MechChem Africa July-August 2022

⎪ Power transmission, bearings, bushes and seals ⎪

the electric motors driving the hydraulic pump and, hence, all the hydraulic needs of the machine. This gives us much better control over total operating efficiency, precision and performance of these con struction machines. “A diesel engine on these machines typi cally runs at a relatively constant rpm, no matter what themachine is doing. By using a converter to control the electric motor driv ing the pump, we can continuously regulate the speed of the hydraulic pump to match instantaneous demand. So the energy used is better matched to the energy actually needed,” he explains. Alström adds that hydraul ic energy losses can further be reduced through solutions such as Individual Metering Control (IMC), direct-driven hydraulics, digital hydraulics or multi-chamber actua tors. “In this excavator, the Danfoss Digital Displacement ® pump makes it possible to operate multiple actuators simultaneously by setting independent pressures and flows for each of them, allowing for a significant energy reduction,” he adds. According to Danfoss’ calculations, a diesel-engine powered (ICE) excavator requires an input of 8.3 units of energy to produce 1 unit of productive work, while an electrified excavator with a conventional hydraulics system requires an input of 3.7 units to produce the same amount of work. So from an efficiency perspective, these vehicles are emission free, and they use less than half the energy. A fully electric and digitalised drive train based in Danfoss’ Digital Displacement technology, would require an input of 1.9 units of energy to produce 1 unit of produc tive work, which is a further 48% reduction on energy use. For certain machines, like excavators, the calculations show that this total electrification solution can offer bet

The Danfoss Digital Displacement ® pump makes it possible to operate multiple actuators simultaneously by setting independent pressures and flows for each of them, allowing for significant energy reductions.

ter total costs of ownership (TCO) than a standard diesel engine within five years. For the drive side of hybrid electric hydraulic construction vehicles, Alström notes that Danfoss’ hydraulic components are used for everything except the cylinders. “We do the joysticks, hoses, fittings, track and slew hydraulic motors, the pump and the valve stack. We also manufacture the electric motor, the converter and the entire control system,” he says. “Hav i ng recent l y acqu i red Eaton Hydraulics, we remain stronger than ever in hydraulics, which we see as a part of our emission-free future for years to come, and when electrical actuators with the power densities required become available, we will happily supply these instead so that the larger construction vehicles can also be fully electrified,” he says. When asked if there is a future role for vehicles powered by hydrogen via fuel cells, he responds that fuel-cells technology may be theway forward for very heavy construc

tion vehicles. “It also depends on the duty cycle of the machines. If the excavator is not used for manyminutes during aworking day, it makes sense to keep it electrical, because it can be charged when the workers go to lunch and after 30 minutes, it will be ready for the rest of the day. “In a mining scenario that might not be possible, so fuel cells might be preferred, particularly for really heavy duty opera tions. There are also some large excavator developers exploring fuel cell technology, though as parallel developments. The diesel engine power unit can just as easily be re placed by a hydrogen fuel cell, which drives the electric motor – and the rest of the drive train can also be hydraulic or fully electric. “More efficient construction machines are good for people, the planet and prof its – and the technologies already exist to improve energy efficiency and elec trify construction equipment,” Eric Alström concludes. www.danfoss.com/en-za/

Compact construction machines are ideally suited to full electrification, which can reduce energy consumption by more than 75%.