Modern Mining: Featured News

One of the most innovative solar energy installations yet seen in a mining application is now operational at the Otjikoto gold mine of B2Gold in Namibia. The Otjikoto Solar Farm, as the installation is known, will reduce the mine’s dependence on its existing heavy fuel oil (HFO) power plant and has already delivered savings of several hundred thousand litres of HFO since being commissioned in early March this year. Modern Mining’s Arthur Tassell attended the official opening of the facility in late May.

Otjikoto is by no means the first mine in Africa to commission a photovoltaic (PV) solar power system but it is probably the first to have a fully autonomous installation which can manage the combined thermal and solar resources available to the mine largely without human intervention. With a capacity of 7 MW, the Otjikoto Solar Farm is also one of the biggest installations of its type in Namibia and indeed in sub-Saharan Africa.

Otjikoto Aerial

The Otjikoto Solar Farm is one of the biggest installations of its type in Africa (photo: B2 Gold).

The solar farm was inaugurated by Namibia’s new – and highly regarded – Minister of Mines & Energy, Tom Alweendo, before around 120 guests. Apart from the Minister, other speakers at the event included Mark Dawe, Country Manager and Managing Director of B2Gold Namibia (the 90 %-owned Namibian subsidiary of Vancouver-based B2Gold Corp); Bill Lytle, Senior VP Operations of B2Gold (who led the team that built Otjikoto); Dr Leake Hangala, Chairman of B2Gold Namibia; and John Roos, Manager Projects & Compliance, B2Gold Namibia. Roos was responsible for managing the solar farm project.

An open-pit operation, Otjikoto is located in the Otjozondjupa Region of Namibia, approximately 300 km north of Windhoek and just off the national highway linking the towns of Otjiwarongo and Otavi. Officially opened in mid-2015 (although it achieved its first gold pour in late 2014), it has been one of the most successful gold mine start-ups seen in Africa in recent years. In 2017 it produced a record 191 530 ounces at a remarkably low cash operating cost of US$468/oz. It forms the backbone of Namibia’s gold-mining industry, the only other gold operation in the country being the much smaller Navachab mine.

Otjikoto is what is known as an ‘island energy producer’ – meaning that it is off the Namibian national grid. Although not in a particularly remote area, it is powered by a thermal plant which was installed during the development phase of the mine when it became evident that relying on a grid connection would have delayed the start-up of operations. The plant has a generating capacity of 23,5 MW – which is almost twice the mine’s average demand – provided through four Cat MaK 12CM32 medium-speed HFO generators, capable of generating a combined 19 MW, and three Cat 3516 high-speed diesel engines, with a total capacity of 4,5 MW. The plant has performed extremely well, delivering a 99,8 % power output availability since commissioning.

Outlining the rationale for the solar farm project, Roos says that tight control of energy costs is essential for a low-cost producer such as Otjikoto, given that electricity generation has typically accounted for approximately 12 % of the mine’s overall operating costs and 35 % of total processing costs. “Going the solar route will allow us to achieve a very significant reduction in our consumption of HFO – which is steadily increasing in price – with the saving amounting to approximately 3 million litres a year,” he states.

“Moreover, it fits in well with B2Gold’s commitment to environmental stewardship. It will, of course, reduce the mine’s carbon footprint and the likelihood is that it will remain as an income-generating asset long after the mine has closed, benefitting both local communities and the wider Namibian economy.”

The Otjikoto solar project was approved by B2Gold Corporate in October 2016 after intensive feasibility studies. Subsequent to the approval being received, a rigorous vendor evaluation process was initiated with the assistance of B2Gold Namibia’s appointed engineer, GS Feinsinger & Associates, a consulting engineering practice based in Windhoek, with several major players in the solar energy industry being invited to submit proposals. Ultimately, the contract was awarded to Barloworld Namibia, in partnership with Barloworld Power in South Africa, the Caterpillar dealer in Southern Africa, and Caterpillar Microgrid Solutions in the US.

