A survey was conducted on 12 cable yarding operations in northern Italy, with the purpose of determining fuel consumption and time use. The observation unit was the individual operation, intended as all the activities needed to complete the harvesting of a sale (mean = 500 m³ of timber). All teams were equipped with a tower yarder, an excavator-based loader or processor and a truck or a tractor with trailer, if intermediate transportation to a larger roadside landing (two-staging) was required. The crew size was 3 or 4 operators. Time and fuel use were recorded separately for the following tasks: relocation; set up & dismantle; commuting; yarding; processing and/or loading; major delay events. Fuel consumption averaged 5.1 L m⁻³, of which 2.2 L m⁻³ was incurred by two-staging. In general, the yarder accounted for less than half the total fuel consumption of the operation: the processor was indeed the main consumer. Relocation had a very small incidence on time and fuel use. Set up and dismantle did not incur significant fuel consumption but occupied a meaningful share of total time (mean = 22%). Commuting also incurred unexpectedly large (and generally neglected) fuel and time use—with means at 13% and 7%, respectively. Technology developments aimed at reducing fuel consumption should target both main consumers: the yarder as well as the excavator-based processor. Significant benefits would also be achieved through improved planning and infrastructure development, aimed at minimizing the need for intermediate transportation (i.e. two-staging).

Meeting ever-tightening emission regulations and ambitious climate targets requires drastic efficiency improvements and emission reduction across all sectors. Hybridization as an intermediary step towards electrification is a prominent approach to achieve this. Within the forestry sector, most equipment still relies on conventional mechanical or hydraulical drivetrains. This work focuses on the design of hybrid tower yarder drivetrains, in order to facilitate the technological transition to more sustainable equipment. Tower yarder duty cycle data are extracted from the literature and organized into a set of reference duty cycle data via Matlab simulations. Based on typical performance requirements, various technological solutions are studied for the following key tower yarder subsystems: energy storage, winch drive, energy source, and energy dissipation. The objective is to determine the most performing design considering system cost, performance, weight, and durability. Challenging control considerations are discussed and control algorithms are presented. Further presented are drivetrain architecture alternatives to boost overall efficiency. The best hybrid drivetrain, based on a large set of operation data gathered from other studies, is finally subjected to design calculations and a case study involving a 5-ton tower yarder. Results indicate that off-the-shelf electric drives, reduction gearing, and energy dissipation systems can satisfy all performance requirements, including a maximum power of about 100 kW per drive. A 15–45 kWh power-dense battery pack or a 100 kWh energy-dense battery pack may be required to cope with a power of up to 70 kW RMS, pointing to a need for substantial overdesign and confirming that the energy storage system represents the largest design challenge. The engine should achieve at least 41.5 kW of power to compensate for combined average net energy consumption in the yarder. These results confirm the feasibility of tower yarder hybridization and the large potential for energy recovery. This is especially true in the closed-loop setup, with a recovered energy of up to 5 kWh per transport cycle. Finally, differences between the proposed optimal design and the commercial hybrid design by Koller Forsttechnik are discussed.

Radical changes are necessary to address challenges related to global warming and pollution. Ever-tightening emission standards for combustion engines have already led to a drastic reduction in the amount of harmful gas and matter emitted. Drivetrain hybridization and electrification, which are becoming increasingly popular in all sectors, are two additional ways to achieve that goal. However, within the forestry sector most of the equipments still rely on conventional mechanic or hydraulic drivetrains. An example of this is tower yarders, the workhorse of the alpine logging industry. This work simulates the duty cycle and energy flow of tower yarders in logging operations, both with conventional diesel–hydraulic configuration and a proposed hybrid configuration. The objective is to determine the potential of hybridized drivetrains for tower yarder applications. Detailed models are developed to describe the cable-based extraction of timber and tower yarder internal processes. Extensive simulations were performed to determine force, power and energy components during the harvesting operation for both the diesel–hydraulic and hybrid drivetrains. Results confirm the large potential of the hybrid configuration for efficiency improvement and emission reduction, with estimated fuel savings of 45% and 63% in the uphill and downhill configurations, respectively. Extensive sensitivity analysis further demonstrates that the hybrid concept remains effective across a wide range of cable setup and transport characteristics. This confirms the large potential of electrified drivetrains, especially in the presence of very dynamic duty cycles, as is the case in cable-based logging equipment.