Practical application of building integrated photovoltaic (BIPV) system using transparent amorphous silicon thin-film PV module

An analysis has been carried out on the first practical application in Korea of the design and installation of building integrated photovoltaic (BIPV) modules on the windows covering the front side of a building by using transparent thin-film amorphous silicon solar cells. This analysis was performed through long-term monitoring of performance for 2 years. Electrical energy generation per unit power output was estimated through the 2 year monitoring of an actual BIPV system, which were 48.4 kWh/kWp/month and 580.5 kWh/kWp/year, respectively, while the measured energy generation data in this study were almost half of that reported from the existing data which were derived by general amorphous thin-film solar cell application. The reason is that the azimuth of the tested BIPV system in this study was inclined to 50° in the southwest and moreover, the self-shade caused by the projected building mass resulted in the further reduction of energy generation efficiency. From simulating influencing factors such as azimuth and shading, the measured energy generation efficiency in the tested condition can be improved up to 47% by changing the building location in terms of azimuth and shading, thus allowing better solar radiation for the PV module. Thus, from the real application of the BIPV system, the installation of a PV module associated with azimuth and shading can be said to be the essentially influencing factors on PV performance, and both factors can be useful design parameters in order to optimize a PV system for an architectural BIPV application.     

太阳能光伏光热建筑一体化系统的研究

太阳能光伏光热一体化不仅能够有效降低光伏组件的温度,提高光伏发电效率,而且能够产生热能,从而大大提高了太阳能的转换效率。对光伏光热建筑一体化(BIPV/T)系统的两种主要模式:水冷却型和空气冷却型系统的工作原理和系统模型进行了理论介绍,详细说明了两种系统中热产品在家庭中的应用。并对目前研究情况下两个系统中存在的问题提出了改进方案。与常规建筑相比,光伏光热建筑减少了墙体得热,改善了室内空调负荷状况,提高了建筑节能效果。     

Available remodeling simulation for a BIPV as a shading device

A building integrated photovoltaic system as a shading device is used as an application and remodeling model. This study applies the simulation program SOLCEL and the computational fluid dynamics method to cases with solar irradiance components analysis and a ventilated double façade remodeling of the BIPV. For the validation of the theoretical work, experimental results of the Samsung Institute of Engineering and Construction Company building are used with a wind velocity of the weather data of Suwon area, Korea, where the real building is located. A photovoltaic system can be used only to generate electricity, but if a photovoltaic module can be used as an element of a double envelope, it could be more useful at the point of view of renewable energy usage and night insulation. Increase of PV module surface temperature is negative for power generation by installing PV module as an element of double envelope. A reasonable combination between renewable energy usage and power generation should be well analyzed for better usage of natural energy to design a BIPV.     

Modeling and coordinate control of photovoltaic DC building module based BIPV system

This paper presents the modeling method and coordinate control strategy for photovoltaic dc building module (PV-DCBM) based building integrated photovoltaic (BIPV) system. The PV-DCBM based BIPV system consists of plenty of PV-DCBMs and a centralized inverter which are coupled to the common dc bus in parallel. Each PV-DCBM is integrated with a PV building material to extract maximum power from it and then a centralized inverter is used to transfer the power to the grid. The PV-DCBM based BIPV system has some significant advantages for building integrated applications, such as individual MPPT, inherent data monitor, low cost and excellent expandability. A coordinate control strategy based on energy balance of the PV-DCBM based BIPV system is proposed to realize the individual control for each PV-DCBM and the centralized inverter. The accurate small-signal model of the PV-DCBM based BIPV system is built based on the proposed operation principle and a detailed design approach of the coordinate controller is proposed. Experimental results on the laboratory prototype verify the validity of the proposed modeling and coordinate control method.     

BIPV/T技术在新徽派民居中的应用探索

针对新徽派民居中存在的建筑能耗大、热舒适性差及室内空气品质低等问题,探索在保持建筑典型特点的前提下,将太阳能光伏光热建筑一体化(BIPV/T)新技术和新方法在新徽派民居中综合运用.文章主要基于作者团队最新的研究,探讨了兼顾"黛瓦"的光伏瓦技术、兼顾"粉壁"的集热?除甲醛多效墙体技术、兼顾"马头墙"的通风?除菌杀毒多效太...     

