Solar-Powered Pumping System Components
A solar-powered water pumping system has the following minimum components:
- water well
- PV array
- array mounting bracket and rack
- pump controller
- electrical ground for controller
- DC pump with safety ropes, mount, and well seal
- discharge tubing or piping
- storage tank
- tank flotation switch
- water taps or access points
When installing a new well, it is recommended to contact a licensed water well contractor. If the well is not properly developed prior to installing the solar powered pump it can reduce the life expectancy of the pump. If you are retrofitting a windmill pumping system, the well should be redeveloped before installing a solar powered pump. The goal of redeveloping the well should be to remove biofouling from the sidewalls and sediments from the bottom of the well.
Pumps designed specifically for solar power utilize direct current (DC) and tend to be very efficient, but they usually cost more than a comparably sized alternating current (AC) pump. Surface mounted pumps can be used for a SPPS but are discouraged because of their limitations when used in deep wells. Based on the specifications from several manufactures, the typical lift abilities for surface pumps designed for solar power are between 10 and 20 feet. Surface pumps also have greater exposure to the climate making them more vulnerable to freezing weather.
The size of the pump will depend on several factors including: available water supply, available power, available storage, total dynamic head, diameter of well, and water need. Assume that the pump will only be operating during peak sunlight hours. Try to install the most efficient and simplest system that meets the project demands.
The pump should be specifically designed for solar power. It is strongly recommended to purchase the pump controller from the same manufacturer as the pump. Using another manufacturer could cause several unforeseen problems and even invalidate the pump’s warranty. If the pump does not contain a built-in check valve, one should be installed to keep the water from flowing back into the well. Very few pumps can handle reverse flow without reducing the life expectancy of the pump. Pumps that are designed to drain during non-operation are meant for extremely cold conditions to keep water from freezing in the lines. The pump should be set no deeper than 2 feet above the bottom of the well to help prevent heavy silt and sand from entering the pump’s intake and causing it to seize.
Solar Power Source
Solar power comes from photovoltaic (PV) cells that convert the sun’s energy into usable DC electricity. A module consists of PV cells and an array consists of several modules. A factor of 1.25 times the pump wattage requirements is often used to determine the preliminary size of the required array. This accounts for the energy losses in the modules and controller. If batteries and a regulator are added into the system, the PV array demand will be higher. The PV array needs to be mounted securely to a tilted rack that is fixed to the ground. If the modules are fixed, the orientation of the tilt is to the south and should be equal to the site latitude. If they are on an adjustable mount, the tilt should be the latitude minus 10 to 15 degrees in the summer and the latitude plus 10 to 15 degrees in the winter.
Other Pump Equipment
The pump controller is a highly specialized item and can vary significantly between manufacturers. A technical term for a pump controller is a ‘linear current booster.’ The purpose of the pump controller is to regulate and match the flow of DC electricity to the needs of the pump. The pump controller contains the recognition components for the storage tank flotation switch and the low-well switch. The controller should last approximately 10 years.
The storage tank should be sized to hold at least three days’ worth of water demand to account for evenings and cloudy days. If the controller is not attached to the array mounting bracket it can be placed in a secure shed or pump house, preferably water tight and dust free.Last updated: October 18, 2017 at 12:00 pm