This paper presents results of experimental investigations and numerical simulations of a vertical-axis H-type wind turbine, considering the influence of propeller blade pitch angle on turbine characteristics. An innovative airfoil profile based on a modified symmetric NACA0015 airfoil profile was used as the designed blade profile, which was tested in a wind tunnel over a range of Reynolds numbers from 50,000 to 300,000. The phenomenon of angle-of-attack variation and the resulting forces acting on the blades, particularly in the horizontal configuration and vertical axis of rotation, were discussed. Series of experiments were conducted on a 1:1 scale four-bladed turbine model in the wind tunnel to determine the characteristics, specifically the power coefficient distribution over the tip speed ratio for various Reynolds numbers and blade pitch angles. Subsequently, the turbine was modeled using Qblade software, and a series of calculations were performed under the same conditions. The numerical results were validated with the experimental data.

Lead-free single crystals of Na_0.5Bi_0.5TiO₃-BaTiO₃ (NBT-BT) system were prepared by Czochralski method and their dielectric and pyroelectric properties have been studied. The results were compared with these for pure NBT. The obtained samples show pure perovskite structure with rhombohedral symmetry at room temperature. Low frequency (100 Hz–100 kHz) investigations reveal the diffuse phase transitions. The obtained results are discussed in terms of local electric and strain fields caused by different ionic radius of (Na, Bi) and Ba ions. The NBT-BT system is expected to be a new promising candidate for lead-free electronic crystals.

The paper analyses the possibility of reducing the amount of pollution using photovoltaic systems. The analyses indicate the main sources of pollution. It was estimated how much pollutants are released during the energy production required to ensure the security of energy supply. Simulations of the production of determined amounts of energy by photovoltaic panels were carried out. During the simulation of selected solar devices, the amount of avoided emissions was estimated. Ecological gains were calculated for electricity production from solar systems for a given time interval, the chosen technology and the location.

The paper presents the relationship between the intensity of solar radiation and air pollution on energy and economic area. The relationship between the energy of solar radiation that reaches the ground and atmospheric pollution is described. Energy and economic analysis has been carried out for energy lost caused by the presence of the pollutants in the air. When analysing selected solar devices, losses in the production of electricity from the surface of the solar panel were simulated and calculated for a given time interval, the chosen technology and the selected location of solar devices.