A prototype photovoltaic/thermal system integrated with transpired collector

Building-integrated photovoltaic/thermal (BIPV/T) systems may be utilized to produce useful heat while simultaneously generating electricity from the same building envelope surface. A well known highly efficient collector is the open-loop unglazed transpired collector (UTC) which consists of dark porous cladding through which outdoor air is drawn and heated by absorbed solar radiation. Commercially available photovoltaic systems typically produce electricity with efficiencies up to about 18%. Thus, it is beneficial to obtain much of the normally wasted heat from the systems, possibly by combining UTC with photovoltaics. Combination of BIPV/T and UTC systems for building facades is considered in this paper - specifically, the design of a prototype façade-integrated photovoltaic/thermal system with transpired collector (BIPV/T). A full scale prototype is constructed with 70% of UTC area covered with PV modules specially designed to enhance heat recovery and compared to a UTC of the same area under outdoor sunny conditions with low wind. The orientation of the corrugations in the UTC is horizontal and the black-framed modules are attached so as to facilitate flow into the UTC plenum. While the overall combined thermal efficiency of the UTC is higher than that of the BIPV/T system, the value of the generated energy - assuming that electricity is at least four times more valuable than heat - is between 7% and 17% higher. Also, the electricity is always useful while the heat is usually utilized only in the heating season. The BIPV/T concept is applied to a full scale office building demonstration project in Montreal, Canada. The ratio of photovoltaic area coverage of the UTC may be selected based on the fresh air heating needs of the building, the value of the electricity generated and the available building surfaces.     

Experimental operating cell temperature assessment of BIPV with different installation configurations on roofs under Mediterranean climate

The presence of an air gap between a photovoltaic (PV) module and roof facilitates ventilation cooling under the device and consequently reduces cell temperature and improves its performance. In case of rack-mounted PV installation, the Nominal Operating Cell Temperature (NOCT) method could be effectively used to predict the temperature of the module for various environmental conditions.Many countries, for esthetic purposes, offer economic advantages (tax deductions, incentives, etc…) for the installation of building integrated photovoltaic modules (BIPV), with water-tightness capability and adequate mechanical resistance in order to substitute tile covering or part of it. Nevertheless, poor or absent ventilation under BIPV panels could cause them to overheat and reduce their efficiency. Lack of validated predictive tools for the evaluation of BIVP energy performance could be another barrier to their widespread application.In this study, we investigated the thermal performance of PV modules installed in a real scale experimental building over a traditional clay tile pitched roof in Italy for almost one year (from August 2009 to June 2010). One PV module was rack-mounted over the roof covering with a 0.2 m air gap; the others were fully integrated and installed at the same level of the roof covering (one with an air gap of 0.04 m, the other mounted directly in contact with the insulation).Temperature and heat flux measurements for each panel, and environmental parameters were recorded.Two temperature prediction models, NOCT model and SNL (Sandia National Laboratory) model were used to predict BIPV temperature and energy efficiency so that their suitability for BIPV could be evaluated. SNL model takes into account also the wind speed.Experimental results demonstrate that even though the rack-mounted PV module constantly maintains cell temperature below that of the other full-building integrated modules, due to the presence of a higher air gap, the difference in the energy produced by the BIPV modules estimated for the entire monitoring period is less than 4%.The two predictive models, NOCT and SNL, cause the differences in predicted and calculated temperature up to 10 °C. However, subsequent percentage variations on the energy predicted compared to that arising from the temperature measured generally turn out to be lower than 5%.An optimization of empirical coefficients used for calculations based on the SNL method allows for the reduction of this value below 2.5%.     

