How to Size a Solar Pump
Step 1
When sizing a solar system for water pumping it is necessary to select a site that maintains good sun exposure throughout the year. Make sure there are no obstacles that will cast a shadow on the solar array and thus impede performance of the solar pumping system.
Step 2
Determine the total water needed in a 24 hour period. Peak sun hours vary with geographical locations and a PV or Solar-Direct system must be able to achieve the desired production within the given sun-hours available. For livestock watering we use 20 gallons per cow/calf pair per day.
EXAMPLE: 100 pairs = 2000 gallons per day.
Step 3
Determine your well recovery rate and desired pump flow rate. Lorentz water pumps come with an optional low-water probe for dry-run protection. However, you will achieve greater amounts of water if the pump is matched to pump at your recovery rate and not shutting down for 20 minutes every time the well is pumped dry.
EXAMPLE: 5.5 gallon per minute recovery.
Step 4
It is very important that the total dynamic head is calculated for a given system accurately. An example might be a desire for 5 gallon per minute with a 100ft well that maintains a 60ft static water level. The system is designed to have an open discharge at a stock tank that is located 150 ft from the well in a 1” pipeline and 25ft higher than the well head. To determine head loss in the 150 ft pipe run, refer to the pipe sizing chart located in the back of this manual. Total dynamic head is calculated by taking the static water level + the rise beyond the well head + pipeline head loss.
EXAMPLE: 60ft+25ft+1.215ft (for pipeline head loss) = 86.215 feet of total dynamic head.
Step 5
Select the pump and solar array that meets your requirements.
Solution:
2600 Gallons Per Day using 350 Watts of power. When sizing an array, it is wise to add 20% or total 437 watts + for cloudy days. This will add daily capability and yield.
Reminder: 2.31 feet of vertical head = 1 PSIFor additional assistance, please contact us.
