Semi-transparent Building Integrated Photovoltaic Research Articles

Literature Review Study for SHGC Performance Evaluation Methods of Semi-transparent BIPV System

A building-integrated photovoltaic (BIPV) system is a renewable energy system that generates electricity and functions as a building envelope for zero energy buildings (ZEBs). BIPV can be applied to roofs, façades, and window systems. In particular, a semi-transparent BIPV applied to window systems is designed to satisfy the thermal performance requirements of national standards. The solar heat gain coefficient (SHGC) is used to estimate the solar radiation that passes through the glass relative to the amount of solar radiation hitting the glass. The SHGC of a semitransparent BIPV system change with the PV cell ratio, design, and electrical performance of the system. However, studies on the performance evaluation of SHGC for semitransparent BIPV systems are scarce. In this study, a method for evaluating the SHGC of a semitransparent BIPV system was investigated. The results indicate that SHGC values for the semi-transparent BIPV system should be studied for different operating conditions as indicated by maximum power point (MPP) and open circuit (OC) values. This is because the SHGC of the system changes with the power generation of the PV cells.

An Analysis of Real-Time Measured Solar Radiation and Daylight and Its Energy Implications for Semi-Transparent Building-Integrated Photovoltaic Façades

For analyzing cooling loads, day-lighting, and building-integrated photovoltaic (BIPV) systems, solar radiation and daylight illuminance data are required. However, these data are sparse. Furthermore, studies have shown that the energy potential of building-integrated photovoltaic (BIPV) systems for the entire building skin (BS) and unconventional orientations, such as east, west, and north need further exploration. Thus, this study presents findings from measured solar data and an energy analysis of semi-transparent BIPV. Firstly, solar radiation and daylight data measured from June 2019 to May 2020 in Hong Kong are presented. The analyzed solar-radiation data were used to determine the solar-energy potential of BIPV for BS and the four principal building orientations (i.e., N, E, S and W). With a simple analytical approach, the solar data’s building-energy implications for semi-transparent BIPV were assessed. The findings showed that the annual average horizontal global-, diffuse-, and direct-irradiance values were 291.8, 164.3, and 127.5 W/m2/day, respectively. Similarly, 120, 72, and 107 klux were obtained as the peak global, diffuse, and direct illuminance, respectively. Furthermore, the results show the potential of using BIPV on the entire BS in Hong Kong. It was also observed that a semi-transparent BIPV façade integrated with daylight-linked lighting controls could offer significant energy savings in electric lighting and cooling while also producing energy. In particular, BIPV façades with a large window-to-wall ratio (WWR) of 80% can provide an overall energy benefit of up to 7126 kWh.

Location of Photovoltaic Panels in the Building Envelope in Terms of Fire Safety

Abstract The increasing amount of energy consumed by the operation of buildings results in an increasing environmental burden. This has a direct impact on the innovation of renewable energy technology and its application in building industry. In accordance with the requirements of the “Europe 2020 Strategy” and “Europe 2030 Project”, the long-term goal is to achieve the maximum use of renewable energy sources in the buildings´ operation. One of the solutions is the building-integrated photovoltaic power plant. The paper analyses efficiency and incorporation of photovoltaic (PV) systems into the roofs and perimeter walls. PV systems are a renewable energy source used in the construction of zero energy buildings producing minimal environmental pollution. Semi-transparent building-integrated photovoltaics (BIPV) are one of the technologies that have the potential to increase the building´s energy efficiency as well as aesthetically complete the building´s design. The paper deals with material characteristics of PV panels in terms of the fire risk and definition of the fire hazardous area that arises during their combustion. It is focused on the incorporation of various types of PV technology into the facades and roofs, structural and material solutions of fire-dividing structures to which PV systems are fastened considering their location in the fire hazardous area. Based on the external fire simulations, conclusions in this paper bring the optimal position of PV systems in the building envelope in relation to fire open areas, fire lines and fire hazardous areas. The safety of firefighters during the intervention also depends on the position of PV systems. The case study presented in this paper uses a model solution to give the optimal position of PV systems in the building envelope considering the fire safety.

