How optimised energy management delivers sustainability at the Fekola Gold Mine
By Luke Witmer, General Manager, Data Science, Wärtsilä Energy Storage and Optimization
Since B2Gold first acquired the Fekola gold mine, located in a remote corner of southwest Mali, exploration studies revealed the deposits to be almost double the initial estimates.
A recent site expansion has just been completed, and while the existing power units provide enough power to support the increase in production, the company sought to reduce its energy costs, cut greenhouse gas emissions, and increase power reliability. The addition of a 35MWp solar photovoltaic (PV) plant and 17MW/15MWh of energy storage to the existing 64MW thermal engine plant was decided.
Such an elaborate hybrid configuration needs a powerful brain to deliver on all its potential: Wärtsilä’s GEMS, an advanced energy management system, has been set up to control the energy across the fleet of power sources, thermal, renewable, and battery storage. The integration, control, and optimization capabilities provided by GEMS allow the thermal units to be run at the most efficient rate and enable the battery storage to handle the large load step changes and volatility of the solar PV generation assets.
Integrated Hybrid Energy Solution
In the context of the Fekola mine, which is an off-grid electrical island, the battery is performing a lot of different services simultaneously, including frequency response, voltage support, shifting solar energy, and providing spinning reserves. The energy load is very flat, with a steady consumption rate around 40MW as the mining equipment is operating consistently, 24/7. However, if an engine trips offline and fails, the battery serves as an emergency backstop. The controls reserve enough battery energy capacity to fill the power gap for the time it takes to get another engine started, and the software inside each inverter enables the battery to respond instantaneously to any frequency deviation.
The reciprocating engines operate most efficiently at 85-90 percent of their capacity, this is their “sweet spot”. But if there is a sudden spike in demand, if a little more power is needed, or if mining equipment is coming online, then another engine needs to be run to meet the extra load. With the battery providing spinning reserves, the engines can be kept running at their sweet spot, reducing the overall cost per kilowatt hour. Moreover, with the solar plant providing power during the day, three to four engines can be shut down over this period, providing a quiet time to carry out preventive maintenance. This really helps the maintenance cycle, ensuring that the engines operate in a more efficient manner.
Solar PV volatility can be intense. On a bright day with puffy clouds passing by a solar farm of this size can easily see ramps of 25MW over a couple of minutes. This requires intelligent controls, dynamically checking the amount of solar that can be let into the grid without causing an issue for the engine loadings or without overloading the battery.
Conducting the Orchestra
The GEMS intelligent software provides the optimization layer that controls all the power sources to ensure that they work together in harmony. The user interface (UI) gives access to all the data and presents it in a user-friendly way. Accessible remotely, all operations are simulated on a digital twin in the cloud to verify the system controls and simulate the most efficient operating scenarios to lower the cost of energy. This is an important software feature, both during and after commissioning as it allows operators to train on the platform ahead of time and familiarise themselves with the automated controls and dynamic curtailment of renewables. The UI provides the forecast for renewables and the battery charge status at any given moment, it can provide push email or phone notifications for alerts; telling operators when to turn off an engine and when to turn it back on.
The software is constantly analysing the data and running the math to solve the economic dispatch requirements and unit commitment constraints to ensure grid reliability and high engine efficiency. Load forecasting integrates the different trends and patterns that are detectable in historic data as well as satellite based solar forecasting to provide a holistic approach to dispatching power. The Fekola site has a sky imager, or cloud tracking camera with a fisheye lens, that provides solar forecasts for the next half hour in high temporal resolution.
To ensure that operators really understand the platform, and have visibility over the advanced controls, the UI provides probability distributions of the solar forecast. Tracking the forecast errors enables operators to see whether the solar is overproducing or underproducing what the forecast was expecting at the time and provides visibility to the operators on the key performance indicators. This feedback is an important part of the machine/human interface and provides operators with insight if an engine is required to be turned on at short notice.
Automated curtailment enables the optimization of the system providing a reactivity that people cannot match. By continually monitoring the engine loadings and battery, the system is ready to clamp down on solar if it gets too volatile or exceeds some spinning reserve requirement. For example, if a large, unexpected cloud arrives, the battery is dispatched to fill the gap while the engines ramp up. Once the cloud disappears, however, the engines remain committed to operating for a few hours, and the solar power is transferred to recharge the battery.
