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.     

Trade-off between environmental and economic implications of PV systems integrated into the UAE residential sector

PV technology offers clean resource and environmental advantages over fossil-fuel-based electricity generation; however, it remains more expensive than conventional technology in most grid-connected applications. The trade-off between environmental and economic parameters represents a challenge for governments. The objectives of this study are: firstly, to review studies in relation to the use of PV systems in the Gulf region and secondly, to assess the trade-off between environmental and economic parameters that influence the value of building integrated photovoltaic (BiPV) technology applied into the UAE building sector. This work examines residential buildings and concludes that the economic viability of BiPV systems is subject to capital cost, system efficiency and electricity tariff. To be a cost-effective option in the UAE, subsidies for PV investments and reasonable electricity tariff must be implemented. It is suggested that BiPV systems offer cost reductions in both energy and economic terms over centralised PV plants, especially if the costs of saved operating energy and avoided building materials are taken into account. Each square meter of BiPV is capable of making a significant reduction in CO₂ emissions generated by conventional power plants. This will limit the impact of global warming on the UAE and others.     

Pilot study on building-integrated PV: Technical assessment and economic analysis

Building-integrated photovoltaics (BIPV) is an innovative green solution that incorporated energy generation into the building façade with modification on the building material or architectural structure. It is a clean and reliable solution that conserves the aesthetical value of the architecture and has the potential to enhance the building's energy efficiency. Malaysia's tropical location has a high solar energy potential to be exploited, and BIPV is a very innovative aspect of technology to employ the available energy. Heriot-Watt University Malaysia (HWUM) has a unique roof design that could be utilized as an application of the BIPV system to generate electricity, reducing the carbon footprint of the facility. Eight BIPV systems of different PV technologies and module types and with capacities of 411.8 to 1085.6 kW were proposed for the building. The environmental plugin software has been integrated with a building geometry modelling tool to visualize and estimate the energy potential from the roof surface in a 3D modelling software. Additionally, detailed system simulations are conducted using PVSyst software, where results and performance parameters are analysed. The roof surface is shown to provide great energy potential and studied scenarios generated between 548 and 1451 MWh yearly with PR range from 78% to 85%. C-Si scenarios offer the best economical profitability with payback period of 4.4 to 6.3 years. The recommended scenario has a size of 1085.5 kW and utilizes thin-film CdTe PV modules. The system generates 1415 MWh annually with a performance ratio of 84.9%, which saves 62.8% of the electricity bill and has an estimated cost of 901 000 USD. Installation of the proposed system should preserve the aesthetical value of the building's roof, satisfy BIPV rules, and most importantly, conserves energy, making the building greener.     

BIPV for the high-temperature, high-rise, high-density cities of S. China: The related projects of PV HKU research group to facilitate BIPV application

In cities where high-rise commercial developments have overtaken industry as the peak electricity consumer, sophisticated building integrated photovoltaics (BIPV) can offset the demand by generating electricity during daytime peak consumption. The PV HKU Research Group's related projects, in a triple strategy of Technology Assessment, Technology Application & Regulatory Framework, aims to provide the government and community with the information, experience and appropriate legislation to facilitate widespread BIPV applications, and assist compliance with the Kyoto Protocol on CO₂ emissions reduction.     

BIPV: a real-time building performance study for a roof-integrated facility

Building integrated photovoltaic system (BIPV) is a photovoltaic (PV) integration that generates energy and serves as a building envelope. A building element (e.g. roof and wall) is based on its functional performance, which could include structure, durability, maintenance, weathering, thermal insulation, acoustics, and so on. The present paper discusses the suitability of PV as a building element in terms of thermal performance based on a case study of a 5.25?kW_p roof-integrated BIPV system in tropical regions. Performance of PV has been compared with conventional construction materials and various scenarios have been simulated to understand the impact on occupant comfort levels. In the current case study, PV as a roofing material has been shown to cause significant thermal discomfort to the occupants. The study has been based on real-time data monitoring supported by computer-based building simulation model.     

Energy and economic evaluation of building-integrated photovoltaics

This paper applies energy analysis and economic analysis in order to assess the application of solar photovoltaics (PVs) in buildings. Comparison is made both to electricity supply from centralised PV plants and to conventional electricity sources. The comparison with conventional sources reveals that there is currently a significant trade-off between the environmental and economic implications of PVs: there are substantial resource benefits to be gained from using PVs to supply electricity, but the economic cost of doing so is significantly higher than conventional sources. This trade-off is reduced when the benefits of building integrated PVs (BiPVs) are considered. By comparison with centralised PV plants, BiPV systems offer the “double dividend” of reduced economic costs and improved environmental performance. This double dividend is increased if the economic and energy costs of avoided cladding materials are taken into account.     

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.     

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.     

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.     

Photovoltaic cogeneration in the built environment

Building integrated photovoltaic (BiPV) systems can form a cohesive design, construction, and energy solution for the built environment. The benefits of building integration are well documented and are gaining significant public recognition and government support. PV cells, however, convert only a small portion of the incoming insolation into electricity. The rest is either reflected or lost in the form of sensible heat and light. Various research projects have been conducted on the forms these by-products can take as cogeneration. The term cogeneration is usually associated with utility-scale fossil-fuel electrical generation using combined heat and power production. It is used here in the same spirit in the evaluation of waste heat and by-products in the production of PV electricity. It is important to have a proper synthesis between BiPV cogeneration products, building design, and other HVAC systems in order to avoid overheating or redundancy. Thus, this paper looks at the state-of-the-art in PV cogen from a whole building perspective. Both built examples and research will be reviewed. By taking a holistic approach to the research and products already available, the tools for a more effective building integrated system can be devised. This should increase net system efficiency and lower installed cost per unit area. An evaluation method is also presented that examines the energy and economic performances of PV/T systems. The performed evaluation shows that applications that most efficiently use the low quality thermal energy produced will be the most suitable niche markets in the short- and mid-term.     

