Integrated solar – Windcatcher with dew-point indirect evaporative cooler for classrooms

Abstract

This work investigates the performance of a novel passive ventilation and cooling system for a classroom in hot and semi-arid climate. The system integrated a combined solar chimney – windcatcher system with a fan-assisted cross-flow dew point indirect evaporative cooler (DP-IEC) to condition the fresh air supplied to the space. The classroom exhaust, driven by the solar chimney, was used to cool a double layer window and reduce the radiation asymmetry. A mathematical model was developed to size the system’s components and optimize its hourly operation to achieve the required thermal comfort and indoor air quality at minimal fan energy and DP-IEC water consumption. The integrated model was validated with published data in the literature. The validated integrated model was used to simulate the proposed system for a typical classroom in the semi-arid climate of Beqaa, Lebanon. It was found that the cooling system was able to meet the space thermal and air quality requirements throughout the summer with a temperature of 24.8 °C (±0.3 °C), a relative humidity ranging between 43% and 58%, and a CO2 level less than 900 ppm. Moreover, the radiation asymmetry was less than 3.5 ℃ which is within the acceptable range (less than10 °C). The system’s highest energy and water consumptions of 3.6 kWh/day and 185 L/day occurred during the peak load month of July where the DP-IEC was operated with a high fresh air flowrate of 1 kg/s with no bypass throughout most of the day. Over the summer period (May to September), the system achieved 70% reduction in operational cost as compared to the conventional systems.