COOLING LOAD REDUCTION WITH TRANSPIRED SOLAR COLLECTORS

Year 2022, Volume: 23 Issue: 1, 1 - 10, 30.06.2022

Balazs Bokor , Hacer Akhan , Doğan Eryener , László Kajtár

Abstract

When considering energy reduction issues of the building sector, one cannot overlook the importance of cooling load reduction. Depending on a country’s primary energy conversion factor, producing one unit of cooling energy with a chiller can require three times as much primary energy, than producing one unit of heating energy with a boiler. A remarkable amount of the cooling load of a building reaches the interior through the roof, as roofs can be as hot as 70 °C under strong solar radiation. Roof ventilation with double-layer structures offers a reliable temperature reduction between the solar exposed upper layer and the lower one, which is the actual building roof. The transpired solar collector (TSC) is a proven technology for solar air heating with numerous installed and successfully operated systems around the world. This paper reflects on its passive cooling potential, when the perforated metal plate absorber is installed on a building’s roof. At night, the perforated plate acts as a radiating shield, which loses heat towards the cold sky. Thus, after the perforated plate has cooled below ambient temperature, outdoor air can be cooled, which is later used for nocturnal ventilation of the building. However, the predicted cooling energy during an analysis of the radiant cooling strongly depends on the sky temperature model chosen. Different models of sky temperature are compered in their result on the longwave radiant heat flux towards the sky. The comparison is carried out for four cities with different climate. Results reflect on a novel application of the transpired solar collector, which therefore can be used for the reduction of building energy consumption over the entire year.

Keywords

Transpired solar collector, Roof ventilation, Nocturnal radiation, Passive cooling, Solar cooling load reduction

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