Abstract. Moisture content is a main problem of using straw in form of bales for energy production. The paper presents possibility of straw drying in dedicated, innovative and patented in Poland straw dryers which using flue gasses as a drying medium. Paper presents an improved way of drying which proved to be very sufficient. Temperature and humidity of straw during the process of drying were measured. The measurements helped understand and perform numerical model of heat and mass transfer inside the straw bale. By using CFD codes it was possible to perform analysis of phenomenon occurring inside the dried straw bale. Based on the CFD model, proposals of the optimization and improvement process of drying have been discussed. Experimental and computational data have been compared in terms of convergence. A satisfying degree of agreement has been achieved. Applying improved drying method, homogenous field of moisture content and temperature in the straw bale is achieved in a very cost effective way.
Abstract. This paper shows the results of analysis of the wind potential in selected locations in the southern Poland (placed in the Małopolskie, Świętokrzyskie and Podkarpackie Voivodships). The measurements and analysis of the wind resources in potential locations of the wind turbines are important part of the investment process. The statistical analysis involves the creation of histograms (e.g. histogram of the wind speed and direction) and fitting those histograms to theoretical distributions (e.g. Weilbull distributions of wind speed). Such analysis has been described and conducted using measurement data for four selected locations. Basis on the conducted analysis, the economy efficiency and environmental impact of wind turbine operation has been estimated. Three market available wind turbines have been included to calculate NPV, IRR and SPBT indicators. Then, the avoided emissions of CO2, NOx, SO2 and dust have been calculated. There were also conducted some calculation using TRNSYS simulation software. The results of simulations have been compared with measurement data and the level of convergence have been found.
Abstract. The paper presents selected results of thermogravimetric (TG) analyses for softwood (pine) and hardwood (beech). The composition of the studied fuels has been defined and described. Both wood types used in the TG tests were studied in order to define their content of basic components such as lignin, cellulose and hemicellulose. Types of wood used in the TGA have been combusted on the experimental stand which is equipped with a set of temperature sensors and an exhaust analyser. A comparison of the TG analysis and the combustion in the heating unit has been performed to find relations between the kinetics of devolatilisation for different wood species and to determine the exhaust composition. Numerical modelling using computational fluid dynamics (CFD) has been performed for the process of carbon monoxide oxidation to supplement the tests results. The results of the comparisons of the performed analyses can be useful in all areas related to the process of optimisation and improvement of combustion, pyrolysis and devolatilisation process conditions in small scale heating units.
Among all the energy production technologies based on renewables, the photovoltaic panels are the ones with the highest rate of development and applications worldwide. In this context, significant efforts are put into research on innovative materials in order to improve the performance of photovoltaic cells. Nevertheless, possibilities available to enhance the energy yield of existing technologies also exist and are explored, such as the cooling of photovoltaic modules. This approach can decrease the mean operation temperature of photovoltaic cells, leading to an increase in efficiency and energy produced. In the present paper, this method is investigated by developing and testing a dedicated water cooling system for photovoltaic panels. In order to investigate the performance of the cooling system, two market-available monocrystalline photovoltaic panels with a power of 50 and 310 Wp were tested under laboratory and real operation conditions, respectively. Based on the results obtained under laboratory conditions, the most promising variant of the cooling system was selected and assessed under real operation conditions. For this system, the maximum temperature of the water-cooled 310 Wp panel was lower by approx. 24 K compared to an uncooled panel, as pointed out by a measurement performed during a typical sunny day when solar irradiation was approximately 850 W/m2. This improvement of the cell temperature led to a 10% increase in power generated by the water-cooled photovoltaic panel compared to the uncooled one. The economic analysis revealed that the estimated simply payback time for installing the cooling system in typical domestic photovoltaic installations can be less than 10 years, while from the point of view of net present value, the introduction of the water cooling system can be a profitable option for a 10-year period when a discount rate of 5% is considered.
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