Architectural Design Strategies for Building-Integrated Photovoltaics in residential building renovation processes

Tomorrow's European cities are already largely built, as much of the existing building stock ¿ with a low level of energy performance ¿ will still be standing in 2050. Urban renewal processes therefore play an essential role towards their sustainable transition. In this context, Building-integrated photovoltaic (BIPV) systems can potentially provide a crucial contribution to achieve current energy and mid- to long-term carbon targets based on the 2¿000-Watt society concept in Switzerland, and to fulfil the objectives of the energy turnaround for 2050. Functioning both as envelope material and electricity generator, BIPV systems can simultaneously reduce the use of fossil fuels and greenhouse gases (GHG) emissions, while providing savings in materials and electricity costs. These are precisely the objectives of most European energy directives, from zero- to positive-energy buildings. However, despite continuous technological progress and increasingly favourable economic conditions, the significant assets of BIPV remain broadly undervalued in the current practice. Various obstacles related among others to technology choice, low demand (which induces small volume production of BIPV products), and lack of information and of aesthetically convincing renovation examples, tend to increase the costs and prevent the acceptance of BIPV solutions. Considering that BIPV can be integrated into the design process, but in a case-specific rather than in a systematic way, this thesis aims at offering support to stakeholders ¿ especially architects ¿ involved in the design process of renovation projects. Focusing on an integrated architectural design process for addressing renovation projects of residential buildings, the approach involves four main phases: (1) building stock analysis to identify representative (archetypal) situations, (2) detailed analysis of real case studies, (3) architectural design of different renovation scenarios using BIPV strategies, and (4) multi-criteria assessment of each scenario. The concrete contributions of this thesis are twofold. First, a set of integrated design strategies ¿ illustrated through real case studies ¿ is defined to promote the integration of BIPV in urban renewal processes. It integrates: (i) passive strategies, to improve the envelope through low embodied-energy materials and construction systems, (ii) BIPV strategies, using innovative photovoltaic products as a new material for façades and roofs, and (iii) active strategies, adapting heating, ventilation, and air conditioning (HVAC) systems to improve the efficiency of the BIPV installation and reduce the dependence on feed-in-tariffs to ensure the profitability of investments. Second, a multi-criteria assessment methodology is developed to compare the different intervention scenarios, based on a qualitative and quantitative approach. The proposed workflow thus allows comparing different design solutions in terms of BIPV performance, final energy balance, Life-Cycle Analysis (LCA) and Cost (LCC) of the whole renovation process. This approach shall provide architects and engineers with advanced BIPV renovation strategies that depend on the building typology, the architectural design goals, and the level of intervention, thus supporting and inspiring them towards a low-carbon built environment

Towards integrated design strategies for implementing BIPV systems into urban renewal processes: first case study in Neuchâtel (Switzerland)

In view of the importance of urban renewal processes, building-integrated photovoltaic (BIPV) systems can potentially provide a crucial response to the challenges of the energy turnaround. Functioning both as envelope material and electricity generator, they can simultaneously reduce the use of fossil fuels and greenhouse gases (GHG) emissions while providing savings in materials and electricity costs. These are precisely the objectives of most European energy directives, from zero- to positive-energy buildings. In Switzerland for instance, one way to achieve the objectives of the “Energy strategy 2050” is to install PV systems to cover 1/3 of the annual electricity demand. However, despite continuous technological and economic progress, the significant assets of BIPV remain broadly undervalued in the current practice. Various obstacles (technology choice, small volumes, lack of information and good examples, etc.) tend to increase the costs and reduce the acceptance of BIPV solutions. The present paper is an integral part of an interdisciplinary research project. Focusing on the architectural design issues, it presents the first results of a representative case study carried out in the city of Neuchâtel (Switzerland). The approach involves four main phases (Fig.1): (i) archetypes identification, (ii) building detailed analysis, (iii) development of architectural renewal design scenarios, and (iv) multi-criteria assessment of each scenario (energy consumption, electricity production, cost-effectiveness, and Life-Cycle Analysis). The application of the proposed approach on a case study allows us to initiate the first step towards a holistic and reliable multi-criteria comparison methodology for BIPV-adapted solutions in urban renewal design processes in the Swiss context.Peer ReviewedPostprint (published version

Integrated design strategies for renovation projects with building-integrated

As tomorrow’s cities are already largely built, and as many of their buildings have a low energy performance level, urban renewal processes are essential for the sustainable development of European cities. In this context, Building-Integrated Photovoltaic (BIPV) systems, using innovative PV products as new construction material for façades and roofs, can potentially provide a crucial response for achieving long-term carbon targets. This paper presents an integrated architectural design process for addressing renovation projects. Presented through a comparison of two case studies on archetypal residential buildings from the 1900s and 1970s in Neuchâtel (Switzerland), this approach includes the design of different renovation scenarios integrating passive, active and BIPV strategies. An optimization of the potential BIPV (or active) surfaces based on the annual irradiation threshold is conducted to maximize self-consumption (SC) and self-sufficiency (SS). The scenarios, before and after this optimization-based refinement, are evaluated in terms of Life-Cycle Assessment and Cost. Results demonstrate the importance of the optimization to ensure the cost-effectiveness of the strategy and increase the independence from energy suppliers. The main outcome provides, to architects and engineers, advanced BIPV renovation strategies along with results from a multi-criteria evaluation that are crucial for reaching carbon neutralityPostprint (published version