Energy Analysis of Semi-transparent Building Integrated Photovoltaic Window in Hyderabad, India Using Automated Parametric Simulations

In recent years, semi-transparent building-integrated photovoltaics (BIPV) technology has attracted attention for its renewable energy utilization. This research aims to develop a methodology for assessing the energy-saving potential of semi-transparent photovoltaic (STPV) window, which has a complex relationship with daylighting and air conditioning (AC) electricity consumption. A case study has been developed for the composite climate of Hyderabad, India. The study examines four commercially available single and double pane STPV windows and similar non-photovoltaic windows. For evaluation, an automated parametric simulation tool was developed to compute the net electricity consumption (NEC) for a representative model building with different window systems, and several window-to-wall ratios (WWR) and orientations. The result shows benefit in adopting the STPV window system across all directions and higher optimal WWR in STPV window as compared to normal window with the same opto-thermal characteristics.

Review of Transparent and Semi-Transparent Building-Integrated Photovoltaics for Fenestration Application Modeling in Building Simulations

Building-integrated photovoltaics (BIPV) have attracted interest due to their capacity to feasibly supply buildings with renewable power generation, helping to achieve net-zero or net-positive energy goals. BIPV systems include many different solutions depending on the application, the PV technology, and the envelope material they substitute. Among BIPV systems, the last two decades have seen a rising interest in transparent and semi-transparent BIPV (T- and ST-BIPV), which add features such as daylighting and solar radiation control. T- and ST-BIPV mainly consist of opaque PV cells embedded in fenestration systems (PV cladding), while most recent research considers semi-transparent PV cells (homogeneous PV glazing) with improved optical properties. The evaluation of T- and ST-BIPV systems in building performance is complex, as it needs to combine optical, thermal, electrical, and daylighting calculations. Therefore, adequate modeling tools are key to the development of these technologies. A literature review is presented on T- and ST-BIPV. First, the types of T- and ST-BIPV technologies present in the literature are summarized, highlighting the current trends. Then, the most common optical, thermal, and electrical models are described, finishing with a summary of the T-and ST-BIPV modeling capabilities of the most common building simulation tools. Regardless of the implemented modeling tools, the main challenges to be considered are the optical model, the inclusion of the PV output in the window energy balance, and the calculation of the cell temperature for the correct assessment of cell efficiency. Modeling research mostly considers conventional PV (Si-based PV and thin-film) technologies, and research studies rarely address the cost evaluation of these T- and ST-BIPV systems.

Dynamic coupling of a heat transfer model and whole building simulation for a novel cadmium telluride-based vacuum photovoltaic glazing

In recent years, building-integrated photovoltaic (BIPV) windows have drawn attention from both the building industry and academic society. As a multifunctional application of photovoltaic technologies, semi-transparent BIPV panels can generate renewable energy in situ and play the role of typical windows. Unlike those PV windows made by crystalline silicon solar cells, the semi-transparent cadmium telluride (CdTe) photovoltaic (STPV) windows can admit natural daylight with a certain degree of transmittance without any shading. Therefore, it can provide better visual comfort to occupants. However, typical BIPV windows are not suitable for cold regions due to inadequate thermal insulation. To improve the thermal performance of the BIPV glazing, a novel CdTe-based vacuum PV glazing (VPV) is developed with a highly integrated three-layer structure. To fully understand the dynamic heat transfer process and thermal behaviour, this study developed a mathematical heat transfer model for the CdTe-based VPV. The dynamic heat transfer model was validated with laboratory tests. To investigate the whole year performance of the VPV, a dynamic coupling approach is proposed to integrate the transit heat transfer model with a whole building simulation model conducted by EnergyPlus to obtain more accurate simulation results. Comparing the simulation results of the decoupled and coupled methods, it was found that EnergyPlus tends to slightly underestimate the cooling energy consumption and overestimate the heating energy consumption to a considerable level. Therefore, the dynamic coupling approach is more reliable than the EnergyPlus model, especially in the heating-dominated regions.

