Quantitative assessment of the HVAC system of zero-energy houses of the Solar Decathlon Middle East 2021

Abstract

HVAC systems consume up to 50% of the total energy demanded by buildings. This paper aims to provide quantitative assessment of the HVAC solutions used on the highly efficient houses competing in the Solar Decathlon Middle East 2021. This international competition challenges university students to design, build, and operate sustainable zero-energy houses. The analysis includes the system selection, capacity, and coefficient of performance (COP), as well as the monitored indoor temperature, relative humidity, and CO2 levels. The university teams’ selection capacity (systems availability) and budget were affected by the COVID-19 pandemic. However, they designed their houses to respond appropriately to arid climates and reduce HVAC consumption. The study evaluates the HVAC solutions of all eight projects, providing more information about the four top-ranked teams. Most homes use air-to-air, decentralized, and multizone air-conditioners. The teams made the best effort to select systems that significantly exceed the COP required by the local regulations. Some also exceed the local energy codes regarding refrigerants’ global warming potential. The average COP (at T1 i.e., Moderate Climate Conditions) of air-to-air systems was 3.71 kW/kW, and the air-to-water system was 3.42 kW/kW. The lower installed cooling capacity per area of air-to-water HVAC systems was 57 W/m2 and 122 W/m2 in the air-to-air ones. In several cases, the HVAC systems’ consumption was affected by the short assembly period (15 days), nonprofessional student construction, and the lack of a testing period before starting the competition. Nevertheless, these houses exhibited excellent performance, and their analysis brought relevant lessons for buildings in arid climates.