Mitigation of climate change requires a decrease in greenhouse gas emissions. It motivates an increase in renewable electricity generation. Farmers can develop renewable energy and increase their profitability by allocating agricultural land to PV power plants. This transition from crop production to electricity generation needs ecological and economic assessment from alternative land utilization. The novelty of this study is an integrated assessment that links economic and environmental (carbon dioxide emissions) indicators. They were calculated for crop production and solar power generation in a semi-arid zone. The results showed that gross income (crop production) ranges from USD 508/ha to USD 1389/ha. PV plants can generate up to 794 MWh/ha. Their market cost is EUR 82,000, and their production costs are less than wholesale prices in Ukrainian. The profitability index of a PV project ranges from 1.26 (a discount range is 10%) to 3.24 (a discount rate is 0). The sensitivity analysis was carried out for six variables. For each chosen variable, we found its switching value. It was revealed that the most sensitive variable is a feed-in tariff. Operational expenses and investment costs are the most sensitive variables. Carbon dioxide footprints range from 500 to 3200 kgCO₂/ha (depending on the crop). A 618 kW PV plant causes a release of carbon dioxide in the range of 5.2–11.4 gCO₂/kWh. The calculated carbon dioxide payback period varies from 5 to 10 months.

The focus of today’s agriculture is to reduce fuel consumption and pollutant emission. More than 50% of the fuel energy is lost with the exhaust gas and coolant of diesel engines. Therefore, waste heat recovery systems are a promising concept to meet economical and ecological requirements. Agricultural vehicles have an operating cycle that is quite different from on-road trucks (higher engine load factor and less annual utilization). This has influence on the efficiency of waste heat recovery. The purpose of this paper was to analyze different waste heat recovery technologies to be used in agricultural applications. In the study, technical and economic indicators have been used. According to suggested classification, four pathways for utilization were studied. Turbocompounding, electric turbocompounding, and heating of transmission oil for hydraulic clutch gearboxes have proved to be effective for agricultural vehicles. For the economical conditions of the European Union (EU), a turbocompounding diesel engine is acceptable if agricultural tractor rated power is more than 275 kW, and combine harvester rated power is more than 310 kW. In cold climates, heat recovery transmission warm-up may be recommended. Waste heat absorption refrigerators have proven to be a viable technology for air conditioning and intake air cooling systems.

An increase in energy demand, fossil fuel reserves depletion, and environmental issues are primary reasons for renewable energy use, including power generation. Bioenergy is the primary alternative to conventional hydrocarbon fuels. Biomass-based power generation is increasing due to some reasons, including a gradual decrease in the levelized cost of electricity and a reduction of carbon dioxide emissions. Sorghum is a promising energy crop for semi-arid climate zones, including southern Ukraine. It can be used for both biofuel production and power generation. However, there is a lack of methodology for energy and environmental assessments of sorghum-based power generation. Some possible technologies were analyzed. The novelty of this study is the accounting of energy consumed and carbon dioxide emissions during crop cultivation. We have determined that sorghum-based power plants can generate from 2 to 12 MWh per hectare. Their operation significantly reduces carbon dioxide emissions (from 613 to 3652 kg of carbon dioxide per hectare of sorghum silage cultivation). Sorghum-based biogas plants have energy and environmental advantages if they use co-generation technologies and utilize digestate as a biofertilizer. The utilization of digestate (obtained from silage production per hectare) substitutes up to 12.8 MWh of indirect energy. The results obtained can be used by farmers and authorities for bioenergy development.

The methods of increasing the efficiency of internal combustion engines through heat utilization are examined. A proposed classification of heat utilization systems for mobile energy vehicles is presented. External utilization harnesses the heat generated by a diesel engine to fulfill the needs of consumers not directly related to the engine, such as interior heating and air conditioning systems. Internal recycling focuses on enhancing the power, environmental performance, and economic performance of an engine and its related systems. Various heat utilization schemes are compared. For the economic conditions of the European Union (EU), a turbocompounding diesel engine is acceptable if its agricultural tractor rated power is more than 275 kW and its combine harvester rated power is more than 310 kW. Steam injection into the combustion chamber is utilized to improve the technical and economic performance of gas turbine engines. This technology is also produced in Ukraine and is proposed for use in internal combustion engines. It is suggested to inject water vapor into a turbocharger turbine. This approach reduces the number of components in the heat recovery system, thereby lowering its cost. A recycling chiller can be employed to cool the air after it passes through the air cleaner, enhance the efficiency of the air cooler, and improve the performance of the thermoelectric generators. This device is particularly effective at relatively high air temperatures and can be recommended for agricultural machinery that operates in such conditions, such as combines. With the application of this new technology, it is possible to increase the power of diesel engines by 15…20% and reduce fuel consumption by up to 14%. Further research will focus on substantiating the parameters of recycling systems for different classes of vehicles. Developing a methodology to justify the effective application of heat utilization systems in agricultural mobile energy vehicles is advisable.

This paper reports the analytically established conditions for the onset of auto-balancing for the case of a flat rotor model on isotropic elastic-viscous supports and an auto-balancer with a single load. The rotor is statically unbalanced, the rotation axis is vertical. The auto-balancer has a single cargo – a pendulum, a ball, or a roller. The balancing capacity of the cargo is equal to the rotor imbalance. The physical-mathematical model of the system is described. The differential equations of motion are recorded in dimensionless form relative to the coordinate system that rotates synchronously with the rotor. The so-called main movement has been found; in it, the cargo synchronously rotates with the rotor and balances it. The differential equations of motion are linearized in the neighborhood of the main movement. A characteristic equation has been constructed. It helped investigate the stability of the main movement (an auto-balancing mode) for the cases of the absence and presence of resistance forces in the system. It was established that in the absence of resistance forces in the system: – the rotor has three characteristic rotational speeds, and the first always coincides with the resonance frequency; – auto-balancing occurs when the rotor rotates at speeds between the first and second ones, and above the third characteristic speed; – the value of the second and third characteristic speeds is significantly influenced by the ratio of weight to the mass of the system; – the second and third characteristic speeds monotonously increase with an increase in the ratio of cargo weight to the mass of the system. Resistance forces significantly affect both the values of the second and third characteristic speeds and the conditions of their existence. Small resistance forces do not change the quality behavior of the system. With high resistance forces, the number of characteristic speeds decreases to one. The paper reports the results applicable to an auto-balancer with many cargoes when it balances the imbalance that equals the balancing capacity of the auto-balancer

On the limited accuracy of balancing the axial fan impeller by automatic ball balancers