Over time, as load patterns shift, the load forecasting algorithm will also be dynamically updating to match the changing realities of the load. As mining equipment hits layers of harder rock, increasing the power load, the system will adjust and dispatch the engines accordingly.
The Fekola mine project incorporates the largest off-grid hybrid power solution in the world, demonstrating the growing case for clean energy and its sustainable and economic potential for mines in Africa and beyond.
As the cost of batteries and solar panels continues to become more competitive, hybrid solutions are proving to be a realistic and effective means for increasing energy reliability and lowering operating costs in any context, thus freeing up resources to improve the human condition; whether through cheaper materials and gainful employment, or by providing broader access to reliable electricity for healthcare, education, and improved quality of life.View more
Renewables, energy storage and the future of smart cities
Smart cities are a topic of constant conversation, and they’ve already come to fruition across the globe.
From Singapore to San Francisco, organisations, government officials and city planners have made incredible efforts to support the development of intelligent communities. According to a recent report by IHS Technology, there will be at least 88 smart cities all over the world by 2025, up from 21 in 2013. While the majority of these are likely to be located in Asia, Europe is expected to be home to more than thirty.
With smart cities and the general population on the rise, one of the major issues facing industry leaders today is how to power these interconnected cities effectively and efficiently. As a result, many global leaders have publicly asked for a suitable and sustainable answer – one that would support critical infrastructure yet not add to the global emissions challenge.
While joblessness and migration from rural poverty to anticipated urban wealth has led to rapid urbanisation in South Africa and elsewhere in sub-Saharan Africa, putting pressure on limited resources, designing smart cities – or even including elements of smart cities in existing metropolises, may help communities leapfrog obstacles that would impede more complex locations.
The increasing need for such a solution, coupled with the dropping costs of renewable technologies, has made the transition to a fossil fuel-free environment more likely than ever before. In the last year alone, global renewable energy investment has increased to the point where it’s now surpassing investment in fossil fuels, according a recent UN report.
From wind to solar, nations all over the globe are taking advantage of this shift to create innovative and energy efficient solutions from natural power. In Saudi Arabia, a $200 billion solar power development has just been signed off, potentially tripling the country’s electricity generation capacity. Over in China – one of the most highly populated countries in the world – the Jiuquan Wind Power Base, also called Gansu Wind Farm Project, was recently approved by the government. The windfarm, which is currently installing capacity of more than 6,000 MW, is projected to grow to a total of 10,000 MW, solidifying China’s ambition to be a global leader in renewable energy.
South Africa is home to eight of the ten largest solar plants in Africa, including the 175MW Solar Capital De Aar Project, the 100MW KaXu Solar One project (South Africa’s first commercially operated thermal electric power plant), and the 100MW Ilanga-1 CSP Plant, among others.
Though renewable energy is the way of the future, there are still some concerns about how this will all be feasible – especially as our cities continue to get bigger, smarter and more demanding. This uncertainty has led many industry leaders to start asking valid, but tough, questions. For example, as renewable energy from wind and solar is weather dependent, will we be able to be permanently independent of coal, oil, and natural gas? And with the shift to electric cars, will our energy system be able to handle the increased demand on the grid?
The answer? While clean energy technologies are evolving tenfold, much more flexibility will be necessary for these energy sources to provide the reliability we require. This includes investing in interconnected systems, having ample control over when and how we use energy, and most importantly – safe, reliable and efficient energy storage.
The surplus energy that is generated from renewable sources, such as solar or wind, is stored and used later when they are no longer generating energy – further eliminating emissions from imported electricity. This excess energy can also then be sold back to the grid, giving business the chance to improve on their own return on investment, while lowering overall energy costs.
Business benefit for energy storage
Investing in battery storage projects like Eaton’s microgrid also enables businesses to ensure reliable power continuity during grid outages – especially during peak times. This is particularly interesting for financial investors, as many see this as a way to play on the grid service markets.
