Ground cooling and heating potential in a Mediterranean climate : an evaluation of temperature extremes in Malta

Abstract

In consideration of the ever-increasing energy demand for cooling in Malta, a typical Mediterranean Island, this paper evaluates the potential for ground cooling as part of a strategic passive design scheme towards low energy architecture. It also extrapolates the potential for heating in winter, given that inverse seasonal temperature differences occur over a six month time lag. The potential lies with the indigenous rock, globigerina limestone, having a high thermal mass and moisture content. In principle this uses an air-to-air heat exchange process, where two sets of 200mm diameter pipes were laid vertically and horizontally in excavated trenches at 3.0m below ground level. Ambient air was extracted through the pipes into a purposely built test cell. Environmental conditions were monitored throughout. Results indicated favourable ground conditions for cooling, more than for heating, given time lag response of globigerina limestone. The vertical pipe exceeded the horizontal pipe in its performance. Results can be exploited to reduce indoor spring and summertime temperatures, thus reducing the energy demand for cooling. Keywords: energy, ground cooling, earth tubes, natural ventilation, passive cooling, carbon footprint.