Energy efficiency, fuel consumption, and productivity of cable yarding operations using hybrid tower yarder and electrical carriage in the North-Eastern Italian Alps

In the last decades, low-emission and zero-emission technologies have been applied to light and heavy-duty vehicles. Even though hybrid and full electric propulsion systems are widely studied for road vehicles and city mobility applications, there is currently a considerable knowledge gap in regard to hybrid and full electric propulsion systems applied to forest operations sector, and in particular to cable-based harvesting system. This study monitored a hybrid tower yarder equipped with an active slack-pulling electric carriage during uphill yarding operations for 30 work days, in order to evaluate energy efficiency, fuel consumption, and productivity of cable yarding operations. A total of 915 work cycles on four different cable lines were analyzed. Energy consumption and productivity were recorded by integrating long-term monitoring using Can-BUS data and direct field observations. Subsequently, energy efficiency, fuel consumption, and productivity were evaluated in terms of net energy consumption, Net EC (kWh), total energy efficiency, TEF (%), fuel consumption per unit of timber extracted (l/m3 ), and productivity (m3 /PMH15). The inhaul-unload work element consumed, on average, 63% of Net EC per work cycle, while the outhaul and the lateral skid consumed 15% and 22% of Net EC, respectively. The highest Net EC of 1.150 kWh (Mean= 0.617 kWh; SD=0.453 kWh) occurred during inhaul-unload. In contrast, lower energy consumption of 0.035 kWh (Mean= 0.172 kWh; SD=0.155 kWh) and 0.086 kWh (Mean= 0.184 kWh; SD=0.092 kWh) were recorded during outhaul and lateral skid, respectively. The electric-hybrid technology led to the reduction of the engine's running time up to 38% of the total productive time. In addition, mean TEF of each monitored cable line varied between 35% to 41%. Fuel consumption and productivity were estimated to be 0.54 .