More Battery-powered Options for LHDs
Recognizing the benefits of zero emissions, miners consider lithium batteries.
By Jesse Morton, Technical Writer
“The biggest hurdle is market acceptance,” said Mike Kasaba, CEO of Artisan Vehicle Systems, maker of the 153, a 3-metric-ton (mt) (tramming capacity), lithium battery-powered LHD. “We’re talking about an industry that plans and gets investment on assets that don’t mature into profits for five years, even 10 years—very long development cycles, and long, slow acceptance of new technology.”
The market for underground mining machines is still in the beginning stages of a “paradigm shift” that will ultimately see battery-powered equipment make its diesel competition obsolete, he said. “We have not yet reached the tipping point where everyone has decided that in the future they are only going to use battery equipment, and zero emissions equipment, underground. That tipping point is coming and it is coming soon,” Kasaba said. “I anticipate that by the year 2020, all major mining companies will be issuing requests for proposals and requests for quotes for only zero emission equipment underground.”
Indeed, the mining sector is primed for the technology, and by mid-2018, battery-powered LHDs could grab 60% of the space now held by diesel competitors, Jeannot Courchesne, vice president, RDH Mining Equipment, said. Miners are adopting the technology in principle today, and in practice tomorrow, he said. “The growth is not there yet. A lot of mines are inquiring about the equipment but are not purchasing it yet,” he added.
Taral Shah, senior product manager, underground mining, General Electric, said performance drives marketplace penetration. Acceptance will be the result of proof of overall performance, specifically operating range, that is competitive to that of diesel equivalents, he said. “Battery technology is ideally suited for underground mining,” he said. “The speed of adoption will be driven by the mines’ comfort level with the technology and the OEM’s ability to deliver a solid product that will operate for a full shift.”
Antonio Nieto, associate professor with the Energy and Mineral Engineering Department at Pennsylvania State University, agreed. “Battery equipment—lithium, lead or sodium—is getting there,” he said. “Battery-based equipment makes complete sense for the miner and for the economics” of underground hard rock mining. The reliability of the technology, and the growing awareness thereof, will determine its future, he said.
Manufacturers say the data shows battery- powered machines are both reliable and outperform their diesel equivalents on a number of measures. “Over five years ago now, the first [battery-powered] units went into service at Kirkland Lake Gold,” Kasaba said. “They have more than 100,000 hours now at Kirkland Lake alone. They now have approximately 25 battery-powered units in their fleet. They are running very well and have been absolutely critical to their success in accessing additional orebodies that are adjacent to their primary orebody.”
Kasaba said Artisan’s LHD outperforms diesel LHDs on several metrics. “The 153 unit has three times, 300% of, the horsepower (hp) of a diesel equivalent unit—and more torque on top of that,” he said. “All of that extra power can be used to make a unit that is smaller, more dense, yet carries more and does more work than a diesel equivalent unit.”
“We had good feedback from the customer,” Courchesne said. “It has saved them a lot of money” with respect to ventilation and the need for another shaft for more air. GE’s lead acid battery-powered (7-mt) LHD is operating in underground hard rock mines in Peru and Canada and “the feedback has been positive,” Shah said. “The customer is very happy with speed and performance. It has a tremendous tractive effort, which results in superior mucking power and bucket fill.”
At least three other battery-powered LHDs, with varying specifications and amenities, are currently operational and on the market. They differ primarily in size, power and bucket capacity.
Artisan’s 3-mt (tramming capacity) 153 is 225 inches (in.) long by 65 in. high by 60 in. wide. Total power is 214 kilowatts (kW); tractive effort, 75 kilonewtons; and loaded speed (on 17% grade), 12 kilometers per hour (km/h). The powertrain motor’s peak power is 127 kW or 170 hp. Its peak torque is 695 newton meters (nM), or 513 foot pounds (ft-lb). It is powered by a 600-volt (V) DC, 88-kW hour (kWh) lithium iron phosphate battery. The bucket is 1.2 cubic meters (m3), or 1.5 cubic yards (yd3). Lift breakout force is 4,899 kilograms (kg) (10,888 pound force [lbf]); tilt breakout force is 7,031 kg (15,500 lbf). Total operating weight is 9.5 mt.