Evaluation of phase change materials for thermal regulation enhancement of building integrated photovoltaics

Regulating the temperature of building integrated photovoltaics (BIPV) using phase change materials (PCMs) reduces the loss of temperature dependent photovoltaic (PV) efficiency. Five PCMs were selected for evaluation all with melting temperatures ∼25 ± 4 °C and heat of fusion between 140 and 213 kJ/kg. Experiments were conducted at three insolation intensities to evaluate the performance of each PCM in four different PV/PCM systems. The effect on thermal regulation of PV was determined by changing the (i) mass of PCM and (ii) thermal conductivities of the PCM and PV/PCM system. A maximum temperature reduction of 18 °C was achieved for 30 min while 10 °C temperature reduction was maintained for 5 h at −1000 W/m² insolation.     

Life cycle assessment study of solar PV systems: An example of a 2.7 kWp distributed solar PV system in Singapore

In life cycle assessment (LCA) of solar PV systems, energy pay back time (EPBT) is the commonly used indicator to justify its primary energy use. However, EPBT is a function of competing energy sources with which electricity from solar PV is compared, and amount of electricity generated from the solar PV system which varies with local irradiation and ambient conditions. Therefore, it is more appropriate to use site-specific EPBT for major decision-making in power generation planning. LCA and life cycle cost analysis are performed for a distributed 2.7 kW_p grid-connected mono-crystalline solar PV system operating in Singapore. This paper presents various EPBT analyses of the solar PV system with reference to a fuel oil-fired steam turbine and their greenhouse gas (GHG) emissions and costs are also compared. The study reveals that GHG emission from electricity generation from the solar PV system is less than one-fourth that from an oil-fired steam turbine plant and one-half that from a gas-fired combined cycle plant. However, the cost of electricity is about five to seven times higher than that from the oil or gas fired power plant. The environmental uncertainties of the solar PV system are also critically reviewed and presented.     

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.     

BIPV系统经济性分析

太阳能作为21世纪最具潜力的洁净能源之一,其相关产业在近几年里发展十分迅速。本文论证了在我国发展太阳能产业的可行性,描述了BIPV系统的结构和优越性,并且结合南京市光伏—建筑一体化系统的实例,通过对其发电效益以及动态平直供电成本的计算对该系统的经济性和环境效益进行了分析。计算结果表明,该实例虽然可以带来很好的环境效益,但是目前发电成本偏高。BIPV系统的普及有赖于太阳电池组件产品价格的降低和相关政策的支持。     

On the value of decentralised PV systems for the GCC residential sector

Based on the rich natural potential of the Gulf region, solar energy is expected to play a greater role in the future of the Gulf Corporation Council (GCC) countries. This study examines whether the integration of the photovoltaic (PV) into individual residential buildings in the GCC countries is worth the investment. A prototype residential building is developed and a building integrated photovoltaic (BiPV) system is then designed. The system performance is simulated, and through economic analysis, it is shown that the current BiPV technology is not a cost-effective option for the GCC countries based on the present electricity tariff, PV system cost and system efficiency. The only way such a system would be viable with current technology is if the electricity tariff were to increase substantially. However, if the tariff remains constant for the foreseeable future, BiPV solar energy technology will only be feasible if the total system cost drops drastically. This study shows that BiPV systems offer cost reductions in both energy and economic terms over centralised PV plants, especially if the costs of avoided building construction materials are taken into account. To bring about the benefits of BiPV technology for the GCC residential sector, therefore, the first logical and most practical step is the implementation of a continuous promotion strategy that consists of both subsidies for investments and reasonable tariffs.     

Energy and cost analysis of semi-transparent photovoltaic in office buildings

Solar energy conversion systems and daylighting schemes are important building energy strategies to produce clean energy, reduce the peak electrical and cooling demands and save the building electricity expenditures. A semi-transparent photovoltaic (PV) is a building component generating electricity via PV modules and allowing daylight entering into the interior spaces to facilitate daylighting designs. This paper studies the thermal and visual properties, energy performance and financial issue of such solar facades. Data measurements including solar irradiance, daylight illuminance and output power for a semi-transparent PV panel were undertaken. Using the recorded results, essential parameters pertaining to the power generation, thermal and optical characteristics of the PV system were determined. Case studies based on a generic reference office building were conducted to elaborate the energy and cooling requirements, and the cost implications when the PV facades together with the daylight-linked lighting controls were being used. The findings showed that such an integrated system could produce electricity and cut down electric lighting and cooling energy requirements to benefit the environmental, energy and economic aspects.     

Energy analysis of an improved concept of integrated PV panels in an office building in central Greece

During the last decade, steel constructions with glazed façades became popular for commercial buildings in Greece. Moreover, expensive metal, natural stone, marble, ceramic, granite as well as special glass is employed for aesthetic and energy efficiency reasons. This creates opportunities for the introduction of Photovoltaic (PV) modules in double façades. PV modules on south-facing building walls are better placed at a distance from the wall to allow heat rejection and avoid overheating and efficiency loss. Exploiting the rejected heat of the PV modules is also a challenge. In this paper, we examine an improved concept of incorporating PV modules to the south façades of an office building, exploiting both the electricity produced and the heat rejected by the module, to increase building energy efficiency. The PV modules are integrated to the building wall by means of a double façade, which employs intervening ducts for ventilation purposes. The ducts are heating outdoor air, which is employed to cover the ventilation needs of the building, as well as a part of the heating loads. Simulations for typical winter and summer weather and solar insolation conditions are carried out to investigate the building’s energy performance improvements.     

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%.     

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.