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Borehole engineering encompasses the part of mining that involves the process of drilling boreholes and their utilization (e.g., for research, exploration, exploitation, and injection purposes). According to legal regulations, mining pits must be closed after their use, and this applies to pits in the form of boreholes as well. The Laboratory of Geoenergetics at AGH University of Krakow is involved in adapting old, exploited and already closed boreholes for energetic purposes. This includes geothermal applications, as well as energy storage in rock formations and boreholes. Geoenergetics is a relatively new concept that combines geothermal energy with energy storage in rock formations (including boreholes). One type of analysed borehole is a freezing borehole. They are used, for example, in drilling mining shafts that are in the vicinity of aquifers and are drilled using the rotary drilling method with a reverse circulation of drilling mud, or in peat bogs. For borehole heat exchangers based on freezing boreholes for long-term mathematical modelling, several heating scenarios were considered with several thermal loads. The maximum average power obtained after one year of usage of four boreholes with variable temperatures was 11 kW. With the usage of 10 boreholes the power reached over 27 kW. The heat-carrying temperature was assumed to be 22 °C during early summer (June and July) and 2 °C during the rest of the year. When considering stable exploitation during a 10-year period with four boreholes with the same temperatures, a heating power of over 12 kW was obtained, as well as a power of over 28 kW when considering using 10 boreholes. The maximum amount of heat obtained during the 10-year period using 10 boreholes was over 8.8 thousand GJ. Once they have fulfilled their function, these boreholes lose their technological significance. In the paper, the concept is outlined, and the results of the analysis are described using the numerical program BoHEx. [ABSTRACT FROM AUTHOR]

This comparative study examines the potential for green hydrogen production in Europe and the Middle East, leveraging 3MWp solar and wind power plants. Experimental weather data from 2022 inform the selection of two representative cities, namely Krakow, Poland (Europe), and Diyala, Iraq (Middle East). These cities are chosen as industrial–residential zones, representing the respective regions' characteristics. The research optimizes an alkaline water electrolyzer capacity in juxtaposition with the aforementioned power plants to maximize the green hydrogen output. Economic and environmental factors integral to green hydrogen production are assessed to identify the region offering the most advantageous conditions. The analysis reveals that the Middle East holds superior potential for green hydrogen production compared to Europe, attributed to a higher prevalence of solar and wind resources, coupled with reduced land and labor costs. Hydrogen production costs in Europe are found to range between USD 9.88 and USD 14.31 per kilogram, in contrast to the Middle East, where costs span from USD 6.54 to USD 12.66 per kilogram. Consequently, the Middle East emerges as a more feasible region for green hydrogen production, with the potential to curtail emissions, enhance air quality, and bolster energy security. The research findings highlight the advantages of the Middle East industrial–residential zone 'Diyala' and Europe industrial–residential zone 'Krakow' in terms of their potential for green hydrogen production. [ABSTRACT FROM AUTHOR]

The particle deposition on the surface of solar photovoltaic panels deteriorates its performance as it obstructs the solar radiation reaching the solar cells. In addition to that, it may cause overheating of the panels, which further decreases the performance of the system. The dust deposition on the surfaces is a complex phenomenon which depends on a large number of different environmental and technical factors, such as location, weather parameters, pollution, tilt angle and surface roughness. Hence, it becomes crucial to investigate the key parameters which influence dust accumulation and their interrelations. In this study, the phenomenon of dust deposition was studied experimentally in the urban area at one of the most polluted cities of Europe, i.e. Kraków, Poland. Solar photovoltaic panels tilted at angles 15° and 35° were exposed to atmospheric conditions for the period of eighteen months from 6 May 2017 until 30 November 2018. Dust samples were collected from the panels for the exposure period which ranged from one day up to 11 days. It was observed that lower tilt angles promote dust accumulation on the surface and that in the absence of wind and rain, deposition of particles on the surface of panels follows the pattern of concentration of PM2.5 and PM10 in the atmosphere. Wind and rainfall usually promote the removal of dust particles from the surface. However, rainfall not always aids the cleaning of panels, and it was observed that low-intensity rain results in a very low rate of PMs in the air and in much higher than typical dust deposition on the panel surface. It also accelerates the cementing of already deposited dust. It was only rainfall whose intensity was at least 38 mm/h that was sufficient to remove dust particles from the panels. [ABSTRACT FROM AUTHOR]

The impact of the photovoltaic module temperature and natural dust deposition on the module front surface on the photovoltaic system performance was investigated. The study was conducted in the city center of Krakow, Poland, characterized by high pollution and low wind speed. The objective of this study was to evaluate the photovoltaic module power output decrease and energy conversion loss as a function of the dust deposition mass and cell operating temperature. The results show a significant decrease in photovoltaic efficiency when the mass deposition or temperature increases. The maximum mass deposition observed for exposure periods of one week on a single module exceeds 480.0 mg and results in an efficiency loss equal to 2.1%. The results that were obtained enable the development of a correlation for the efficiency loss caused by dust deposition which is desired by the system designers. [ABSTRACT FROM AUTHOR]