A Comprehensive Review of the Indoor Visual Comfort Indices and the Effect of Semi-Transparent Building-Integrated Photovoltaics on the Visual Comfort Indoors

A Comprehensive Review of the Indoor Visual Comfort Indices and the Effect of Semi-Transparent Building-Integrated Photovoltaics on the Visual Comfort Indoors

Visual Comfort Analysis of Semi-Transparent Perovskite Based Building Integrated Photovoltaic Window for Hot Desert Climate (Riyadh, Saudi Arabia)

Buildings consume considerable amount of energy to maintain comfortable interior. By allowing daylight, visual comfort inside a building is possible which can enhance the occupant’s health, mood and cognitive performance. However, traditional highly transparent windows should be replaced with semitransparent type window to attain a comfortable daylight inside a building. Evaluation of visual comfort includes both daylight glare and colour comfort analysis. Building integrated photovoltaic (BIPV) type windows are promising systems and can possess a range of semitransparent levels depending on the type of PV used. In this work, the semitransparent Perovskite BIPV windows was investigated by employing daylight glare analysis for an office building located in Riyadh, KSA and three wavelength dependent transmission spectra for colour comfort analysis. The results showed that the transmissions range between 50–70% was optimum for the comfortable daylight for south facing vertical pane BPV-windows. However, excellent colour comfort was attained for the transmission range of 90% which provided glare issues. Colour comfort for 20% transparent Perovskite was compared with contemporary other type of PV which clearly indicated that wavelength dependent transmittance is stronger over single value transmittance.

17.1 %‐Efficient Eco‐Compatible Organic Solar Cells from a Dissymmetric 3D Network Acceptor

AbstractTo elevate the performance of polymer solar cells (PSC) processed by non‐halogenated solvents, a dissymmetric fused‐ring acceptor BTIC‐2Cl‐γCF3 with chlorine and trifluoromethyl end groups has been designed and synthesized. X‐ray crystallographic data suggests that BTIC‐2Cl‐γCF3 has a 3D network packing structure as a result of H‐ and J‐aggregations between adjacent molecules, which will strengthen its charge transport as an acceptor material. When PBDB‐TF was used as a donor, the toluene‐processed binary device realized a high power conversion efficiency (PCE) of 16.31 %, which improved to 17.12 % when PC71ThBM was added as the third component. Its efficiency of over 17 % is currently the highest among polymer solar cells processed by non‐halogenated solvents. Compared to its symmetric counterparts BTIC‐4Cl and BTIC‐CF3‐γ, the dissymmetric BTIC‐2Cl‐γCF3 integrates their merits, and has optimized the molecular aggregations with excellent storage and photo‐stability, and also extending the maximum absorption peak in film to 852 nm. The devices exhibit good transparency indicating a potential utilization in semi‐transparent building integrated photovoltaics (ST‐BIPV).

17.1 %-Efficient Eco-Compatible Organic Solar Cells from a Dissymmetric 3D Network Acceptor.

To elevate the performance of polymer solar cells (PSC) processed by non-halogenated solvents, a dissymmetric fused-ring acceptor BTIC-2Cl-γCF3 with chlorine and trifluoromethyl end groups has been designed and synthesized. X-ray crystallographic data suggests that BTIC-2Cl-γCF3 has a 3D network packing structure as a result of H- and J-aggregations between adjacent molecules, which will strengthen its charge transport as an acceptor material. When PBDB-TF was used as a donor, the toluene-processed binary device realized a high power conversion efficiency (PCE) of 16.31 %, which improved to 17.12 % when PC71ThBM was added as the third component. Its efficiency of over 17 % is currently the highest among polymer solar cells processed by non-halogenated solvents. Compared to its symmetric counterparts BTIC-4Cl and BTIC-CF3 -γ, the dissymmetric BTIC-2Cl-γCF3 integrates their merits, and has optimized the molecular aggregations with excellent storage and photo-stability, and also extending the maximum absorption peak in film to 852 nm. The devices exhibit good transparency indicating a potential utilization in semi-transparent building integrated photovoltaics (ST-BIPV).

