Efficient motors help save energy for desalination plants

Desalination plants are known to require large amounts of electrical energy to pump high volumes of water through their systems. The use of high efficiency motors in such applications helps to ensure the efficient and cost-effective running of desalination plants. 

“Desalination plants employ numerous pumps for various functions in the process – all of which need to be driven by electric motors,” says Zest WEG public sector specialist Dillon Govender. “The reverse osmosis system also requires relatively high pressures to be maintained, to enable salts to be removed through the use of semi-permeable membranes.”

Reducing the specific energy consumption ( measured in kWh/m3) is therefore a strategic requirement underpinning these plants’ viability and performance and WEG’s range of high efficiency motors are being employed across the complete range of desalination plant pump applications, he says.

These include the intake of raw water (sea water) into the pre-treatment section for the first filtering, high pressure pumping through the reverse osmosis phase itself, post-treatment and storage, and the final pumping to distribution networks and facilities.

“Our motors are also used for the pumping of concentrated sea water or brine back into the ocean,” he says. “Only about half or around 45% of the volume of the seawater entering the plant through the intake system actually leaves as potable water.”

To further enhance the efficiency of the pumping circuit, Zest WEG supplies gearboxes and variable speed drives (VSDs) with integrated programmable logic controllers. This helps to optimise energy consumption while ensuring the required pressure and flow through the desalination membranes, as well as reliable performance in auxiliary systems such as backwashing, dosing, chemical cleaning and brine pumping systems.

The company explains that its Pump Genius software enables a standard VSD to be dedicated to specific pumping systems with various motor and pump combinations, thereby providing improved control and monitoring capability as well as maximising energy savings and reducing downtime.

“We are able to design and supply the necessary electrical enclosures and motor control centres in low and medium voltages, as well as container-type electrical rooms,” says Govender. “Zest WEG also provides solutions for emergency power generation, power distribution and alternative energy generation. Using the Motion Fleet Management tool will also reduce operational costs for maintenance tasks.”

Owing to the corrosive coastal environment typically associated with the location of desalination plants, the WEG high efficiency motors have integral IP66 protection, facilitating protection against salt water ingress caused by heavy seas and higher tides. Installation of heaters as well as the epoxy coatings of the motors, helps achieve greater longevity under these arduous conditions. WEG’s VSDs and soft starters are also available with IP55 ingress protection improving longevity, while all critical components within the VSDs and soft starters are covered with an additional anti-corrosive coating.