Kgwanyape Energy Solutions

Nowhere else is the news of an invention that provides significant energy savings more welcome than in the mining sector.

Accused of being the major electricity guzzlers in the South African industry, mines can almost breathe a sigh of a relief with an innovation that comes from HVAC International.

The company looks to have placed South Africa at the global cutting edge of power saving technology for deep mines, with reports of its energy saving technologies having, to date, reduced electricity consumption by a total of 200 MW.

It won an eta Award in the industrial category for 2008. This is the fifth time that HVAC International has won the award. Energy efficiency is part of Eskom’s drive to ensure sustainable electricity supply into the future and is the core focus of the nineteenth annual eta Awards.

Four projects assessed for the awards had seen electricity use reduced by an average of 37%, producing a saving of 96,452 MWh. The yearly energy cost savings, based on 2008 prices, was nearly R12-million.

Similar projects have been implemented at ten sites and another 11 projects are on the cards. This could realise an energy reduction of 114 MW on the national grid and energy savings of up to R100,5-million a year. Each MWh saved means 0,97 t of carbon dioxide (CO₂) not being released into the atmosphere or, for the 21 projects altogether, close to 750 000 t/y.

HVAC International chairperson and founder Professor Edward Matthews said that energy savings were extracted from compressors, which he says are responsible for 15% to 30% of the total energy consumed in a myriad of applications in deep gold and platinum mines. The applications include powering of underground drills, machinery and refuge bays where compressed air plays a significant part in ensuring that miners have uncontaminated air to breathe during emergencies.

“We achieved the savings by tackling the problems associated with optimising and automating a typical compressed air supply and distribution network with automatic feedback which, until then, had never before been successfully implemented in a complex deep mine environment,” said Matthews.

This involved automating the supply side before automating the integrated compressor supply and distribution network. This process overtook the normal procedure at mines which saw the stopping and starting of the mine compressor being undertaken manually.

These stopping and starting procedures are similar to the methods used on older aircraft engines where prescribed procedures have to be followed to start and stop engines. In new aeroplanes, these procedures have been automated. The same has to be done for compressors if they are required to automatically respond to the feedback from an integrated energy system. This requires that temperatures, pressures and other data must be measured so that decisions taken by the integrated system allow automatic stop, start or cutbacks,” explained Matthews.

After automation of the supply equipment, the next step was the automation of demand control equipment. A communications backbone was an essential component of the installation and had to be installed in all points of a complex air distribution network at multiple sites.

When this infrastructure was completed, we had to add simulators, optimisers, controllers and feedback loops, all part of a real time energy management system. Achieving acceptable results, however, meant that implementation costs had to be in line with potential savings that could be achieved.

“Our technology’s simulation capabilities show costs versus energy savings. For example, at a typical 10-level, single-shaft mine, one control unit results in 30% savings, ten control units in a 75% saving and 20 control units in 85% savings. These results can be used to calculate payback periods,” Matthews said.

Eskom demand side managements interest in energy savings technologies, and its subsidisation of energy services companies’ projects, measured against a range of criteria, was an essential component to the process of introducing energy saving technologies to South Africa, Matthews said.