A performance-driven simulation workflow for PV integration into the design process: application on an innovative building project in Switzerland

In the construction sector, the integration of active elements functioning both as building envelope material and on-site electricity generator is identified as a key measure to achieve the 2050 targets and carbon neutrality (Aguacil Moreno, 2019; Aguacil Moreno, Lufkin, & Rey, 2019). Despite an increasing confluence of the photovoltaic (PV) industry and the building glass manufacturers, which offers high design freedom in relation to size, colour and texture, architects and engineers continue to address the issue in a traditional way, by limiting themselves to the application of "standard" catalogue products that particularly constrain their designs (Bonomo, Frontini, De Berardinis, & Donsante, 2017; Zanetti et al., 2017). This way of working, which makes it difficult to integrate PV systems into the building envelope and, therefore, into the overall building design, often leads to a method of sizing that largely makes abstraction of the building’s electricity needs. This article presents the application – in an ongoing design process – of an innovative active surfaces selection method adapted to the design phases using 3D-modeling and hourly-step simulations (Aguacil Moreno et al., 2019) using Rhino (Robert McNeel & Associates, 2019) and Grasshopper (Davidson, 2018). Through an integrated-design approach, the proposed workflow allows to quickly obtain visual and quantitative results on the building envelope, and supports a design decision-making process that proposes an alternative approach to usual practice.

Active façades : life cycle environmental impacts and savings of photovoltaic power plants integrated into the building envelope

Gianluca Cattaneo, Angela Clua Longas

Aim and approach used Increased energy supply from photovoltaics is a main priority in the “Energy Strategy 2050”. Within the joint research project "Next generation photovoltaics" funded by the Swiss National Science Foundation, we analysed different options for the enhanced integration of photovoltaic technologies into the envelope of Swiss buildings (BIPV). The PV modules for building integration are using novel monolithic silicon heterojunction organometallic perovskite tandem cells (SHJ-PSC) with adaptions to improve the visual acceptance. In a joint effort of product developers, architects and scientists, this project aimed at providing pathways for the wide-scale use of BIPV façade solutions, and developing integrated designs based on emerging high-efficiency module technologies to improve the visual aspect and acceptance of PV systems installed in Switzerland. These so-called active façades incorporating BIPV modules to generate electricity can provide a significant contribution to the energy transition away from fossil and nuclear fuels. We compared the environmental impacts of different façade construction systems with and without SHJ-PSC BIPV modules with improved visual design, using a prospective life cycle assessment with a time horizon of 2025. The comparison includes a conventional brick and roughcast façade, a timber frame façade, and the Advanced Active Façade (AAF), which integrates SHJ-PSC BIPV modules in a low embodied impact façade substructure. In addition, we compared the environmental impacts caused by the construction of the above described façades with the environmental impacts saved due to the electricity produced by BIPV modules incorporated into the AAF. 2. Scientific innovation and relevance Our research focuses on the combined expertise of life cycle thinking, PV module development and façade design. The major scientific innovations are: 1) the prospective life cycle assessment of novel monolithic silicon heterojunction organometallic perovskite tandem cells (SHJ-PSC); 2) the comparison of different façade construction systems and their environmental impacts; 3) the quantification of the saved environmental impacts arising from the electricity generated by the active façade; and 4) the visual adjustments of PV modules to improve their acceptance. The main advantage of integrating PV into building façades is the large available area, which can be limited on rooftops. In order to reach the market penetration for PV required for the energy transition, PV modules must be integrated into façades as well as into rooftops. 3. Results and conclusions An equilibrium must be achieved among different technical and aesthetic issues when integrating energy generation systems into the building envelope, especially into the façade for its public condition and exposure. Based on these prerequisites, the research team has developed the AAF which combines passive and active energy design strategies while meeting contemporary architectural requirements. This façade design is based on low-embodied-energy construction principles, it is defined by a non-loadbearing wood-panel substructure and it integrates a double layer of natural insulation: cellulose and wood-fibre. In addition, its design incorporates an opaque SHJ-PSC BIPV façade-cladding following contemporary façade design trends. (Figure 1). The use of photovoltaic modules integrated into the façade cladding or roof will increase the environmental impact of the building envelope, compared to using conventional construction materials. The environmental impacts of the AAF using PV modules are two to four times higher compared to a conventional façade. The PV modules cause the highest share of greenhouse gas emissions of the AAF with about 375 kg CO2-eq per square meter (see Figure 2). The additional materials required to build the AAF including exterior panels, insulation and other materials cause about 75 kg CO2-eq per square meter of façade. The brick and timber frame façades cause greenhouse gas emissions around 200 and 100 kg CO2-eq, respectively. If the greenhouse gas emissions caused by the PV module is excluded this will result in a reduction between 25 and 125 kg CO2-eq per square meter of façade. However, the environmental impacts of the AAF are significantly reduced if the whole life cycle is considered due to the PV electricity produced by the building. Therefore, we calculated the saved greenhouse gas emissions due to the electricity produced by the advanced active façade and fed to the European electricity grid using the greenhouse gas emissions caused by the current European electricity mix as reference. These calculated savings due to the electricity produced by the BIPV are about 4 times higher than the impacts of the advanced active façade. Incorporating BIPV panels into building’s façades will cause net savings of about 1700 kg CO2-eq per square meter over the whole life cycle of BIPV façades, while simultaneously saving up to 125 kg CO2-eq per square meter of façade for the reduced material demand to build the façade (see Figure 3). We performed this analysis for 16 different environmental impacts according to the recommended midpoints by the Joint Research Council of the European Commission. The results were comparable to greenhouse gas emissions with the net saved environmental impacts being many times higher for all the environmental impacts analysed except mineral resource use caused by the indium used in the novel SHJ-PSC tandem module (see Figure 4). To conclude, the use of PV modules in AAF can reduce the greenhouse gas emissions per square meter of façade between 25 and 60 % if the production of the PV module and its produced electricity are excluded. If the production and life cycle of the PV modules are included into the analysis the AAF will cause net greenhouse gas savings up to four times higher than the production of the AAF itself. The results for environmental impacts other than greenhouse gases were similar except for mineral resource depletion. Overall, the building integration of photovoltaic modules as AAF will reduce the environmental impacts of the building while simultaneously providing a visually appealing building envelope.

