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 systemsThis work has received funding from the European Union H2020 Framework Programme under Grant Agreement no. 826002 (Tech4Win)Postprint (published version

Process integration of thermal energy storage systems – Evaluation methodology and case studies

As a key tool for decarbonization, thermal energy storage systems integrated into processes can address issues related to energy efficiency and process flexibility, improve utilization of renewable energy resources and thus reduce greenhouse gas emissions. However, integration of these systems is dominated by the variety of potential processes in which the storage technologies can be deployed as well as the various benefits they deliver. Therefore, the requirements for thermal energy storage systems vary greatly depending on the chosen application, just as the systems themselves have different capabilities depending on their technical principles. This paper addresses this issue by developing a systematic methodology that approaches the challenge of characterizing and evaluating thermal energy storage systems in different applications in three concrete steps. To begin, a set of guidelines for process analysis has been created to disclose process requirements for storage integration. The methodology continues by explicitly defining the system boundary of a thermal energy storage system, as well as addressing technical and economic parameters. Finally, the approach concludes by determining the benefit of an integrated thermal energy storage system to an application and examines how key performance indicators vary based on the perspectives of different stakeholders. Within this work, the methodology is then applied to two case studies of high-temperature storage in concentrating solar power and cogeneration plants. Also introduced are the concepts of retrofit and greenfield applications, which are used to clarify differences between integrated storage systems. The paper shows how such a systematic approach can be used to consistently analyse processes for storage integration, facilitate comparison between thermal energy storage systems integrated into processes across applications and finally grasp how different interests perceive the benefits of the integrated storage system. This type of systematic methodology for technology integration has not been previously developed and as such, is a novel and important contribution to the thermal energy storage community. In the long term, this work builds the basis for a discussion on benefits of thermal energy storage system integration with diverse stakeholders including storage system designers, process owners and policy makers.This work has been partially funded by the German Federal Ministry of Economic Affairs and Energy in the framework of the TESIN project (03ESP011) and the THESAN project (03ET1297). This work has also been partially funded by the Ministerio de Economía y Competitividad de España (ENE2015-64117-C5-1-R (MINECO/FEDER)). The authors at the University of Lleida would like to thank the Catalan Government for the quality accreditation given to their research group (2017 SGR 1537). GREA is certified agent TECNIO in the category of technology developers from the Government of Catalonia. Jaume Gasia would like to thank the Departament d'Universitats, Recerca i Societat de la Informació de la Generalitat de Catalunya for his research fellowship (2018 FI_B2 00100). The authors are responsible for the content of this publication