The article suggests that the rate of plant biomass gas generation is proportional to the amount of plant biomass, which can still be gasified. To analyse the change in fuel mass during the operation of the gasifier for a certain period of time, three models can be used with the following assumptions: the change in fuel mass is inversely proportional to the fuel mass and time, the change in fuel mass is inversely proportional to the fuel mass, the change in fuel mass is inversely proportional to time. The coefficients of the fuel gasification rate are experimentally found.

The gasification rate of fuel, biomass gasification in particular, is an important parameter which is worth considering in the process of creating a gasifier with a continuous operation process. The gasification of biomass is a complex thermochemical process. The theoretical and practical studies of the gasification rate of biomass are complicated because of a high thermochemical rate of reactions in the functioning zones of a gasifier. The complexity of the study prevents the achievement of the required accuracy of the analytical model of the gasification rate of biomass. The known theoretical models of the gasification rate only partially describe the dynamics of the gasification rate of biomass. Moreover, most scientific studies are focused on establishing the effects of gasifier parameters and the gasification process on the quality indicators of the received gas but not on the gasification rate of fuel. To build an accurate model of the gasification rate the authors propose a series of experimental studies in a well-defined range of the parameters of a gasifier. The paper suggests a simple mathematical model of the gasification rate of biomass, which is proportional to the amount of plant biomass that remained non-gasified. The coefficients of the gasification rate for straw pellets, wood pellets and wood in pieces have been determined. Under a minimal air supply into an active zone of a gasifier (0.00088 m3/s) a coefficient of gasification rate is nearly the same for the test fuel materials and it differs by 4.7% between wood pellets and straw pellets. When the air supply increases, the gap between the coefficients increases as well and it reaches 9.44 × 10−5 c−1 for wood pellets, 1.05 × 10−4 c−1 for straw pellets and 8.64 × 10−5 c−1 for wood in pieces under air supply into an active zone of a gas generator of 0.01169 m3/s. Straw pellets have the highest gasification rate and wood in pieces has the lowest gasification rate.

This paper offers an algorithm to account for potential actions on the efficient production of renewable energy. The algorithm consists of a substantiated choice of a certain type of renewable energy, the evaluation of its potential, and the regulation of the processes of obtaining that renewable energy. Also, potential resources for agricultural biofuel production have been analyzed and it has been determined that there is real biomass potential in Lithuania. It will thus be beneficial to make appropriate managerial decisions on the methods of biofuel processing and consumption, as well as on means of receiving the economic, energy and environmental effects. The total potential of by-product biomass of crop production was determined, and the thermal and electric potential of the crop by-products were calculated. Additionally, the potential for production of gas-like types of fuel (biomethane, biohydrogen, and syngas) from crop by-products was determined. The potential for the production of diesel biofuel from oil crop waste (bran) was also found, and the potential for livestock by-products for receiving gas-like types of fuel (biomethane, biohydrogen) was established. The corresponding thermal and electric equivalents of the potential were found and the potential volumes of the biomethane and biohydrogen production were calculated. The total energy equivalent equals, on average, 30.017 × 106 GJ of the thermal energy and 9.224 × 106 GJ of the electric energy in Lithuania. The total potential of biomethane production (taking into account crop production and animal husbandry wastes) on average equals 285.6 × 106 m3. The total potential of biohydrogen production on average equals 251.9 × 106 m3. The cost equivalents of the energy potential of agrarian biomass have been calculated. The average cost equivalent of the thermal energy could equal EUR 8.9 billion, electric energy—EUR 15.9 billion, biomethane—EUR 3.3 billion and biohydrogen—EUR 14.1 billion. The evaluation of the agricultural biomass potential as a source of renewable energy confirmed that Lithuania has a large biomass potential and satisfies the needs for the production of renewable energy. Thus, it is possible to move to the second step, that of making a decision concerning biomass conversion.

When designing the structural and functional schemes of the vacuum systems of a portable milking machine it is important to conduct a research on the impact on the milking machine efficiency. The technological efficiency and the regime of a vacuum system functioning are the basis of the research. The unstable pressure may cause the decrease in animals productivity and may have negative impact on cows welfare. That is why it is necessary to determine some rational parameters and choose the linking vacuum system decisions. It will result in getting stable working regimes of a portable milking machine. A research on the effects of different components variants as well as of vacuum system parameters on the consistency of operation has been conducted. The results of the research made it possible to estimate the impact of vacuum pump fast reaction as well as the vacuum system parameters on the job stability. It has been proved that the vacuum system efficiency is determined by the level of its conductivity. The conductivity is the inverse value to the vacuum system resistance. The research has determined how the vacuum system packaging affects the pressure loses. A mathematic model which enables to find the rational volume of a vacuum tank and determine the vacuum system conductivity has been received. On the results of the experimental research the vacuum system rational structure has been substantiated and estimated on a special efficiency coefficient.

Journal of Environmental Engineering and Landscape ManagementPublication details, including instructions for authors and subscription information:Abstract. In designing a natural ventilation system for animal sheds it is necessary to assess the ventilation induced by thermal buoyancy and wind forces during different seasons and under different animal housing conditions. By applying analytical and experimental investigation a methodology was prepared to establish ventilation intensity caused by thermal buoyancy and wind and data were achieved on thermal buoyancy and wind values and their relationship. The innovation of the methodology can be described by the fact that a simple equation was formed to calculate the air speed in inlet and outlet openings, a mathematical expression of thermal buoyancy and wind ratio was achieved and the required inlet opening area to let in fresh air compared with the outlet opening area to let out polluted air was substantiated to ensure that all polluted air is removed through a rooftop open in winter. It was calculated that the average air speed in the rooftop outlet opening of a typical cold-type cowshed is 1.3 m/s (when there is no wind, this speed decreases to 0.3 m/s), thermal buoyancy and wind ratio is 0.27 and in order to have all polluted air removed through the rooftop open in winter the inlet opening area in the walls must not exceed 40% of the rooftop opening area. The accuracy of the prepared methodology was tested under natural conditions of barn operation when the distance between air inlet openings and outlet openings was 6.5 m. During the investigation indoor and outdoor temperatures, air speed in the outlet and wind speed were measured. During the experiments the difference of indoor and outdoor temperatures varied from -2 to +16 o C and air speed in the outlet -from 1.2 to 1.9 m/s. The analytical results reflect the mean values of experimental data under natural conditions of operation rather accurately. The difference between the experimental and calculated air speed values in the outlet opening was insignificant and was within 0-8% range.