Most solar-thermal collectors are ‘glazed’ meaning they arecontained within a shallow box with a glass cover to insulate theabsorber from heat loss by convection (e.g. from wind) whileallowing the majority of the solar radiation to pass through to theabsorber. Flat-plate solar collectors are typically tilted tooptimise their solar energy absorption. The tilt angle affects therate at which heat is lost from the collector due to naturalconvection. A collector is 0.96 m high and 2.4 m wide and has a gapbetween the absorber and glass of 24 mm. Assuming the absorberplate (the surface that heats the water) is maintained at 90 °C andthe inside surface of the glass cover is maintained at 45 °C,calculate the rate of heat loss by natural convection between theabsorber plate and glass cover for tilt angles of 0°, 45° and 90°from horizontal.
