Effect of Tilt Angle Variation on the Performance of the Flat Collector Solar Thermal System (Passive Type)

Abstract

The study demonstrates the importance of proper design and installation of a passive solar thermal system and the need to consider the appropriate collector tilt angle for optimal thermal performance. The experimental setup consisted of a 200-liter passive system installed alongside with an existing 500-liter active thermal system, enabling a solar hot water capacity of 700 liters. The temperature of the flat-type collector outlet and inlet, hot tank outlet, and ambient temper-ature were recorded using temperature sensor data loggers, while solar irradiance was measured using a pyranometer placed on the collector surface. Four system metrics, namely collector effi-ciency, thermal efficiency, heat loss, and mass flow at different tilt angles, were studied. The thermal performance of the system improves with a steady change in solar irradiation when the collector is placed between the tilt angle of 25° and 30°. However, when the tilt angle is increased above 30 degrees, the system efficiency decreases. The thermal efficiency of 60-70% can be obtained at a collector angle of 20° to 30° at the daily solar irradiance of 300 to 900 W/m². Furthermore, the experiment emphasizes the importance of timely draining out of hot water from the system. This practice helps maintain the system's efficiency and sustainability.