¹û¶³´«Ã½

The Netherlands has made significant efforts to reduce carbon emissions, pushing the built environment to meet stringent energy standards. Achieving net-zero energy in multi-storey buildings has become increasingly challenging, as only the use of rooftop renewables are no longer sufficient to achieve higher energy requirements. Windows have always played a fundamental role in the built environment. They provide occupants with daylight, thermal comfort, and outdoor connection. However, as buildings strive to become more energy self-sufficient, the function of the window continues to evolve in response to these energy dynamics in the building. In recent years, there is growing attention for finding ways to give transparent parts of the facade the ability to generate electricity. Such fenestration systems need to satisfy multiple competing requirements that can be difficult to harmonize; from admitting too much solar radiation, excessive daylight, causing glare and overheating, to blocking most of the solar radiation leading not only to insufficient daylight but also losing valuable solar radiation that could have been well-harvested for energy generation. 

The Ziezo concept addresses these challenges by transforming larger surfaces of multi-storey building facades into ‘solar facades’. This helps complementing rooftop renewables with window-integrated photovoltaics to meet the net zero energy requirement. In Ziezo, the window is coupled with dynamic solar shading and bifacial solar cells to admit adequate and yet controlled daylight, reduce glare, capture and convert the excess solar radiation into electricity. The novel contribution of Ziezo lies in the bifaciality of the solar cell. As part of the light is admitted through the window, it is reflected off the venetian blinds and redirected to the back side of the solar cell to contribute to additional electric energy. 

My Engineering Doctorate project aimed to develop a multi-parameter model and decision support tool as the technological design outcomes. The model translates the ideas behind Ziezo into a complex fenestration system. The materials of real products are converted into Radiance materials for component modeling in visible and solar spectra. The geometry and materials generate the transmission matrix by using bidirectional scattering distribution function in Radiance, which is essential for daylighting modeling and simulation. In the course of light travel through the window, this transmission matrix captures the physical phenomena of transporting daylight through the window and describes the interaction of light with the window. The model, moreover, translates the captured behavior to the relevant key performance indicators. By establishing relationships between geometry and material of each component, this model bridges the gap between modeling real products, passing it to the room-level modeling to evaluating their daylight and energy performance in the building-level. This EngD project, moreover, developed a software application tool for the target user of Pilkington. It aims to achieve threefold objectives: 1) provide a large database of simulations with respect to climate, window sizes and orientations; 2) evaluate the performance of Ziezo variants in office environment; and 3) provide the user with insights into the performance of Ziezo window on the component and room levels to support their decisions. In addition to the two main outcomes, this project also develops: 1) a three-dimensional BSDF viewer, 2) novel approach to model the optical and thermal characteristics of solar cells in WINDOW LBNL; 3) classification algorithm for raytracing of light; 4) initial development of Grasshopper plugin for Ziezo concept, and 5) a poster publication contribution at the Daylight Academy Conference in Trondheim, Norway. This work shed the light on the story of Ziezo from different perspectives, complementing and validating one another, which enriched and added value to the project.

Mina Ishac
March 2025