Evolution of all-glass nearly Zero Energy Buildings with respect to the local climate and free-cooling techniques

This paper presents research on the nearly Zero Energy Buildings (nZEB) metrics of an all-glass office building with advanced multi-layer six-pane glass and building integrated photovoltaic (BIPV) facade structures in different climate conditions. The study was carried out in the following steps: i) development of a time series model of dynamic thermal response of multi-layer six-pane glass and BIPV facade structures on the basis of transient computational fluid dynamics simulations, ii) integration of the facade structure dynamic model into the building dynamic model by adapting TRNSYS software code, iii) determination of the final energy balance including heating, cooling, ventilation, lighting, and on-site electricity production, iv) nZEB metrics evaluation considering night-time cooling by ventilation, evaporation cooling and hybrid ventilation of case study office buildings. It is shown that energy need for the cooling of the studied office building is dominant in all considered climate conditions, although it can be decreased up to 23% in most favourable considered climate conditions by implementing free cooling techniques. The case study buildings with BIPV structures on their east and west facades meet more stringed nZEB criteria; in addition, final energy demand decreases by 17-37% in comparison to the reference all-glass building. In the case of all-BIPV buildings, the final energy demand is decreased by 36-48%. Such buildings can significantly contribute to the mitigation of global climate change, as BIPV electricity production exceeds the building's energy demand.