Renewable energy sources (RES) play an important role in the European Union’s energy sector as a result of the energy policy framework adopted. Its share in the final energy consumption varies depending on the country and the adopted energy policy. The article presents the structure of electricity production from renewable energy sources in Poland in the years 2002–2019. It was found that the share of energy production from hydroelectric power plants in Poland in relation to the amount of energy produced from renewable energy sources in the analyzed years has strongly decreased. The reason for this state was an increase in the production of energy coming from wind and biomass energy combined with an increase in subsidies for these energy producers. Additionally, unstable hydrological conditions, mainly low river flows, may be the reason for the low share of energy produced in power plants. As a case study, data for five small hydropower plants (SHP) located on the Gwda river (north-western Poland) were analyzed. Electricity production volumes were analyzed depending on the size of the Gwda river flow. It was found that the lower amount of electricity produced at SHPs on the Gwda river is mainly due to lower flows in the river. In the future, unstable electricity production from renewable energy sources may have a significant impact on achieving Poland’s energy targets in 2030.

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Electric vehicles are increasingly present on the roads of the whole world. They have the opinion of ecological vehicles, not polluting the environment. Society is more and more often persuaded to buy electric cars as an environmentally friendly solution but is this for sure? Electric cars need quite a lot of electricity accumulated in batteries to drive on a long range. During the charging process, this energy is obtained from the electricity network, to where it is supplied by power plant. Electricity production from renewable sources is a privilege for the rare. However, electric cars are charged from the electricity grid, which in large part energy comes from non-renewable fuels. The efficiency of energy production in power plants and the energy transmission and conversion chain causes that only part of the energy produced in this way goes to the vehicle’s wheels. Although the power plants are equipped with more and more efficient exhaust gas cleaning systems, they do not clean them up to 100%. Sulphur, nitrogen, mercury and heavy metals remain in the exhaust. The article is an attempt to answer the question whether the total emission of toxic components associated with the use of an electric vehicle is not bigger than in a traditional internal combustion engine.

Article presents the energetic balance of small-unmanned vehicle hybrid power transmission. The vehicle equipped with serial hybrid transmission consisted of electric engines connected to the battery pack and small Diesel power generator. In mentioned construction, battery is used as energy buffer and combustion engine is used more as emergency power supply, and is turned on when battery is depleted. In other condition, power generator can be turned off, without reducing power of transmission parameters, except its range. Vehicles with hybrid drive are very common chosen vehicles by users. More and more often, we also talk about searching for replacement fuels for internal combustion engines, so also for those with hybrid drive. The research was carried out on an unmanned land platform equipped with a hybrid propulsion system supplied as standard with Diesel oil. The article presents the problems of comparing the efficiency of a hybrid vehicle fuelled with Diesel oil, but also with alternative fuels based on kerosene and other components. For test, three types of fuels were used, standard Diesel oil, F-34 and with experimental mixture of Jet A-1 fuel with 10% of 2-ethylhexanol. Energy used for charging of the battery, from tank-to-wheel, was calculated. This also enables to calculate total efficiency of such hybrid power transmission, powered with different fuels.

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