Short rotation forests (SRF) can be used for biomass production for energy applications in Latvia. Establishment of plantations could be one of possibilities how to reach targets of renewable energy resource (RES) consumption of 40% in 2020. In Latvia’s conditions, one of most suitable species that could be used for SRF is willow (Salix sp.). Abandoned agricultural lands are suitable for establishment of plantations. Productivity of 8 oven- dried tons (ODT) ha-1 year -1 can lead to Rate of Return (IRR) of 17.1% and Net Present Value (NPV) 1099 Latvian Lats (LVL) if the biomass price is 33 LVL ODT-1. Establishment, harvesting and transporting costs account for 88% of the total cost of production. Price of wood chip and fuel plays the most important role in economics of plantation.

Due to currently aggravating problems of global warming, more and more alternatives are being developed using a mixture of different fuels. The rapid development of science and engineering solutions can be the most efficient burning of the local biofuels to a minimum harmful substances from combustion process - including the CO2 emitted into the atmosphere. The research concerns fuel problem of choice between cost-effective, but environmentally harmful fuels. Research data will help further studies on the fuel in order to increase energy efficiency and rational use. The research was done in 2010, in Riga Technical University laboratories. An aspen wood and hard coal was used to create this fuel mixture. During the research, sampling, grinding, sifting and blending of different proportions, moisture and calorific value determination were carried out. It was determined that the calorific value of the mixture would increase linearly, exactly in the proportion of coal quantities added.

This paper investigates the effect of fuel bias between the primary and secondary injectors of a staged fuel injection system on the performance of a high output single cylinder spark-ignited internal combustion engine. It is known that staged fuel injection systems are widely used in motorsports applications where high engine speeds are coupled with high power output, therefore, the aim of this study is to evaluate the effect of a secondary fuel injector installed on a Honda CRF450R single cylinder four-stroke gasoline engine. The said engine was equipped with a programmable Performance Electronics PE3-SP0 control unit and a secondary fuel injector identical to that of OE. Power measurements were carried out on a Dynojet-200ix chassis dynamometer in four different modes with altered fuel proportion between injectors, with each measurement being repeated three times. Ambient conditions were monitored with Performance Electronics Pe3Monitor software and the fuel map was adjusted to produce a stable air-fuel ratio. The results were averaged and compared numerically and by coefficient of correlation. It was observed that the data as obtained from the chassis dynamometer software SportDyno 4 contains a lot of noise, both mechanical and electrical in nature, and the changes in power output are highly dependent on engine and equipment temperature. The best results were obtained by using both injectors with fuel proportion biased to the front of the system.

Fuel as the main energy resource in agriculture and forest production is surveyed in the work. Specific weight of fuel and lubricants in applicable expenses in country farms is analysed, average fuel and oil consumption in farms of different specialization, as well as changes in oil price in farms of different size and specialization are shown.

The study aims to find out the efficiency of periodic training of the harvester (cut-to-length) operator, using the automatically saved data of the harvesterʼs information system. It has been established that logging service providers and training institutions do not analyse the operatorʼs work before starting the training; therefore, the training is carried out according to certain, standard programs, without going into the previous performance of each trainee operator. The research uses data automatically saved by Ponsse harvesters during the year, obtained from Ponsse Manager. The study found that by using automatically saved data of the harvester information and performing data grouping with subsequent analysis, it is possible to determine the progress in the execution of specific stem processing operations and to identify operations where the instructor should pay increased attention during training. The research analysed the data of 3 operators, obtained while working with Ponsse harvesters in clear-cutting. In the study, it was found that operator A reduced stem processing time by 3%, labour productivity increased by 15%, and fuel consumption per l m⁻³ decreased by 14% over 3 months. Operator B, after training, saw a 20% reduction in stem processing time, a 13% increase in work productivity, and a 5% increase in fuel consumption l m⁻³ over 3 months. Operator C had a 10% increase in stem processing time, a 1% increase in labour productivity, and a 2% increase in fuel consumption l m³ after training.

It is very important to use the exact investment model for energy enterprises. Giant investment is necessary for establishing continued energy systems using renewable energy resources. Demand of the heat energy usually is higher in a winter period compare to the summer time. Program combinations of different heating modus are researched using EnergyPRO.

The objective of this research was to design an economically efficient logistics management model for fuel retail enterprises to improve their competitiveness. In the current global market situation, fuel retail enterprises face various challenges, such as sharp increase in raw material price, intense market competition, high price sensitivity, low profitability, and significant logistics costs. By combining theoretical and practical insights, an improved logistics management model was designed, which provides significant competitive advantage for fuel retail enterprises. The designed model incorporates and integrates three distinct logistics arrangements, resulting in considerable advantages for fuel retail enterprises. These advantages include a reduction in logistics costs and increased independency from the fluctuating logistics service expenses. To determine the economic efficiency of the designed logistics management model, it was validated by using data obtained from a fuel retail enterprise based in Sweden. Results of the research indicated that the fuel retail enterprise can anticipate an annual reduction in logistics costs ranging from 2.91% to 3.32% from the implementation of the improved logistics management model. On top of that, the developed logistics management model is projected to be economically viable until 2027, assuming the continuation of the current market trends and conditions. The findings of the research suggest that other fuel retail enterprises may also benefit from implementation of the designed model in the current market conditions.

Lowering emissions expelled from internal combustion engines has been the focus of researchers worldwide. Adding hydroxy gas to current internal combustion engines can be an effective way of lowering CO2, CO, HC and particle emissions, as well as improve combustion. Because of this, a review of previously conducted research on the addition of hydroxy gas to different internal combustion engines has been produced. During this review, it was concluded that addition of hydroxy gas can be an effective way of lowering fuel consumption and CO, CO2 and HC emissions in petrol engines, as well as fuel consumption and CO and HC emissions in diesel engines.