Experimental Study on Energy Efficiency of Multi-Functional BIPV Glazed Façade Structure during Heating Season

Building integrated photovoltaics (BIPV) is technology that can significantly increase the share of renewable energy in final energy supply and are one of essential technologies for the nearly zero-energy buildings (nZEB), new build and refurbished. In the article (a) an experimental semitransparent BIPV glazed façade structure with 60% of PV cell coverage is shown; (b) energy efficiency indicators were developed based on identified impact parameters using experimental data; and (c) multi-parametric models of electricity generation, preheating of air for space ventilation, and dynamic thermal insulation features that enable prediction of solar energy utilization in different climate conditions are shown. The modeled efficiency of electricity production of BIPV was in the range between 8% and 9.5% at daily solar radiation above 1500 Wh/day, while low impact of outdoor air temperature and ventilation air flow rate on PV cell cooling was noticed. Between 35% and 75% of daily solar radiation can be utilized by preheating the air for space ventilation, and 4.5% to 7.5% of daily solar radiation can be utilized in the form of heat gains through opaque envelope walls.

Method to improve performance of building integrated photovoltaic thermal system having optimum tilt and facing directions

A building integrated photovoltaic (BIPV) system can be installed at optimum tilt and orientation angle to maximize the electrical output. PV output is negatively correlated with the increase in the PV panel temperature. This paper aims at investigating the influence of water flow over the BIPV roof of a two-storied single-family house on the performance of the proposed optimally tilted semi-transparent BIPV thermal system having different facing directions. The periodic nature of insolation, ambient air temperature, BIPV cell temperature, slab temperature, water flow temperature and room temperature have been considered while solving energy equilibrium differential equations. The insolation values used in the energy equilibrium equations are computed employing periodic HDKR (Hay, Davies, Klucher and Reindl) model, which is based on anisotropic sky concept. Results indicate that the average BIPV cell temperature is reduced annually by approximately 10 °C and efficiency is enhanced by 6% when a water flow rate of 1.1 kg s−1 is provided over the BIPV roof. It is also observed that on the most critical day of the year, the temperature of outlet water is 11.5 °C higher than that of inlet water temperature which resulted in 4 kW extraction of exergy.

Thermal performance of semitransparent CdTe BIPV window at temperate climate

Semi-transparent photovoltaic (PV) technology is attractive for building-integrated photovoltaics (BIPV) due to its ability to lower the admitted solar heat gain, to control the penetrating daylight and to generate onsite benevolent direct current power. In this work, semi-transparent cadmium telluride (CdTe) based BIPV as window was experimentally characterized using outdoor test cell in temperate UK climate. Spectral measurement confirmed its 25% visible transmission and 12% solar transmission. Thermal transmission and solar heat gain coefficient were calculated from measured thermal data. Overall heat transfer coefficient (U-value) of 2.7 W/m2 K was found for outdoor and indoor characterization of CdTe BIPV window. A comparison with single glazed window has been produced emphasis its feasibility for Facade buildings.

Semitransparent Building-Integrated Photovoltaic: Review on Energy Performance, Challenges, and Future Potential

Buildings consume large amounts of energy, and their transformation from energy users to producers has attracted increasing interest in the quest to help optimize the energy share, increasing energy efficiency and environmental protection. The use of energy-efficient materials is among the proposed approaches to increase the building’s energy balance, thus increasing the performance of building facades. Semitransparent building-integrated photovoltaic (BIPV), being one of the technologies with the potential to increase a building’s energy efficiency, is considered as a feasible method for renewable power generation to help buildings meet their own load, thus serving dual purposes. Semitransparent BIPV integration into buildings not only displaces conventional building facade materials but also simultaneously generates energy while retaining traditional functional roles. The awareness in improving building energy efficiency has increased as well as the awareness in promoting the use of clean or renewable energy technologies. In this study, semitransparent BIPV technology is reviewed in terms of energy generation, challenges, and ways to address limitations which can be used as a reference for the BIPV stakeholders.

