by Marie Gehrhardt

The interdisciplinary research of Bau Kunst Erfinden deals, among other things, with intelligent surfaces and materials in the context of civil engineering. What was your motivation behind researching dye-sensitised solar cells in combination with concrete?

We are currently facing enormous social challenges. Today, 75 percent of the population in Europe and 55 percent of the world’s population live in conurbations, which account for 60–80 percent of the world’s total energy consumption. If the current conditions are maintained, global energy consumption in buildings is expected to double or even triple by 2050. As industrial nations burn fossil fuels more than a million times faster than they can renew them, and as the needs of developing E7 countries increase, current estimates suggest that fossil fuel as a resource will be depleted in less than 100 years. In short, buildings consume energy, water and materials, and construction causes waste as well as CO2 and particulate emissions. Given the enormous size of the construction sector, even small reductions can help to make a big difference. The research project Dye-Sensitised Solar Concrete (DysCrete, DssCrete) focuses on electricity production resulting from the targeted material synthesis of cement-based building materials and photoreactive particles. Functional layers that can convert light into electrical energy according to the principles of technical photosynthesis are applied to concrete surfaces and are thus refined. The advantage is that sustainable energy generation is also possible with atmospheric light, using freely available components at comparatively low production costs. For this reason, the innovative material system has the potential of a low-cost energy source. 

Dye solar cells have been patented since 1992. Nevertheless, artistically motivated research into dye solar cells is relatively rare. Where do you see the potential of dye-sensitised solar cells (compared to silicon solar cells)?

For some years now, there has been investigation into solar cells made of organic materials (e.g. dye-sensitised solar cell) and inorganic materials (e.g. Kesterite and Perowskite). However, their application in opaque building materials such as concrete has so far been ignored, since attention was initially focused on the great development potential of glass-based translucent modules. Based on the technology of dye-sensitised solar cell (O’Regan and Grätzel, 1991), organic dyes are used in the material system dye-sensitised solar concrete in order to absorb light and generate energy by electrochemical reactions. The advantages that result include the better availability of all raw materials, a relatively inexpensive production, various design possibilities and the ability to use atmospheric light, so that no special orientation to the sun is necessary. The material system is also regenerable, largely recyclable and offers great potential in terms of design.

The installation of solar cells on buildings is a major issue – also because the building sector is responsible for a considerable amount of greenhouse gas emissions in Germany. Do you see restrictions for creative freedom in the use of solar energy – and if so, where would you see such restrictions?

The ability to also use the energy of atmospheric light is a particularly noteworthy feature of dye-sensitised solar concrete, as there are hardly any restrictions with regard to structural implementation compared to conventional PV systems. This opens up almost unlimited application and design possibilities in terms of form, design and location. 

Where do you see the biggest challenge in the use and spread of solar panels in public space?

Nowadays, building is characterised by tradition, is highly risk-averse and, as far as possible, offline. The construction industry should use new technologies and materials in its own interest and both adapt and renew its processes and business models. Otherwise there is a risk that the success experienced over a long period of time will result in neglect of developments that can undermine the success of its own business model. The public sector is also challenged. It should act as a “smart client” – in other words, make targeted use of public procurement, set an example with best-practice projects and best-practice sharing as well as implement pilot projects. Tendering procedures must be reformed so that the cheapest bid is not the one that wins, but rather the best bid in terms of quality. Bids must be evaluated with regard to innovation, use of new technologies and processes as well as life-cycle costs and sustainability.

In the magazine Zukunft Bau, dyscrete is described as a ‘cementitious material for innovative facade, wall and floor systems in the construction industry’. What other goals do you have for your research? What role does the Plotbot/Crawler play in this context? 

The aim is to develop a fully component-integrated photovoltaic material. For this specific application, we developed an easy-to-use, web-based, sensor-guided automatic motion controller – the Plotbot/Crawler – at the Bau Kunst Erfinden research platform. Thanks to the Plotbot/Crawler, complex layering systems for the functionalisation of building surfaces can be applied. By means of a consistently interlocked logic between tool and software, the surfaces of construction elements of any geometry are instantly controlled or coated according to a previously digitally created processing system. The Plotbot/Crawler is mainly used to apply and renew photoreactive layers on facades. The facade robot is suitable for applying these functional layers, but can also be modified to accommodate other functional systems – for example, to apply pigment coatings, sealants, guidance systems and decorative layers or to detect moisture, cracks and other defects on facades. 

In general, how do you imagine using dyscrete or solar energy in a future scenario?

The sun is already an important source of energy today, and photovoltaics will become one of the most important power supply technologies of the future. Buildings play an important role here. They increasingly operate with the energy system and have the potential to become decentralised energy centres. The dominant material in building-integrated photovoltaics (BIPV) today is the silicon solar cell. Panels connected to solar modules have largely established themselves as on-roof solar power systems. While silicon, the basic material required for its manufacture, is available in unlimited quantities, materials such as indium, gallium, tellurium and selenium, which are also necessary, must be critically evaluated in terms of their material economy, resource consumption and environmental compatibility. Such plants also require space, which is only available to a limited extent in conurbations. Furthermore, silicon-based photovoltaics must be oriented to the south in order to use the sunlight effectively. Since the geometry of buildings and panels are not coordinated, an unattractive aesthetic is additionally created that does not allow any artistic composition. The photovoltaic implementation of opaque building materials offers a high degree of flexibility for architecture and gives the building industry the opportunity to significantly increase the amount of space available for generating solar energy and also to shape this new technology at an early stage – in order to develop aesthetically sophisticated systems that can be incorporated into planning as photoactive and structurally shaping systems at the same time. 

Your work at Bau Kunst Erfinden is based on interdisciplinarity between different creative and scientific fields. What does research by designers look like and to what extent does it differ from science in terms of your experiences?

Today, designers, architects, engineers, computer scientists and researchers are involved at different times in the development of products, buildings and infrastructures. At the research platform Bau Kunst Erfinden, we work together in a way that is definitely interdisciplinary right from the very beginning of a project and at a very early stage. In the projects, artistic strategies, basic science and application-oriented engineering strategies overlap. This creates better dovetailing of the processes involved as well as added value for all participants. Art means asking questions and connecting knowledge. Interdisciplinary work is about thinking ahead and placing one’s own discipline and one’s own work in a different context. Leaving one’s own comfort zone is something that one simply has to get involved in. 

Photo: Boris Trenkel

Heike Klussmann is an artist and a professor working in the field of fine arts and architecture at the University of Kassel since 2005. She also runs her own studio in Berlin, is represented in exhibitions, films and publications, and has received numerous awards. In 2009, she founded the interdisciplinary research platform BAU KUNST ERFINDEN in Kassel. The platform combines expertise from various fields, including the fine arts, architecture, urban planning, experimental physics and technological material research. BAU KUNST ERFINDEN is dedicated to the development of innovative materials systems and intelligent surfaces.