Effect of flow distribution on the photovoltaic performance of a building integrated photovoltaic/thermal (BIPV/T) collector

The phenomenon of non-uniform flow distribution and its influence on thermal performance within a traditional solar thermal collector is well known. Its effect on the photovoltaic conversion of a hybrid photovoltaic/thermal (PV/T) collector however has received little attention. In this study an investigation has been carried out to determine what effect flow distribution will have on the photovoltaic yield of a BIPV/T collector of various size. A three step numerical analysis was conducted to model flow distribution, temperature variation, and photovoltaic yield for a PV/T collector of various design (manifold sizes), geometric shape (aspect ratio), and operating characteristics (mass flow rate and flow direction in manifolds) in order to vary flow uniformity within the collector. The results revealed that flow distribution within the collector will have a significant influence on the photovoltaic performance of a hybrid PV/T collector. For the scenario where flow distribution was most uniform, photovoltaic performance was improved by over 9% in comparison to a traditional photovoltaic (PV) collector operating under the same conditions. For poor flow however, performance was only improved by approximately 2%. Parameters found to influence flow distribution include the manifold to riser pipe ratio where a ratio of 4:1 was found to be ideal and that increasing to a 6:1 ratio offered negligible improvement. Additionally it was found that array geometry (characterised by its aspect ratio in this study) plays an important role on both flow distribution and photovoltaic yield. This study has identified that the optimal mass flow rate is dependent on the shape or aspect ratio of the array.     

Influence of a building’s integrated-photovoltaics on heating and cooling loads

Building integrated photovoltaics (BIPV) has the potential to become a major source of renewable energy in the urban environment. BIPV has significant influence on the heat transfer through the building envelope because of the change of the thermal resistance by adding or replacing the building elements. Four different roofs are used to assess the impacts of BIPV on the building’s heating-and-cooling loads; namely ventilated air-gap BIPV, non-ventilated (closed) air-gap BIPV, closeroof mounted BIPV, and the conventional roof with no PV and no air gap. One-dimensional transient models of four cases are derived to evaluate the PV performances and building cooling-and-heating loads across the different roofs in order to select the appropriate PV building integration method in Tianjin, China. The simulation results show that the PV roof with ventilated air-gap is suitable for the application in summer because this integration leads to the low cooling load and high PV conversion efficiency. The PV roof with ventilation air-gap has a high time lag and small decrement factor in comparison with other three roofs and has the same heat gain as the cool roof of absorptance 0.4. In winter, BIPV of non-ventilated air gap is more appropriate due to the combination of the low heating-load through the PV roof and high PV electrical output.     

Experimental validation of an improved concept of building integrated photovoltaic panels

Recent progress in the implementation of the Energy Performance of Buildings Directive resulted in a significant increase of rooftop PV installations in European buildings. In certain cases the PV installation is extended to cover also south- or west-facing walls byair cooled Building Integrated PV panels (BIPV). The cooling effect maintains a highconversion efficiency of the panels and the heated air may be exploited by the HVAC or service water heating system. Sizing and design of the double façade system is critical to its energetic performance.In this paper, the transient thermal behavior of the basic structural module of a double-skin photovoltaic façade is experimentally investigated in real insolation conditions.Theresults are employed in the validation and further improvement of integration of a BIPV concept to the HVAC system of a building.     

Assessing the technical and economic performance of building integrated photovoltaics and their value to the GCC society

This paper assesses the technical and economic performance of PV technology integrated into residential buildings in the Gulf Cooperation Council (GCC) countries. It highlights the value of PV electricity for the GCC society from the perspective of consumers, utilities and environment. Through a systematic modelling analysis it is shown that the efficiency of PV system drops by 4–6% due to high range of module temperature and also a change in power output due to high ambient temperatures. Consequently, the outputs of horizontal and vertical PV modules are found to be less than estimates based on standard test conditions. Economically, this study shows that building integrated photovoltaic (BIPV) systems are not viable in GCC countries and cannot compete with conventional electricity sources on a unit cost basis. From a society point of view, however, the integration of PV technology into buildings would have several benefits for the GCC countries, including: first, savings in capital cost due to central power plants and transmission and distribution processes; second, an increase in the exported oil and natural gas used for electricity generation; and third, a reduction in the CO₂ emissions from conventional power plants. When these considerations are taken into account then BIPV should become a feasible technology in GCC countries.     

