While renewable energy use in the resources industry is slowly but surely gaining more and more traction, how the energy is stored on mine sites is vital. Simon Hackett explains energy storage and how it can cut costs.
T he renewable energy revolution is providing Australian miners with a powerful new tool to slash energy costs at remote mine sites by using energy storage systems to deliver 24/7 power.
Energy storage systems alongside solar arrays can offer significant cost-savings when compared with the infrastructure costs of setting up gas reticulation, remote electricity links or diesel generators.
The good news for miners is that Australia is entering the second phase of its renewable energy revolution. The first phase, which saw solar panels and wind farms appear throughout the country, had a significant limitation – intermittency. The sun doesn’t shine all the time nor does the wind always blow. The second phase brings widespread deployment of big batteries to allow renewable energy to be stored and supplied when it is required.
Competition in the energy storage sector is now creating a wider range of choices and driving down prices. Global companies such as Tesla, LG, Panasonic and Enphase have entered the market with lithium-based batteries, which are based on an energy storage chemistry developed for portable electronics, such as notebook computers and mobile phones and, most recently, electric vehicles.
Australia also has its own horse in this race in the form of Redflow Limited, a company that has developed the world’s smallest flow battery – an alternative chemistry to lithiumbased batteries, which offers compelling advantages for on-grid and off-grid stationary energy storage applications.
So, how do you choose the best energy storage system for your mining operation?
While lead acid batteries offer proven technology at an affordable price, their shortcomings include size, toxicity, risk of overheating during charging, irreparable damage from complete discharge and a typical cycle life of just 300 to 500 cycles. These inconveniences become major challenges when you deploy them at remote sites.
The new challenger is lithium-based batteries, as championed by Tesla, the company behind the world’s best-known electric cars. Last year, leveraging strong social media mojo for its brand, Tesla made a global splash by announcing its Powerwall home battery. For perhaps the first time ever, the concept of energy storage became sexy.
But it’s important to recognise that the Powerwall is not an energy storage breakthrough. Tesla has merely re-factored its lithium-based vehicle (power) battery packs into an “energy” role.
The difference between power batteries and energy batteries is important to understand. A power battery is designed to charge and discharge quickly, delivering plenty of power when needed. A power battery is a sprinter, not a marathon runner.
Lithium based-chemistries are well-suited to power applications, such as electric cars, which place a low average stress level on the battery, apart from short periods of high demand – such as accelerating – with long periods of resting time.
By contrast, an energy battery is a marathon runner, not a sprinter. Energy batteries need to work with renewables to emulate the longterm, relatively constant power draw typically met by a baseload power generation plant.
Mining companies need to consider three key criteria when evaluating energy storage solutions:
- Energy storage capacity, both initial and lifetime
- Performance in challenging environments
- Scaling to grid level.
ENERGY STORAGE CAPACITY
Let’s assume a lifetime of 10 years, reflecting the warranties offered by most energy storage batteries, including Tesla and Redflow.
A typical lithium ion energy battery comes with a total storage capacity of 7kWh (kilowatt hours), of which only 6.4kWh is actually usable. This is because lithium-based batteries must reserve a portion of their capacity to prevent damage to the battery. To put this in context, 6.4kWh is just over one-third of the widely cited 18kWh of energy used by the average Australian house each day.
By contrast, Redflow’s ZCell and ZBM2 flow batteries come with an initial energy storage capacity of 10kWh, which is more than half the average house power draw. Flow batteries also discharge 100 per cent of their energy storage capacity on a daily basis without any damage to the battery.
Significantly, lithium batteries also lose energy storage capacity over time. For example, Tesla’s January 22 warranty states the Powerwall battery will retain at least 85 per cent of its initial rated capacity after two years, 72 per cent after five years and 60 per cent after 10 years. That means a Powerwall with initial storage capacity of 6.4kWh may only store 4.6kWh of energy after five years – halfway through its warranted life – and 3.8kWh at the end of 10 years.
Redflow batteries are designed to deliver 100 per cent of their 10kWh energy delivery capacity over the warranted 10-year life of the battery electrode stack.
BATTERY PERFORMANCE IN CHALLENGING ENVIRONMENTS
Many batteries heat up when they are worked hard, so design and deployment are critical factors to ensure effective heat dispersal. Due to their chemistry, lithium-ion batteries can pose a fire hazard if they’re not installed properly or if poor quality batteries are used. This can make them prone to ‘thermal runaway’ – that is, bursting into flames – if they overheat or are damaged.
Flow batteries contain no risk of thermal runaway because they use a fluid zincbromide electrolyte (bromide is a flame retardant). In the unlikely event of a problem, the battery’s pumps stop running, automatically shutting down the unit. Also, Redflow’s flow batteries do not require active cooling, even in ambient temperatures as hot as 50 degrees – an important consideration for deployment in remote areas of Australia.
SCALING UP TO A GRID LEVEL
For Australian mining sites, just a battery or two will not cut the mustard, so you need to look at how to scale energy storage systems up to grid-scale deployments.
At last year’s launch,Tesla CEO Elon Musk claimed the company’s Powerpack battery – the Powerwall’s big brother – is “infinitely scalable”. He said Powerpack consisted of 100kWh blocks that could be clustered to meet any project size. While Tesla has begun installing Powerpacks in the US, there are no reported installations in Australia.
Redflow’s grid-scale solution, the LSB (largescale battery) – a container-size form factor holding as many as 60 flow batteries storing 600kWh of energy – is already installed in Australia. I have one at my Adelaide office, providing four days of energy storage for the 2777 square metre business centre, which houses as many as 50 people. Redflow’s design allows the interconnection of multiple LSBs, delivering as much energy storage capacity as you need.
The purpose of this column is not to sell you on one energy storage solution over another, but to explain that not all batteries are created equal, so you should look closely at the respective merits of each energy storage system before making your choice.
Download Redflow’s published whitepaper about energy storage for mining companies, citing pioneering projects such as the DeGrussa Sandfire mine, 900km north-east of Perth, and Rio Tinto’s Weipa operation in Far North Queensland here: http://redflow.com/madeformining/.
SIMON HACKETT – CEO, REDFLOW LTD
Simon Hackett is Executive Chairman of ASXlisted Australian battery company Redflow Limited, which has developed the world’s smallest flow battery. Simon, a technology entrepreneur who invests in innovative Australian businesses, sold his company Internode in 2012 and subsequently served as a director for iiNet and NBN Co.
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