What is the simple design for solar water heaters?

Role of thumb for sizing the SWH.

Average daily solar energy at most of Arab countries on horizontal surfacs is between5 to6 kWh/m2.

Assume average daily solar energy =5.6 kWh/m2

Average solar collector efficiency =40 %.

If daily of hot water needed is500 liters at55° C.

Useful energy =5.6 kWh *0.40 = 2.24 kWh /d /m2

Q = m * Cp * (55 –18)

=500 kg *4.186 kJ/(kg °C) *37 °C =77,441 kJ / d

77,441 kJ /3,600 = 21.5 kWh / d

Collector area = 21.5 / 2.24 =9.6 =10 m2

Thermo-Syphon System