Building Integrated Photovoltaic Facade Research Articles

Workflow to support cost-benefits comparison and sensitivity analysis of BIPV case studies: Three examples of BIPV facades in the south of Switzerland

The building skin surfaces represent a vast potential for decentralising renewable energy investments and offering unique opportunities for prosumers thanks to the built environment. Despite the recognised potential of building-integrated photovoltaics (BIPV), cost-effectiveness is still a market barrier to accelerate deployment. The literature reports investigations on costs at product level and cost-effectiveness scenarios and prospects. However, the literature assessing the economic viability of real building processes is scarce. BIPV costs are strongly project-related and affected by construction work factors that cannot be generalised or observed at a macro-scale. Thus, the lack of concrete and documented applications in existing buildings is a missing gap for the sector and doesn’t support the market in clarifying the real economic costs and benefits of BIPV systems or the main parameters influencing the economic variability in real constructions. This study contributes to the field by developing a cost-benefit analysis of established BIPV case studies situated in the southern region of Switzerland. The approach employs a comprehensive economic evaluation, utilizing the net present value method. A sensitivity analysis is developed to assess costs by varying key economic input parameters that significantly impact the financial aspects of BIPV installations. This research aims to conduct a comprehensive analysis of specific case studies, presenting original findings that elucidate the interplay between energy and construction factors. By discerning these relationships, the study seeks to unveil the determinants of cost competitiveness, ultimately contributing to the increase of attractiveness within the realm of BIPV facade benefits throughout the entire value chain.

Evaluating BIPV Façades in a Building Envelope in Hot Districts for Enhancing Sustainable Ranking: A Saudi Arabian Perspective

Enhancing contractual construction project documents with sustainability and green building requirements reflects growing concerns for the majority of organizations in hot zone districts. The aim is to provide a healthy, best functional performance, safe environment with occupant comfort, and an efficient building performance as an environmental-friendly building. This research study develops a holistic evaluation system for the façade composite of contractual documents. The aim of the current study was to enhance building energy performance under the sustainability rating system focusing on adapting active envelope energy applications. The research used technical evaluation with energy simulation based PVsyst V7.1.0 software and contractual status evaluation for an ongoing unique case study project in Saudi Arabia. Feasibility analysis was carried out for a sustainable active envelope using the adopted specifications of the Building Integrated Photovoltaics (BIPV) façade item instead of the contractual passive item in the Giftedness and Creativity Center project. The project was registered in the sustainability rating system called Leadership in Energy and Environmental Design (LEED). The results showed that using BIPV facades as an active renewable energy source enhances building energy performance over the project life cycle. Additionally, it generates 68% of energy demand as a nearly-zero energy project. Several other advantages include lower cost than tender cost without any contractual conflicts, energy savings per year, project upgrade to the platinum certificate, added value to the public investment, CO2 emission reduction, and barrels of oil saved.

Assessment of thermal and electrical performance of BIPV façades using simplified simulations

Building integrated photovoltaic (BIPV) facades are a solution to consider when it comes to electricity generation on the building site. One of the main challenges attributes to this technology is finding the best trade-off between the electrical efficiency of BIPVs and the energy use of the building. This study aims to identify a scenario that yields the optimized results for electrical and thermal performance in a test building. Among the scenarios, the original wooden cladding in the test building is either replaced with PV panels or the PV modules are added to the existing facade. Rhinoceros 3D CAD software and its visual programming plugin Grasshopper are used to perform various simulations for both east-oriented and west-oriented façades with low and high thermal inertia wall structures. Although a complex flow phenomenon behind BIPVs is simplified in the 3D heat transfer model, relatively reliable results are obtained using the chosen simulation tool. It is observed that the east-faced BIPV facade in the test building has higher electrical efficiency. This could be attributed to the lower inertia of the east wall that allows easier propagation of heat through the structure.

Evaluation of in-situ thermal transmittance of innovative building integrated photovoltaic modules: Application to thermal performance assessment for green mark certification in the tropics

