Development of cost and energy efficient digital hydraulic winch system

MacGregor works with the partners University of Agder, Diinef and Imenco Bauer Hydraulics to use digital, hydraulic high-torque motors to drive large winches for use in offshore and maritime operations. The winches can typically lift from 100-900 tons and they compensate for the ship's or platform's movements in the waves so that the load is at rest. Therefore extreme demands are made on torque and precision. Preliminary results in the project show that one can significantly reduce the need for installed power and significantly reduce the energy consumption in operation without having a cost increase on the winch compared to current solutions by using such digital hydraulic high-torque motors. This therefore means that such a solution is commercially attractive, while being more environmentally friendly. In digital hydraulic motor technology, new electronic control valves are used to connect each individual motor cylinder. The valves control access to high pressure and low pressure as needed and thus provide full control of the motor. Such a unique digital motor concept has been developed and tested by the project partners Diinef AS and Imenco Bauer Hydraulics AS. In this project, these motors are therefore, together with their control units, further developed. Several control units can now be connected together, to get synchronized control of several motors against a common winch. Furthermore, a complete winch system with control system has been developed, which is to be demonstrated by running a test winch with digital motors and associated control system and energy supply. Hardware-In-Loop testing of the control system has also been carried out on a winch simulator and a separate HMI for the test has been developed. Testing was done at Mechatronics Innovation Lab (MIL) in Grimstad where we use MIL's Winch Lab, which was developed and built for this purpose, and includes test towers with 25 tonnes test load and 25 tonnes winch with electric drives to test several operational scenarios. Demonstration of the functionality has been conducted for the partners.

Preliminary results in the project show that one can significantly reduce the need for installed power and significantly reduce the energy consumption in operation without having a cost increase on the winch compared to current solutions by using such digital hydraulic high-torque motors. This therefore means that such a solution is commercially attractive, while being more environmentally friendly

The idea of this project is to use new high torque low speed radial piston motors with digital distributor valve systems in large Active Heave Compensated (AHC) offshore and maritime winches. According to Maritim21, CO2 footprint of maritime business must be reduced and therefore there is a definite pressure towards energy efficient solutions. State of art solutions comprise hydraulic solutions with secondary control(i.e. the winch is controlled by adjusting a variable hydraulic motor) and energy recovery. These solutions are proprietary and expensive, and even if they are the most energy efficient hydraulic solutions, they still suffer from significant losses in gearboxes and hydraulic motors. More cost effective solutions are often preferred, but these are more complex and energy efficiency is even much worse. By using High Torque Low Speed radial piston motors with digital distributor valves (digital HTLS motors) it is possible to increase efficiency above state of art, to reduce cost below cost effective systems and to improve performance and reduce the number of components compared to both: 1)Digital HTLS motors have less than half the losses of hydraulic winch motors used today and need no gearbox 2)Digital HTLS motors can operate with a unique combination of full speed and full torque, thereby increasing performance and operating window of a vessel 3)Reduced number of components will result in a less complex winch system that is more robust and easier to maintain and assemble 4)Cost of winch drives with digital HTLS motors is estimated to be less than the cost of today's most cost effective solutions Further, the idea is to develop a hydraulic energy storage system as a part of the winch system and to recover long-range lowering energy and send it to other consumers on the vessel. The result will be heavy duty winch systems with significantly less CO2 footprint than any present solutions.