光伏-光热复合装置内流动与传热的数值研究

对用于建筑物立面的空气冷却型光伏光/热一体化装置(BIPV/T)内流动与传热特性进行了数值研究,获得了不同流道结构参数和气象参数下BIPV/T装置内部及附近区域的温度场和速度场。研究表明,BIPV/T装置的空气流道高度对PV板温度的影响较小,流道高度在2～4 m时,其高度越低,PV板温度越低;增大流道出口尺寸可降低PV板温度,但出口尺寸越大时,温度随其变化越小;流道出口尺寸固定时,存在一个最佳的装置流道深度尺寸,使PV板的温度达到最低。该研究结果对合理优化BIPV/T装置的结构设计具有参考价值。     

Grid-connected building-integrated photovoltaics: a Hong Kong case study

The first building-integrated photovoltaic system (BIPV) in Hong Kong has been working successfully for three years, as remote system for the first year and grid-connected system in the last two years. A number of issues have been investigated on the experimental system including technical, economical, operation and management topics. This paper presents the findings from this research project funded by the Industrial Support Fund of the Hong Kong SAR Government. Simulation and data monitoring have been completed for energy performance of the BIPV system under Hong Kong weather conditions. The natural ventilation effect of an air gap on PV module’s power output and heat transfer across the PV wall and PV-roof have been investigated. Good agreement between simulation and experimental results was achieved. The system can provide about 41% of electric power for an indoor lighting floor area circuit of 250 m². The harmonics of the power output from the PV system was also measured to check the interference level to the utility grid. Experiments show that the total harmonics current distortion of the grid-connected BIPV system is far lower than that from some conventional equipment, such as personal computers. The total harmonics from this BIPV system is less than 12% for most of the time, even when the incident solar irradiation is very weak.     

Energy and economic evaluation and multicriteria optimization of different arrangements of integrated photovoltaic thermal and heat recovery wheel system

The present research deals with the multicriteria optimization of two arrangements of a combined system including a building-integrated photovoltaic thermal (BIPV/T) with a heat recovery wheel (HRW) for Kermanshah weather condition in Iran. The considered arrangements have two operational approaches including heat and cool approaches. In the heat approach of the arrangement (I), the fresh ambient air is preheated in two steps by flowing first among the HRW and then through the BIPV/T collector. In the cool approach of the arrangement (I), the outdoor air stream enters the HRW and is precooled there by exchanging heat to the building exhaust air. The exhaust air then enters the BIPV/T collector and cools the PV panels, thereby augmenting their efficiency. The cool approach of the arrangement (II) is like the arrangement (I), while in the heat approach of the arrangement (II), the outdoor air first gets into the BIPV/T collector and then flows among the TW. The uniform end of annual cost (UAC) and yearly available energy are considered as the objective functions. The obtained results revealed that however energetic performance of the arrangement (I) is more suitable than the arrangement (II); its UAC is 4441$ higher than that of the arrangement (II).     

太阳能光伏建筑一体化应用现状及发展趋势

部分发达国家从20世纪90年代初就开始大力发展太阳能光伏建筑一体化(BIPV)应用研究,但其在我国尚处于起步发展阶段。2009年5月21日,财政部与住房和城乡建设部联合出台的《关于加快推进太阳能光伏建筑应用的实施意见》正式启动了我国的"太阳能屋顶计划"。本文首先介绍光伏与建筑系统结合的多种形式及光伏建筑一体化的诸多优点,重点说明其在国内外的应用现状,最后从政策法规、技术标准、认证制度等方面阐述其在我国的发展趋势。光伏建筑一体化是未来光伏应用中最重要的领域之一,其发展前景十分广阔,具有巨大的市场潜力。     

Natural convection in an internally finned phase change material heat sink for the thermal management of photovoltaics

Elevated operating temperatures reduce the solar to electrical conversion efficiency of building integrated photovoltaic devices (BIPV). Phase change materials (PCM) can be used to passively limit this temperature rise although their effectiveness is limited by their low thermal conductivities and crystallisation segregation during solidification. This paper presents an experimental evaluation of the effects of convection and crystalline segregation in a PCM as a function of efficiency of heat transfer within the finned PV/PCM system. The thermal performances of bulk PCM with crystallisation segregation for different internal fin arrangements are presented. It is noted that the addition of internal fins improves the temperature control of the PV in a PV/PCM system.     

