Design of an Architectural Element Generating Hydrogen Energy by Photosynthesis—Model Case of the Roof and Window

As is well known, the realization of a zero-waste society is strongly desired in a sustainable society. In particular, architectural elements that provide an energy-neutral living environment are attractive. This article presents the novel environmentally friendly architectural elements that generate hydrogen energy by the photosystem II (PSII) solution extracted from waste vegetables. In the present work, as an architectural element, the window (PSII window panel) and roof (PSII roof panel) were fabricated by injecting a PSII solution into a transparent double-layer panel, and the aging properties of the power generation and the appearance of these PSII panels are investigated. It was found that the PSII roof can generate energy for 18 days under the sun shining and can actually drive the electronic device. In addition, the PSII window, for which light intensity is weaker than that for the PSII roof, can maintain power generation for 40 days. These results indicate that the PSII roof and PSII window become the architectural elements generating energy, although the lifespan depends on the total light intensity. Furthermore, as an additional advantage, the roof and window panels composed of the semitransparent PSII panel yield an interior space with the natural color of the leaf, which gradually changes over time from green to yellow. Further, it was also found that the thermal fluctuation of the PSII window is smaller than that of the typical glass window. These results indicate that the roof and window panels composed of the PSII solution extracted from waste vegetables can be used as the actual architectural elements to produce not only the electrical energy but also the beautiful, transparent natural green/yellow spaces.