2019

Active façades : life cycle environmental impacts and savings of photovoltaic power plants integrated into the building envelope

Gianluca Cattaneo, Angela Clua Longas

Goal Increased energy supply from photovoltaics is a main priority in the “Energy Strategy 2050”. Within the research project “PV2050: Sustainability, market deployment and interaction to the grid – the impacts of advanced photovoltaic solutions” funded by the Swiss National Science Foundation, we analysed different options for the enhanced integration of photovoltaic (PV) technologies into the envelope of Swiss buildings using novel monolithic silicon heterojunction organometallic perovskite tandem cells (SHJ-PSC) with adaptions to improve the visual acceptance. In a joint effort of product developers, architects and scientists, this project aimed at providing pathways for the wide-scale use of PV façade solutions, and developing integrated designs based on emerging high-efficiency module technologies to improve the visual aspect and acceptance of PV systems installed in Switzerland. These so-called active façades using photovoltaic modules to produce electricity can provide a significant contribution to the energy transition away from fossil and nuclear fuels. 2. Methods We compared the environmental impacts of different types of construction for building façades with and without integrated monolithic silicon heterojunction perovskite tandem modules (SHJ-PSC) with improved visual design using a prospective life cycle assessment with a time horizon of 2025. The comparison includes a conventional roughcast façade, a wooden façade, and two different active façades using photovoltaic modules. Furthermore, we compared the environmental impacts caused by the construction of the different façades with the environmental impacts saved due to the electricity produced by the active façades composed of photovoltaic modules. In addition, we analysed the reduction in environmental impact of the building using building-integrated photovoltaics due to substitution of construction materials for the façade or roof. 3. Results The use of photovoltaic modules as façade or roof will increase the environmental impact of the façade or roof compared to the use of conventional construction materials. However, the environmental impacts over the whole life cycle are significantly reduced due to the PV electricity produced by the building. The environmental impacts of the BIPV façade are about two to three times higher compared to a conventional façade, but the savings due to the electricity produced by the BIPV are five to eight times higher than the impacts of the conventional façade. The use of BIPV panels in the façade of buildings will cause net savings of about 600 kg CO2-eq per square meter over the whole life cycle of BIPV façades, while simultaneously saving 100 kg CO2-eq per square meter of façade for the reduced material demand.

