Applying the Enhanced Free Cooling Concept: A Case Study on Reducing Mechanical Cooling Demand

Abstract

Increasingly stringent energy directives of the European Union, combined with rising cooling demands due to climate change, urge the investigation of energy-efficient cooling solutions. Free cooling offers a viable approach to reducing energy consumption. However, its effectiveness and applicability across different building types remain insufficiently established. This study aims to minimise mechanical cooling energy demand through the implementation of enhanced free cooling (EFC) as an operational control strategy in office, residential, and small commercial buildings. The introduction of the efficiency of EFC (ηfc) supports this analysis by quantifying how effectively EFC exploits free cooling potential in defined thermal and mechanical conditions based on an analytical approach supported by simplified simulations (in Microsoft Excel). The case study indicates that the east-oriented office building with a 40% glazing ratio achieves the highest cooling energy savings (49.63%) on the target summer day. For the residential building, savings are lower (37.78%) but more stable across the hot and the extremely hot days. The results further show that the influence of building orientation diminishes as external temperature increases, while higher glazing ratios stabilise ηfc across the examined thermal conditions. Analysis of the connection between air exchange rate and mechanical cooling energy savings identifies a critical resistance point (nopt), defined as the ventilation rate beyond which no further cooling energy savings occur. The results enable practical applications in building operation and support both improved energy efficiency and the advancement of sustainable HVAC design.