Gantry cranes: Terminal delivery

Gantry cranes, either railmounted or rubber-tyred, are the default for the intermodal industry. Part of Norfolk Southern Corporation’s intermodal terminal at Austell just outside Atlanta, Georgia, is to be operated by six new Künz Freerider rubber-tyred gantry cranes (RTGs). They will not only load and unload trucks and trains, but also handle a container stack.

In the existing operation the RTGs are mainly powered by diesel gensets. Philipp Gmeiner is in charge of product management for container cranes at Künz, and he explains the disadvantages – and Künz’s new energy-saving innovation: “The main problem of an RTG powered by a conventional diesel genset is that the size of the diesel engine is determined by the peak power demand, which occurs only occasionally. This means the electric output power of the genset has to be more than 400kW. However, during most of the operational time, the genset is immensely oversized, which leads to very high fuel consumption and emissions.”

An option is to replace diesel-only machines with a diesel-electric hybrid solution – in other words, RTGs powered by a combination of a smaller diesel genset and a lithium-ion battery as an energy storage system. The diesel genset is only used to charge the battery. Therefore, the required power is much lower – just 120kW of electrical output – and the power demand is at a constant level.

“The battery is not only charged by the genset,” says Gmeiner, “but also by regeneration – recuperation and reuse of the energy from braking and lowering the loads. This increases the fuel savings even more, in fact by up to 60%. Compared to the large-capacity gensets currently used at the Austell site this hybrid solution would have led to an annual reduction of carbon emissions of more than 1,000t for six cranes.

“However, the diesel-electric hybrid is only an intermediate solution. For Austell the real goal was a zero-emission operation with fully electric RTGs powered by cable reels. Besides the tremendous reduction in operational costs, there is also the benefit of a physical connection to the terminal network via fibre optics in the cable – which are much more reliable than wireless methods for control, communication and future upgrades to remote operation.

“Usually,” Gmeiner continues, “the way to go with electrification is a cable reel with a medium-voltage supply using a voltage level of, for example, 15kV. Medium voltage means that high power levels can be distributed to the cranes while the cable cross section can be kept relatively small and therefore light and cost-effective. Nevertheless, a medium-voltage power grid can involve excessive infrastructure costs and this was the case at Austell. So the requirement was that the cranes should be powered by means of a low-voltage supply of 480V, delivering a maximum ‘shore power’ of 100kW. However, the peak demand of each crane is more than four times higher than that. Künz, therefore, came up with the idea of an energy storage system on each individual crane – the all-electric hybrid solution.”

A lithium-ion battery is used as the energy store, he says. It is charged by the shore power through the cable reel, and also by recuperated energy from braking and lowering the loads. All the recuperation energy is directly reused on the crane and the demand from the shore power is kept at a constant level of 100kW. The peak demands are provided by the energy storage system, not from the grid. The diesel engines are entirely eliminated, which for Austell’s six cranes, results in an enormous reduction of more than 2,100t of CO2 per year. The operational costs are also cut tremendously because there are no costs for diesel fuel, and there is much less maintenance effort and downtime.

“The same reasoning is applicable not only for RTGs such as are used at Austell, but also for rail-mounted gantry cranes (RMGs). This is a new approach in the industry,” says Gmeiner.

Three particular advantages apply: “First is the lowered voltage level. The application at Austell shows that energy storage systems make it possible to power cranes using low voltage and a power level of only 100kW.

“Peak shaving, the minimisation or even avoidance of power peaks, has been described above. For larger RMGs the advantages can be even greater. Their grid supplier frequently adds peak demand charges – higher payments for peak power. An energy storage system that reduces power peaks leads to a significant savings here. For example, the short-term power peaks of large RMGs, which are higher than 900kW, can be lowered by 50%.

“Thirdly, the on-board battery means that typically up to 30% of the energy can be stored and reused. Especially in times of rising energy costs, this is an important aspect.”

KONECRANES BRAZIL

At the end of 2023 Konecranes delivered two gantry cranes, as well as seven forklift trucks, to a new cellulose terminal in Port of Santos in Brazil. It completed an order that also involved joint planning and consulting on the layout of the terminal.

The terminal in Port of Santos, Latin America’s largest port, is designed to process close to 8,300t of pulp bales daily, delivered by rail and truck, for export to 45 countries. Port owner Eldorado Brasil approached Konecranes for support in planning the layout of the terminal and to provide the specialised equipment to keep it running.

“Eldorado came to us after using a Konecranes indoor overhead crane at another pulp mill for over a decade,” says Leandro Belotto Bosco, senior account executive, Industrial Cranes, Konecranes.

The two Konecranes gantry cranes are tailor-made with a customised open winch, a spreader clamp for pulp bales and the option to attach a container spreader when needed. A variety of smart features give smooth and accurate movement, and braking energy is recycled. Radio controls and a remote operating station (ROS) allow full crane control with maximum operator safety. Konecranes is also providing Eldorado Brasil with TruConnect remote monitoring, which collects near real-time diagnostics to optimise the performance, maintenance and eco-efficiency of all the equipment, both cranes and forklifts. This data is available 24/7 through the online customer portal YourKonecranes.

“The new cellulose terminal is a state-of-the-art digital ecosystem that brings the highest levels of efficiency and safety to lifting in the pulp and paper industry,” says Andrés Ramirez, regional sales manager, Lift Trucks, Konecranes.