The big draw
Automation poses some tough power supply-related questions for ports, explains Stevie Knight
Automated terminals are more efficient in their use of power but they also pull hard on the electrical infrastructure, so what happens if there’s a power cut?
In most cases the subject of automation only comes up when a terminal is well established and has a firm footing in its power supply but this still means a large power step change as the old diesel yard equipment get replaced by swanky new, grid-powered systems. Peter Mallin of Mott MacDonald points out that while there’s no doubt automated equipment is more efficient than diesel, it puts much more demand on the power supply.
To give an idea of the scale of the electrical demand, traditional ports’ quay cranes are king of the power draw, often with peak demands of around 2,000 kVA he explains. While a typical automated stacking crane (ASC) may only peak at around 50% to 60% of that when running and hoisting, an automated terminal could easily be looking at upwards of two or three dozen of them depending on terminal size and throughput profile.
On the flipside, there are some areas of savings: “Automated and unmanned ARMGs and ASCs can operate in darkness so no flood lights in the yard are needed...a significant consumer,” says Fredrik Johanson of ABB. Further, much automated equipment recycles the energy from lowering actions of both container cranes and handling equipment – ABB’s ASC’s regenerate around 70% of their consumption.
However, there’s still a potentially large step up in power demand between non-automated and fully automated terminals. Mr Mallin’s colleague Alex To says while it is difficult to pin down how much of a step this presents as it depends on the existing equipment, based on experience, he estimates an approximate 25% rise when switching from electric RTGs to ASC operation on a like-for-like basis. Given that many will be launching themselves from diesel equipment, an equivalent facility could potentially be faced with an even higher power jump.
So installing backup power can get pricey and as it will certainly require at least several megawatts per berth, Mr Mallin points out that it “represents a significant investment”.
Kevin McKinney of MTU Onsite Energy says that a fairly modest 10MW backup system, for example, can be made by paralleling three or four large generators but the total cost for them alone (not including the installation) comes to $4m or $5m.
Of course, to get the most out of automated terminals, you want clever energy management and this is where the sums get complex: many quay cranes have a power-sharing system between ‘paralleled’ units, but some of the big cranes, along with automated handling equipment such as ABB’s ASCs, are taking this one stage further and have developed an energy efficient system that puts what’s left over back into the grid – remember that 70% figure? Of course, most of it will probably be taken up by the other, paralleled equipment but it’s variable. So what happens to the extra energy when the systems are off the grid?
The fact is it has to be treated fairly carefully. Mr McKinney says that the gensets cannot absorb regenerated energy from the equipment: “You can’t push power back into the generators,” he explains. So for safety’s sake a terminal may well need to include a load bank where resistors can safely take off the surplus. It may not affect the general overall picture that much, but the calculations do have to take the potential peaks in demand with both generators and safety systems sized accordingly.
Further, it can be quite a challenge to find the space in the heart of a port: “Terminal’s can be quite congested areas, so if within the terminal, the area for backup generation has to be balanced with what amount of revenue per hectare might be lost,” explains Mr Mallin. Mr McKinney adds that going back to a 10MW system, you’d need something like a 420m2 area, and though lower, sub-600V systems require the generators set quite close to the consumers; if the port can deploy medium or high voltage lines the power generation area can then be set some way away from the site.
One important point is while these backup gensets might not be run that often, the fuel for them can’t just be left to sit: fuel, especially biodiesels containing FAME derivatives, can degrade pretty badly especially in a damp port environment. So, you do have to keep rotating what is in the tanks, he says, as the last thing you’d want is an expensive backup power system failing in a crisis.
While most big ports are situated in a fairly well developed areas, some high volume facilities may find themselves in places that lack a completely guaranteed, 24/7, 365-days-a-year electrical supply. Mr McKinney says: “Even if the power outages only happen three or four times a year, there may be good reason to put in enough power generation to cover most of the operations... it all depends how sensitive the port is to stopping work.”
In fact, Tim Vancampen of ICTSI says that there are questions about how to tailor the backup investment: a power cut to the big quay cranes can mean stranding personnel up in the air or even leaving loads – of maybe 90 tonnes – swinging uncontrollably. Again, it’s a matter of choices: “Even a small power plant is expensive and if you have eight quay cranes, a port might consider putting in a supply that would run full power to just a few of them.”
There’s also accommodating the power layout. “A lot of people are learning as automation evolves,” says Mr Mallin. The problem is, ports are having to plan into the future now.
Mr To explains: “Ports tend to phase in the automation, moving from one set of equipment to another but each stage can build up issues for the next. For example, a port might be looking at automated straddle carriers to replace manual straddle carriers at some point in the future, but automated straddle carriers tend to operate in the backreach of the quay crane, not underneath, so this has a knock on effect on the area used for the apron.”
He adds that this can have an impact long in advance as associated services like ducting and sensors are buried beneath the surface over quite a large area: “For one project we are already talking about pushing all the ASC stacks landward even though plans for automated straddle carriers are just at the concept stage.”
“It’s a challenge,” he says. “You have a finite space and lots of implications, if you get it wrong now, then stepping toward full automation could be a problem.”
The stability of the power supply does make a difference to terminal plans, explains ICTSI's Tim Vancampen. “In certain places like Madagascar you need not just the generator backup, but a backup to your backup, as you can be left relying on the generators for days at a time.”
Further, he explains: “There are things that you have to choose, you have to make compromises about what you can do without.” For example, he says, for many export ports in Africa, the reefers are responsible for a large draw “and you can’t be left facing a court order because goods perished”, while he points out the offices may usually be left without aircon for a while without courting disaster.
But, he adds, you have to be very clear about keeping power running to critical systems: “While the terminal operating system servers aren’t a huge load in themselves, they need constant air conditioning,” he explains; in a hot climate this represents a substantial pull. Further as a facility simply can’t afford to have the TOS go down, it means a sizeable investment on an uninterruptable power supply (UPS) – basically a large battery bank – to guarantee a seamless changeover.
In emerging economies, the choices can be limited: Mr Vancampen explains that some port’s only real option is to sit tight with diesel-powered mobile harbour cranes, so despite the chance to electrify “you need to take into consideration the relative instability of the power supply”.
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