There is no doubt that smart cities are the future – and many would even argue they are our present. But given their environmental impact, and their ability to put vast amounts of pressure on the grid, the way that they’re currently set up is simply unsustainable.
The need for renewable energy sources has come to a head, and while many nations are taking the right steps forward, more needs to be done.
A strong, efficient, and sustainable future depends on the creation of smart technologies to provide flexibility – and energy storage is just the first step.
Because without sustainability, the smart cities we envision are likely to remain closer to fiction than reality.
How to choose a storage battery: Think of an onion
South Africa’s stretched energy grid has led to a rapid uptake of uninterrupted power supply (UPS) systems and a marked increase in renewable energy investments.
Freedom from the grid needs reliable storage batteries – where the energy created by turbines or solar panels is stored for continuous power, or in the case of a UPS system in a home or business, the power from the grid is stored for use when the power trips. “When you understand what makes a high-quality storage battery, it makes choosing the right battery system a lot easier. I always tell people to see it as they would an onion with its multiple layers,” Felix von Bormann, co-founder of REVOV says.
There are four layers that make a good battery, says Von Bormann. They are:
First layer: The chemistry
“This is perhaps one of the most crucial elements,” says Von Bormann. “If the chemistry inside the battery is not right, it will not only be ineffective, but dangerous as well. Different chemistries are better suited for specific environments. For instance, automotive-grade battery cells deliver extreme temperature resilience and high energy density, which makes them well-suited to environments that rely on these characteristics.”
Second layer: Charging capacity
Once you are satisfied with the chemistry, you need to ensure that the battery chosen has the right capacity insurance. “This is to provide the ability to support the charging required and remain within the 48-volt paradigm critical for renewable energy.”
Third layer: Well-designed box
The battery cells must obviously be of the highest grade. Von Bormann says: “The chemistry means little if the battery is not constructed correctly. The physical box must be rugged while the connections to the cells for monitoring and power delivery must be solid. The battery must have a well-designed box that can take shocks.”
Fourth layer: Safety
“The final part is ensuring the battery does not leak or explode,” says Von Bormann. “The safety specification of the battery you choose is an important consideration. Chemical devices need to be designed and stored correctly as this speaks directly to their safety.”
A lithium battery, for instance, features a battery management system (BMS) that monitors and shuts down the battery if something goes wrong. “There are also physical signs to check out as well such as whether the battery is misshapen or has watermarks on it,” says Von Bormann.
Interestingly, says Von Bormann, repurposed, or second life, batteries from electric vehicles (EVs) are tailor-made to deliver the performance and safety required to be quality, robust storage batteries. “Of course, it is not a case of simply removing them from a car and plugging them into a solar solution. Care must be taken to select the right kind of battery that can deliver this second life and that is equipped to deal with the demands of long-term storage.
“If you consider that these carefully chosen and repurposed second life batteries have 10 to 15 years of use once we have repurposed them from EV into storage batteries, the value is two-fold: first, you pay less for high-grade batteries and second, by repurposing EV batteries that would have ended up in landfills by their tons, we can move off the grid in a carbon-sensitive and sustainable manner.”
He adds that quality batteries should be put through rigorous testing so that by the time they are built into commercial or residential systems, the end-user knows they have bought quality. “Ongoing testing really is non-negotiable. When you are choosing a battery, ask about the testing. Our 2nd LiFe lithium-ion phosphate batteries, for instance, have been quality checked and have gone through rigorous testing to ensure they are fit for purpose, that is long-term energy storage.”
READ MORE | Repurposed EV batteries a boon for stational energy storage
Out of the coal age and into the stor-age
Seydou Kane, managing director for South Africa at Eaton, considers the shift away from coal towards renewables – and the potential for a future microgrid energy market in South Africa
South Africa’s energy generation capacity is dominated by fossil fuels, with this source accounting for 91.2% of the country’s energy, according to the 2019 Integrated Resource Plan. While the country is likely to continue turning to coal as its main source for generating electricity, plans are well underway to diversify South Africa’s energy mix. With multiple solar projects already operational, along with numerous wind farms producing energy too, it’s clearer than ever before that South Africa is well on its way to sourcing as much as 25% of its energy mix from renewables by 2030.
