Energy-efficient drives offer solution for green recovery

9th October 2020

Energy-efficient drives offer solution for green recovery

STEPHEN BROWN Given the need to increase energy supply in a globally carbon constrained environment, the mining trade needs to improve its energy-efficient technologies

The mining industry must forgo its traditional energy consumption patterns to ensure that it decarbonises toward a greener and sustainable method of exploration, says mechanical products and controls manufacturer Danfoss Drives Turkey Middle East and Africa business development manager Stephen Brown.

He adds that given the need to increase energy supply in a globally carbon constrained environment, the mining trade needs to improve its energy-efficient technologies. These technologies include electric variable speed drives (VSDs), which could reduce energy consumption drastically.

The fundamentals of alternating current (ac) variable frequency speed drive technology persist but many elements are rapidly changing to aid to move towards a more sustainable and environment-friendly mining future.

Increasingly, software is embedded in today’s mine processing components, offering new functionalities and enabling the ac drive to play a larger role in the processing plant.

“Conventionally, motors run at a fixed speed, regardless of actual output requirement, wasting a tremendous amount of energy. Energy output use can be reduced by 60% by controlling motors with electrical VSDs.”

New motor types are appearing, placing additional demands on motor-drive control, says Brown.

This in turn means that the ac drive needs to be able to control an expanding variety of motor types, without burdening the end-user with more complexity. In addition, new energy-efficiency requirements lead to more variable speed applications.

He explains that certain ac drives are designed for exactly the needs of mining and mineral processing plants, coping with extreme conditions, heavy loading and controlling equipment installed a long distance away.

“No matter how well the plant design has been optimised, there is always a way to drive down costs even further. ac drives are used extensively for this purpose, extending equipment lifetime, optimising processes, reducing maintenance and saving energy costs.”

The mining and minerals industry presents some of the most challenging environments for production, adds Brown. Mine sites, mineral processing facilities, associated stockyards and ports facilities, are large scale and often in remote locations.

He points out that all Danfoss drives are greater than or equal to 90 kW. These drives also incorporate a back-channel cooling design, with separate cooling paths for the power components, control electronics and an IP54 seal, between these two paths.

“This back-channel cooling removes about 85% to 90% of the power loss directly through the heatsink, leaving only 10% to 15% of the total loss dissipated in the switch room.”

Additionally, consideration has to be given to the outside air quality, explains Brown. However, if it is suitable – by using the heatsink cooling fans and appropriate mounting and ducting – filtered external air at temperatures of up to 50 ºC can be used to exhaust about 85% to 90% of the heat loss from these VSDs. This can be done directly outside the switch room, without affecting the switch room pressurisation.

He explains that the switch room air conditioning system only needs to be sized for the remaining 10% to 15% losses.

“Using this feature can dramatically reduce the air conditioning requirements of the switch rooms and provide significant project cost savings, along with operational ongoing cost savings, compared to VSDs without such a design feature.”

“The mining industry is a major consumer of energy and is responsible for more than 40% of the total industrial energy use. In sub-Saharan Africa, the Energy Intensive User Group alone consumes over 40% of electricity produced in South Africa,” according to former Energy Minister Jeff Radebe.

This need for energy-efficient technology, has seen Danfoss South Africa embarking on a series of informative webinars, geared towards mining engineers, specifiers, buyers, mining houses and investors alike, says Brown.

These interactive webinars will enable stakeholders to think differently about their current energy usage and how the right drives are enabling energy costs savings.