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Dear Layali

Here is a response to your enquiry from John Cody, another of our RedR Water and Sanitation experts:

"There is insufficient information to provide a specific answer to your question; To select an appropriate pump you will have to match pump characteristics to the distribution network characteristics (static heads and friction losses at a design flow rate), selecting a pump that will operate near its design point in the network. If you select VSD pumps you will add significant complexity, capital and O&M costs to your system, for which there is little justification in your query. If you are looking at VSD to compensate for fluctuations in the PV supply then I think it would likely to be cheaper and operationally more efficient to install a reservoir in the system to allow your delivery network to be designed as a gravity or constant head pumped system, using pumps to provide the required heads by pumping to an elevated reservoir. The elevated reservoir will allow you to compensate for fluctuations in the PV supply without the need for pump controllers, and simple valves can be used to control the distribution network.

"The PV supply will be a function of elevation of the sun, orientation, cloud cover and maintenance of the PV panels. It would be standard to provide a reservoir within the system to even out diurnal and seasonal fluctuations in the power supply. A water reservoir is almost certainly cheaper over the lifetime of a system than battery storage for example. A reservoir would also allow for irrigation at night, which may significantly improve water use efficiency and reduce long term salinisation issues."

Please let us know what you would like to do and how we might be able to help.

Kind regard, Leigh

LC Jones RedR KnowledgePoint Moderator