No abstract

Energy cannot be produced without consumption of some part of the energy, and the proportions in which this occurs are a key indicator of the efficiency of the production process. Energy return on investment (EROI) of energy production shows the relationship between obtained and invested energy in the production process. This relationship is a key factor in sustainable global energy supply. Wood chips and onemetre firewood are used to produce thermal energy. Amount of energy obtained by burning depends on the moisture content and the features of the energy plant. This chapter deals with the issue of the amount of energy required to produce in the process of wood chips and one-metre firewood production and its transport to the heating plant. When calculating the energy balance, it is important to include as many input parameters as possible (parameters of energy consumption), which represents an almost impossible task because one parameter directly binds several others. According to several authors, the relationship between obtained and invested energy or EROI for energy wood is 30:1 which is a better ratio than the production of oil, for which relationship between obtained and invested energy is about 20:1. The results of study show that most of the energy during the production and supply of energy wood products from final felling of oak stands is used for fuel for machinery and vehicles in the production process. Ultimately, the relationship between obtained and invested energy is approximately 25:1 in the case of moisture content in the wood chips in the limit (market) value of 35% and the mean distance truck transportation of wood chips of 50 km. The relationship of obtained and invested energy used for one-metre firewood is bigger than 25:1 because of less invested energy which does not include machines like wood chipper. This is a satisfactory relationship, but it decreases with a greater transport distance. Such is the case when chips manufactured in Croatia, due to the lack of heat plants, are transported over long distances to neighbouring countries.

The paper presents a hypothetical conversion of a conventional cable skidder powertrain to its hybrid version. Simulations of skidder operation were made for two existing forest paths, based on the technical characteristics of the engine, transmission system and the characteristics of the winch. Fuel and time consumption were calculated per working cycle considering the operating conditions (slope, load mass). The model was then converted to a hybrid version by adding a battery energy storage system in parallel with the electrical power generator and by employing an energy management control strategy. The dimensions of the battery and the power generator were chosen based on the characteristics of the existing winch with the aim of completely taking over its operation. The management strategy was selected using the specific fuel consumption map. All simulations were repeated for the hybrid drive under the same operating conditions. The results show that fuel savings of around 13% can be achieved with the selected hybrid drive and steering strategy.

background and Purpose: Fuel consumption in timber harvesting operations is significant for both economic and environmental reasons. In economic sense, one significant part of timber harvesting costs is reduced to fuel costs, and in environmental sense 80% to 95% of exhaust emissions and soot particles in forest machinery are in fact associated with fuel consumption. Materials and Methods: The research object was a 6-wheel Valmet 840.2 forwarder and research was conducted in Forest Administration Vinkovci (lowland part of Croatia) during seeding felling in a stand of pedunculate oak and narrow-leafed ash. For the purpose of measuring fuel consumption on the researched forwarder a differential flow device was installed together with FMS (Fleet Management System) which was used for data transfer. results: Fuel consumption is expressed in six different ways concerning: cycle, extraction distance of 100 m, time (hour), load mass (tons), gross load volume (m 3) and product of mass and transporting distance (tkm). Fuel consumption amounted to 0.56 l•tkm-1 during the extracting of logs and 0.78 l•tkm-1 during the extraction of energy wood. The results also show an increasing trend of fuel consumption expressed per ton of transported load with the increase of travelled distance during the extraction. Conclusions: Fuel consumption expressed in l•tkm-1 is the most accurate fuel consumption indicator because it allows a realistic comparison of different types of machines with different loads (t, m 3) at different extracting distances. The higher fuel consumption of an unloaded forwarder compared to a loaded forwarder can be explained with an increased wheel slip of an unloaded forwarder due to reduced traction between wheels and the soil both in the extraction of logs and energy wood.

Technical development and system optimization during the last decades have targeted more efficient, socially acceptable and ecologically sustainable ways to use forestry machines and tools. This is supported by the development of electronics and electrical components, as well as battery technology, without which it is impossible to imagine doing some forestry work in forest areas with no permanent source of electricity. Today, we cannot imagine life without e.g. a cell phone, and also doing business in the forestry sector without a field computer. There are numerous examples in everyday life, but also in industry, where portable devices make life and business much easier, and the basis for the operation of these devices is battery technology. The importance of the development of battery technology is proven by the fact that in 2019 the Nobel Prize in Chemistry went into the hands of scientists who developed a lithium-ion battery - a lightweight, rechargeable and powerful battery that is used today in numerous products from mobile phones to laptops and electric vehicles. This paper will outline the historical development of battery technology and the use of battery powered devices, tools and machines with their advantages and disadvantages in forestry sector.