Feasibility analysis of solar photovoltaic array cladding on commercial towers in Doha,Qatar – a case study

Building-integrated photovoltaic (BIPV) technology has become a major area of research due to environ-mental concerns. This article studies the feasibility of cladding high-rise towers in Doha with solar photovoltaic modules. Specifically, the case of the Qatar Financial Centre (QFC) is discussed. The major aim of the work is to evaluate the technical feasibility, economic impact and environmental effects of using photovoltaic panels on commercial towers in Qatar. Experimental data on solar irradiance and the effect of shading on the QFC Tower are presented. Numerical calculations are done using solar pathfinder software. The studies show that, although there is a significant amount of saving in CO₂ emission by using BIPV on towers in Doha, the payback period is still very long due to the cheaper cost of grid electricity in Qatar and poor conversion efficiency of PV panels. The complete system layout is presented and viable solutions are investigated.     

Performance evaluation of photovoltaic thermal solar air collector for composite climate of India

The objective of present study is to evaluate the performance of the photovoltaic (PV) module integrated with air duct for composite climate of India. In this case, thermal energy is produced along with electrical energy generated by a PV module with higher efficiency. An analytical expression for an overall efficiency (electrical and thermal) has been derived by using energy balance equation for each component. Experimental validation of thermal model of hybrid photovoltaic/thermal (PV/T) system has also been carried out. It has been observed that there is a fair agreement between theoretical and experimental observations. Further it is concluded that an overall thermal efficiency of PV/T system is significantly increased due to utilization of thermal energy in PV module.     

Performance monitoring results of the first grid-connected BIPV system in Colombia

This paper summarizes the operational performance results of the first grid-connected building integrated photovoltaic (BIPV) system installed in Colombia (in Bogotá, at 4°35′ latitude and 2.580 m altitude) after two years of monitoring. The performance monitoring was carried out with a sophisticated monitoring system, designed and implemented by us using the virtual instrumentation concept. The following parameters were measured: DC and AC power, inverter and system conversion efficiency, energy generated by the PV array, AC energy produced by the BIPV system, parameters to analyze power quality (%THD, harmonic components, frequency, voltage, flickers, power factor, active power, apparent power and reactive power), solar radiation in the inclination plane of the panels and environment temperature.The data obtained allowed to evaluate the general performance and the quality of the electric power generated by the photovoltaic plant. The results indicated that the power generated by the grid-connected BIPV plant fulfills the specifications demanded for such systems by National and International standards.     

The effect of using two PCMs on the thermal regulation performance of BIPV systems

Building Integrated Photovoltaics (BIPVs) is one of the most promising applications for Photovoltaics (PVs). However, when the temperature in the BIPV increases, the conversion efficiency deteriorates. A PV/PCM system using Phase Change Materials (PCM) for BIPV thermal control has been experimentally and numerically studied previously. One of the main barriers for this application is how to improve the low thermal conductivity of the PCM in order to achieve a quick thermal dissipation response with longer thermal regulation in PVs. Although the metal fins inserted inside the PCM can improve the heat transfer, the thermal regulation period declines as the volume of the PCM is substituted by the metal mass of the PV/PCM system. A modified PV/PCM system integrated with two PCMs with different phase transient temperatures for improving the heat regulation needs to be investigated. The use of combinations of PCMs, each with a set of different phase transient temperatures, is expected to enhance the thermal regulation effect of the PV/PCM system and lengthen the thermal regulation time in PVs. In this study a developed PV/PCM numerical simulation model for single PCM application has been modified to predict the thermal performance of the multi-PCMs in a triangular cell in the PV/PCM system. A series of numerical simulations tests have been carried out in static state and realistic conditions in UK. The thermal regulation of the PV/PCM system with a different range of phase transient temperature PCMs has been discussed.