Architectural design scenarios with building-integrated photovoltaic solutions in renovation processes: case study in Neuchâtel (Switzerland)

In view of the importance of urban renewal processes, building-integrated photovoltaic (BIPV) systems can potentially provide a crucial response to the energy turnaround challenges. Functioning both as envelope material and electricity generator, they can simultaneously reduce the use of fossil fuels and greenhouse gases emissions while providing savings in materials and electricity costs. However, despite continuous technological and economic progress, the assets of BIPV remain undervalued in the current practice. Various obstacles (technology choice, small volumes, lack of information and good examples) tend to increase the costs and reduce the project acceptance. To overcome these barriers, an interdisciplinary research project developed an approach based on four main phases: 1) selection of archetypal residential buildings, 2) detailed analysis of the buildings, 3) development of renewal design scenarios and 4) multi-criteria assessment of each scenario. Focusing on the architectural-scale, this paper presents design strategies with BIPV solutions of a representative case study realized in Neuchâtel (Switzerland). A multi-criteria assessment of the proposed design scenarios allows comparing the different strategies. It highlights the influence of the design decisions on the final performances, helping us to move towards an optimization of the BIPV surfaces in order to maximize self-consumption regarding the building consumption profile.Postprint (published version

Influence of design-decisions on the energy performance of renovation projects with building-integrated photovoltaics: results for a 1968 residential archetype in Neuchâtel (Switzerland)

The renovation of existing buildings is one of the priorities of western countries and needs to be promoted to increase the current low renovation rate, estimated to be of 0.6% per year in the European and Swiss contexts. In parallel, the implementation of building-integrated photovoltaic (BIPV) elements during the renovation process can provide a crucial response to achieve the 2050 targets in terms of greenhouse gas (GHG) emissions and energy savings. In this context, architects, designers and engineers have a key role in achieving these objectives, mainly because they are responsible for the design decisions during the development of the projects, especially during the early-design phase when the most influential decisions are taken. Through a real-case study built in 1968, this research shows how certain design-decisions in renovation processes can affect or compromise the final performance of the building from a global life-cycle and multi-criteria approach. Life-Cycle Analysis (LCA) and Cost (LCC) results show the importance of not losing the opportunity to go beyond current practices when a building needs to be renovated and highlight the necessity to take into consideration BIPV strategies to guarantee both economic and environmental targets.Postprint (published version

Active surfaces selection method for building-integrated photovoltaics (BIPV) in renovation projects based on self-consumption and self-sufficiency

In light of the Paris Agreement's objectives and the related European and Swiss goals of decarbonising the built environment, the importance, relevance, and potential benefits of integrating Building-Integrated Photovoltaic (BIPV) within building renovation processes are acknowledged. Functioning both as envelope material and on-site electricity generator, BIPV can simultaneously reduce the use of fossil fuels and greenhouse gas emissions. Motivated by the current barriers and misconceptions that withhold a widespread integration of BIPV, particularly regarding financial implications and solar exposure levels that are believed to be unfavourable, this paper aims at bringing new knowledge and a rigorous and adaptable method to inform decision-making and promote the use of BIPV in urban renewal processes. Focusing on the architectural design, we here present a methodology to select active (BIPV) surfaces during the retrofitting process based on a trade-off between the self-consumption (SC) and self-sufficiency (SS) of a building. The approach consists in iteratively identifying surfaces that achieve a varying annual irradiation value (threshold). It also includes the evaluation of the effect of electricity storage systems. The methodology and the results of its application are presented through the comparison of two case studies in Neuchâtel (Switzerland). The outcomes of this new approach for addressing building renovation projects in the urban context can help architects, designers and engineers to better size the installation and the repartition of active surfaces in the renovated thermal envelope. Results show that it is important to take into account a larger range of irradiation levels to choose the active surfaces, especially in high-rise buildings with a greater proportion of façade than roof. In such cases, the irradiation threshold can vary between 600 and 800 kWh/m2•year depending on the strategy adopted in terms of Heating, Ventilation and Air-conditioning (HVAC) system improvement or storage system implementation. Such findings demonstrate the need for context-specific methods towards a proper evaluation and better valorisation of BIPV potential.Peer ReviewedPostprint (author's final draft

Energy performance analysis in interdisciplinary education – Lessons learned from a simulation-based teaching approach

The education of building practitioners is challenged by the increasing need for interdisciplinary profiles in the professional practice. To progress toward the goal of a sustainable built environment, a common language must be shared among fields such as architecture and engineering, between which persisting barriers remain. This paper presents an interdisciplinary teaching approach that aimed at getting architecture and engineering students to develop – around a unique case study evolving in parallel to the course – an understanding of the relationships between architectural and constructive aspects, simulation parameters, and energy and thermal comfort performance. Lessons learned from this experience include: the (in)adequacy of using an advanced software (EnergyPlus) imposing a steep initial learning curve, the limitations of working on a case study whose scope extends beyond the context of the class, and the conflict between achieving pedagogical objectives and valuing ‘real-time consultancy’ work in an evolving project. These challenges however seem to have been key to enable students to develop a solid knowledge of the concepts and technical language, as well as strong simulation competences, pushing them to embrace the added value of interdisciplinarity possibly more effectively than if a theoretical exercise had been used.Postprint (author's final draft