Upconversion-Assisted Dual-Band Luminescent Solar Concentrator Coupled for High Power Conversion Efficiency Photovoltaic Systems

A luminescent solar concentrator (LSC)-based photovoltaic (PV) system, consisting of an LSC panel that harvests light and an edge-mounted solar cell that produces electricity using the photoluminescent light, is promising for semitransparent building-integrated photovoltaics (BIPVs). Here, we demonstrate a highly efficient and highly semitransparent LSC-PVs capable of harvesting dual wavelength bands. We used a triplet–triplet annihilation-based photon upconversion (UC) LSC that luminesce high energy green light by absorbing low energy red light, as well as downshift LSC that luminesce green light by absorbing ultraviolet light. The luminescent light concentrated from the two LSCs is absorbed by a dye-sensitized solar cell (DSSC) having a high extinction coefficient at this wavelength. Our optimized dual band LSC-PV exhibited 27% higher power conversion efficiency than the LSC-PV that absorb a single wavelength band. With respect to practical applications, the dual band LSC-DSSCs were fabricated in the fo...

Investigation on the energy performance of a novel semi-transparent BIPV system integrated with vacuum glazing

The development of vacuum glazed windows in recent decades has provided a foreseeable energy saving opportunity in the design of low-energy consumption buildings and the application of building integrated photovoltaic (BIPV) has experienced rapid development for application in buildings. This paper reports our investigations on the combinations of the vacuum glazing and BIPV integration. Semi-transparent photovoltaic windows can convert solar energy into electricity, but most of absorbed solar heat is transferred into indoor environment which becomes additional cooling load. The proposed vacuum photovoltaic insulated glass unit (VPV IGU) in this paper combines vacuum glazing and solar photovoltaic technologies, which can utilize solar energy and reduce cooling load of buildings at the same time. Various experiments were conducted to evaluate the thermal performance and determine the key characteristics of the VPV IGU in this study. It was found that the VPV IGU can achieve very low total heat gain coefficient (U-value) of around 1.5 W/(m2 K) and block most of undesired solar radiation from penetrating through the window. Compared with a common double-pane glass sheet, the vacuum PV glazing can maintain the indoor environment at a relatively low temperature due to its excellent thermal insulation performance in summer. A detailed simulation study has been conducted by EnergyPlus and Berkeley Lab WINDOW. The simulation work has indicated that the cooling load can be reduced by 14.2% by a south-oriented VPV IGU compared with common glazing products while power generation is not compromised compared with normal BIPV systems. The results show that the application of the VPV IGU has a huge energy saving potential and can minimize the drawback of common PV insulating glass units.

Energy payback time and life-cycle cost analysis of building integrated photovoltaic thermal system influenced by adverse effect of shadow

This article presents the Life-cycle Cost Analysis (LCCA) and Energy Payback Time (EPBT) of Building Integrated Photovoltaic (BIPV) thermal systems with reference to Indian weather conditions. The insolation and optimum tilt angle values are based on modified HDKR (Hay, Davies, Klucher, Reindl) model which accounts for hourly insolation considering shadow effect. Electrical and thermal performance of semi-transparent BIPV thermal system is evaluated for different mass flow rate of air through the duct with series combinations. EPBT and LCC of BIPV thermal systems are evaluated for three different orientations of PV modules i.e., optimum tilt angle, horizontal and vertical orientations by considering adverse effect of shadow. The cost of energy produced by the system ranges between 1.61 and 3.61 US$/kW h depending on the climatic conditions of the place and the EPBT of the system is found to be ranging between 7.30 years and 16.9 years which is lower than the expected service life (30 years) of the modules. Both LCCA and EPBT are increased because of shadow effect but these values are decreased due to air flow through the duct which is provided below the PV module. Thus, the BIPV thermal system is viable both financially and environmentally and this may be used as a major renewable energy source. A contour map of EPBT and LCA is presented for all state capital of India for BIPV thermal system oriented with optimum tilt angle.

