A good solar pumping system is the one properly designed and sized to fit the job requirements. Various designs exist for a variety of applications, requiring research and technical design to avoid system insufficient performance or unnecessary cost incurrence.
Unlike traditional utility or private generator powered systems, where large pumps are normally installed to pump water in large volumes whenever power is available, solar PV pumping requires more austerity as system components are really expensive and efforts need to be done to bring system set up cost to a minimum.
During the design phase, system designers need to decide on whether the system is to be on-grid or off-grid, with storage or without it and whether storage is in batteries or in elevated water tanks. They need to decide on the type of pump being used and whether the application requires a submersible or a surface pump, using AC or DC power. These all are factors that affect the system performance and feasibility of the proposed solution.
Grid and Storage
On-Grid vs Off-grid
Typical PV systems are grid-connected, allowing feeding produced electricity into the utility mains and thus using it as a storage volume. The concept behind on-grid systems is to reduce the additional expenses of batteries and avoid lost excess energy that is being produced but unused due to low demand.
In solar pumping applications, when the grid is available, some systems are hooked into the grid allowing for a two-way exchange of power, working as such:
(1) When solar energy is available, and there is demand for water, water is directly pumped to end use using solar power
(2) When solar energy is available, and there is demand for water but not consuming all the electricity produced, excess electricity is fed into the grid
(3) When solar energy is available, and there is demand for water but requiring more power than what is produced by the solar PV system, extra electricity provided from the grid
(4) When solar energy is available, and there is no demand for water, electricity is fed into the grid
(5) When solar energy is not available, and there is demand for water, water is directly pumped to end use using grid power
For applications where the utility grid is not available, mainly remote and not electrified regions, the PV system is installed as a stand-alone system, sometimes connected to a private generator and sometimes just left as a stand-alone unit.
The private generator plays the roles (1), (3), and (5) of the grid mentioned above. It provides electricity when needed unless there is a storage system in place. This storage system allows to store electricity or water to offer availability during night times and winter seasons.