Electrified powerhouses: Sarens equips its "Sarens Giant Cranes" for varying projects

Rental cranes must be configurable at short notice: The power rating and number of winches vary depending on the construction site, location, or lifting task. At the same time, there are high standards for safety and availability – even under harsh environmental conditions and across diverse global power supply systems and climate zones, from subpolar to tropical. Sarens therefore needed a design that could scale across hardware and topologies, accelerating deployment and reconfiguration.

"The transition from established hydraulic systems to electric drive technology was challenging," explains Kris Colman at Sarens. "In addition to robust components, we needed a control and supply concept capable of managing the enormous power output reliably and precisely. Bosch Rexroth was already established as our partner for hydraulic and electrical drive and control technology – and we were able to build on that."

Modular power containers

At the heart of technology is a modular container concept (electric power container, EPC): Several EPCs feed into a common DC-bus; each container provides 680 kW of power. In the future, depending on the crane and power requirements, up to five containers per system will be possible. This allows the power rating to be scaled without having to rethink the entire system.

In each container, a ctrlX COREplus X7 including ctrlX I/O works as a centralized platform for control and communication tasks. The EPC’s slewing units and winches rely on appropriate safety and logic components from Bosch Rexroth.

For the central crane control system, Sarens uses an embedded control XM22, which is programmed by the customer. Visualization is carried out via the web-based HMI WebVisu and can be accessed in the crane control station – easy to maintain and flexibly extendable. The electric drive technology for pumps and ventilation coolers is realized via ctrlX DRIVE and coupled with the DC supply (including via IndraDrive ML).

Decentralized axes – winches and additional drives – are combined with rugged eLION off-highway inverters and motors to withstand weather and harsh conditions. Hydraulic units remain where they are functionally required – for example, for controlling the rotary motors and activating brake relief cylinders.

Droop curve: stable energy distribution

A continuous DC network combines the power supply and drives. A droop curve ensures stable, load-adaptive power distribution in the DC-bus and facilitates the interaction of multiple power supplies. The EPC suppliers are connected in a ring topology, creating a redundant DC power supply that increases availability.

In cases where recuperation cannot be used, water-cooled braking resistors ensure controlled energy dissipation. In addition, DC load outputs are monitored and axes are uniquely assigned, including through the use of test voltage. This speeds up diagnostics, service, and modular reconfiguration.

Electrification – right where it makes the difference

A key aspect of electrification was the rotary motion: An eLION electric motor drives an A2FM axial piston motor as a pump and provides the required volume flow and pressure in the closed circuit (nominal pressure up to 350 bar, peak pressure up to 400 bar). Flushing and feeding circuits ensure oil quality through filtration and cooling. eLION motors also drive auxiliary pumps for braking functions, and position switches on brake valves support the safety logic by providing clear brake position feedback.

Commissioning during live operation: in at the deep end in Rotterdam

Around one and a half years passed between developing the concept and the first prototype. Functions such as droop curve control, monitoring logic, and synchronous operation of the eLION drives via CAN bus were finalized in the fully assembled system. The prototype was put into service at the port of Rotterdam, where it was immediately put to the test: During commissioning, it had to load a ship with the foundations for offshore wind turbines. Short-term outages were quickly resolved thanks to redundant DC topology and service support. The project was implemented by Bosch Rexroth Belgium in close cooperation with Bosch Rexroth Germany.

The result: greater efficiency, more precise control and less maintenance work

Sarens is achieving significant effects with the new generation of drives: up to 50% higher energy efficiency (depending on the application profile, including through recuperation and optimized energy distribution), more sensitive control for more precise and safer load positioning, and reduced maintenance effort compared to classic hydraulic-based concepts. At the same time, local emissions during operation are reduced, and the hydraulic component is limited to necessary sub-functions, representing an important step toward sustainability in the heavy-duty segment.

"We were able to unlock multiple benefits at once: scaling capacity to meet demand, increasing availability, and significantly optimizing energy consumption," says Kris Colman. "The precise electric control system makes it easier to safely position the heaviest of loads – and the modular design helps us configure and assemble cranes for new projects more quickly."

Ready for expansion

The system is designed for growth: the crane can be expanded to include additional hoisting winches, travel drives for rail-guided movements, and an additional DC supply. Thanks to the modular concept, the additional components can be integrated in a short time.

In the next step, the electrification of existing hydraulic cranes is to be evaluated. This will enable Sarens to further develop its existing cranes going forward and significantly reduce the CO2 footprint of any crane.

("Image source: SARENS")

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