Solar power windows: Connecting scientific advances to market signals

Recent materials advances have enabled researchers to envision and develop highly efficient, partially transparent photovoltaic (PV) prototypes, exposing a potentially large and untapped market for solar energy: building integrated (BI) solar powered windows. In this perspective, we assess the case for market deployment of BIPV windows, specifically intended for commercial U.S. high-rise buildings. Research and development on solar powered windows has been predicated on the hypothesis that sunlight-to-electrical power conversion efficiency (PCE) and device cost per unit area are the key figures of merit that might drive market adoption. Here we investigate the market landscape and desirability for solar powered windows by identifying and evaluating the customer needs for the commercial high-rise building window market. In the course of this assessment, we performed 150 interviews with experts across the value chain for commercial windows. We found that the market forces are complicated by a misalignment of incentives between the end users of BIPV windows and the key decision makers for building projects that could incorporate this technology. Our assessment leads us to frame new figures of merit for BIPV windows that address the underlying needs of prospective customers as well as technical metrics for energy generation. We finally discuss one possible direction for BIPV window technology in which photovoltaics are integrated with switchable windows. Here, the integrated PV converts visible and infrared light transmission into useable electricity enabling standalone, self-powered active windows that can potentially address market needs for smart windows, thereby enabling a pathway for BIPV window deployment

Carbon counter electrode mesoscopic ambient processed & characterised perovskite for adaptive BIPV fenestration

This is the final version. Available on open access from Elsevier via the DOI in this recordIn this work, carbon counter electrode perovskite was developed at the laboratory environment and building integrated photovoltaic (BIPV) window application using this material was investigated. At 1 sun (1000 W/m2) continuous incident solar radiation from an indoor simulator, this particular type of perovskite had 8.13% efficiency. Average solar and visible transmittance of this perovskite BIPV window was 30% and 20% respectively. Solar heat gain for different incident angle was evaluated for this perovskite glazing. For the University of Exeter, Penryn (50.16° N, 5.10° W) UK location, solar heat gain coefficient (SHGC) or solar factor (SF) varied from 0.14 to 0.33 at the highest and lowest incident angle respectively. Overall heat transfer coefficient (U-value) of 5.6 W/m2K was realized for this glazing while calculation was performed by window performance analysis programme, WINDOW 6.0. Daylight glare control potential of this glazing was investigated using subjective rating methods and comfortable daylight penetrated through glazing in a typical cloudy condition. Colour properties of this material showed that 20% visible transmittance is threshold limit, and below this value colour or visual comfort using this glazing is not achievable.Engineering and Physical Sciences Research Council (EPSRC

Color Comfort Evaluation of Dye-Sensitized Solar Cell (DSSC) Based Building-Integrated Photovoltaic (BIPV) Glazing after 2 Years of Ambient Exposure

This is the final version. Available on open access from the American Chemical Society via the DOI in this recordData availability: in support of open access research, all underlying article materials (data, models) can be accessed upon request via email to the corresponding author.Transmitted external daylight through semitransparent type building integrated photovoltaic (BIPV) windows can alter the visible daylight spectrum and render different colors, which can have an impact on building's occupants' comfort. Color properties are defined by the color rendering index (CRI) and correlated color temperature (CCT). In this work, a less explored color comfort analysis of N719 dye-sensitized TiO2 based dye-sensitized solar cell (DSSCs) BIPV window was characterized and analyzed after 2 years of ambient exposure. Three different DSSCs were fabricated by varying TiO2 thickness. The reduced average visible transmission was observed while enhanced color properties were obtained for all three DSSCs. This study could pave way to future developments in the area of BIPV technology using DSSC in terms of their long-term exploration.Engineering and Physical Sciences Research Council (EPSRC

Realization of poly (methyl methacrylate) encapsulated solution-processed carbon-based solar cells: emerging candidate for buildings’ comfort

This is the final version. Available from the publisher via the DOI in this record.The self-assembling characteristics allow carbon nanomaterials to be readily explored, environmentally benign, solution-processed, low-cost, and efficient solar light-harvesting materials. An effort has been made to replace the regular photovoltaic device’s electrodes by different carbon allotropebased electrodes. Sequential fabrication of carbon solar cells (SCs) was performed under ambient conditions, where FTO/ graphene/single-walled carbon nanotubes/graphene quantum dotsfullerene/carbon black paste layers were assembled with poly- (methyl methacrylate) (PMMA) as an encapsulating layer. The PMMA layer provides significant improvement toward the entry of water vapor, hence leading to stability up to 1000 h. The photoconversion efficiency of the PMMA-encapsulated carbon SC has been increased by ∼105% and the stability decreased by only ∼10% after 1000 h of exposure to environmental moisture. Besides, the building integrated photovoltaic window properties achieved using this carbon SC were also investigated by using the color rendering index and the correlated color temperature, which can have an impact on the buildings’ occupants’ comfort. This study leads to an extensive integration to improve carbon-based materials because of their effective and useful but less-explored characteristics suitable for potential photovoltaic applicationsEngineering and Physical Sciences Research Council (EPSRC

