September 30th, 2024
Comparison between the total cost of a BIPV solution (rainscreen facade glass/glass c-Si) and a traditional system (rainscreen facade composite panel) and extra cost BIPV of the administrative case study. The extra cost is 280 CHF/m². Source: SUPSI.
Authors: Paolo Corti (researcher at SUPSI), Dr. Pierluigi Bonomo (Head of the Innovative Envelope Team at SUPSI), Alberto Follo (PhD student).
Workflow to support cost-benefits comparison and sensitivity analysis of BIPV case studies: three examples of BIPV facades in the south of Switzerland
Project presentation
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.
The 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 (NPV) 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.
Conclusions
This paper shows a holistic project-based evaluation framework for BIPV facades by presenting a cost-benefit comparison applied on BIPVcase studies in Switzerland through the application of the NPV method and a developed sensitivity analysis. The innovation of this research is the definition of a BIPV façade sensitivity analysis for cost assessment and its application to real BIPV case studies. The goal is to describe a workflow to be replicate for assessing the techno-economic competitiveness of BIPV façade solutions that can be used by the stakeholders of the construction value-chain. An overview of three existing solar buildings as best practice demonstrated how these evaluation steps applied to case studies allow optimizing design parameters in terms of cost-benefits and attractiveness through a sensitivity analysis. The analysis is based on a cost breakdown of the BIPV building envelope, on the economic evaluation as NPV and on the assessment of a sensitivity analysis that allows to figure out the variation of the cumulative NPV after the variation of key parameters. Based on three references of Swiss BIPV opaque and ventilated façades, the analysis and the results will serve for other BIPV opaque and ventilated systems in Switzerland and other countries. The analysis of three different case studies concludes that each solar building is an independent case in which different parameters play an important role.
The results of the case-studies have shown that installing an integrated, customised and performing BIPV solution can achieve positive investments. In particular, after 30 years, the administrative and the residential solution performed a normalised revenue of about 11’000 and 52’000 CHF, respectively. The specific analysis of the BIPV opaque and ventilated facades in Swiss case studies allows some considerations, particularly from the cost breakdown assessment. It emerged that the cost of the cladding and the related substructures represents about 70% of the total cost of BIPV. The electric BOS is about 5-13% of the Total Cost of BIPV. The labour costs correspond with 20% of the Total Costs of BIPV. Finally, the sensitivity analysis has also shown that an accurate solar design increases solar system performance. The extra cost, energetic yield, self-consumption, discount rate and cost of energy are the parameters that most influence the success of BIPV installations. However, the absence of a singularly dominant parameter is highlighted, with their effects exhibiting variability across input values. A 20% reduction of the extra cost corresponds with a significant fluctuation of the NPV, 26.9% for the multifunctional building and 82.7% for the administrative building. The transition from 100% to 0% self-consumption results in a substantial negative impact on the NPV, amounting to approximately -190%, as shown in the case of the administrative building.
The analysis and the strategies presented within this study allow BIPV specialists, real estate investors (such as public authorities, real estate developers, and private building owners) and the building value chain stakeholders to focus on key-aspects of investments to maximise the economic value, the definition of a business model for BIPV facades and support the decision-making since the early-design stage.
