When the facade becomes a power plant
To date, photovoltaic modules have primarily been used on roofs and open spaces. Yet multi-story residential and office buildings in particular offer large vertical surfaces that can be utilized for energy generation. Even though vertically mounted modules often yield less energy on an annual average than optimally oriented rooftop systems, they provide valuable electricity at times when conventional systems underperform: in the morning, in the evening, and during the winter months when the sun is low in the sky. In this way, they complement conventional rooftop systems precisely when their output is lower and energy is still needed inside the buildings.
Building-integrated photovoltaics, or BIPV for short, combines energy generation with architecture. Solar modules are not merely technical components but become part of the building envelope. However, this places greater demands on their design. Facades vary in dimensions, grid patterns, materials, and architectural appearance. Consequently, the shape, size, and design of the required solar modules also vary.
This is precisely where the Digi-PV research project comes in. Together with the Institute for Solar Energy Research in Hamelin (ISFH), the Institute of Solid State Physics, and other industry partners, the Institute of Assembly Technology and Robotics (match) at Leibniz University Hannover is developing methods for the flexible and automated production of customized photovoltaic modules.
Batch size 1 meets industrial production
Conventional photovoltaic production lines are designed for large quantities of identical modules. For BIPV, this principle is only partially applicable, as even within a single building, numerous different module sizes and shapes may be required. The key challenge is to combine the advantages of automated production with the necessary variety of configurations: A manufacturing system must be able to produce different modules, including one-off pieces, without long changeover times compromising precision and process reliability.
This places particularly high demands on component handling. A key focus at match is on so-called cell strings—rows of solar cells electrically connected to one another. These are delicate, vary in length, and must be precisely picked up, transported, and positioned during the manufacturing process.
Rigid grippers designed for a specific cell format are only suitable to a limited extent. The research team is therefore developing a modular vacuum gripping system whose nozzle positions can be adjusted to accommodate different cell sizes, spacings, and string lengths. Tests show that this system allows for the damage-free handling of various formats.
Sensors and digital twins enable flexibility
However, a flexible gripper alone is not enough to solve the challenge. The solar cells must not only be transported safely but also placed with high precision. That is why the project combines flexible hardware with sensors and digitally supported process control.
Digital twins play an important role: First, building surfaces are digitally mapped and analyzed for their solar potential. This results in a digital model of the building that provides information for module design. This data is linked to a digital model of the manufacturing facility. This creates a seamless connection between the building and production: The facade’s requirements determine which modules are needed, while the facility’s digital twin describes how they can be manufactured. If the geometry or material properties change, the process planning can be adjusted accordingly.
At the same time, production data is fed into the digital model. Analyzing this data helps identify correlations between process parameters and product quality. In the future, artificial intelligence methods may also help evaluate process data and adapt the production line more quickly to new product variants.
Custom solar modules without hidden costs
For users, the key benefit lies in the combination of customization and cost-effectiveness. Architects gain greater design freedom without custom module shapes necessarily requiring fully customized manufacturing. Manufacturers can use their production facilities more flexibly and produce smaller quantities more cost-effectively.
This is particularly relevant for the renovation of existing buildings, where photovoltaic solutions must adapt to existing facades, window areas, and architectural structures. In addition to varying sizes and shapes, different colors and finishes therefore also play a role. As a result, solar modules can blend more seamlessly into the design of a facade rather than being perceived as retrofitted technical elements.
Flexible production also reduces the effort required to switch between different variants. Today, such changes can be time-consuming and costly and can result in scrap. When gripping systems, sensors, and process control respond to new formats automatically or with minimal effort, even small batches and custom modules can be produced efficiently. Research at match focuses not only on the handling of cell strings; other components such as films and glass panes must also be processed flexibly in the future. Only when the individual manufacturing steps work together will a production chain emerge that manufactures different BIPV modules automatically and reliably.
One facade, many possibilities
In the long term, this type of production will transform the role of photovoltaics in buildings. In the future, solar modules may no longer be viewed primarily as standardized components for which a suitable surface area must be found. Instead, the building itself will dictate which modules are manufactured.
Individual module geometries can then be derived from digital building data and directly transferred to a flexible manufacturing process. Production facilities adapt handling, process parameters, and quality control to the specific variant. This enables cost-effective production even with a high degree of variation and small batch sizes.
The vision thus extends beyond a single manufacturing facility: photovoltaics become a flexibly configurable component of the building envelope. Facades of new and existing buildings can specifically contribute to energy generation without having to pit architecture against technical standardization. The easier it is to design and cost-effectively manufacture individual modules, the larger the usable area for solar energy becomes.
