بررسي پارامترهاي موثر در بهبود عملكرد جمع كننده هاي خورشيدي فتوولتائيك- گرمايي

چكيده انگليسي :

Investigation of Effective Parameters in Improving the Performance of Solar Photovoltaic Thermal PV T Collectors Mahtab Tafazoly Yazdy m tafazoli@me iut ac ir September 21 2013 Department of Mechanical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Ahmad Saboonchi ahmadsab@cc iut ac ir Abstract communities for energy Replacing these sources with sustainable and safe sources of energy is necessary Renewable energies are permanent available and clean sources of energy and proper choice for replacing present sources of energy Solar energy is one of the most widely used kinds of renewable energies which is used today in different ways Solar energy applications can be classified under two main groups of thermal and electrical Despite the many benefits of solar thermal and electrical systems there are some constraints on the development of this type of energy Long payback period because of low electrical efficiency of photovoltaic panels decrease in efficiency of panels by increase of temperature high cost of manufacturing and installation of panels and requirement of large space for installing separate systems are some problems which should be considered for using solar systems The combination of solar thermal and electrical systems in one unit system results in better performance of solar systems This unit system is called solar photovoltaic thermal collector In addition to occupying less space Hybrid system has higher overall efficiency than separate electrical and thermal systems In this study a hybrid system is simulated and effects of system parameters on its performance are investigated Hybrid systems with sheet and tube geometry can be easily manufactured by combining available thermal and electrical systems of the present market because of their simple structure and they are good replacement for present thermal and electrical systems sheet and tube systems also have proper efficiency for these features this geometry is used for simulation Due to low boiling point flow of refrigerants in the pipe becomes two phase in low temperatures and because of high value of two phase heat transfer coefficient photovoltaic thermal systems which use refrigerants as working fluid have lower working temperature and therefore higher electrical efficiency in comparison with similar systems with water Because of this at first use of refrigerant as cooling fluid of system is investigated To do this refrigerant two phase flow is simulated in straight and modeling of two phase flow and empirical works finally single phase flow of water is used for the simulation Temperature and mass flow rate of inlet fluid and also use of cover are some of factors that affect the performance of hybrid systems According to the results increase of inlet temperature by 20 K results in 8 and 15 increase in thermal and electrical efficiencies Increasing mass flow rate from 0 005 kg s to 0 1 kg s causes 4 3 and 9 7 increase in electrical and thermal efficiencies and 4 9 decrease in outlet temperature of fluid Therefore mass flow rate should be chosen according to the type of system and priority of thermal and electrical efficiencies or quality of outlet temperature of fluid Adding one layer of cover on the system results in 19 increase in thermal efficiency and 1 1 decrease in electrical efficiency Key Words Photovoltaic thermal systems Simulation Thermal efficiency Mass flow rate PDF created with pdfFactory trial version www pdffactory com

تفضلي يزدي، مهتاب

بررسي پارامترهاي موثر در بهبود عملكرد جمع كننده هاي خورشيدي فتوولتائيك- گرمايي

شبيه سازي حرارتي , بازده حرارتي , دبي جرمي