Green buildings with adequate renewable energy penetration are fundamental pillars of global sustainability. Moreover, pertinent to ever-increasing impacts of cooling loads, air-conditioning systems, and elevated energy consumption in the tropics, building energy performance plays a crucial rule in achieving self sustainability. In this context, the proposed work experimentally evaluates the thermal performance of five innovative building integrated photovoltaic (BIPV) technologies, and assesses its feasibility to be integrated as building envelopes to attain the required green mark certification benchmarks in Singapore. For which, experiments are first performed using a state-of-art indoor laboratory equipped with a calibrated Calorimeter Hot Box for thermal transmittance (U − Value) measurements. Later, distinctive to existing works, this article extends the application of U − Values to obtain the Envelope Thermal Transfer Value (ETTV) by utilizing an analytical model for sensitivity analysis. In particular, this assessment is performed to provide an accurate quantification of the thermal characteristics of the tested BIPV technologies in compliance with the prevailing green building codes. Extensive case studies considering various window to wall (WWR) ratios have also been conducted to identify the optimal values that could guarantee successful BIPV deployment with green mark compliance. Altogether, this paper reports 720 benchmark test case results accounting for five cladding, and three fenestration systems considering various WWR ratios ranging from 0.1 to 0.9. It is foreseen that the ETTV sensitivity analysis carried out in this manuscript would assist researchers, and building professionals in abreast decision making for future adoption of BIPV facades at early design stages itself.

Performance of building integrated photovoltaic facades: Impact of exterior convective heat transfer

Building integrated photovoltaic (BIPV) applications are key to increase the share of renewable energy in the built environment. A large potential for BIPV deployment is related to building facades. The assessment of BIPV facades depends on the accurate modelling of exterior convective heat transfer coefficients (eCHTC). However, eCHTC models commonly used in BIPV modelling tend to be simplified. This paper proposes a simulation framework that combines detailed computational fluid dynamics with a multi-physics BIPV model to investigate the influence of eCHTC on the performance of BIPV facades (cell temperature and power). The evaluation is performed for different building geometries, wind speeds, wind directions, solar irradiations, and ambient temperatures. The results show that local variations in eCHTC can cause variations in cell temperature up to 42 °C between the BIPV modules across the facade. These temperature differences are associated with differences in power up to 17% across the BIPV facade. In general, lower temperatures (and higher power output) occur near the edges of the facade while higher temperatures (and lower power output) occur at the middle and at the bottom of the facade. Therefore, a detailed assessment of wind effects is recommended in order to verify the local operating conditions of the BIPV modules. The framework and findings presented in this work are relevant for applications in which the knowledge of the local behaviour is important, such as degradation studies.

Understanding the behaviour of naturally-ventilated BIPV modules: A sensitivity analysis

Abstract Building integrated photovoltaic (BIPV) is a key concept for the realisation of sustainable buildings. Despite the progress in BIPV modelling, the use of sensitivity analysis (SA) is still scarce in the BIPV literature. SA can help the modeller to identify which model inputs influence the model outputs the most. This paper presents a simulation framework that combines global SA methods with a multi-physics BIPV model. The analysis focuses on the performance of naturally ventilated BIPV facade elements (cell temperature and power). Building performance indicators, such as the total heat flux to the building interior and the building wall temperature, are also analysed. Inputs to the SA include convective heat transfer coefficients, cavity airflow rate, and weather conditions. As expected, the SA results were found to be highly dependent on the range selected for the inputs. For a narrow variation in weather conditions, the exterior convective heat transfer coefficient was identified as the input with the strongest influence on the BIPV performance. Results also showed that cavity ventilation becomes more important as the exterior convective heat transfer decreases. These findings indicate the need for accurate models to represent exterior convective heat transfer in BIPV facades and corroborate the importance of cavity ventilation.

A physics-based high-resolution BIPV model for building performance simulations

Building integrated photovoltaic (BIPV) systems are considered a promising solution to increase the share of renewable energy in the built environment. To evaluate the BIPV performance at the building level, the implementation of BIPV models in building performance simulation tools is an essential step. This paper presents the development of a multi-physics BIPV model for the simulation of BIPV facades within the openIDEAS framework for building and district energy simulations. The model couples a high-resolution electrical model to physics-based thermal and airflow models. The combination of these two modelling approaches is not common in BIPV models, particularly for building performance simulations. The model predictions are compared to three months of experimental data from a naturally ventilated BIPV module installed in the facade of a test building in Leuven, Belgium. A good agreement is obtained in terms of both BIPV energy yield and temperature. The error in daily energy yield estimations is on average below 3 % and the error in the monthly energy yield is below 2%. The back-of-module temperature is predicted with a MAE lower than 2 °C and RMSE lower than 5 °C.

