Solar energy is the fastest-growing energy source in the European Union, with production costs decreasing by 82 percent in the 2010s. In this context, the presence of solar panels on single-family homes, offices, and public buildings has become the norm, with this energy source having accounted for over 269 GW in EU by the end of 2023. 

In this interview, Vesna Kosorić, Head of Architecture at Zurich Soft Robotics, dives into Solskin, an innovative adaptive solar facade based on a mosaic of small photovoltaic panels that follow the sun and provide solar shading.

Supertrends: Could you introduce yourself and explain what your company does?

Vesna Kosorić: Thank you very much for the invitation. My name is Vesna Kosorić, and I’m an architect, researcher, and BIPV (Building Integrated Photovoltaics) expert with 20 years of experience in the field of sustainable design and solar architecture. I studied architecture at the Faculty of Architecture in Belgrade and completed my PhD in the field of building integration of solar systems. After that, I went to Singapore, where I did my postdoc at the Solar Energy Research Institute of Singapore. I have worked as an architect in Switzerland, Serbia, and Singapore. For the last two and a half years, I've been Head of Architecture at Zurich Soft Robotics, an official ETH spin-off that is bringing smart climate-adaptive solar building skin to the market under the name Solskin.

The adaptive solar facade has been conceptualized and researched for eight years at the Chair of Architecture and Building Systems (A/S) by Professor Dr Arno Schlueter at ETH Zurich. Our CEO, Bratislav Svetozarevic, did his PhD at the A/S with a focus on soft robotic actuators, which are at the heart of adaptive solar facade systems. Our Co-CEO and Head of Technology, Gabriel Kreuzer, was also intensively involved in the research of adaptive solar facades. Together with Alexander Zuest, Lucas Lichtensteiger, and Anil Sethi, they founded Zurich Soft Robotics in 2022.

We are now in the phase of bringing our product to market, and we believe it can solve many challenges which our buildings and cities are currently facing and will increasingly face. Firstly, in the future, cities will consume much more electricity, mainly due to electric cars and laws mandating electric heating as the only option. We all know that rooftops are perfect spaces for integrating solar systems, but they are also limited in cities. That's why we also need to integrate photovoltaics on facades in city areas. 

Secondly, there are a lot of existing buildings that are not attractive or efficient anymore, and they need to be modernized. We should make them more comfortable, more energy-efficient, and more aesthetically appealing. Good PV facade solutions provide great opportunities to redesign these buildings. Additionally, temperatures are rising due to climate change, which is making it more difficult to live and work in cities due to the overheating of buildings. 

Our system is unique because it can tackle all these problems at once, being highly multifunctional. It's an all-in-one solution that offers multiple benefits: electricity production, adaptive solar shading, daylighting control, a reduction in the energy needed for air conditioning, and enhanced user comfort with appealing aesthetics.

Supertrends: From a technical point of view, how does it work?

V.K.: Solskin consists of a mosaic of small photovoltaic panels that follow the sun and provide adaptive solar shading thanks to our innovative pneumatic actuators and artificial intelligence control. Due to the solar tracking in two axes, it produces up to 40% more electricity compared to static photovoltaic systems. For example, in summer it can be positioned so that it blocks the sun, preventing overheating, while in winter it can do the opposite, opening the panels and letting the sun in to heat up the space behind it. 

Solskin panels can be controlled individually or in a row, either automatically or manually. Thanks to smart control, Solskin can adapt at any time according to energy needs or user comfort needs, such as thermal comfort and visual comfort needs. With these features, the facade is dynamic, which offers many possibilities. It's not just about energy efficiency and maximum electricity production but also about thermal and daylight comfort, including adaptations to energy and user needs. With its dynamics—the ability to move each panel individually—Solskin can communicate and send a message to people inside and outside of the building. For example, the panels can be moved to greet you, or they can be positioned so they write out the word “Hello”.

Supertrends: What materials are needed to produce your products?

V.K.: Solskin consists of several components. These include photovoltaic panels with soft material actuators. We also have a metal rod net that conceals all cables—electric and air—and a metal frame around for mounting to building envelopes. To produce Solskin, we use stainless steel, EPDM rubber, PU tubes, photovoltaic panels based on silicon, glass fiber, and ETFE foil. The photovoltaic modules we use are lightweight and very durable, reflecting our efficient use of materials.

Supertrends: How sustainable is your product on that end? How do you ensure sustainability?

V.K.: Our product is a lightweight, modular, and prefabricated system that ensures high material use efficiency. It is several times lighter than some typical standard glass-glass photovoltaic modules. The Solskin system's overall design and integration process are focused on sustainability, with circularity principles embedded in its design. For example, we make sure that the components are easy to separate for repair and refurbishment, and reuse is possible. Moreover, we monitor and optimize their environmental footprint by conducting life cycle assessment studies.

