Renewable energy is the key pillar and plays an important role in the energy systems of European Union member states and in mitigating climate change. It is supporting the transition towards a greener, resource-efficient and more competitive, low-carbon European Union economy. Above-average, average and below-average values of monitored indicators in member states of the European Union in 2009–2016 were ascertained by using principal component analysis. Monitored indicators of the renewable energy sector included electricity generation, electricity capacity, investments of public financial institutions, number of employees and turnover achieved from the economic activities related to production, distribution, installation, operation and maintenance of equipment (all of them per capita). Based on the achieved results, we can state that the situation changed during the period under review. Member states have moved between above-average, average and below-average levels of renewable energy indicators. However, a lack of change in the indicators was recorded in some member states throughout the eight-year period (Finland, France, Ireland, Germany, Austria and Spain did not move significantly). Renewable energy sources (hydro, wind, solar, geothermal and energy from biomass) were evaluated as a whole due to different natural, economic and legislative conditions of European Union countries.

Greening the economy requires green innovations, and innovations require investments. Most countries of the world are still relying on conventional (fossil-based) sources of energy. The transition toward green or renewable energy sources is an effective and innovative way to meet ever-increasing demand as a result of the rising population. Another reason for innovations in the field of green energy is the need to mitigate climate change and avoid pollution, especially in developing countries. The monitored investments into renewable energy sources are usually public. Therefore, this paper aims to determine whether the selected countries of the world produced renewable energy efficiently, considering the investments made by public financial institutions and installed electricity capacity for renewable energy sources, for the period 2013-2017 (for a deeper analysis, the year 2017 was chosen). For this purpose, the Stochastic Frontier Analysis model in the logarithmic form of the Cobb-Douglas production function is used, which helps to judge the competitiveness of countries based on effectively transforming the inputs into outputs. Results suggest that the effect of the first variable "installed electricity capacity" on electricity generation was highly statistically significant, and the impact of the second variable "public investments" was characterized as statistically insignificant. The monitored countries were divided into 10 groups according to the different range of estimated output-oriented technical efficiency from 0.00 to 1.00. Most countries should increase the renewable electricity generation approximately by 40-49%, given the level of inputs (16 countries of 6th group with estimated output-oriented technical efficiency 0.51-0.60) for the year 2017.

The increasing consumption of energy, as well as exhaustibility of fossil resources, initiate the necessity of finding renewable resources. Especially biofuels represent the important role in terms of renewable resources, development of which is often question under debate in many countries. By increasing of blending mandate in the European Union (EU), the SR after joining the EU forced to implement the changes in its action plan for renewable energy in transport and set benchmarks share of methyl ester of rapeseed oil in diesel fuel. The aim of the paper is to evaluate the economic impact of biodiesel production in the Slovak republic. At the same time, biofuel production has an impact on the price of conventional fuels. The relationship between biofuel production and prices of agricultural crops as well as conventional fuels we examined through regression and correlation analysis, which showed that between production of biodiesel and the prices indicated exists certain dependency.

In the presented paper, we evaluated the quality of work and the economics of use of irrigation system consisting of micro-sprinklers. The experiment took place on the football field in countryside of southwest Slovakia. The original irrigation system was replaced with a modern one, using a control unit, rainfall sensor, in-ground distribution pipes and micro-sprinklers. The irrigation system consisted of components forming the main and detailed irrigation equipment for irrigating an area of 4,272 m2. The water source was a drilled well with a depth of 80 m. Detailed irrigation equipment consisted of sector micro sprinklers of two types. We monitored 13 rotary micro-sprinklers on the given playground in total. During the measurements, we proceeded according to the international standard ISO 7749-2, while the rain measuring containers were distributed into eight beams. The value of the quality of the work of individual sprinklers, expressed by the coefficient of uniformity of spraying, reached a maximum of 78.18%, but with total coverage it was higher than 90%. Anova statistical analysis did not show a significant dependence of the quality of work on the type of micro-sprinkler (for micro-sprinklers A1, A2 A3: F = 2.95, P >0.05; for micro-sprinklers B, C: F = 0.35, P >0.05). From the viewpoint of evaluating the economic return, the investment proved to return within the period of 4.2 years.

The economic theory distinguishes mainly three production factors, namely labour, soil, and capital. Soil, as a product of nature, is not a free good – its amount is not unlimited. It can be used for agricultural purposes, as energy and non-energy source, and for minerals. Soil is one of the factors of production and at the same time the most important natural resource. We have used three indicators, namely the degree of plowing, the degree of agricultural use and area of agricultural and arable land per capita. The result of the work was the finding that in the observed period (10 years), the area of agricultural and arable land in Slovakia is decreasing. To improve the situation in agriculture, the following could be done: merging fragmented land into larger units, changes in the system of inheritance or a change in allocation of subsidies. Especially the inhabitants of the territory should support the state buy buying on the domestic market and supporting domestic production.