Performance of BIPV modules under different climatic conditions

Building integrated photovoltaic (BIPV) technology has gained attention as a solution to achieve low energy buildings. However, unlike conventional PV applications, BIPVs typically operate at non-optimal orientation, imposed by the building geometry. Moreover, the building integration reduces the heat exchange to the exterior, leading to higher temperatures. This paper investigates the performance of BIPV modules in different locations by simulating a representative office room in a high-rise building having a BIPV facade. The locations considered are Riyadh (Saudi Arabia), Seville (Spain), Naples (Florida, USA), Cape Town (South Africa), and Munich (Germany). The facade is vertical and faces the equator for all locations. Results show the highest annual BIPV energy yield occurs in Seville, followed by Cape Town, Riyadh, and Naples. In terms of monthly yields, the highest values are observed in Riyadh and Seville in wintertime. Monthly yield is more uniform over the year in Munich, while important differences between summer and winter have been obtained for Riyadh. These results confirm the influence of the latitude on the BIPV yield, with equator-facing facades in high latitudes receiving up to 40 % less irradiation compared to a horizontal surface, with important reductions especially in the summer. In these locations, the use of west and east facades may be necessary to achieve a balanced profile over the year. Moreover, the highest average cell temperatures occur in Riyadh, Naples and Seville, while lowest temperatures are verified in Cape Town and Munich, which is consistent with the corresponding ambient temperatures. Finally, with lower BIPV temperatures and relatively high solar irradiation, Cape Town achieves the highest performance ratio (PR) values. Conversely, the combination of high solar irradiation and high temperatures leads to lower PR values in Riyadh and Seville

An approach for daylight calculation of a building integrated photovoltaic (BIPV) Façade

ABSTRACTContemporary use of Building Integrated Photovoltaics (BIPV) façades is increasing rapidly. However, A BIPV façade can impact natural lighting because of opaque solar cells in the panels. This paper explicates an approach for daylight calculation in an indoor environment with the BIPV facade system installed. A brief review of daylight calculation is given to reveal the drawbacks of previous methods that are not suitable for our situation, which includes a BIPV façade and requires manual calculation. The detailed calculation, including the mathematical formulas used at each stage, is explained. First, the position of the sun is calculated. Second, we calculate the daylight availability. Our third calculation is of sun and sky illuminance on the ground and vertical façade. This is followed by the calculation of reflected light. As a result, indoor illuminance can be calculated. In the section of results and discussion, theoretical simulations are accomplished with parametric tools. In the comparison, results from the simulation and the calculation are matched, especially in the case of the overcast sky. By these means our approach can be proved effective. In summary, our research provides an accurate and quick approach of daylight calculation, with due consideration given to practical factors in various aspects.

A novel methodology for the pre-classification of façades usable for the decision of installation of integrated PV in buildings: The case for equatorial countries

Abstract Building-integrated photovoltaics (BIPV) is a growing reality worldwide and its development involves implementing techniques to log and estimate the solar resources available. In this paper an easy methodology for the pre-classification of facades in BIPV projects has been described. This step is previous to the calculation of the complete solar potential in a building, and don't include the shape and shading factors. The proposed methodology covers the development of a new model that allows the irradiation factor (IF) to be estimated on facades with only 2 input parameters: the latitude of the place and the azimuth angle of the photovoltaic generator. The necessary tools to assess the “Energetic Efficiency Rating” for BIPV facades are provided, as an initial stage to be applied by architects and engineers.

Towards Zero Energy School Building Designs in Hong Kong

Abstract The energy saving and electricity production schemes for a school building in hot and humid climate were studied by a building energy package eQUEST. High-performance building envelops, energy-efficient air-conditioning systems and lighting fixtures were employed to save energy consumption and building integrated photovoltaic (BIPV) panels were adopted to meet the energy needs. The annual electricity demand was 300 MWh, and 97.5% of it can be supplied by the vertical BIPV facades. Further PV installations on the roof can generate more electricity to balance the energy use. The results show that school block is possible to achieve the zero building energy consumption.

Application of a BIPV to cover net energy use of the adjacent office room

Purpose The purpose of this paper is to investigate the potential of the experimental building integrated photovoltaic (BIPV) façade to cover net energy use in the adjacent office room. Electricity generated by PV panels was intended to cover the energy demand for the mechanical ventilation and the supplementary lighting. Analyses were performed for two orientations of the façade (east and west) and two occupancy profiles considering one or two employees per one office room. Design/methodology/approach The study was conducted by carrying detailed numerical analyses of energy produced by the BIPV façade and its consumption in adjacent office room. Calculations of energy generated by PV panels were made using simulation programme ESP-r. Advanced model, used in analyses, take into account dependence of the main electrical parameters of photovoltaic cell from temperature. Findings The findings reveal that energy generated by photovoltaic panels during transitional and cooling seasons is sufficient for lighting and ventilation requirement. However during winter months BIPV facade can cover energy demand only for ventilation. Originality/value The paper provides an original analysis of experimental BIPV façade system as a source of on-site produced renewable energy to cover energy demand in offices building under certain climate conditions. The results reported in presented paper shows the potential of BIPV facades and display this potential in a context of building net energy balance.