Supertrends: How are you integrating AI tools into your product? What advantages are you finding on that end?

V.K.: AI helps us model the overall system more precisely. It helps us better understand how and when the system moves. We should clarify that these panel movements depend on many complex factors, including the building's orientation, room layout, and the number of occupants and their preferences and needs. It's normal that some people want to have more sun than others in their working space or higher temperatures, while some people prefer lower temperatures. It's really hard, almost impossible, to come up with a general solution. That’s where AI comes into play. We want to use it to learn specific behaviors and adapt to different situations, making Solskin more personalized. To conclude, AI helps us to optimize Solskin performance in accordance with very diverse factors: outdoor conditions, indoor conditions, and occupants' needs. 

Supertrends: How does your product integrate with existing facades? What modifications in a building structure are required?

V.K.: It can be mounted in front of both unglazed and glazed building surfaces. It is applied mostly in the form of an external solar shading system or second building skin. We offer great design flexibility, allowing the system to be easily integrated into various building types and construction structures due to its lightness. We need fixation points, usually columns or ceilings—the installation process is relatively straightforward and similar to other facade systems.

We also consider various aspects, like the cleaning of the main facade. It's important to understand how the windows of the existing buildings can be opened or cleaned. For example, based on that, we define at which distance the Solskin system should be mounted. The distance to the main facade mainly can be from 15 to over 70 centimeters. 

Supertrends: You mentioned a couple of times the lightness of Solskin. How light is it per square meter?

V.K.: It is, of course, case-dependent, but we can say it's between 12 and 20 kilos per square meter, including modules, frames, and the rest of the equipment needed. 

Supertrends: How does your product comply with possible aesthetic regulations? Are you encountering problems when you need approval from authorities?

V.K.: Applying solar systems to existing buildings requires careful consideration and expertise, because you have to take into account a lot of different elements and find a solution that is harmonious with the existing architecture of the building. That’s why we designed our product to be modular, customizable, and aesthetically appealing, displaying the panels in a mosaic structure. Solskin units are mainly customized so that their size and shape fit perfectly to the building project. Our PV modules are smaller in comparison with standard PV panels on the market. The standard photovoltaic modules we use are dark modules in a size of 42 by 42 centimeters, but we can also use smaller and bigger modules in other colors. But even with the standard one we have a lot of possibilities to create aesthetic designs which achieve a successful architectural integration both for new and existing buildings. 

Our experiences working with local building construction authorities have been very positive so far, and we have already received building permits for several projects. However, it can sometimes be challenging to convey to interested parties how our product will look, as most examples so far are prototypes, and solar panels are typically placed on roofs. But with the help of prototypes, digital visualizations, and good communication, we are tackling this issue. 

We've had only positive experiences so far, and we believe our system is aesthetically appealing, opening up new design possibilities for both new and existing buildings.

Supertrends: What type of customers are you finding so far? Residential buildings, office buildings, factories?

V.K.: Up until now, we have seen interest from all of them. We've also seen interest from single-family homeowners. For example, this year we are building smaller projects with systems that cover up to 30 square meters. We are pleased to see significant interest from larger companies looking to implement our product in offices, commercial buildings, factories, as well as institutional buildings such as schools, universities, and hospitals. There is a huge interest for applications for diverse buildings such as hotels, pharmaceutical facilities, factory buildings in the watchmaking industry, banks, shopping centers, and entertainment centers.

We are excited to have secured our first large-scale project in Winterthur, Switzerland, and we are noticing that more architects are using our system in architectural competitions. There’s a really diverse interest coming from architectural offices, building developers, and real estate companies.

The first flagship application of Solskin will be rolled out under the KELLER Diamant project at the new high-tech production facility of KELLER Druckmesstechnik AG by Strut Architekten AG in Winterthur. This project was also the winner of an architectural competition. The Solskin system is acting as the second building skin on the south facade of the building, providing the functionality of a shading system and a PV system. It will cover an area of 1,300 square meters and will be constructed in 2025. This facade will demonstrate how Solskin erases the boundaries between PV facades and solar shading systems, merging the advantages of both to create a fascinating system that fully showcases sustainability.

Supertrends: In which regions are you finding the biggest pool of customers?

V.K.: Up until now, we have primarily focused on Switzerland, as we are based there. The research part was done at ETH Zurich, and our first prototypes were built there. We have a lot of interest in this region so far. However, there's also significant international interest for our unique facade product, not only from southern Europe but also from companies in countries like the UK, Denmark—and in Asia, particularly Thailand and Singapore. But now we are mainly focused on Switzerland and we are starting to expand our international activities.

Supertrends: In figures, how much can a user save by implementing your solution?

