Assessment of Water Flow Glazing as Building-Integrated Solar Thermal Collector

Abstract

In buildings with ambitious energy goals or limited roof areas for on-site energy generation, building-integrated solar thermal collectors are one of the main strategies to provide on-site renewable energy to the built environment. In addition, designing large glazing facades is a challenge to achieving the goal of zero-energy buildings due to the thermal load produced by standard double or triple glazing. This research shows that Water Flow Glazing (WFG) can produce domestic hot water as a building-integrated solar thermal collector by flowing water through the chamber between glass panes and can help reduce thermal loads through facades. In this article, the solar collector’s efficiency was defined according to the UNE-EN 12975-2 standard and then applied to the Water Flow Glazing. As a result, the transparent Water Flow Glazing’s optical efficiency η0 varies from 0.648 to 0.742, whereas the thermal loss coefficient a1 ranges from 9.51 to 4.16. Those values are like those of commercial plate collectors. Afterward, the model to predict the efficiency of WFG was tested in an existing facility by calculating the Normalized Root Mean Square Error (NRMSE) to assess the deviations between the simulation and measured values. Using building-integrated solar collectors can improve the integration of renewable energies in facades and roofs but also increase the uncertainties that affect their efficiencies, such as internal heat loads and heating, cooling, and ventilation systems. Therefore, testing existing facilities can help understand the impact of these technologies in the Zero Energy Building paradigm.