Our Blogs

During 2018, Energy Drive presented a business case to Glencore to install Variable Speed Drives (VSDs) on their eight (8) 1300 kW, 11 kV kiln ID fans at Lion Smelter. The project would fit our typical Zero Capex model and offered Glencore considerable energy and monetary savings. Together with guaranteed savings, Energy Drive would maintain the VSDs and associated equipment for as long as the kit is operational on-site.

After finalising contracting and funding for this impressive R50m project, we started procurement in March 2019. Our project teams, made up of key sub-contractors, spent a total of 16 weeks (incident free) on-site to deliver a world-class installation of which we are very proud.

Commissioning of the VSDs was completed in October 2019, and we have already witnessed significant energy-savings during early stages of system optimisation. The leadership and staff at Lion have been very supportive during the project execution, and we look forward to ongoing collaborative relationships with them.

BUSINESS CASE

Off a 65 GWh/year pre-Energy Drive baseline, we are targeting 50% energy reduction and a net saving (after our fee) of R5,5m/year to Lion Smelter. The net saving is guaranteed, and with our transparent monitoring and reporting systems, it’s easy to hold us to account.

DESIGN

After VSD selection, the next step was to design a suitable layout and e-Cabin to house the VSDs and ancillary equipment. Due to the location of the motors and existing substations, we had to construct two (2) e-Cabins to house four (4) VSDs each. Attention is always paid to cooling of the VSDs since they can generate up to 4% of their rated capacity in heat losses at full load. All of the 2000 kVA VSDs chosen for the project have their thirty (30) power cells split back-to-back, requiring cool air intake on both sides of the drive. Eight (8) suitably sized ducted splits per e-Cabin would give us the cooling required plus redundancy. From the aircons, we use an internal wall cavity to deliver the cool air to the VSDs and the ceiling void to return the warm air.

Once the layout of equipment is confirmed, the detailed e-Cabin design can be finalised. The structural steel base on which the e-Cabin and all its contents sits was designed in-house. The medium voltage (MV) circuit followed our traditional offering where the VSDs sits in parallel with the client’s existing system. We used Ring Main Units (RMU) to allow selection between VSD and the existing direct-on-line modes of running the motors. The low voltage distribution and control systems were specified and built. 100 kVA dry-type transformers were used to step down the available voltage onsite to 400 V, which is the requirement for all our auxiliary power. Each complete system, A, B, C and D are completely stand-alone allowing MV and LV isolations of either system for maintenance while the others are unaffected.

CONSTRUCTION

The 6-month lead time on the VSDs allowed a large chunk of the construction to happen outside the critical path of the project. The 27,5 x 6 m steel bases were fabricated and assembled off-site before being broken down again for painting and transport. The on-site work started with a level concrete slab that was laid by Glencore, followed by assembly of the steel bases on which the panelised e-Cabin was assembled. The roof would later be removed to rig the VSDs into position on arrival. Having the roof on allowed for the placement of the RMUs, control panels, aircons and transformers so the electrical installation could continue. Our electrical installation team did everything from lighting to final VSD installation and MV terminations and spent the most time on-site totalling 16 weeks. The sixteen (16) aircons were installed and commissioned, followed by the fire detection and suppression system. Calibrated utility-grade energy meters were retrofitted at the existing starter panels and protection relays configured to suit new installation.

COMMISSIONING

Profibus communication was established between Energy Drive and Glencore’s existing control systems. Over this network, all the necessary info is shared for effective control of the VSDs. The RMUs are motorised to enable DOL/VSD selection from the control room without any manual switching. This is tested thoroughly with has layers of electrical and software interlocks for safety.

The VSD manufacturer sent their commissioning engineers to support the commissioning process, which proved very successful. From 31 October 2020, all eight (8) VSDs have been in operation with no technical issues. We have started to tweak the control philosophy in collaboration with Glencore and continue to strive towards process stability and energy efficiency.