2019

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

Sergi Aguacil Moreno

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.

EPFL2019

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

Sergi Aguacil Moreno

EPFL2019

Active façades : life cycle environmental impacts and savings of photovoltaic power plants integrated into the building envelope

Gianluca Cattaneo, Angela Clua Longas

Aim and approach used Increased energy supply from photovoltaics is a main priority in the “Energy Strategy 2050”. Within the joint research project "Next generation photovoltaics" funded by the Swiss National Science Foundation, we analysed different options for the enhanced integration of photovoltaic technologies into the envelope of Swiss buildings (BIPV). The PV modules for building integration are using novel monolithic silicon heterojunction organometallic perovskite tandem cells (SHJ-PSC) with adaptions to improve the visual acceptance. In a joint effort of product developers, architects and scientists, this project aimed at providing pathways for the wide-scale use of BIPV façade solutions, and developing integrated designs based on emerging high-efficiency module technologies to improve the visual aspect and acceptance of PV systems installed in Switzerland. These so-called active façades incorporating BIPV modules to generate electricity can provide a significant contribution to the energy transition away from fossil and nuclear fuels. We compared the environmental impacts of different façade construction systems with and without SHJ-PSC BIPV modules with improved visual design, using a prospective life cycle assessment with a time horizon of 2025. The comparison includes a conventional brick and roughcast façade, a timber frame façade, and the Advanced Active Façade (AAF), which integrates SHJ-PSC BIPV modules in a low embodied impact façade substructure. In addition, we compared the environmental impacts caused by the construction of the above described façades with the environmental impacts saved due to the electricity produced by BIPV modules incorporated into the AAF. 2. Scientific innovation and relevance Our research focuses on the combined expertise of life cycle thinking, PV module development and façade design. The major scientific innovations are: 1) the prospective life cycle assessment of novel monolithic silicon heterojunction organometallic perovskite tandem cells (SHJ-PSC); 2) the comparison of different façade construction systems and their environmental impacts; 3) the quantification of the saved environmental impacts arising from the electricity generated by the active façade; and 4) the visual adjustments of PV modules to improve their acceptance. The main advantage of integrating PV into building façades is the large available area, which can be limited on rooftops. In order to reach the market penetration for PV required for the energy transition, PV modules must be integrated into façades as well as into rooftops. 3. Results and conclusions An equilibrium must be achieved among different technical and aesthetic issues when integrating energy generation systems into the building envelope, especially into the façade for its public condition and exposure. Based on these prerequisites, the research team has developed the AAF which combines passive and active energy design strategies while meeting contemporary architectural requirements. This façade design is based on low-embodied-energy construction principles, it is defined by a non-loadbearing wood-panel substructure and it integrates a double layer of natural insulation: cellulose and wood-fibre. In addition, its design incorporates an opaque SHJ-PSC BIPV façade-cladding following contemporary façade design trends. (Figure 1). The use of photovoltaic modules integrated into the façade cladding or roof will increase the environmental impact of the building envelope, compared to using conventional construction materials. The environmental impacts of the AAF using PV modules are two to four times higher compared to a conventional façade. The PV modules cause the highest share of greenhouse gas emissions of the AAF with about 375 kg CO2-eq per square meter (see Figure 2). The additional materials required to build the AAF including exterior panels, insulation and other materials cause about 75 kg CO2-eq per square meter of façade. The brick and timber frame façades cause greenhouse gas emissions around 200 and 100 kg CO2-eq, respectively. If the greenhouse gas emissions caused by the PV module is excluded this will result in a reduction between 25 and 125 kg CO2-eq per square meter of façade. However, the environmental impacts of the AAF are significantly reduced if the whole life cycle is considered due to the PV electricity produced by the building. Therefore, we calculated the saved greenhouse gas emissions due to the electricity produced by the advanced active façade and fed to the European electricity grid using the greenhouse gas emissions caused by the current European electricity mix as reference. These calculated savings due to the electricity produced by the BIPV are about 4 times higher than the impacts of the advanced active façade. Incorporating BIPV panels into building’s façades will cause net savings of about 1700 kg CO2-eq per square meter over the whole life cycle of BIPV façades, while simultaneously saving up to 125 kg CO2-eq per square meter of façade for the reduced material demand to build the façade (see Figure 3). We performed this analysis for 16 different environmental impacts according to the recommended midpoints by the Joint Research Council of the European Commission. The results were comparable to greenhouse gas emissions with the net saved environmental impacts being many times higher for all the environmental impacts analysed except mineral resource use caused by the indium used in the novel SHJ-PSC tandem module (see Figure 4). To conclude, the use of PV modules in AAF can reduce the greenhouse gas emissions per square meter of façade between 25 and 60 % if the production of the PV module and its produced electricity are excluded. If the production and life cycle of the PV modules are included into the analysis the AAF will cause net greenhouse gas savings up to four times higher than the production of the AAF itself. The results for environmental impacts other than greenhouse gases were similar except for mineral resource depletion. Overall, the building integration of photovoltaic modules as AAF will reduce the environmental impacts of the building while simultaneously providing a visually appealing building envelope.

