-conditioning is efficient when used in efficient buildings. Work can be done to decrease cooling load. In actual office building simulations, auxiliaries have a great impact on the whole building energy consumption. Limitations – Next developments - Steady state absorption chiller model - Control strategy improvements should be done (e. g. adjust hot water temperature to cooling load) - Convergence problems with hot water storage 24