Solar Water Pumping: A Practical Introduction

A Careful Design Approach

When a generator or utility main is present, we use a relatively large pump and turn it on only as needed. With solar pumping, we don't have this luxury. Photovoltaic panels are expensive, so we must size our systems carefully. It is like fitting a suit of clothes; you need all the measurements. For solar water pumps, first identify how much water you need per day and the vertical lift required.

Next, we will determine whether a submersible pump or a surface pump is best. This is based on the nature of the water source. Submersible pumps are suited both to deep well and to surface water sources. Surface pumps can only draw water from about 20 feet (3m) below ground level, but they can push it far uphill. Where a surface pump is feasible, it is less expensive than a submersible, and a greater variety is available.

Now, we need to determine the flow rate required. Here is the equation, in the simplest terms:

Gallons per Hour = Gallons Per Day / Available Peak Sun Hours per Day

Peak Sun Hours refers to the average equivalent hours of full-sun energy received per day. It varies with the location and the season. For example, the arid central-western USA averages 7 peak hours in summer, and dips to 4.5 peak hours in mid-winter. These Sun Hours can be considerably less in northern climates.

Next, refer to the performance charts for the type of pump that is appropriate. They will specify the size and configuration (voltage) of solar array necessary to run the pump. The charts can be found in the specification page or in the Product Documentation tab of the product's specification page.

 Copyright © 1999 by Dankoff Solar Products, Inc. (Edited by Alt E 2008)