Using technology proven in coal mines and tested at hard rock mines, General Electric’s 7-mt (tramming capacity) LHD runs on a 320-V (287 kWh) lead acid battery and features a 4-yd3 (3.1-m3) bucket. It is 369 in. long by 94 in. wide by 88 in. high. Operating weight is 34 mt. Lift breakout force is 13,662 kg (30,120 lbf). Tilt breakout force is the same. Operating range for the two-battery system is from six to 10 hours (three to five hours per battery). “The battery exchange system is integrated into the vehicle itself, so it doesn’t require mine infrastructure to exchange batteries,” Pat Jansen, senior engineer, underground mining, said. GE is developing lithium battery technology with Li plus exchange or rapid charge, which will add flexibility and adaptability, GE reported.
RDH Mining Equipment’s Muckmaster 600EB LHD features a 470-V DC lithium iron phosphate battery system that requires two to three hours to charge and operates for four hours at 400 amps per hour. “They can swap out the battery, which takes 15 to 20 minutes, and then the scoop is back in operation,” Courchesne said. The bucket capacity is 3.4-5.4 m3 (4.5 to 7 yd3); nominal payload capacity is 11 mt. The LHD is 10 m long by 2.5 m high by 2.4 m wide. Approximate weight is 31 mt. The 100- 200 hp four-speed electric powertrain motor is liquid cooled and features AC traction drive.
RDH’s 300EB LHD also is powered by a 470-V DC lithium iron phosphate battery system that requires 90 minutes to two hours to charge and operates for four hours at 260 amps per hour. The bucket is 1.5-2.3 m3 (2 to 3 yd3). With a 2.3-m3 bucket, the LHD is 8.3 m long by 1.8 m wide by 2.2 m high. Approximate weight is 15.8 mt. The liquid-cooled, 100-300 hp three-speed electric powertrain motor employs AC traction drive.
Atlas Copco’s 7-mt (tramming capacity) two-battery Scooptram ST7 LHD offers a quick battery change strategy, which enables 24/7 operation, and an adjustable bucket that comes standard at 3.1 m3 volume at 2.2 tons per m3 (t/m3) material density. The Artisan 1200 Series traction motor’s peak power is 149 kW. The lithium iron phosphate battery model is also made by Artisan, and is 630 V DC, or 165 kWh. Hydraulic breakout force is 11,750 kg (25,904 lbf). Mechanical breakout force is the same. On level grade, in fourth gear, the maximum speed is 23.1 km/h. It is 90 in. wide. Approximate weight is 21.5 mt.
Unveiled at MinExpo 2016, Sandvik’s 6.7-mt (tramming capacity) LH307B is powered by lithium titanate oxide battery technology, which features rapid (15 minute) recharging for continuous operation with a single battery pack. Compatible with Sandvik mine automation and information management systems, and comprised of components from the diesel LH307, it features a 6.7-mt payload and a 3-m3 (3.9-yd3) bucket. Peak engine power is 150 kW. Peak speed is 26 km/h. Lift breakout force is 13,700 kg (30,203 lbf). Tilt breakout force is 11,400 kg (25,133 lbf). The diesel LH307 is 340 in. by 83 in. by 87 in. Approximate weight is 22 mt. The single-battery quick recharge system nixes the need for backup batteries and a dedicated swap, service and recharging area, which cuts capex costs.
Five of the six above-mentioned LHDs are powered by lithium ion batteries, technology that had to overcome several hurdles before being deemed safe, reliable and practical.
Lithium Battery Development
Lithium ion batteries are everywhere. They are found in mobile devices, flashlights, laptops, and various vehicles. A 2013 report1 co-authored by Dr. Nieto summarized how the technology works. “Lithium (Li)-ion batteries work by shuttling Li-ions between molecular lattices, which temporarily hold the lithium until the cell is in use. Non-aqueous electrolytes are used to keep the Li-ions mobile between the lithium hosts at the negative and positive electrodes.” The report stated, “There are a plethora of compounds, which can be used for the positive electrode. The most common positive electrode materials include lithium transition metal oxides (Li- M2O4 or LiMO2) and lithium transition metal phosphates (LiMPO4). Graphite is most commonly used for the negative electrode, although it is certainly not the only option. Lithium titanate spinel (Li4Ti5O12) is also a viable option and is praised for being a safer alternative to graphite with a high cycle life (~20,000) and rapid (constant current) charging ability.”
Nieto mentioned a minimum of three challenges to development and widespread use of the technology to power mining machines.
Lithium batteries fail with abuse, specifically punctures, Nieto reported. “A puncture could create an internal short, which would generate a large amount of heat. If the hermetic seal has been breached, moisture from the environment could react with the lithium generating heat and hydrogen gas. The heat from either could initiate a decomposition reaction, leading to a thermal runaway enhanced by oxygen gas.”
