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Abstract Global sensitivity analysis of the efficiency of borehole thermal energy storage (BTES) during long-term operation on the borehole heat exchanger (BHE) arrangement was investigated to advance understanding of the system’s thermal performance. Three parameters were assessed to determine the BHE arrangement: the first parameter designate the distance between BHE axis in x direction, the second in y direction and the third an angle between top surface of the rock mass and boreholes axis. Conducting research on the real system is extremely expensive, so it was decided to conduct simulation studies utilising a finite element method. The ANSYS software with a newly implemented heat and mass transport model in BHE was used. Based on conducted numerical simulations, and according to the design of the experiment, a multidimensional response surface was achieved. The global sensitivity was conducted based on a response surface model. It was found that the BHE inclination ( S Eeff P 3 = 0.97 – FAST algorithm) has a crucial impact for the BTES efficiency. The area on response surface, where the optimal BHE arrangement to maximise BTES efficiency could be reached, is an inclination P 3 = 0 ° and BHE spacing in the range of P 1 = P 2 = ( 1.5 – 3 m ) .

Abstract An investigation has been made of graphite exposed to moderate doses (90 Gy–92 kGy) of β irradiation from the point of view of applications to material engineering. The average energy of the β particles was 196 keV. In STM images no significant modification of surface topography was observed. Irradiated samples reveal weak thermally stimulated emission (TSE) signal. Irradiation effects are also hard detectable in EPR and IR spectra. On the other hand, even small radiation doses influence high temperature surface resistance characteristics in ambient air. This result suggests an alteration of surface properties under low irradiation doses.

Abstract The main objective of the Central Design Team (CDT) project is to establish an engineering design of a Fast Spectrum Transmutation Experimental Facility (FASTEF) that is the pilot plant of an experimental-scale of both an Accelerator Driven System (ADS) and a Lead Fast Reactor (LFR), based on the MYRRHA reactor concept, planned to be built during the next decade. The MYRRHA reactor concept is devoted to be a multi-purpose irradiation facility aimed at demonstrating the efficient transmutation of long-lived and high radiotoxicity minor actinides, fission products and the associated technology. An important issue regarding the reactor design of the MYRRHA/FASTEF experiment is the In-Vessel Fuel Storage Facilities (IVFSFs), both for fresh and spent fuel, as it might have an impact on the criticality of the overall system that must be quantified. In this work, the neutronic analysis of the in-vessel fuel storage facility and its coupling with the critical core was performed, using the state of the art Monte Carlo program MCNPX 2.6.0 and ORIGEN 2.2 computer code system for calculating the buildup and decay heat of spent fuel. Several parameters were analyzed, like the criticality behavior (namely the Keff), the neutron fluxes and their variations, the fission power production and the radiation damage (the displacements per atom). Finally, also the heat power generated by the fission products decay in the spent fuel was assessed.

Abstract A significant part of the world’s population (about 40%) cooks their meals and provides heating for their homes using wood-burning heating devices. Due to the relatively low cost of fuel and their aesthetic design, solid fuel stoves capable of heat accumulation are convenient and common. The use of dedicated small-scale power generators provides also additional benefits. This paper presents the results of a study conducted to verify the possibility of generating power using stove-fireplaces with heat accumulation systems. In such units, the temperature of the flue gas should be kept at a certain level for the purposes of storing heat, which results from certain limitations of the thermoelectric generators. To verify the possibility of applying thermoelectric modules in such heating devices, a dedicated system with thermoelectric generators was selected from among various microcogeneration systems and implemented. Three types of heat exchangers were studied and the most efficient unit was selected for further testing. Two types of generators, with maximum operating temperatures of 320 and 175 °C, were compared. Subsequently, the characteristics of the latter were determined. The conducted tests allowed to determine the performance and the total efficiency of the generators that were used. It has been demonstrated that the maximum power of the generator would not exceed ca. 30 We and that there is no economic justification for such a device. However, providing a self-powered and self-sufficient operation of stove-fireplaces with heat accumulation systems remains an important goal.

