MINING ENERGY
The rise of renewables
John Chadwick considers traditional power systems for mine sites and also notes the expected growth in the use of and great potential for renewable energy sources and power storage
Ananth Parameswaran, Director of Power Systems and Global Marketing at Cummins Power Generation, says“ only generators robust enough to operate at high reliability under extremes of ambient temperature or at high altitude can be considered for applications at mining sites. For this reason, diesel engines already proven in large mining equipment are the preferred choice for onsite power generation installations, as they offer a proven performance.”
“ This engine commonality greatly simplifies the diesel engine servicing required on the mine site, contributing to easier and lower cost of service.
“ Generator sets and installations are typically rated according to the number of hours and the related duty cycle they operate, ranging from emergency standby power( ESP) to limited-time running power( LTP), prime power( PRP) and continuous( COP). Each of these applications place increasingly higher running time and load hours on the generator set, with a corresponding reduction in rated output to ensure reliable operation. Generator frequency may be either 60 Hz or 50 Hz, depending on which area of the world the mine site is located, adding a further influence on the rated output of the generator set.”
A popular generator used on mines, such as the DQK Series from Cummins Power Generation using a Cummins QSK60 diesel engine, will be rated 2,250 kW at 60 Hz for emergency standby use, while for continuous use will be rated lower at 1,600 kW for unlimited hours use. Mines requiring 50 Hz frequency operation will use the same generator with a lower 2,000 kW rating at standby and 1,230 kW for continuous applications.
Onsite power systems are typically installed as a connected series of containerised generator sets with associated power control and switchgear systems. In other examples, customised enclosures or even a dedicated power station facility is constructed to accommodate larger, open generator sets.
There is a power choice mines can make between using a larger number of lower rated generators, or a smaller number of higher rated generators. Depending on the specific power requirements, economies of scale can be achieved by using a fewer number of higher output generators to reduce the requirement for paralleling switchgear and automatic transfer switches.
Apart from the generator sets themselves, mine power projects will often require transformers, paralleling systems, switchgear, containerisation or acoustic enclosures, cooling and remote monitoring.
Parameswaran notes that the power load demand of an off-grid mine is dependent upon the size of the infrastructure supported, the commodity being extracted and if the mine is open pit or underground. Metals mining may undertake processing onsite with crushing, concentration and even smelting, accounting for a high power demand.
The Raglan mine wind turbine is well situated to take advantage of the power of wind. Courtesy of TUGLIQ
“ Underground mines can use double the amount of electrical power per tonne of mined material compared to open pits. Shafts and lifts require power, as do extractor fans, lights and dewatering pumps. Deep mines require air conditioning, while mines in cold climates may require heating. This equipment can impose load ups of typically 5 MW demand, with additional power requirements for standby generators in place for emergency situations.”
Of course, if a mine is close enough to a gas pipeline to make tapping in a feasible option, natural gas fuelled generators can offer an attractive option in place of diesel-powered generators for base load prime power and can help mine operators to significantly reduce their cost of energy.
“ While the rebound in commodity prices will improve the viability of new and existing sites throughout Africa, reliable power supply remains a significant challenge facing new mines, especially in areas that are not connected to the grid,” says Clayton Marsland, Regional Sales Director at APR Energy – a leading provider of fast-track mobile turbine power.
This is of course true of projects in many other parts of the world, especially as the trend recently has been to develop more mines in remote areas, far removed from existing power infrastructure.“ In some cases, it can take five to six years for mines in these areas to be connected to the grid,” Marsland says.“ As a
In Madagascar, the Ambatovy operation purchased 30 Cummins Power Generation generator sets – 30 1,000 kW C1250 D2R generator sets using KTA50-G3 engines and STAMFORD P7 alternators. The rental-spec generator sets suit the harsh conditions
70 International Mining | SEPTEMBER 2016