Researchers have tested the system’s weather endurance and performed measurements with several prototypes on the Hönggerberg Campus. They found that the movable solar panels harvest around 50 percent more energy on a clear summer’s day than static solar panels mounted on a building façade.
Savings potential simulated
However, the façade not only generates electricity, but can also regulate how much light and heat permeate the building envelope, thus regulating the internal climate. An adaptive learning algorithm controls the movement of the panels so that the savings made in heating and cooling internal spaces lowers the net energy demand. At the same time, the algorithm also takes into consideration how the building’s current use and adjusts the climate accordingly.
To determine the degree to which a room’s energy consumption could theoretically be reduced, the researchers simulated several scenarios using data from prototypes. They calculated the energy-saving potential of building envelopes fitted with movable solar façades in Cairo, Zurich and Helsinki. In doing so they ran simulations for spaces in both office and residential use.
Biggest potential in temperate zones
The results show that energy savings tend to be higher in offices than in living spaces, in warm rather than in cold climates, and above all in temperate zones such as Central Europe. Arno Schlüter sums up the findings: “The more variable the ambient conditions, the greater the benefits of the adaptive façade”.
The best energy balance was seen in the simulations for office space in a temperate zone (in this case Zurich) in buildings constructed to the latest standard. In this scenario, where both interior heating and cooling were required over the course of the year, the adaptive façade generated 115 percent of the energy required for a comfortable room environment.
An equally good result came from the simulation for an office space in a house in Cairo constructed before 1920, which required much more shade and cooling. In this case, the façade produced 114 percent of the total annual energy requirement. In other words, the study highlights the energy savings potential for both new and old buildings, but the façade must always be considered in conjunction with the interior space and its use.
“We would like to resolve the trade-off between user comfort and energy efficiency in buildings,” Arno Schlüter says. “In theory, the most energy-efficient space would have no windows. We are therefore glad to demonstrate how an intelligent interface between the interior and exterior of a building can provide optimal user comfort and also generate excess energy.”
Professor Schlüter’s group will soon be able to measure the impact of the adaptive solar façade on a physical building: the system is part of the futuristic “HiLo” unit currently being constructed on the topmost platform of the NEST research building in Dübendorf (see box).