If the future of South African energy is going to depend increasingly on renewables, effective storage will be vital to better connect these energy sources to the grid. Energy storage will also be key to making our national energy infrastructure more resilient and, importantly, enabling it to increasingly rely on clean energy sources.
Learning to rely on renewables
Renewable energy has long been treated with skepticism. Some policymakers argue against renewable energy sources as unreliable, and this has resulted in a roller-coaster market for renewables as policies sometimes shift rapidly – seemingly without consideration for the impact to benefits such as jobs and energy independence. Yet, the ever-decreasing cost of renewables as technology advances has kept the South African market growing, albeit more slowly than is required to meet stated commitments for carbon reduction.
One major argument against renewables is that they do not produce a consistent baseload power like fossil fuels. The common refrain is that the wind does not always blow, and the sun does not shine at night. Of course, these are true, but it must be remembered that we are in a transition to a cleaner future – it is not an overnight change. It will take time, but the day will come when we run completely on renewable and clean power.
This is being accelerated by the falling cost of battery storage which helps optimise the use of intermittent renewable energy on the grid – further opening up the possibility of powering South Africa with clean, renewable energy while shifting further away from our reliance on fossil fuels.
When renewable energy sources generate more energy than businesses or homes require, the excess can be stored securely. This energy can then be released during times of peak demand, which means less need for conventional fuel generation. This reduces the carbon footprint of South Africa’s energy supply. Even better, this energy can be located anywhere on the grid or in private consumer homes, so that businesses and houses can help eliminate harmful emissions and save costs.
The deployment of pioneering energy storage solutions will be crucial in this process as we attempt to embed sustainability within the national energy grid.
Creating a more resilient grid with a ‘behind the meter economy’
Another increasingly interesting application of storage is in microgrids which can efficiently and economically plan for local energy generation and distribution, while increasing reliability. The implementation of local, distributed power generation and storage can be designed to allow portions of the grid and critical facilities to operate independently of the larger national grid when necessary, helping reduce the potential for unforeseen blackouts. The storage systems that are part of these microgrids – whether large or small – can also provide ancillary services to the grid, again strengthening performance and reducing the use of carbon generation.
Energy storage gives businesses and consumers the power of choice to optimise their energy costs and provides them with flexibility for the future. We are already seeing advanced aggregators working with businesses to educate and inform them on the extra money to be made while supporting the transition to a smarter, environmentally-friendly energy grid.
The investment opportunity
The ever-falling price of energy storage technology today is creating an increasingly viable and attractive investment opportunity – but many South African businesses are still not aware of this potential.
Energy storage technology can be complicated to understand from a commercial perspective when it comes to exactly how it will save money for a particular site. However, the option to sell surplus energy back to the grid through ancillary services opens up new revenue streams that help offset the cost of electricity and dramatically strengthen the business use case. Adapting the South African regulatory framework to remove barriers to entry in the ancillary services market will facilitate this option and better support the development of a healthy energy grid.
The shift to a cleaner future is already taking place as South Africa moves away from coal and towards renewables. Eskom CEO Andre de Ruyter affirming that renewable energy will have to have a place in the country’s energy portfolio if the utility is ever to provide reliable energy, along with recognising that the company cannot continue to violate environmental laws. Energy storage will accelerate this trend and help ensure a clean, stable, and cost-effective supply of electricity for the country.View more
VIDEO | Storage: The missing link to renewable energy
TED2012 | DONALD SADOWAY
What’s the key to using alternative energy, like solar and wind? Storage — so we can have power on tap even when the sun’s not out and the wind’s not blowing. In this accessible, inspiring talk, Donald Sadoway takes to the blackboard to show us the future of large-scale batteries that store renewable energy. As he says: “We need to think about the problem differently. We need to think big. We need to think cheap.”
Donald Sadoway is working on a battery miracle – an inexpensive, incredibly efficient, three-layered battery using liquid metal.