2019

Active façades : life cycle environmental impacts and savings of photovoltaic power plants integrated into the building envelope

Gianluca Cattaneo, Angela Clua Longas

Goal Increased energy supply from photovoltaics is a main priority in the “Energy Strategy 2050”. Within the research project “PV2050: Sustainability, market deployment and interaction to the grid – the impacts of advanced photovoltaic solutions” funded by the Swiss National Science Foundation, we analysed different options for the enhanced integration of photovoltaic (PV) technologies into the envelope of Swiss buildings using novel monolithic silicon heterojunction organometallic perovskite tandem cells (SHJ-PSC) with adaptions to improve the visual acceptance. In a joint effort of product developers, architects and scientists, this project aimed at providing pathways for the wide-scale use of PV façade solutions, and developing integrated designs based on emerging high-efficiency module technologies to improve the visual aspect and acceptance of PV systems installed in Switzerland. These so-called active façades using photovoltaic modules to produce electricity can provide a significant contribution to the energy transition away from fossil and nuclear fuels. 2. Methods We compared the environmental impacts of different types of construction for building façades with and without integrated monolithic silicon heterojunction perovskite tandem modules (SHJ-PSC) with improved visual design using a prospective life cycle assessment with a time horizon of 2025. The comparison includes a conventional roughcast façade, a wooden façade, and two different active façades using photovoltaic modules. Furthermore, we compared the environmental impacts caused by the construction of the different façades with the environmental impacts saved due to the electricity produced by the active façades composed of photovoltaic modules. In addition, we analysed the reduction in environmental impact of the building using building-integrated photovoltaics due to substitution of construction materials for the façade or roof. 3. Results The use of photovoltaic modules as façade or roof will increase the environmental impact of the façade or roof compared to the use of conventional construction materials. However, the environmental impacts over the whole life cycle are significantly reduced due to the PV electricity produced by the building. The environmental impacts of the BIPV façade are about two to three times higher compared to a conventional façade, but the savings due to the electricity produced by the BIPV are five to eight times higher than the impacts of the conventional façade. The use of BIPV panels in the façade of buildings will cause net savings of about 600 kg CO2-eq per square meter over the whole life cycle of BIPV façades, while simultaneously saving 100 kg CO2-eq per square meter of façade for the reduced material demand.

2019