Selective splitting of solar spectrum radiation allows various possibilities of applications of photovoltaic modules, as well as a solar thermal collectors. It is particularly interesting in the case of the simultaneous production of electricity and heat in so-called hybrid or photovoltaic solar collectors. It is known that increased temperature has a negative impact on both the efficiency of photovoltaic cells, as well as on the efficiency of the solar thermal collector, which in the latter reflects through the heat losses. In the project the solar collector with solar spectrum splitting was designed and analyzed and its optimal conceptual solution was selected. In this way we identified the most appropriate mechanisms and evaluated them in the terms of the simplest solutions for application in the prototype device. We further experimentally verified the concept of selective photovoltaic (heat) solar collector. With that goal the experimental set-up to evaluate the characteristics of the photovoltaic modules (PV) and of the selective and hybrid photovoltaic modules with built-in thermal collectors (PVT) was developed. The experimental set-up allow the measurements of the electricity (PV and PVT) and thermal power (PVT) of the modules in real time. In addition, the set-up was designed to vary the operating conditions of the solar collector of the hybrid module in order to determine its characteristics for different temperature regimes. For the establishment of the experimental set-up the measuring-control system, which was connected with the appropriate regulatory elements and gauges was developed. Based on the results of the project, in which we have developed a unique prototype, it was concluded that the prototype and the claimed technology is very suitable for further development towards the industrialization.
F.09 Development of a new technological process or technology
COBISS.SI-ID: 13900315The article gives a review on different design concepts of electrocaloric refrigeration devices. For these concepts, the operation characteristics, estimated by numerical simulations, are shown and compared. Up to date, only few electrocaloric prototype devices were developed. Their operation confirm the basic principle of operation, however, a relatively large deviation between the numerical and experimental results can be seen. The reason for this deviation partly lies in a number of different effects (heat transfer to the environment, Joule heating, hysteresis losses, etc.). These effects are usually not taken into account when modeling an electrocaloric cooling device. Therefore the article gives more detailed information on this issue. In order to provide most realistic evaluation of the performance of the electrocaloric devices, the above mentioned effects should be incorporated within numerical models. The results obtained from such models can then provide guidelines for the construction and operation of the electrocaloric cooling devices.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 14175515The main objective of the preliminary project entitled Development of dynamic computational model for refrigerators was: a study of the recent state and existing solutions in the field of dynamic modeling of combined refrigeration & freezing appliances (RFA) and the development of the basic framework of the computer software. A study of the recent state and existing solutions in the field of dynamic modeling of RFA has revealed that researchers are mostly using numerical approaches to solve differential equations and empirical correlations based on experiments. The models used in the reviewed literature describe both stationary and transient operation of the cooling system/particular component. Selected tools used in the modeling of RFA were as follows: Gambit and Fluent (CFD), EES platform (engineering solver equations), REFPROP 7 (calculation of the thermodynamic properties of refrigerants), ESI - OpenCFD, Matlab / Simulink, Modellica. Most of the models presented in scientific articles are validated, while in other sources of literature the experimental validation is less often. The development of the basic framework of a computer software was based on integration of REFPROP models in NI LabVIEW software package. The REFPROP models allows the calculation of the thermodynamic and transport properties of important refrigerants, used in industry and their mixtures. Next, the design of the graphic user interface (GIU) of a computer software to simulate the operation of the RFA was done. The GUI is built as an intuitive user interface with multiple controls, indicators and graphs. The block diagram links various code (LabView, Matlab, C ++ code and integrated dynamic link library - dlls) with the controls, indicators and graphs from the user interface. A block diagram, which employs a simple mathematical relation of thermodynamics and heat transfer in RFA, is therefore linked to physical background operation of RFA. The computer software allows us the preprocessing of the data in the pre-simulation, where the basic geometrical and other data are processed and sent to simulation part of the computer software. Simulation calculations are as follows: cooling power, heat flow – condenser, current power consumption of the compressor, actual COP, Carnot COP, efficiency of the cooling process, pressure ratio, evaporation temperature, evaporation pressure, condensation temperature, condensing pressure, initial pressure in the system, isentropic efficiency of the compressor, current temperature of the refrigerated part of the RFA, current temperature of the freezing part of the RFA.
F.10 Improvements to an existing technological process or technology
COBISS.SI-ID: 14301979Reducing energy consumption and eliminating energy wastage are among the main objectives of the European Union. There is significant potential for reducing consumption, especially in energy-intensive sectors such as buildings, manufacturing, energy conversion and transport. The EU countries account for energy demand in the building sector approximately 40% of total energy use. In Slovenia, the major part of that energy is used for heating. We expect that it will have the same trend as in the rest of the world, increasing the proportion of energy for cooling and ventilation. As part of the activities for energy efficiency they are also required regular inspections of air-conditioning systems. The purpose of the periodic inspection of air-conditioning systems is to prepare proposals for increasing the energy efficiency of the system or its replacement. Regular inspections of air conditioning systems in combination with a system of automation , control and measurement of energy consumption enables users numerous advantages (achieving and providing favorable living and working conditions , optimum performance devices , energy saving , repeatable and predictable process control, easier to detect and correct errors , more efficient maintenance).
F.17 Transfer of existing technologies, know-how, methods and procedures into practice
COBISS.SI-ID: 14013467The fact that the environment and human beings interact with each other has been known for centuries. In the present study, elderly’s heart rate (HR) and blood pressure response to indoor thermal comfort and indoor air quality (IAQ) were investigated. Indoor thermal comfort was characterized by Humidex, IAQ by CO2 concentrations. The results show that HR increase which is a prognostic factor for cardiovascular mortality is related to an increase of heat burden and low air quality. Meanwhile blood pressure would decrease as physiological response to these conditions. Our study demonstrates that common impact of heat burden and poor air quality on blood pressure and HR is greater than impact of exposure to each of them. Planners and decision makers that work in the field of designing indoor environment for elderly people or other risk groups should be aware of interactive influence of the thermal environment and the air quality on health and that unsuitability conditions could be ascertained by the occupants’ physiological response.
F.02 Acquisition of new scientific knowledge
COBISS.SI-ID: 4653931