Energy benefits from semi-transparent BIPV window and daylight-dimming systems for IECC code-compliance residential buildings in hot and humid climates

Abstract Interest in semi-transparent solar cell window systems, also called building integrated photovoltaic (BIPV) windows, has increased worldwide because the windows generate electricity and also provide natural light transmission. This study evaluates the potential energy benefits of integrating semi-transparent solar cell windows and daylight-dimming systems for a 2009 International Energy Conservation Code (IECC) code-compliant residential building in a hot and humid climate. This study used whole-building energy simulation models, a DOE-2.1e BIPV window module created for this study, and an existing daylight-dimming system module. Based on the simulation results, peak demand, energy use, and electricity production from each orientation (east-, west-, south-, and north-facing) were all analyzed. The south-facing window showed the greatest potential to generate electric power and reduce cooling loads/use, whereas the east-facing window resulted in the largest annual lighting energy savings. As compared to the code-compliant base-case model, the BIPV windows showed great potential for energy savings: about 12–21% in annual energy use, and 14–26% in peak cooling demand. In addition, the parametric study varying the window-to-wall ratio (WWR) with the BIPV window resulted that the larger BIPV window provided more savings in annual total energy use.

Performance of building integrated photovoltaic thermal systems for the panels installed at optimum tilt angle

Building integrated photovoltaic (BIPV) thermal technology is an emerging area of recent development which can be implemented to make net zero energy building. In this technology, PV panels serve as structural elements and air duct is provided below the PV panel for air flow in order to increase both electrical and thermal efficiencies. In this study, HDKR (Hay, Davies, Klucher, Reindl) model based insolation corresponding to optimum tilt angle of the panel is used in energy equilibrium equation for developing mathematical model of BIPV thermal system. Different mass flow rate of air through the duct with series combination is taken for evaluating the electrical and thermal performance of both semi-transparent and opaque BIPV thermal system installed at optimum tilt angle. Both electrical and thermal output increases with increase in mass flow rate and the output converges at certain value. The results also indicate that the semi-transparent BIPV thermal systems are more efficient than opaque BIPV thermal system for all values of tilt angle of PV panel. Room temperature of BIPV thermal system having mass flow rate of 1 kg/s through the duct are presented for different state capital of India at their respective optimum tilt angle.

Improving the Performance of a Semitransparent BIPV by Using High-Reflectivity Heat Insulation Film

Currently, standard semitransparent photovoltaic (PV) modules can largely replace architectural glass installed in the windows, skylights, and facade of a building. Their main features are power generation and transparency, as well as possessing a heat insulating effect. Through heat insulation solar glass (HISG) encapsulation technology, this study improved the structure of a typical semitransparent PV module and explored the use of three types of high-reflectivity heat insulation films to form the HISG building-integrated photovoltaics (BIPV) systems. Subsequently, the authors analyzed the influence of HISG structures on the optical, thermal, and power generation performance of the original semitransparent PV module and the degree to which enhanced performance is possible. The experimental results indicated that the heat insulation performance and power generation of HISGs were both improved. Selecting an appropriate heat insulation film so that a larger amount of reflective solar radiation is absorbed by the back side of the HISG can yield greater enhancement of power generation. The numerical results conducted in this study also indicated that HISG BIPV system not only provides the passive energy needed for power loading in a building, but also decreases the energy consumption of the HVAC system in subtropical and temperate regions.