“Barloworld and Caterpillar offered us the most advanced solution based on their Cat® Microgrid Solutions technology,” says Roos. “This offered a total and seamless integration between our existing HFO plant and the proposed solar farm, with the integration being managed by Caterpillar’s  Microgrid Master Controller (MMC). Also influencing our decision was the fact that our HFO plant is a Caterpillar installation. None of the other potential vendors were able to match the state-of-the-art capabilities of the Cat® Microgrid technology.”

He adds that the technology is relatively new on the market and, at the time B2Gold was evaluating proposals, had not yet been used in a commercial application, the only installation being at Caterpillar’s Proving Ground near Tucson in Arizona. “We were able to visit this and see for ourselves the system in operation. As far as I’m aware, we’re the first company in the world to deploy it in a mining application.”

The engineering, procure and construction (EPC) contract to deliver the solar farm was awarded to Barloworld Namibia in June last year. Shortly after B2Gold received the necessary environmental approval from Namibia’s Ministry of Environment & Tourism, debushing and ground levelling of the 22 ha site started. The first shipment of solar panels arrived on site at the end of October and the first PV module was installed on 1 November. Construction of the solar farm was completed by late February 2018 and in early March the powerline exporting energy to the HFO plant was energised successfully. On 14 May the MMC and its associated SCADA system, the ‘brain’ of the system, was commissioned.

Comments Roos: “The project was completed on schedule and within its budget of N$115 million or US$8,5 million. We’re particularly proud of the fact that a total of 105 000 man hours was worked without a single LTI incident and that the Namibian content of the project was maximised, both in terms of procurement and construction.” He adds that many members of the construction team were trainees sourced from the Namibian Institute of Mining & Technology (NIMT).

The completed solar farm comprises 62 400, 115-W Cat-branded thin-film solar panels, manufactured by its joint venture partner First Solar, Inc, which has its headquarters in Arizona. The panels are mounted on a PiA single-axis tracking system. The DC power is converted to AC power through Sunny tri-power three-phase SMA string inverters and is then distributed to the HFO plant via Schneider switchgear in the PV control building through a 3,5 km overhead powerline.

According to Roos, the Cat-branded thin-film panels have a specific yield advantage over traditional polycrystalline panels in hot conditions and have a superior shading response. The solar farm has a modular design, allowing PV energy to be added to (or removed from) the Otjikoto microgrid in 1 MW increments.

In integrating the solar farm with the HFO plant to create a hybrid power system, the MMC works in conjunction with the HFO plant’s SCADA system, developed in a collaborative effort between the Barloworld/Caterpillar technical team and Namibian-owned IAE, which specialises in industrial automation and engineering.

Explaining how the MMC works, Roos says it not only regulates the energy being fed to the HFO plant but allows for the seamless selection of the mine’s two energy sources (HFO or solar), choosing the most economically viable option at any point in time. “Most importantly, the MMC enables the mine to switch off one of its HFO generators during day-time based on algorithms monitoring irradiance, cloud cover and PV penetration,” he states. “This not only allows us to save HFO but also reduces the operating hours on our large HFO gensets.”

Looking to the future, Roos says B2Gold Corporate is considering two further phases of development for the Otjikoto solar project. “Phase 2 envisages Otjikoto being connecting to the national power grid, which could see up to 45 % of the mine’s power requirements being supplied by Nampower on an off-peak tariff, while Phase 3 contemplates the expansion of the solar farm, which would be easily achieved given the modular nature of the installation. We may also, at some point in the future, even look at the possibility of energy storage, allowing the solar energy generated by the solar farm to be used at night-time or at times – for example, when there is cloud cover – when conditions for generating solar energy are unfavourable. Caterpillar and other vendors already have proven systems that could be used.”

The operation of the project has thus far met all of B2Gold’s expectations, with 468 155 litres of fuel having been saved from the first day of recording solar energy at the HFO plant (8 March 2018) through to 27 May. Over the nine-year modelling period for the project (effective 1 April 2018), it is anticipated that approximately 26,3 million litres of HFO will be saved resulting in operational savings of an estimated US$16 million. On this basis, the payback period of the project is estimated at 4,5 to 5 years.

Photos by Arthur Tassell (unless otherwise acknowledged)

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Name: Arthur Tassell
Email: mining@crown.co.za
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Fax: +27 11 615-6108

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