Overcharging can lead to thermal runaway, fire and explosion, Nieto reported. “Li-ion cells are not very tolerant of being overcharged. Upon overcharging, the cell experiences expansion, which is significant enough, in some cases, to cause a cell breach. The cell temperature increases rapidly upon overcharge, which if unchecked would lead to thermal breakdown of metastable components releasing heat and oxygen. This positive feedback leads to a thermal runaway.”
Kasaba said Artisan has answered these challenges. Artisan battery packs are engineered “such that they stay close to whatever the ambient temperature is in the mine,” he said. “So for an air temperature of 35°C to 40°C, we are trying to keep our batteries in that same range too.”
Artisan has developed a battery management system that prevents the possibility of overcharging. “Our battery system controls the charger so the battery system knows exactly what its state of charge is and it tells the charger how much charge it wants, when to start reducing the current levels as it approaches 100% charge, and when to shut off. So the battery is always in full control of the charge itself.”
The battery management system factors in overall mine design to prevent overcharging due to regenerative braking. “We look closely at any scenario where there might be a chance to get to full charge and then have to go downhill. We find that this is an extremely limited event that rarely ever happens, but if it ever happens, our system is designed to dump that power out in heat through the hydraulic system versus trying to charge the battery,” Kasaba said.
Battery packs are designed to withstand abuse, and Artisan reportedly does not use the more volatile chemistries in their designs. “Anything like that, that creates a risk of a lithium fire, we stay away from those chemistries completely. The lithium iron phosphate is much safer in that regard.”
Headlines reveal lithium battery technology has made marked gains in reliability despite some noteworthy setbacks. While in September Samsung was ramping up a recall of one of its lithium battery-powered phones on the basis of reports of it igniting, Jaguar was planning to unveil its first “fully electric,” 90-kWh lithium battery- powered car. In December, Apple began offering replacements for 6S batteries after a number of reports of them igniting. Meanwhile, the state of Colorado green lighted infrastructure for and road testing of battery-powered transit trucks. Shortly thereafter, Amazon delivered a 14-lb package by battery-powered unmanned aerial vehicle to a rural U.K. residency within 15 minutes of order placement. At roughly the same time, the United Parcel Service began road testing battery-powered trike machines for deliveries in Portland. These and other battery-powered technologies and machines are esteemed because of their utility and operability, and because they are emissions-free. In mining, battery-powered equipment, now beyond the testing phase, shows a propensity to save companies money while expanding capabilities and improving public and investor relations.
Real and Hypothetical Savings
The bottom line could drive the switch to battery-powered LHDs and underground hard rock mining machines, said Pierre Mousset-Jones, Ph.D., professional engineer, professor emeritus of mining engineering, Department of Mining Engineering, MacKay School of Earth Science and Engineering, the University of Nevada at Reno. Nonetheless, those savings are difficult to generalize and project because the market share for battery-powered mining machines remains comparatively minute.
“In a particular mine, there are other reasons for requiring airflow to be at a certain level, such as to keep the miners breathing, reduce dust levels and poisonous gases (other than diesel particulate matter and exhaust gases) below regulation limits, provide sufficient cooling in hot mines, dilute radon daughters and radiation levels,” he said. “Certainly, electric- powered equipment produces much less heat than diesel power, hence in hot mines they can also reduce the need for airflow or refrigeration in the mine. This can be a significant savings.”
Nonetheless, electric vehicles produce some heat. Further, where virgin rock temperatures are high and the breaking of rock is fast, a significant portion of the total heat load in the heading may be unrelated to diesel machinery usage, Mousset-Jones reported. “In such a case, it is important to be circulating the cooling fluid (air) through the heading even when the LHD is not operating.” Additionally, regulations on ventilation air volume per diesel power kW vary from country to country.
If battery-powered equipment replaces diesel equivalents in existing mines, comparatively little can be done with the established infrastructure. “Fans can be slowed down or stopped and mine expansion can be designed with less airflow or air cooling needs. There are limits to the air velocity in mine airways, which is a function of air quantity and mine airway area. Hence, less air means mine airways, such as shafts and raises, might be reduced in size, which saves a lot in development costs, and may mean underground booster fans don’t need to be installed,” Mousset-Jones said. “Many existing mines use their main decline as an air intake and main haulage way for their trucks. This means that fresh air entering the mine is contaminated with diesel fumes before it ever reaches the working areas. For an existing mines, making the trucks electric removes this problem.” Equipment maintenance and “miner health” savings factor into the equation.
