RUC Mining introduces innovative regenerative energy storage solution for mine hoists utilising Rockwell Automation PowerFlex drive systems
Underground mining hoists, or winders, are powerful machines used to raise and lower minerals and materials in a mine shaft.
They allow efficient vertical transport of materials, which would otherwise require larger machinery and further cost to extract from the mine.
While travelling upward, a large amount of power is required, but this is not the case on the way down.
It’s the downward trip that sparked an innovative idea by underground mine hoist specialists, RUC Mining: what if energy generated on the way down could be stored, then used to power the upward journey?
The sustainability implications and broader contribution to the electric mine of the future were huge – but there was a technically complex and challenging task to figure out first.
RUC electrical manager, Greg Bell, believed this was more than an idea, and began working on how to make it a reality. He and the RUC team chose strategic partners, Rockwell Automation, and Energy Power Systems Australia (EPSA), to create a fully integrated solution that could be rolled out to hoists across the globe.
Collaborating with these partners, the RUC team created what they believe to be the world’s first regenerative energy storage solution for underground mine winders, allowing these machines to run totally on their own stored energy, rather than requiring a separate diesel generator.
In its first application in an Australian mine, RUC installed its RUCShaw 512 single-drum winder, which is powered by 710 kW drives, has a hoist capacity of five metres per second, with 12-tonne line pull, and operates with a design depth of 1,600m.
A technically complex sustainability solution
When hoisting a load up a mine shaft, electric motors consume energy. But when travelling downwards, they have the potential to become generators.
“Most mine hoists use a brake resistor pack with a cooling fan to deal with the heat generated. But these packs create a single point of failure, and are application-specific, so they need recalculation if a variation in brake power is required,” explained Bell.
“Instead, we proposed for the generating power to be supplied back onto the incoming supply bus, to be absorbed by system loads,” he added.
To make this solution a reality, Rockwell Automation, the world’s largest company dedicated to industrial automation and digital transformation, provided Active-Front-End (AFE) Powerflex® 755TR regenerative variable speed drives, Low Voltage Motor Control Centres, and GuardLogix® controllers, as well as ThinManager® software for application management, FactoryTalk® View Site Edition software for a complete real-time overview of HMI operations, network and security services, and product and technical support.
The battery selected to store regenerative energy was a Cat® PGS 1260 Battery Energy Storage System (BESS), supplied by EPSA, which provided added redundancy through its parallel inverter and battery stack architecture.
“We have one operational project where we have implemented this solution with two hoist drives, and we are looking into incorporating this into future projects. We also see potential for this solution to be rolled out on new and existing mine shafts internationally,” said Bell.
Sustainability gains
By reducing the amount of diesel power generation, significant environmental gains are achievable with the regenerative energy storage solution in place. RUC has estimated that in their initial installation, over a 24 month period, the regenerative energy storage solution will achieve:
- An estimated reduction in diesel consumption of 1,427 kilolitres (which saves approximately $2 million)
- A reduction of 3.85 tonnes of CO2 output (that’s approximately equal to travelling 12,700km in a petrol car)
- An approximate 42% reduction in greenhouse gas emissions from power generation
“In addition to these strong sustainability benefits, the regenerative energy storage solution also reduces daily operating costs, reduces plant operating hours and maintenance requirements, and provides an additional level of redundancy to the power system that was not available in passive components such as load banks,” said Bell.
Rockwell Automation regional director – south pacific, Anthony Wong, added, “Sustainability is a key focus for Rockwell, and when RUC came to us with this forward-thinking project, we were enthusiastic to work with them to turn it into a reality, and to help deliver reliability and performance with our hardware and software solutions.”
“While this solution was designed and built in Australia, it will be applicable for mines across the world. It’s a small but significant step towards a more sustainable mining industry and the dream of fully electric mines. We commend RUC for its ingenuity and vision in conceiving this truly innovative solution,” he said.
Collaboration of technical expertise
Not only was there a complex integration of technologies, but the regenerative storage project involved a lot of industry firsts, so there was no existing template to follow.
“Some companies dislike being the first to do something, because there’s no guarantee it will work. But Rockwell was supportive from the start. They helped us select the right drives for powering our hoists, and worked to integrate this seamlessly to achieve regeneration coordination with the battery,” said Bell.
“I can’t speak highly enough of the Rockwell technical team – they are some of the best engineers I’ve worked with. Another major benefit was the Rockwell vendor manuals and technical information. These are first-class documents, and the latest versions are all available online, which was crucial for training the workforce and working remotely. Revision control was taken out of my hands because we were always accessing the latest version,” he added.
Bell also identified several key benefits of the Rockwell hardware used in this project, including:
- Outstanding drive configurability and parameterisation. RUC was working with approximately 1,500 parameters in a custom, first of its kind solution, so Rockwell’s drives delivered the required flexibility
- Built-in safety with SIL3-capable safe torque off function, which was a performance requirement of the mine operator. (SIL, or Safety Integrity Level, is a rating system that associates safety with the numerical probabilities of hazardous failures (0 being the lowest and 4 being the highest) for continuously operating systems or on-demand systems.)
- Purpose-built drives. The Rockwell PowerFlex 755TR is specifically built for cranes, hoists, and lifting equipment, which means it has all the features this demanding application requires.
“In addition to the hardware, Rockwell’s software also seamlessly integrated with our control and safety system, and with our historian/data logger for diagnostics and advanced troubleshooting. There was a simple integration between drive and air circuit breaker metering equipment via Rockwell’s controller add-on instructions,” said Bell.
Extra benefits, and a promising future
While not an initial goal of the regenerative energy storage project, the new solution is delivering “bump-less” performance, as well as an additional level of redundancy within the battery.
“Faults happen when you lose power, and hydraulic braking is aggressive. With the regenerative energy storage solution, we can split the battery with two inverters, so we have an added layer of redundancy. This means if we lose power, the winder does not stop, which delivers smooth, bump-less performance,” said Bell.
“Because power goes straight back to the battery with no heat loss, this type of solution could readily be scaled down to any energy application – even something like elevators. We believe this is the only successful gravity kinetic energy storage system using a hoist in the world, and we are proud to be introducing it here in Australia.
“We have plans to use this technology more widely, because if you think about the electric mine of the future, vertical haulage delivers the most affordable, operable, and achievable solution for transporting material out of the mine. The technology has great export potential, too, so we can showcase Australian innovation on a global scale.
