There are four main configurations for solar pumping systems. Note that the configurations and applications detailed below are not exhaustive; they are designed to give an overview of what’s available. You may wish to seek further information from somewhere else.
Solar Alone
This configuration is one of the most straightforward, commonly deployed, and cost-effective designs. In this configuration, the solar array provides power to a DC electric pump via an array and motor control system. This configuration is well suited to applications where a consistent volume of water must be pumped daily from a water source to the application or water storage.
Solar Combined with Batteries
A solar-battery configuration works well for on-demand, pressurized water systems. This configuration includes batteries and a battery control system. Adding batteries increases the system complexity and adds significant costs, but batteries ‘smooth out’ the solar array output and provide the power required at night. A solar-battery configuration works well for on-demand, pressurized water systems.
Using batteries to store solar-generated power can involve complex design considerations, including accurate sizing, electrical compatibility between the solar array and the battery bank, electrical protection, and maintenance.
Different chemistries and types of batteries (lead-acid, Lithium-Ion, flow batteries, etc.) each hold competitive advantages. Still, the PV industry leaders have cautioned that there is ‘no clear winner’ yet.
Solar Combined with Diesel Generation
This configuration includes a diesel generator and operates on an AC electrical system. Using an AC electrical system requires using a solar ‘multimode’ inverter (a DC to AC converter) to regulate energy flow to the pump from both the solar array and the generator. This type of system is well suited to applications where some nighttime pumping is required and mains electricity is unavailable.
Solar Combined with Power from the Electricity Grid
This configuration powers the pump with a combination of power generated by a solar array and electricity from the grid. The grid provides reliability and enables the pump to be operated flexibly to meet changing requirements. Solar energy reduces the amount of grid electricity required, reducing the cost of running the pump.
Combining solar PV power with power drawn from the electricity grid requires significant design considerations and additional standards. A certified solar designer/installer should be engaged for this configuration.
An additional benefit of a grid-connected system entails the possibility of exporting excess power and utilizing solar-generated electricity for other purposes on-farm. This can help improve the solar system’s financial viability by providing a revenue stream (from exported power) and offsetting electricity from other loads when pumping isn’t required.
A grid-connected system is one of the most viable approaches to meet more significant and intermittent pumping needs, such as those for irrigated broadacre farms.
