Performance Analysis Of Different Configurations Of Semi-transparent CdTe Photovoltaic Integrated Window Systems In China And Bangladesh

Globally,the building sector is estimated to be the consumer and producer of onethird of total fossil fuel and CO2 emissions.The two primary strategies for addressing the concerns of rising emissions and energy demand are thought to be the use of renewable energy and energy efficiency.Around the world,the utilization of solar energy through building integrated photovoltaic(BIPV)is gaining popularity due to its capacity to generate clean energy and reduce building energy consumption.The BIPV window system,on the other hand,provides thermal insulation and produces clean electricity that contributes to lowering CO2 emissions,reducing the usage of commercial grid electricity,and improving building energy efficiency.Therefore,the BIPV window system has become a popular research topic that attracts researchers to develop new window configurations and improve its performance.To enhance the utilization of solar energy in buildings,in this dissertation,we propose a new ventilated double-skin window known as ventilated photovoltaic combined hybrid vacuum glazing(V-PVCHVG)that combines semi-transparent CdTe photovoltaic glazing and vacuum glazing.Applying a semi-transparent CdTe PV glass on the exterior surface of this naturally ventilated window simultaneously generates clean electricity and improves the PV conversion efficiency and indoor daylight illuminance.Moreover,the V-PVCHVG window also offers a variety of operation modes based on the seasonal demands of various climate regions.This multi-function V-PVCHVG window is unique in that,according to the sessional need,it improves thermal performance,generates clean electricity,reduces heat gain in the summer,and supplies additional heat gain in the building in the winter.Besides V-PVCHVG,insulated-type photovoltaic combined vacuum glazing(I-PVCHVG)is also considered here to compare their performance.An outdoor experiment was conducted for V-PVCHVG and I-PVCHVG windows and dynamically tested their thermal,electrical,and indoor daylight behavior.The experiment results revealed that the V-PVCHVG window could reduce PV glazing temperature by approximately 6.2℃ during summer daytime and increase PV conversion efficiency by 1.56%over I-PVCHVG.Furthermore,the V-PVCHVG window could decrease the room air temperature by around 1.2℃ during the daytime.Conversely,the V-PVCHVG window passes slightly less daylight into the room compared to the I-PVCHVG window due to its wider air cavity.Moreover,the experiment data validate an EnergyPlus-based dynamic numerical simulation model.The model was found to be within the acceptable range of accuracy according to ASHRAE Guideline 14-2002.Further,this simulation model was used to predict the annual thermal,daylighting,electrical,and overall energy performance of different CdTe-based BIPV window systems and compare them with conventional window systems under different climate conditions in Bangladesh and China.V-PVCHVG and I-PVCHVG window performances were analyzed in four different climates in China,and their results were compared with those of single-clear(SCLR),double-clear insulated glazing(DCLR-IGU),and photovoltaic insulated glazing(PV-IGU)windows.The computed outcomes showed that the V-PVCHVG window could minimize heating and cooling loads compared to other windows in all climate conditions because of its efficient ventilation strategy.The exception is that it increases the need for heating in the severe-cold region by around 1%in comparison to the DCLR-IGU.In contrast,I-PVCHVG windows require more heating energy than DCLR-IGU and V-PVCHVG windows because they largely prevent secondary heat gain through the insulated air gap and back vacuum glazing.When compared to conventional windows,both PVCHVG windows consume less HVAC energy because of their combined heating and cooling demands.PVCHVG windows also ensure useful daylight illumination,preventing uncomfortable glare for the inhabitants.In addition,a BIPV window set on a south-facing wall produces more power,which is higher in northern,cold locations like Hohhot and Tianjin than in low-latitude regions like Hefei and Xiamen.Furthermore,in Hohhot,Tianjin,Hefei,and Xiamen,respectively,VPVCHVG reduced net energy consumption by around 60%,69%,66%,and 70%compared to the DCLR-IGU window.Similarly,compared to I-PVCHVG in the same climate conditions,it could reduce building energy consumption by about 32.7%,34.5%,36.1%,and 29%.Moreover,V-PVCHVG and I-PVCHVG windows have the best CO2 emission reduction ability in severe cold regions compared to other climate regions.A VPVCHVG window system with around 4 m2 of area could save 1026.8 kg and 616.9 kg of CO2 annually in Hohhot compared to the SCLR and DCLR-IGU window systems.Besides,a simple economic analysis revealed that the payback period of the VPVCHVG and I-PVCHVG window systems compared to SCLR and DCLR-IGU is within their life span.In a heating-dominated region like Hohhot,the payback period for V-PVCHVG is around 5.7 and 7.1 years,compared to SCLR and DCLR-IGU,respectively.However,in a cooling-dominated region like Xiamen,PVCHVGs are not cost-effective to replace the PV-IGU.A parametric study reveals that V-PVCHVG offers better energy conservation with a higher window-to-wall ratio(WWR)in all climate conditions,while a higher cell coverage ratio(CCR)is beneficial for heatingdominated regions.For the cavity width in V-PVCHVG,the heating-dominant regions required a comparatively lower air gap(50 mm)than the cooling-dominant region(400 mm),and vice versa.In addition,single photovoltaic glazing(SPVG),photovoltaic insulated glazing(PV-IGU),and ventilated photovoltaic double skin(PV-VDS)windows are also investigated in light of the tropical climate in Bangladesh,as there are no significant applications or studies on BIPV window systems.The predicted overall energy performance indicates that CdTe-combined BIPV windows could save around 30-61%of electricity consumption annually compared to conventional window systems.Among the BIPV window systems,PV-VDS window systems show better energy conservation ability,considering all climate conditions.At various climate conditions,the SPVG window systems generate 3.2～3.4%and 1.6～1.9%more electricity but consume more electricity for air conditioning,around 11.3～13.5%and 27.8～29.6%compared to PVIGU and PV-VDS windows,respectively.Besides,SPVG,PV-IGU,and PV-VDS window systems generated around 275 kWh,266 kWh,and 270 kWh of electricity in each climate condition,respectively.BIPV windows also ensured indoor daylight illuminance levels of around 300 lux in all climate conditions.Moreover,considering the net electricity savings compared to the SCLR window system,the PV-VDS window system can save 614.51,603.72,and 588.77 kg of CO2 annually in Chittagong,Dhaka,and Rangpur,respectively.On the other hand,the parametric study indicated that in all climate conditions,south-facing BIPV windows are more efficient for power generation,but east-facing windows are more efficient for reducing net electricity consumption.However,a higher CCR is suitable for better building energy conservation in all climate conditions in Bangladesh.