Presume the effects of diesel fumes on the health of miners could be eliminated. “The savings from this benefit are difficult to quantify, but can be significant in terms of increased miner productivity, miner and family wellbeing, and reduced work absences,” Mousset-Jones said. “In addition, the energy efficiency of electric power is superior to diesel power and maintenance costs are less for electric equipment. There is no need to set up fuel bays underground and the piping system to bring fuel underground, which is costly. It reduces the mine fire potential in the fuel bays and for diesel-powered equipment, which is not uncommon for the latter, and which is a significant safety issue in mines.”
The cost saving potential of going electric is obviously compelling, however, diesel machines have all but cornered the market. Gaining traction against the established competition may prove to require more power and torque than anticipated.
From Niche to Widespread Use?
A number of underground mines currently employ battery-powered machinery. Goldcorp announced an ambitious plan for the Borden Lake gold mine in Northern Ontario as a “green mine.” The mine will “eliminate upward of 7,000 tons of carbon dioxide emissions” per year for its projected 10-year life, and “decrease greenhouse gases by 20%,” the company reported. Working with commissioned suppliers Sandvik Mining and McLean Engineering, the mine is reportedly “fully electric,” operating at least one 40-ton battery-powered haul truck. The mine’s on-demand ventilation system is expected to use 50% less energy than it would if a conventional ventilation system was employed. Goldcorp anticipates reduced energy consumption of 15%.
Strategic perception management is a key tactic when overturning a paradigm. Kasaba said “99.9% of underground mining today is dominated by diesel equipment and some electric tethered equipment.” That will change within five years, he said.
Manufacturers like Artisan and Sandvik may envision a near future of market dominance by battery-powered machines, but Mousset-Jones warns that such predictions equate to shooting a moving target. Diesels have responded to the threat to themselves with much more powerful engines (higher productivity) combined with good operator working conditions, due to cleaner engines, cleaner fuel, and air-conditioned cabins, which operators love to have, Mousset-Jones reported.
Battery-powered mining machines need not compete strictly with current diesel-powered equivalents, but also with tomorrow’s diesel technology. Both technologies will continue to improve, he said. Incremental improvements to battery-powered machines will not allow their manufacturers to quickly depose their diesel competitors, he reported. “There would need to be a game changer of some sort to do that.” Shah agreed. “Incremental improvements are only going to yield incremental adoption,” he said. “What will be key is when the user sees no difference in the operation of the LHD other than the fuel he puts in, meaning either diesel or electricity.”
Artisan’s forecast for its LHD jibes with these views, Kasaba said, except the game changer is operational, available and for sale now. It is inevitable that the market will refl ect this in due time, he said. “We have a major performance advantage over diesel equipment,” Kasaba said. “Our electric motors are extremely torque-dense and power-dense, way more than the diesel engine. Imagine a smaller machine moving more ore per hour per shift. That is extremely interesting to the mining companies.”
Other noteworthy advantages will sway mine owners and operators, Kasaba said. “The amount of maintenance required for a diesel machine, versus a battery machine, is substantial. Also, the control- ability of a diesel engine is not nearly as precise as it is with an electric motor.” Shah concurred. “We’ve talked to some mines who say the useful life of a LHD ends when the engine has to be overhauled because the cost is so high. We don’t have a diesel engine, so there is no overhaul and there is only a very limited amount of scheduled maintenance on our units. Over the long term we’ll see a change in the way mines characterize the life of their diesel machines.”
Many operations are currently planning future mine construction and operation in anticipation of retiring their aging diesel fleets, Courchesne said. “A lot of the mines have diesel equipment, but their fleets are getting old. They are trying to restructure their mines to go battery.” For big underground mines, switching to battery-powered machines is the next logical step toward the obviously inevitable, Kasaba said. “When you are talking about essentially creating underground robots, which starts with remote control and ends with autonomy, those are going to be made with electric motors,” he said. “The benefits are so powerful and compelling that we will see this transition: initially to zero emission underground and ultimately to remote control and autonomous operations underground.”
RDH has committed to battery-power to the extent that its 10 year plan is to develop and offer the technology in its entire lineup, which includes a number of drill and bolt rigs, several haulers, and utility vehicles. “We think this is obviously the wave of the future,” Edward said. GE reportedly shares that vision and is preparing for the paradigm shift. “In the short term, I think it will be adopted by mines that have very specific challenges, whether it is temperature or ventilation,” Shah said. “Very quickly, though, it will be a ubiquitous technology in underground mining.”
1 - Using Modern Battery Systems in Light Duty Mining Vehicles, by Richard S. Schatz, Antonio Nieto, Cihan Dogruoz and Serguei N. Lvov; Department of Energy and Mineral Engineering, The EMS Energy Institute, The Pennsylvania State University, Pennsylvania, USA, November 2013.