Benefits of a translucent building envelope made of DSC-integrated glass blocks

The aim of this paper is to analyse the benefits deriving from the replacement of the glazed façades of an office building located in Palermo (Sicily) with a new translucent BIPV envelope made of multifunctional glass block panels integrated with Dye-sensitized Solar Cells (DSCs). The analysed 11-storey building is cladded by a curtain wall determining high management costs, especially during summer, in order to maintain indoor comfort. After the design of the building envelope and of the components for the connection of the glass block panels with existing load bearing structure, the energy performance of the building, before and after the replacement of its envelope, were analysed with the support of Design Builder software. Other software tools – like Therm, Window and Optics – were used to calculate more in detail the thermal properties of the building envelope. The results of the energy performance simulations on the current state were compared with those deriving from the installation of the new envelope made of BIPV glass block panels. Besides the clean electricity production, a significant reduction in building energy consumption related to air conditioning systems was registered, due to the shading effect and solar gain reduction provided by the DSC-integrated glass blocks.

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

Air-Conditioning Energy Production through a Building Shape Optimization

Gianpiero Caruso, Jérôme Henri Kämpf

The air-conditioning energy consumption, for cooling or heating, has currently a growing trend. The purpose of this work is to develop a method suitable to design optimal threedimensional building forms to reduce air-conditioning needs in a chosen location by using weather data. The method exploits in particular both diuse and direct solar radiation; not independently but rather in relation with the external temperature. For this reason this method could be applied in any climatic region. In fact the warmer the region is the more negative the contribution of the solar radiation is in terms of building energy balance. Hence in this case the problem tends to be equivalent to the one of the annual solar irradiation minimization. On the contrary, in the case of cold regions, the problem tends to be equivalent to the one of the annual solar irradiation maximization. The final aim is to guide designers to reduce energy consumptions in buildings, since the first stages of the design process of future buildings. To achieve that aim, an algebraic cumulative sky is introduced for the computation of the annual useful incident solar irradiation on the building envelope. The methodology consists in using weather data to define in which case the solar irradiation on the envelope gives a positive or negative contribution depending on the external temperature in order to maintain internal comfort of the occupants. The contribution is further associated to the data of the solar irradiation for each hour of a typical year. The algebraic cumulative sky constructed on that basis has the advantage to present particular zones where the solar radiation is useful all year long. Finally we use an hybrid evolutionary algorithm (CMA-ES/HDE algorithm) already applied to maximize solar energy utilization to explore the optimal building forms maximizing the annual useful solar irradiation on the envelope.

EPFL Solar Energy and Building Physics Laboratory (LESO-PB)2013

First assessment on the principles for building a mediterranean Active House

Arianna Brambilla

Innovation of the energy saving and optimization of the renewable sources are the most important sides of the building sector in the last years. Considering that buildings consume more than 40% of all the energy we use and about 50% of it is used for the conditioning systems, it is clear the reason why there is a precise need of improvement in the building behaviour and in the way of designing. In the last years the buildings vision itself is changing faster, from the passive house principles we are moving to the zero energy buildings or the latest active houses. Active House is a vision of buildings that create healthier and more comfortable lives for their occupants without impacting negatively on the climate. The concept is based on a responsive behaviour of the building, capable to answer instantly to the climate strains changing automatically its configurations and assuring the indoor comfort and energy saving, and it is promoting by an international no-profit organization, the Active House Alliance. This vision was born in the North European regions and it is moulded on some case studies, model homes built to spread the image of the future houses and designed for northern climate, so it fits perfectly cold climate. Politecnico di Milano, as member of the Alliance, is developing a solution for the adaptation to the south Europe, where the climate and the weather stress are different. VELUXlab is the first prototype of this vision in Italy. It is the first Italian NZEB in a university campus and, soon, it will be certified also as the first Italian Active House. The wireless sensor network system allows to control in real time the duo envelope (multi-layer dry construction) and automation technology performances, strengthening the good results obtained from the virtual dynamic simulations made during the design process.

2014