2.4.5 Solar air heater

colder water. The greater hydrostatic pressure of the colder water forces the water through the system by gravity, resulting in natural convection.

The thermosyphon effect is created by the difference in hot and cold water density. This effect relies on gravity. The hot water has more energy, is less dense, and rises above the cold water, causing the water to circulate.

2.4.5 Solar air heater

A solar air heater sucks air in at the bottom and heats the air through solar radiation in pipes, causing convection. The hot air is pushed out into the room through a fan at the top of the system. The system should be installed on the sunny, northern side of a building to get as much solar exposure and be most effective (Baruah & Choudhury 2017).

Figure 10 shows how the room air is heated with an external solar air heater.

Figure 10: Solar air heater (Fratzel n.d.)

Figure 10 shows how room air enters the system at the inlet and moves underneath the black collector plate. The black collector plate is heated by solar radiation and heats the air as it moves through the gap at the bottom. The hot air rises and enters the room to heat it. Figure 11 shows easy and low cost do-it-yourself solar air heaters examined for this study.