Engineering News

Content created by Lynne McCarthy, Marketing & Communications Specialist Consultant - Turkey, Middle East & Africa, Danfoss (Pty) Ltd - a member of the Danfoss Group

In recent years, South African energy security has been constrained, while the country is also recognised by the Development Bank of Southern Africa as being a water-scarce country. The importance of energy efficiency in assisting with adequate irrigation is of paramount importance.

Danfoss, together with engineering components provider BMG, an authorised DrivePro® service partner of Danfoss, supplied a commercial maize farmer with the technology required to combat challenges around electricity sufficiency, for more effective irrigation purposes and in order to increase production capacity. This initiative has since been followed by other commercial farmers in the wider area.

The challenge: to free up existing electricity supply to increase production capacity

Sydney Govender, Danfoss Country Sales Manager – Drives SSA, says, “A joint Danfoss-BMG collaboration assisted a commercial maize (corn) farmer in Barkly West, within the Northern Cape province, to tackle the hurdles posed by an inadequate 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.”

Mick Baugh, Electronics Manager, Electromechanical Division, BMG, explains, “Pumping and irrigation were the largest consumers of power on this maize-producing farm. The project required assisting the farmer, who was limited by a power supply of only 200 kVA +/- 300 A, to significantly reduce the cost of irrigation per hectare. Additionally, the farmer wanted to expand his crop production to include pecan nuts, but was unable to because of these limitations. The cost of irrigation per hectare therefore needed to be reduced, and the limited power supply needed to be used more efficiently.”

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 +/- 150 A.

• Additionally, the pumps were started by star / delta starters, and the only form of flow control was valves.

Solution: installation of Danfoss Variable Speed Drives on all pump sets

Govender clarifies, “In this case, the energy shortage was the farmer’s main concern, with costs being a secondary consideration. We were therefore looking to free up the existing electricity supply in order to use it elsewhere and thereby increase production capacity. The use of variable speed drives on a pump set was the perfect solution to provide the benefits required.”

The proposal was as follows:

• To install Danfoss VLT® AQUA Drive FC 202 Variable Speed Drives on all pumps.

• To control these pumps by means of pressure transducers set to match the varying demands of the different irrigation scenarios that presented themselves.

• To stop using the valves as a means to limit flow, as this was highly inefficient.

“Danfoss VLT® AQUA Drive FC 202 Variable Speed Drives, which offer additional energy savings when compared with most traditional variable speed drive controls, have been designed for water and wastewater applications, including irrigation,” Danfoss spokesperson says. “These variable speed drives were fitted to all pumps in this installation and controlled by pressure transducers that 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.”

Baugh adds, “There were a number of reasons why BMG chose these particular Danfoss solutions. For example, a notable feature of the Danfoss VLT® AQUA Drive FC 202 Variable Speed Drives is the inclusion of a soft start/stop facility, which prevents water hammer on starting and stopping the pumps, thus reducing the possibility of burst pipes. Wear and tear on couplings, pumps and pipes is also reduced. Furthermore, these variable speed drives are available from BMG in IP55 enclosures, which do not require dedicated panels for mounting, and this eliminates the need for the additional cooling and ventilation measures normally required to extract heat during operation. Furthermore, closed loop controllers mean that the only piece of peripheral equipment required is a pressure transducer - no pump controller is necessary.

“Finally, BMG, as an authorised Danfoss service partner, with accredited technical staff and an extensive spares stock holding, is able to offer farmers support all year round. With regards to DrivePro services, we stock a number of service exchange units and spare parts at the nearest BMG branch, in Kimberley.”