Circulation Pump Power for Solar Water Heater

This publication introduces calculations of circulation pump power for solar water heater, forced circulation system. The theoretical power is estimated as 0.5 Watt, while the nominal power of the relevant pump is 6 Watt. Energy consumption of such pump is 25 kWh/year. The required water flow is 2 liters/minute and the pump's head is 1.5 meter. The publication determines, step by step, water flow, pressure drop in solar collector and pipes, and theoretical power of circulation pump.
Calculations are for solar water heater for residential unit located 9 floors from the solar collector on building's roof. The size of the solar water heater is 150 liters storage tank and 6,150 kcal/day collector. Excessive power of circulation pump increases water flow and decreases stratification in storage tank with negative impact on solar collector's efficiency and energy losses in circulation pipes. Therefore the power and specifications of circulation pump must be carefully determined.