Photovoltaics (PV) is the phenomenon of converting sun energy into electric energy by using photovoltaic cells. Furthermore, solar energy is the major renewable energy source. PV modules are systematically more efficient and manufacturing costs decrease at the same time. The PV module performance is affected by ambient temperature, humidity, wind speed, rainfall, incident solar radiation intensity and spectrum, dust deposition, pollution, and shading, which are environmental factors. The problem of partial shading of the generator often arises when designing photovoltaic installations. If it is not possible to avoid this phenomenon, its impact on the operation of the photovoltaic system should be estimated. The classical method is to measure the current–voltage characteristics, but it requires switching off the installation for the duration of the measurements. Therefore, this paper proposes a method using a computer simulation in the Matlab package with the implemented component “Solar Cell” for this purpose. Three cases of partial shading of photovoltaic modules with different degrees of shading were analyzed. The obtained results of the computer simulation were verified for two types of silicon PV modules: Mono- and polycrystalline.

The nozzle which is applied in industrial pneumatic pulsators is studied. It is a part of the system for unclogging the drains and outlets of silos and hoppers for loose materials. The nozzle is required to achieve the lowest level of energy losses while directing the airflow, which impacts the loose material bed. The energy rate transferred into the bed depends on the temperature and pressure differences between the inlet and outlet of the nozzle. In this study, the available energy is determined assuming compressible and transient airflow through the nozzle, which is a part of the industrial pneumatic pulsator. Numerical simulations are performed using the OpenFOAM CFD toolbox. Energy analysis is carried out by using Reynolds Transport Theorem for specific energy for the variable temperature inside the silo on the basis of CFD results. In fact, the air parameters at the outlet of the nozzle are the ones inside the silo. The study showed that the design of the nozzle is not very sufficient from an energetic point of view.

Sustainable development is a highly interdisciplinary concept that involves the interaction of various systems, such as energy, water, and environment, by using waste from one, as a resource in another, and in the exact moment when it is beneficial to all

An industrially applicable nozzle is the subject of this study. The nozzle is an auxiliary equipment of a pneumatic pulsator system for unclogging outlets of silos which store loose materials. The aim is to determine the amount of heat which is generated during one work cycle of the system. Investigation in this field has not been carried out so far, and the present-day designing process is significantly based on heuristic knowledge. The heat is calculated by using results of a numerical simulation. The Finite Volume Method has been used with a thermodynamically ideal gas model. The airflow is assumed to be transient, compressible and supersonic, and it is driven by a time-varying pressure difference. There is an estimation of discretization error of the numerical results carried out in order to confirm the reliability of the solution. The error estimation shows that the results lie in the vicinity of the exact solution of the governing equations. Instantaneous results of the simulation indicate a locally flow which intensifies flow parameters in a similar way as the converging-diverging nozzles do. The value of the total heat generated during gas conversion within the nozzle is negative; thus, the nozzle could be cooled during its functioning.

The results of experimental data on the heat transfer coefficient during the boiling of pro-ecological refrigerants in a compact tube-shell heat exchanger are presented. The boiling process occurred in the micro-space of the exchanger shell on the surface of horizontal tubes, which were heated from the inside with warm water. The flow of the refrigerant was gravity-based. The heat exchanger was practically flooded with liquid refrigerant at a saturation temperature (ts), which flowed out after evaporation in a gaseous form. The tests were conducted for four refrigerants: R1234ze, R1234yf, R134a (a high-pressure refrigerant), and HFE7100 (a low-pressure refrigerant). Thermal characteristics describing the heat transfer process throughout the entire compact heat exchanger, specifically for the boiling process itself, were developed. It was found that in the case of micro-space boiling, there is an exponential dependence of the heat transfer coefficient on the heat flux density on the heated surface. Experimental data were compared to experimental and empirical data presented in other studies. Our own empirical models were proposed to determine the heat transfer coefficient for boiling in a mini-space for individual refrigerants. The proposed calculation models were also generalized for various refrigerants by introducing the value of reduced pressure into the calculation relationship. The developed relationship enables the determination of heat transfer coefficient values during boiling in a micro-space on the surface of horizontal tubes for various refrigerants with an accuracy of ±25%.