V.K.: Benefits depend on the case. Savings are highly individual and depend on factors like the type of integration, the number of square meters installed, whether it's placed in front of a glazed surface, the building’s energy consumption, the building's sun exposure, among others. Based on our research and simulations, Solskin can reduce the energy needed for HVAC (Heating, Ventilation, and Air Conditioning) by up to 80%. When the system is integrated from the early planning and construction stage, savings are realized from the start in materials and mounting construction. Namely, when Solskin is used to replace traditional external solar shading systems and this is planned from the early design stage, mounting systems can be optimized and materials efficiently used. 

But we also have to mention qualitative benefits that are always difficult to translate into numbers. Solskin can increase the comfort and well-being of users, impacting their satisfaction and productivity directly. Our research focuses on exploring the effect of Solskin on user satisfaction and happiness, the enhancement of user comfort in a given space, and other areas. For example, this is interesting not only for working spaces and office buildings but also for buildings like hospitals—potentially aiding faster patient recovery—and schools, where, for example, it may facilitate children's learning. 

Supertrends: What role are institutions playing in the implementation of these technologies? Are grants a thing in this sector?

V.K.: First of all, I have to say that we are a spin-off of the ETH. In the different stages of the project, we have also received support from the Swiss Innovation Agency, Innosuisse; Klimastiftung, which promotes climate protection; and Klimafonds Stadtwerk Winterthur, which supports projects that use renewable energies and reduce energy consumption. We've also received grants from Energy Lab, an innovation ecosystem comprising various partners and research institutions in Switzerland, aimed at boosting energy transformation through innovations. From the customers' side, there are institutions like Pronovo, which support the installation of these systems.

Supertrends: What's the biggest challenge you are facing right now? 

V.K.: We are facing some of the typical challenges that most startups go through. 

Scaling up, which includes optimization of production, finding proper partners—it all comes with a set of challenges. 

We aim to increase market presence and sales and to ensure a sufficient number of projects. In regards to that, we are experiencing some challenges that are typical for those bringing innovations to the market in the construction sector. In addition, it takes a long time to plan and construct bigger projects, and time is very critical for startups. The social acceptance of new technologies also plays a key role. 

The decision to implement Solskin on a building is made by both architects and building owners. Of course, for a final decision to be made, both parties need to agree. All this often involves a lot of communication, effort, and time. However, we are aware of the challenges and our team is working hard to bring Solskin to the market. We are constructing several smaller projects this year, and next year we will install a facade on our first large scale project. But we need more projects and the support of major investors.

Supertrends: Why should someone invest in this technology?

V.K.: Our product, Solskin, is one of the rare new and innovative technologies in the construction sector. It could bring about significant changes to how buildings look in the future. It can help solve some of the increasing problems in cities such as the need to meet the growing demand for electricity due to electric cars, renovate existing buildings, and address the overheating of buildings. It is becoming clear to us that we cannot solve problems in the built environment with standard solutions that are focused only on individual problems. With Solskin, we offer an unconventional alternative and a flexible solution to multiple problems in the built environment. 

Behind Solskin stands a wonderful multidisciplinary team of dedicated experts from different fields who all work together towards the same goal, truly believing in Solskin’s values. We are all working very hard with the goal of bringing Solskin to life and making the world around us more energy efficient, comfortable, beautiful, and inspiring for generations to come.

Supertrends: Do you think this kind of product will become mandatory for new buildings?

V.K.: Definitely. At least for some types of buildings and spaces. I expect buildings to be energy efficient, user-friendly, flexible, and adaptable. Besides energy efficiency, they will foster user comfort, health, and well-being, and that’s exactly what Solskin does. Smart control systems and AI can help a lot in this area, and there is a lot of potential. We see that investors and other actors in the real estate sector are more aware of these aspects. I believe there will be a greater focus on meeting not only technical requirements but also qualitative and social values while enhancing creativity.

Supertrends: How do you picture this market in 20 years? How would you like it to look?

V.K.: Economies of scale will lower prices and improve applicability in many locations and buildings that are currently unsuitable for economic reasons. There will be many diverse and high-quality solutions and applications, always from an energy-efficient and resilient perspective. Buildings will produce electricity, that’s for sure. However, in order to achieve sustainability, I believe there will be more user-oriented solutions to make spaces not only energy-efficient but also livable and lovable. Zero energy buildings will need to have the ability to adapt to various changing conditions and user needs. Our dynamic solar facade system, Solskin, can greatly facilitate the journey from today’s passive and static structures to tomorrow’s active and dynamic buildings. 

I imagine we can have a lot of Solskin applications all around us which are very aesthetically appealing and user-oriented. Our buildings should be more inspiring, and they should interact more with the people inside and outside of them. We can achieve that through changing shapes and light patterns on buildings with Solskin dynamic facades.

The text is a transcript of an interview conducted on 23 October 2024. The interview was conducted as part of Supertrends' 'Interviews with Experts' series. Please note that the transcript may have been lightly edited for editorial reasons.