Solar Collectors for Air Heating Profitability Analysis
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FACULTY OF ENGINEERING AND SUSTAINABLE DEVELOPMENT Solar Collectors for Air Heating Profitability Analysis Joseba Moreno Mendaza June 2014 Master’s Thesis in Energy Systems 15 credits Master’s Thesis in Energy Systems Examiner: Shahnaz Amiri Supervisors: Björn Karlsson, Stefan Jonsson, Roland Forsberg Preface In this preface I would like to thank those that have supported me during the development of my Master’s Thesis. Foremost, I would like to express my sincere gratitude to my supervisor, Prof. Björn Karlsson, for his patience, motivation, enthusiasm, and immense knowledge. I could not have imagined having a better advisor and mentor for this work. Besides my supervisor, I would also like to thank my co-supervisors, Stefan Jonsson and Roland Forsberg, who gave me the opportunity to carry out this thesis in cooperation with FVB Sverige AB and offered kindly their help when I needed it. Last but not least, I would like to thank my family, girlfriend and friends, for the constant support and encouragement I have gotten throughout my life. Abstract Solar energy constitutes one of the main alternatives for facing the energy problems of the future, taking into account the foreseeable depletion of the fossil fuels. Transpired solar air collectors are relatively simple alternatives, which do not need a continuous supervision and are mostly maintenance free. Their life cycle is relatively high, around 25 years, and the total investment can be fully recovered in the short-term. The aim of this master’s thesis is to analyze the feasibility of installing transpired solar air collectors as secondary systems in big industrial buildings, for heating purposes. The collectors would be designed for compensating the heat losses of a building which is mainly heated up by a heat pump system. Precisely, this work tries to evaluate the profitability of installing these collectors in Gävle, taking into account the particularities of this location in the considered study. This project work is focused on testing if these systems can provide enough thermal energy for heating up big-sized industrial buildings. For this purpose, firstly, the heat demand of the building for each month was calculated; secondly, the maximum output from the collector was estimated, using WINSUN simulator; and, finally, the energy difference that had to be covered by the main system was calculated. Once this was done, the yearly running cost for the main system and the total investment for the transpired air solar collector were estimated. Due to the lack of experimental data, the obtained results can only be taken as approximations. All the calculations and estimations have been made using WINSUN, a simulator that has been configured according to the particularities of the project. The results show that the solar collector provides a total thermal output of 29.700 kWh/year (system which has a total investment of 77.000 SEK). The total heat demand of the building is estimated to be of 87.100 kWh/year, being 51.800 kWh/year fulfilled by the heat pump system (which has a yearly running cost of 24.000 SEK/year). The collector has an average efficiency of 51,04%. Keywords: transpired solar collector, heat pump system, heat demand, thermal output, solar energy, fossil fuels, investment, running cost. Table of contents 1. INTRODUCTION .................................................................................................. 1 1.1. Solar thermal energy in Sweden ........................................................................ 1 1.2. Solar thermal systems ........................................................................................ 3 1.3. Problem description ........................................................................................... 4 1.4. Limitations ......................................................................................................... 5 1.5. Objectives .......................................................................................................... 6 1.6. Previous research ............................................................................................... 7 2. CONTEXT .............................................................................................................. 9 3. THEORETICAL FRAMEWORK ...................................................................... 11 3.1. Working principle of a low-temperature air solar collector system ................ 11 3.2. Components of an air solar collector system ................................................... 13 3.2.1. Solar air collector...................................................................................... 14 3.2.2. Constant speed fan .................................................................................... 19 3.2.3. Dampers .................................................................................................... 20 3.2.4. Air distribution duct ................................................................................. 21 3.2.5. Regulation and control system ................................................................. 22 4. METHODOLOGICAL FRAMEWORK ........................................................... 23 4.1. Calculation of the incident solar radiation ....................................................... 23 4.1.1. Basic definitions ....................................................................................... 23 4.1.2. Calculation of solar parameters ................................................................ 25 4.1.3. Calculation of the total solar radiation upon collector’s surface .............. 26 4.2. Theoretical calculation of the thermal output from the collector .................... 29 4.3. Estimation of the annual thermal output from the collector ............................ 30 4.3.1. Winsun simulation tool ............................................................................. 30 4.4. Main systems for fulfilling the heating demand .............................................. 30 4.4.1. District heating system ............................................................................. 31 4.4.2. Heat pump system .................................................................................... 31 4.4.3. Industrial electric heating ......................................................................... 33 5. RESULTS .............................................................................................................. 35 5.1. Calculation of solar parameters ....................................................................... 35 5.2. Calculation of solar angles ............................................................................... 35 5.3. Calculation of the incident total solar radiation upon collector´s surface ....... 35 5.3.1. Direct solar radiation ................................................................................ 36 5.3.2. Diffuse solar radiation .............................................................................. 37 5.3.3. Total solar radiation .................................................................................. 37 5.4. Calculation of the thermal output from the collector ....................................... 38 5.4.1. Considerations .......................................................................................... 38 5.4.2. Calculations from WINSUN .................................................................... 39 5.4.3. Calculations from Karlsson’s formula ...................................................... 39 5.4.4. Thermal output comparison. ..................................................................... 40 5.5. Energy demand gap ......................................................................................... 41 6. PROFITABILITY STUDY OF THE SOLAR COLLECTOR SYSTEM ....... 45 6.1. Investment cost for a transpired air solar collector system .............................. 45 6.2. Running costs for the main systems ................................................................ 47 7. ENVIRONMENTAL IMPACT OF THE PROJECT ....................................... 49 8. CONCLUSIONS ................................................................................................... 51 REFERENCES ............................................................................................................. 55 APPENDIX ................................................................................................................... 59 1. Calculation of solar parameters and solar angles ................................................ 59 2. Results from Winsun ........................................................................................... 61 3. Building’s heating demand .................................................................................. 64 4. Calculation of the collector’s thermal output using Karlsson’s formula ............. 65 5. Calculations for thermal output comparison. ...................................................... 66 6. Heat losses and internal heat generation (IHG) ................................................... 67 6.1. Heat losses .................................................................................................... 67 6.2. Internal heat generation (IHG) ..................................................................... 70 7. Estimation of the collector’s investment cost ...................................................... 72 8. Estimation of the yearly running costs for the main systems .............................