Renewable Energy and Energy Saving: Worldwide Research Trends

Climate change mitigation and adaptation are key challenges of the 21st century. These challenges include global energy consumption and dependence on fossil fuels, which are addressed in global energy policies. About two-thirds of global greenhouse gas emissions are linked to the burning of fossil fuels used for heating, electricity, transport, and industry. Therefore, the world is looking for the most reliable, cost-effective, and environmentally friendly energy sources coupled with energy saving, which is a clean and low-cost solution to the growing demand for energy. As a clear example of this, cities are integrating renewable energies into their smart city plans. This book aims to advance the contribution of the use of renewable energies and energy saving in order to achieve a more sustainable world

Performance of office building integrated photovoltaic for windows under semi-arid climate in Algeria

Building integrated photovoltaic (BIPV) has become the most significant alternative form of renewable energy for producing clean energy and to protect the environment. In Algeria, some problems arise due to the high energy consumption levels of building sector. Large amounts of this energy are lost through the external envelope façade, because of poor window design. Therefore, this research aimed to investigate the optimum BIPV windows performance for overall energy consumption (OEC) in typical office buildings in the semi-arid climate. Field measurements on a tested office building were carried out during the spring and summer seasons for the calibration and validation of Energy-plus and Integrated Environment Solution Virtual Environment (IES-VE) software. The data was analysed and used to develop a model for (OEC) simulation. The results of the investigation from the site measurements show that the BIPV window application provides a sufficient quantity of uniform daylight with only 20% Visible Light Transmittance (VLT), plus a comfortable indoor temperature and a considerable amount of clean energy production. The base-model and nine commercially-available BIPV modules, with different Window Wall Ratio (WWR), cardinal orientation and tilt angles were applied in an extensive simulation exercise. The simulation was carried out using Energy-plus to evaluate the energy generated through simple and equivalent one-diode models. The thermal performance used the Ideal load Air System (ILAS) model. In addition to IES-VE for the assessment of visual comfort and daylighting performance, through a combination of daylight control method, Useful Daylight Illuminance (UDI) and CEI glare index (CGI) were done. The results from this study revealed that the optimum BIPV window design differentiates in each orientation; which is the double glazing PV modules (A) with medium WWR and 20% VLT in the Southern facade, 30% VLT toward the East-West axis. Meanwhile, the North orientation is not suitable the application of BIPV window. The Maximum energy saving can be obtained with a 60% toward the South orientation by double glazing PV module (D). On the other hand, the PV modules minimize significantly the glare index comparing the base-model. The result established that the energy output percentages in a 3D model can be used by architects and designers in the early stages of design. Thus, the adoption of optimum BIPV window shows a significant improvement of the overall energy saving and visual comfort to deem them as an essential application in the semi-arid climate

Numerical evaluation of an optically switchable photovoltaic glazing system for passive daylighting control and energy-efficient building design

Adaptive control of solar heat gain and visible light transmission through windows is perceived to be a potential measure for enhancing energy conservation and visual comfort in buildings. In this study, a novel versatile window, named Building Integrated Photovoltaic (BIPV) smart window, was proposed to offer simultaneous improvement of daylighting control, on-site electricity generation and building energy efficiency, compared to traditional BIPV windows with static optical properties. The key components of the proposed system include an optically switchable thermotropic layer made of Hydroxypropyl Cellulose (HPC) hydrogel, crystalline-silicon photovoltaic cells, clear glass and low-emissivity (low-e) glass covers. The thermotropic layer can respond to heat by autonomously changing its visible and near-infrared optical properties, with which the amount of solar radiation into building spaces can be manipulated and thus the risks of excessive solar heating and illumination can be prevented. Apart from excellent solar modulation, the BIPV smart window can collect a proportion of the light scattered from the thermotropic layer and concentrate it onto the integrated PV cells for extra electricity generation. An innovative methodology has been proposed to predict the optical, thermal and electrical properties of the BIPV smart window under varying ambient conditions. Numerical simulations have been carried out in EnergyPlus to predict the window's performance when it is applied to an office-type environment in the climate of Nottingham, the UK. The influence of different window design scenarios, in terms of Window-to-Wall Ratio (WWR), orientation and transition temperature, has been investigated. It was found that using the BIPV smart window can achieve an annual energy saving of 36.6% but also a more comfortable indoor luminous environment, compared to the counterpart BIPV window (with no thermotropic layer integrated), when installed in the south-oriented office with a WWR of 25%

Do Building Integrated Photovoltaic (BIPV) windows propose a promising solution for the transition toward zero energy buildings? A review

This is the final version. Available on open access from Elsevier via the DOI in this recordData availability: No data was used for the research described in the article.BIPV windows are the most suitable alternative to conventional windows currently available today. They offer thermal insulation and can generate electricity from the embedded solar cells within their structure while also maintaining the practicality of conventional windows. Different types of BIPV windows will be reviewed in this paper, followed by an assessment of the energy-saving potential, optimal orientation, solar cell technology, Koppen climate impact, and application for each type of BIPV window. From the findings, it was evident that ventilated double BIPV windows had the highest energy-saving potential as well as being the BIPV system that can adapt the most to different Koppen climates. The optimal orientation was the south-facing façade which consumed the least amount of energy while also generating the highest amount of electricity from PV. Amorphous silicon is the most popular solar cell technology in BIPV studies due to its performance however they do have disadvantages. Application of BIPV windows includes BIPV-PCM systems and switchable glazing for smart window technology. Large-scale development integrated with BIPV windows can have a huge influence on meeting ZEB targets. Limitations in the study were observed by limited studies on vacuum BIPV glazing, and limited studies on a variety of Koppen climate classes