This talk was presented at an official TED conference, and was featured by our editors on the home page.View more
Energy arbitrage: A green way of making money
THOUGHT LEADERSHIP |Norman Jackson, Vice-Chairman, South African Energy Storage Association
Every businessman’s dream is to be able to buy low and sell high, without any risk, and on a contract that goes on for dozens of years. – Well that opportunity exists today in energy arbitrage, where you can …
Well, now that I have your attention. Let me tell you that only works in the high-demand “Winter” three months, the remaining nine months, it is a cost of R0.51 and a selling rate of R1.16 – which makes any calculation complicated, so let’s just proportionally blend the tariffs and get a tariff of R1.7660 (Peak), R0.8717 (Standard) and R0.5283 (0ff-peak).
To try and equalise the supply and demand curve for energy in South Africa state utility, Eskom, has a Time of Use (TOU) tariff structure for large users of electricity.
This opportunity has been around for a long time. The issue has been the cost of storing energy for two hours, which was prohibitively expensive. Well, thanks to electric vehicles and green initiatives, science and engineering have brought down the cost and it is not only theoretically, but also commercially, viable.
In simple terms, we are talking about a large uninterruptible power supply (UPS) that comes in one or more shipping containers. In technical terms, it is a battery storage system (BSS) with a discharge rate of two hours (C=2), a rated capacity calculated after the normal depth of discharge, a degradation of less than 20% over 10 years, based upon 6 000 cycles on the full discharge of rated capacity. The round-trip efficiency of the batteries should be 95% and power electrics 97%, having an overall loss of less than 7%.
Typically, a UPS is expensive, but when you compare it to what happens when you have a sudden interruption in power, the cost is negligible.
– But I digress, having a UPS is a by-product, not the intent of the BSS.
Energy storage is an expansive field, all the way from a human body to a pumped storage hydro scheme. The options are endless, and the technologies are constantly improving. For this example, I am going to choose one of the most common battery storage systems, that is readily available – Lithium Iron Phosphate (LFP). A BSS of the above specification is less than US$400 /kWh (R6 400/kWh). This example is more appropriate for consumers of more than 500kW.
“Sweating the asset” – having an expensive asset at our gate and only using it five times a week for the morning peaks is not optimum. We could also use it for the evening peak by charging it during the day (Standard). We can also use it twice on a Saturday charging at Off-peak and discharging at the Standard rate. In summary, 12 times a week, 50 weeks (considering public holidays), 10 years, which is 6 000 cycles.
Ok, we are now ready to do some calculations:
If we take a figure of 3% of CAPEX for maintenance and battery supplement to keep to our 100% rated capacity, we are looking at ROI of about 13% in year one, but with a modest Eskom increase of 8% a year, the ROI is above 25% in year ten.
Increasing the ROI
From the above, I hope that you agree energy arbitrage pays for itself and is an investment, I am not going to talk technical and put a value to having a huge UPS on your doorstep or try to estimate the savings in network demand charges, which for many customers, are significant.
If we add solar PV to our system, we have our very own power station, and we can charge our BSS System during the day as well. For those not familiar with PV, it is a generator that produces electricity from solar irradiance, but usually requires a reference grid (on-grid). With a BSS, the system would be able to work off-grid as well, which is sometimes referred to as island mode.
In Johannesburg, a solar PV system has a CAPEX cost of less than R9 000/kW, and producers yearly an average of about 2 000Wh a year. Which is about 5.5hrs/day of 100% output. (The actual output is more of a bell curve with lots of slices taken out of it due, to clouds and technical issues. – Another discussion.)
The calculation for the saving/income a solar PV system would give looks generally like this:
That is a healthy 17% in Year One (based on an O&M cost of 2%) and with an 8% escalation in energy prices annually, we are looking at over 35% in Year 10 of its 25-year life output warranty.
Going “green” is no longer an emotional or “right thing to do” decision, it is now the right business decision.
Source: Eskom, Tariffs & Charges Booklet 2020/2021 (www.eskom.co.za/tariffs)View more
VIDEO | The missing link to renewable energy
Donald Sadoway | TED2012
What’s the key to using alternative energy, like solar and wind? Storage — so we can have power on tap even when the sun’s not out and the wind’s not blowing. In this accessible, inspiring talk, Donald Sadoway takes to the blackboard to show us the future of large-scale batteries that store renewable energy. As he says: “We need to think about the problem differently. We need to think big. We need to think cheap.”View more