Research On Thermoelectric Performance Characteristics And Comprehensive Utilization Of Building Integrated Photovoltaic Fa(?)ade System

In pursuit of global zero-carbon goals,transformation of energy consumption structure towards renewable energy domination is the fundamental approach to achieve sustainable development.Zero-carbon electricity is expected to become the main energy form in the near future.Currently,building energy consumption accounts for as high as 36%of the total global energy consumption,making energy-efficient buildings a crucial driving force for achieving zero-carbon targets.Renewable energy utilization technologies,especially solar energy,are the main focus in the field of building energy conservation.For urban areas where high-rise buildings are ubiquitous,building integrated photovoltaic fa(?)ade(BIPV facade)technology is considered the most suitable approach for achieving energy-saving goals with continuous vertical facades.However,review of current research on BIPV fa(?)ade field reveals several problems unsolved:low accuracy of air channel heat transfer models,unknown system thermoelectric coupling effect,unclear influence of key parameters on system performance index,and unknown comprehensive thermoelectric utilization effect on buildings.To address these issues,following research contents were conducted:First,theoretical study was conducted on the heat transfer mechanism of BIPV fa(?)ade air channel.Based on the causes and characteristics of internal airflow,heat transfer properties were scientifically defined as transient natural ventilation within limited space.Meanwhile,current heat transfer models establishing process have been combed and analyzed,with limitations found causing low accuracy:simplified experimental object,inappropriate heat transfer definition and limited boundary conditions.By avoiding these limitations,the outdoor experimental test bench for BIPV facade systems was established to monitor key heat transfer parameters.Based on the long-term testing data,temperature distribution along height,thermal shield effect and air channel heat transfer characteristics were analyzed.The heat transfer model for transient natural ventilation inside the air channel was finally established.The proposed model showed the maximum percentage error of 4.39%with measured values,significantly improving the prediction accuracy of air channel heat transfer under actual operating conditions compared to existing models by 17.51%～67.51%.Secondly,based on the outdoor experimental test bench of BIPV fa(?)ade system,long-term electrical and thermal performance parameters were further monitored.System thermoelectric characteristics were analyzed,with thermoelectric coupling regularity determined.Results revealed that under the same daily solar radiation,increasing the air channel width from 100mm to 400mm under premise of notable chimney effect,resulted in notably chimney effect inside the air channel,with 53.22%and 64.07%increase in air channel heat gains and daily mean thermal efficiency,While 18.18%and 12.62%decrease in system electricity generation and daily mean electricity efficiency,respectively.Thermal energy proportion increased by 15%compared to electrical energy proportion.Results indicate that under the premise of the chimney effect,as the air channel width increases,electrical performance is slightly undermined,while thermal performance is significantly improved,resulting in the enhancement of comprehensive thermoelectric performance of BIPV fa(?)ade.Furthermore,the thermoelectric coupling factor and its mathematical correlation of the system were determined,and the surface temperature of the battery in the existing calculation model was replaced by the backplate temperature.A thermoelectric coupling model for BIPV facade under actual operating conditions was established,scientifically quantifying the influence of thermoelectric coupling effect.The errors between the calculated and measured values of the backer surface temperature and electrical efficiency were less than 4.07%and 6.21%,respectively.This simplified the calculation while ensuring the accuracy of thermoelectric performance prediction.Furthermore,based on the established air channel heat transfer and thermoelectric coupling models,a new TRNSYS BIPV fa(?)ade component model was developed using the Fortran language,verified by measured data with high accuracy.Based on experimental results and literature review,BIPV fa(?)ade height,air channel width and building insulation U value were determined as substantial parameters.Unit BIPV fa(?)ade area of annual total electricity generation,air channel heat gains and indoor heat gains were defined as main performance outputs of useful energy generation.A simulation platform for building BIPV fa(?)ade system was established in TRNSYS to simulate the substantial parameters impact on performance outputs in various climatic zones with sensitivity analysis conducted.Results indicated that,in terms of trends,BIPV fa(?)ade height and building insulation U value both exsert unidirectional impact on air channel heat gains and indoor heat gains but with opposite directions.Air channel width impact was bidirectional and exhibited an optimal value.In terms of magnitudes,parameters impact on electricity generation was relatively insignificant.However,considering the large installation area in practical applications,total electricity generation might still be affected under real application.In severely cold and cold climatic zones,air channel width had the greatest impact on the performance outputs,while building insulation U value had the greatest impact in other climatic zones.BIPV fa(?)ade height had the smallest impact on performance outputs in all climatic zones.In all climatic zones,electricity generation and air channel heat gains were most sensitive to air channel width,with sensitivity indices ranging from 1.2%to 2.4%and 38.3%to 42.3%,respectively.From north to south,sensitivity index of the indoor heat gains to air channel width decreased from 51.2%to 20.9%,While sensitivity index to building insulation U value increased from 23.8%to 85.3%.Finally,based on two national building energy standards,GB55015-2021 and GB51350-2019,four types of typical high-rise office buildings models in different climatic zones were established under two configurations respectively.Three BIPV facade system installation layout were determined based on previous research and specific engineering project investigation.The established TRNSYS simulation platform for building BIPV facade system was then used to simulate the system thermoelectric generation and building energy consumption under different layout schemes in different climatic zones.Subsequently,calculation method for comprehensive useful energy utilization was proposed,based on which the heating,cooling and total energy-saving rate,thermoelectric utilization rate and unit area of energy consumption index of BIPV facade systems for the four types of typical high-rise office buildings in different climatic zones were obtained compared to the original building energy consumption baseline.The research results showed that installation BIPV facade systems in typical high-rise office buildings significantly improved energy efficiency.Installation of BIPV fa(?)ade system on south,east and west fa(?)ade can achieve total energy saving rate of 55%at most,with thermoelectric utilization rate of 48%at most.For panel-type high-rise office buildings,under compulsory configuration,unit area of energy consumption index could be reduced to 32-67k Wh/(m~2·a),While under nearly-zero configuration,it could be reduced to 30-65k Wh/(m~2·a).For barrel-type high-rise office buildings,unit area of energy consumption could be reduced to 30-57 k Wh/(m~2·a)under compulsory configuration,and to 28-55 k Wh/(m~2·a)under nearly-zero configuration.To sum up,this study proposed accurate calculation models for the air channel heat transfer and thermoelectric coupling effect of BIPV facade system under actual operating conditions.Research clarified the influence of substantial parameters on system performance characteristics.Based on thermoelectric utilization calculation method,comprehensive thermoelectric utilization effect of BIPV facade system in different climatic zones for typical high-rise office buildings was scientifically quantified.Research provides technical emphasis and specific instructions for promoting the application of BIPV facade technology in building energy conservation,demonstrating academic significance and practical value in promoting energy transformation and zero-carbon goal in building industry.