Aggreko takes hybrid mine power to new heights

Providing power to remote mines is not an activity for the faint hearted. The new Salares Norte open pit gold/silver mine site in the Atacama region of northern Chile, for example, is about as off-grid as you can get, located at an altitude of 4500 m in the Andes mountain range and about 200 km from the nearest town. The weather is also challenging, with extremes of heat and cold, and very high wind speeds.

Power is mission critical both in terms of the mining operations and the welfare of people at the remote site, which can become completely cut-off in freezing weather. In such circumstances “everything is about reliability”, says Uruguay-based Pablo Varela, Latin America managing director, Aggreko, which has signed a 10 year contract with mining company Gold Fields to power the site on a rental basis.

Initially, the solar–diesel hybrid power supply system – to be fully operational by the end of 2022 – will consist of 16 MW of tailor-made high-altitude-performance diesel gensets, combined with 9.9 MW of solar panels, which have been adapted to the demanding site conditions, with mechanical reinforcement and domed PV structures to cope with the winds and redesigned inverters.

The gensets (of the G3+ type, employing Cummins piston engines customised/upgraded by Aggreko) will have a generating capacity of 772 kW each at 4500 m – benefitting from fuel injection and air cooling modifications designed to reduce altitude derating.

The solar/diesel hybrid system will have a total of 22 gensets, with two of the gensets operating as spinning reserve, with one held in cold reserve.

Power is being provided to five ‘generation points’ across the mine site, with the hybrid system connected to generation point 1. Two further pairs of gensets (one running and one in cold reserve) serve generation points 2 and 3, while the first deliveries of gensets, providing power for early construction work on the new mine, are connected to generation points 4 and 5 (two gensets per generation point, one running and one in cold reserve).

Above: Genset layout, solar/diesel hybrid (serving generation point 1)

The deployment of solar power will enable the facility to meet Gold Fields’ requirement for a minimum of 20% renewable power to be used for mining operations, as well as surpassing the Chilean government’s environmental standards. It will also save money, with an estimated $7.4m reduction in energy costs for the mine over the next decade (compared with diesel only) and a further $1.1m in carbon tax offset.

At full capacity, Salares Norte will produce an average of 450 000 oz of gold per year, with Aggreko as the sole power provider.

Above: Microgrid layout, Salares Norte mine

The mountainous terrain in the vicinity of the mine, combined with environmental restrictions, greatly limits siting options for the solar panels (even though the region of course is well endowed with solar radiation). They will therefore be located in three different “crazily shaped” areas, notes Pablo (Platform 15, 0.9 MW; Mirador Alto, 5.9 MW; Platform Botadero, 3.1 MW).

The Salares Norte contract follows on from a successful project completed earlier this year by Aggreko for Gold Fields at its Granny Smith gold mine in Western Australia. This saw the addition of a renewable microgrid consisting of solar panels (8.5 MW) and battery storage (2 MW/1 MWh) to 24.2 MW of existing natural gas fuelled Aggreko gensets.

Interestingly, energy storage is not included in the Salares Norte scheme, as currently configured. Pablo Varela explains that this was because the inverter power electronics were not deemed able to meet the stringent reliability requirements at such high altitudes. The use of pressurised enclosures to house the inverters is being investigated, and Aggreko is committed to research this, but it was decided to go ahead without batteries. “Until we have something proven at high altitude, we are not committing to batteries”, says Pablo. However, under the flexible ten year rental contract with Gold Fields, Aggreko will always be looking for the best options to power the mine, and Pablo says he is quite sure that “in ten years the solutions will be totally different.” Aggreko will “swap engines and deploy new technologies as needed over the coming ten years”, he says, demonstrating the benefits of the rental model for the mine operator. In particular it avoids the operator having to make significant CAPEX outlays on equipment likely to be superseded by improved solutions in a relatively short time, and becoming saddled with less than optimal technologies. Another advantage of renting, says Aggreko, is that O&M costs are included in a flat fee, allowing a clearer view of total costs.

Batteries will probably be added at Salares Norte in the not too distant future, and, in the longer term, gas fuel is a possibility if a reliable source becomes available. Currently the nearest gas supply is over 500 km away, so although a dirtier fuel, diesel was selected for initial operation because it posed the least risk in terms of supply disruption – once again the need for reliability proving to be a key imperative.

The deployment of the diesel engine/PV hybrid at Salares Norte follows Aggreko’s recent launch of Aggreko Solar Power. The company says its rentable solar power offering is “optimised for weak or off-grid energy applications, providing clean and efficient power supply to a range of operations without long-term financial commitments.”

Aggreko solar power installation at the Granny Smith gold mine in Western Australia. The new hybrid system is powered by more than 23 000 solar panels, supported by a 2 MW/1 MWh battery system and 24 MW of existing gas fired Aggreko gensets.

The solar PV will reduce the need to run gas fuelled gensets at the mine, while the battery plant will provide essential services such as PV ramp rate control and transient voltage/frequency support. The assets are being managed by Aggreko’s control software platform “which rapidly deploys automated responses to avoid issues and predicts future problems”, says the company.

Aggreko Solar Power was launched in October 2020, with the announcement of the immediate availability of the company’s solar power rental offer. “The 1 MW PV solution is optimised for weak or off-grid applications and delivers clean energy innovation without long-term financial or technical commitment”, the company said.

It is contracted on a rental basis, with no upfront CAPEX required. Deployment time is three to four months, the system has low O&M requirements, and is said to be well suited for use in harsh and remote environments. Contract durations start at five years, which provides greater flexibility should business operations or market conditions change.

The solar PV seamlessly integrates with Aggreko’s battery storage products and gensets, the company says. “All three assets are managed by intelligent software using one control system. The result is a high-performance hybrid system that operates more efficiently, uses significantly less fuel in combination with backup generators, and has a much lower CO2 footprint.”

The PV panels feature a single-axis tracking system to maximise power production, while enabling a more stable and predictable yield curve. The panels closely track the sun east to west as it moves across the sky. Aggreko estimates that the use of a tracking system can increase the amount of power delivered by 10 to 20% (without exceeding the maximum allowable PV share), saving more fuel without compromising system stability. By combining PV string inverters with containerised controls, the system delivers even greater reliability and resilience with reduced installation time, says Aggreko.