Technical, Safety and Environmental Challenges in the Electrification of Cable Yarding Equipment

Purpose of Review Electrification is the second major shift in the type of drivetrain technology employed in cable yarding equipment, after the gradual transition from mechanical to hydraulic drives that began in the 1960 s. Electric slack pulling carriages are omnipresent today and more advanced electrified solutions are close to market entry. Few studies are available on the performance and efficiency of electric timber harvesting equipment, and none considers the technical aspects. The purpose of this review is to contribute to the accelerated adoption of such equipment by providing valuable insights and addressing technical and safety concerns, with a special focus on their efficiency and the challenges associated with their autonomy, durability, safety and environmental impact. Recent Findings Most electrified cable-logging concepts employ energy recovery. Recovering energy that is otherwise dissipated represents a fundamental improvement. Some slack pulling carriages rely solely on recharging during lateral yarding, such that their fuel-saving potential is highly dependent on the lateral yarding distance. The type of energy storage system employed largely depends on the energy need and weight constraints of the given application. High-power, durability and safety favor supercapacitors. Advanced battery systems, however, are employed increasingly in high power applications, such as logging equipment. This is due to added autonomy and competitive pricing compared with supercapacitors. The risk of electric shock is not a concern as long as the equipment is intact, and is generally negligible for carriages operating at 48 V. Summary In an attempt to boost productivity and reduce costs and emissions, a digital transformation and a transition to electrified equipment is ongoing. Forestry, and in particular cable yarding is no exception. The benefits of electric slack pulling carriages and tower yarders have already been confirmed in practice, and more electrified steep slope cable yarding equipment is close to market entry. All electrified equipment identified in this study is distributed by European manufacturers and in use in European forests. Very little information is available on electrified cable yarding solutions possibly developed outside Europe. If any such products exist, they have not yet reached the market or attracted the interest of the scientific community.