South Africa is limited in both its energy and water resources. The importance of energy efficiency in assisting with adequate irrigation is therefore of paramount importance.
Danfoss, together with engineering components provider BMG, supplied a commercial maize farmer with the technology required to combat challenges around electricity sufficiency, for more effective irrigation purposes and to increase production capacity. This initiative has since been followed by other commercial farmers in the wider area.
The two companies collaborated to assist a commercial maize farmer in Barkly West to tackle the hurdles posed by an in adequate energy supply, which could not be increased by other means. The region in which the farm is situated receives little rainfall throughout the year, making effective irrigation supremely important for successful crop yield.
Pumping and irrigation were the largest consumers of power on this maize-producing farm. At the outset of the project, one of the pump sets supplied five centre pivots and some orchards.
The first pump set consisted of 1 x 37 kW, 1 x 22 kW, and 2 x 11 kW pumps. This equated to an installed power of 81 kW, with an absorbed power of 75 kW, which meant that the pump set drew a current of about 150 A.
Additionally, the pumps were started by star/delta starters, and the only form of flow control was valves. In this case, the energy shortage was the farmer’s main concern, with costs being a secondary consideration. The use of variable speed drives on a pump set offered the perfect solution to provide the benefits required.
Danfoss VLT AQUA Drive FC 202 Variable Speed Drives (VSD), which offer additional energy savings when compared with most traditional variable speed drive controls, have been designed for water and wastewater applications, including irrigation.
These VSDs were fitted to all pumps in this installation and controlled by pressure transducers which were set to match the varying demands of different irrigation requirements. The only peripheral component required was a pressure transducer. Pump controllers and valves were not necessary for flow-control in this system.
After the installation of the variable speed drives and programming the set point to 2,8 bar, the team was able to run this same pump set with an absorbed power of 51 kW, a saving of 24 kW. It is noteworthy that the farmer began with a set of three variable speed drives on three pumps, and because of the energy saving, he eventually installed variable speed drives on every pump on his farm.
Contact: Lynne McCarthy, Danfoss, Tel 011 785-7628, mccarthyl@danfoss.com
