In simple terms, for the same water output, the cost of using energy storage is several times higher than that of direct photovoltaic (PV) drive.
For example, suppose we need to pump 360 cubic meters of water to a height of 180 meters within one day.
People often first think of using a pump with a rated flow of 15 m³/h, a head of 187 meters, and a power of 13 kW, working for 24 hours. This solution (referred to as Option 1) is technically feasible, but the cost is too high. This is because PV systems cannot operate without sunlight. To ensure the pump can work at night, we must equip a large number of batteries, which makes the cost extremely high.
We now propose two alternative options, assuming PV panels can operate effectively for 6 hours a day.
Option 2 is to use a pump with a rated flow of 60 m³/h, a head of 187 meters, and a power of 45 kW, operating for 6 hours.
Option 3 is to use four 13 kW pumps.
The advantage of Option 3 over Option 2 is that when the PV power output is low, for example only 10 kW, some of the pumps can still be run, instead of the system being completely unable to operate. This improves the utilization of the PV system.
Attached are the cost estimates for the three options for reference.