Abstract The new complex selection strategy of low energy ventilating or air conditioning system (HVAC system) from a holistic perspective is presented in the paper. The strategy carries out the solution of the whole optimization problem that consists of the HVAC system model, optimization model and optimization procedure. The practical function is the starting point of the optimization problem, whereas the energy optimal variant of the HVAC system is the final stage. Universal sets of constant parameters, decision variables and limiting conditions of the HVAC system were formulated for the mathematical description of the problem. In optimization procedure, the sets of all variants and permissible variants of the HVAC system were defined based on the system analysis with the use of matrix calculation. The objective function was determined by the use of the simulation model of the HVAC system where the algorithms of energy optimal control is determined by dynamic optimization.

Abstract In this paper, we apply a life cycle thermoecological cost (LC-TEC) approach to evaluate the environmental performance of wind turbines with different capacities and performance characteristics. LC-TEC expresses the cumulative consumption of non-renewable exergy burdening the fabrication of the considered consumption of the product with the additional inclusion of necessity of compensating adverse environmental effects due to harmful waste products rejection. Differently, from what has been recently done in the literature on the environmental performance of wind turbines, where the attention has been mainly drawn by analysis of single turbine, we focus on the synthesis of the results for wind turbines with different capacities and the generalisation of the results under different environmental conditions. The selected functional unit for the comparison was 1 MJ of produced electricity, assuming a service lifetime equal to 20 years. Concerning the contribution analysis, the construction phase is the most intensive one for wind energy technologies with a share varying from 64 to 77% in the overall effect. Substantial differences in LC-TEC are observed for wind turbines of different capacity and different locations of the power plant. Results show that the LC-TEC of electricity significantly decrease while the turbine nominal power increases. For instance, for the average site, described by Weibull distribution parameters of mean wind speed of 5 m/s and shape coefficient 2, the TEC-LC for 1 kW micro wind turbine is estimated to be equal to 0.436 MJex/MJ, while for a larger, 2 MW one, fall in the range of 0.053–0.063 MJex/MJ. We found that a power function can successfully describe such a trend. Moreover, we observed considerable changes in the final results for different Weibull distribution parameters. Specifically, the LC-TEC differs significantly for the sites with lower mean wind speed and different shape factors. Finally, we propose the supporting system for wind energy basing on the LC-TEC and pro-ecological taxing. According to this concept, the power units with LC-TEC below unity are to be supported, and the proposed level of pro-ecological support (ExTAX – Exergy TAX) is proportional to the thermo-ecological cost. The obtained results of exergy supporting for wind energy technologies are applied in the Italian electricity market and compared with the existing financing system for wind energy based on green certificates and feed-in tariff system.

Abstract A clear-sky solar irradiance model is certainly a basic tool in the estimation of solar resources. With all the abundance of such models, there is plenty of room for searching a clear-sky solar irradiance model with general applicability, i.e. to be able to provide high-accurate estimates in most places around the world. This paper reports an upgraded version (further referred to as SIMv.2) of our parametric clear-sky solar irradiance model SIMv.1, aiming to improve the accuracy of estimates in arid environment. The new elements of SIMv.2, such as new equations for aerosol absorption and downward fraction, have been introduced targeting a better capture of the peculiarities of the solar radiation extinction by aerosols. Overall, the results of testing SIMv.2 at twelve stations located in regions with temperate, arid and tropical climate show that SIMv.2 performs much better than SIMv.1, an improvement in nRMSE of 37.1% for global solar irradiance and of 24.7% for the diffuse component being noticed. The comparison with other fourteen clear-sky solar irradiance models at five stations located in arid climate places SIMv.2 in the class of the best performing models. The limitation of the SIMv.2 performance in extreme weather conditions is discussed in two cases.