by Emre Goren, Danfoss  –  

Energy consumption patterns need to be addressed in earnest, in a bid to ensure that all industries de-carbonise towards a greener and sustainable future. With an ever-increasing demand to increase energy supply in a globally carbon-constrained environment, the mining industry needs to improve its energy-efficient technologies, such as electrical variable speed drives, which could reduce energy consumption drastically.

Emre Goren

The recently concluded series of Danfoss Energy Efficiency in Mining webinars demonstrated that the fundamentals of AC variable frequency speed drive technology persist, but that many elements are rapidly changing in a move towards a more sustainable and environmentally friendly mining future. Increasingly, specialised software is embedded in today’s processing components, offering new functionalities and enabling the AC drive to play a larger role in the processing plant.

The content of the webinars clearly demonstrated that conventional motors run at a fixed speed, regardless of actual output requirement, wasting a tremendous amount of energy, but that energy output use can be reduced by 60% by controlling motors with electrical variable speed drives (VSDs).

New motor types are appearing all the time, placing additional demands on motor-drive control. 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.

Certain AC drives are designed to meet the needs of mining and mineral processing plants, coping with extreme conditions, heavy loading and controlling equipment, sometimes installed a long-distance away. No matter how well the plant design is optimised, there is always a way to drive down costs even further.

According to the Department of Mineral Resources and Energy, 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 users’ group alone consumes over 40% of electricity produced in South Africa. Just less than 50% of the energy-intensive users in South Africa are the mines.

The AC drives which are used extensively for this purpose are robust enough to extend durability, optimise processes, reduce maintenance and save energy. The mining and minerals industry presents some of the most challenging environments for production. Mine sites, mineral processing facilities, associated stockyards and ports facilities, are large in scale and are often in remote locations.

All Danfoss drives of ≥90 kW, 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 approximately 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.

Consideration has to be given to the outside air quality, but if it is suitable, using the heatsink cooling fans and appropriate mounting and ducting, filtered external air at temperatures of up to 50°C, can be used to exhaust approximately 85 to 90% of the heat loss from these VSDs directly outside the switch room; without affecting the switch room pressurisation.

The switch room’s air conditioning system only needs to be sized for the remaining 10 to 15% losses. Utilising 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.

Click here to watch the live recording of one of these webinars

Contact Lynne McCarthy, Danfoss, mccarthyl@danfoss.com