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Aside from the industry-standard Gaussian intensity profile, top hat and non-conventional laser beam shapes, such as doughnut-shaped profile, are ever more required. The top hat laser beam profile is well-known for uniformly irradiating the target material, significantly reducing the heat-affected zones, typical of Gaussian laser irradiation, whereas the doughnut-shaped laser beam has attracted much interest for its use in trapping particles at the nanoscale and improving mechanical performance during laser-based 3D metal printing. Solar-pumped lasers can be a cost-effective and more sustainable alternative to accomplish these useful laser beam distributions. The sunlight was collected and concentrated by six primary Fresnel lenses, six folding mirror collectors, further compressed with six secondary fused silica concentrators, and symmetrically distributed by six twisted light guides around a 5.5 mm diameter, 35 mm length Nd:YAG rod inside a cylindrical cavity. A top hat laser beam profile (Mx2 = 1.25, My2 = 1.00) was computed through both ZEMAX® and LASCAD® analysis, with 9.4 W/m2 TEM00 mode laser power collection and 0.99% solar-to-TEM00 mode power conversion efficiencies. By using a 5.8 mm laser rod diameter, a doughnut-shaped solar laser beam profile (Mx2 = 1.90, My2 = 1.00) was observed. The 9.8 W/m2 TEM00 mode laser power collection and 1.03% solar-to-TEM00 mode power conversion efficiencies were also attained, corresponding to an increase of 2.2 and 1.9 times, respectively, compared to the state-of-the-art experimental records. As far as we know, the first numerical simulation of doughnut-shaped and top hat solar laser beam profiles is reported here, significantly contributing to the understanding of the formation of such beam profiles.

Although there are many studies available in literature about biomass pyrolysis or devolatilization using thermogravimetric analysis (TGA), the effects of important operating parameters have infrequently been investigated for pine wood particle combustion. Consequently, the present study investigates the influence of particle size (63 µm to 1 mm), heating rate (5 to 243 °C/min), and air flow rate (10 to 150 mL/min) on the mass loss of pine wood using TGA. Additionally, the kinetic parameters considering the different conditions were determined to be incorporated in a numerical model. The effect of the heating rate on the thermal decomposition behavior has shown that the thermogravimetric and derivative thermogravimetric curves were shifted to higher temperatures with the increase in the heating rate. In this way, the heating rate affects the temperature at which the highest mass loss rate occurs as well as its value. Furthermore, comparing the higher and lower heating rate, the time to complete the combustion and the release are around 22 times higher when a higher heating rate is applied. On the other hand, the effects of four different air flow rates were compared and similar results were obtained. Regarding the kinetic analysis, it was verified at various heating and air flow rates with different particle sizes that the highest activation energy was mostly obtained during char combustion (~131–229 kJ/mol). Furthermore, in the second stage higher heating rates had the highest reactivity, and in the third stage there were not too many changes. In terms of the effect of air flow rates, a maximum variation of 15 kJ/mol was obtained in the third stage and, therefore, no significant effect on the reactivity for all particles was found.

Research on the safety of powerhouse in a hydropower station is mostly concentrated on the vibration of machinery structure and concrete structure within a single unit. However, few studies have been focused on the vibration transmission among units. Due to the integrity of the powerhouse and the interaction, it is necessary to study the vibration transmission mechanism of powerhouse structure among units. In this paper, field structural vibration tests are conducted in an underground powerhouse of a hydropower station on Yalong River. Additionally, the simplified mechanical models are established to explain the transmission mechanism theoretically. Moreover, a complementary finite element (FE) model is built to replicate the testing conditions for comprehensive analysis. The field tests results show that: (1) the transmission of lateral-river vibration is greater than those of longitude-river vibration and vertical vibration; (2) the vibration transmission of the vibrations that is caused by the low frequency tail fluctuation is basically equal to that of the vibrations caused by rotation of hydraulic generator. The transmission mechanism is demonstrated by the simplified mechanical models and is verified by the FE results. This study can provide guidance for further research on the vibration of underground powerhouse structure.

The adoption of smart grids is becoming a common reality worldwide. This new reality is starting to impact energy customers as they face a dynamic grid in which they can actively participate. However, if energy customers are not prepared to participate actively, they can have their energy costs increased. This paper provides a review of acceptance models and customer surveys around the world made to assess the customers’ perception and willingness to participate in smart grids. Contributing to this assessment, this paper presents a survey undertaken in Portugal. The survey results demonstrate a willingness, from the customer’s end, to actively participate in smart grid initiatives. It was found that 92.9% of participants are willing to plan their energy usage to face hourly energy prices and that 95.0% of participants are willing to accept an external control of at least one appliance, enabling direct load control demand response programs. Also, the results identified two cognitive tendencies, negativity bias, and loss aversion, which can impact how customers participate in smart grids. These cognitive tendencies and the literature acceptance models demonstrate the importance of conducting social science studies targeting smart grids to fully achieve the efficient participation of end customers.

This paper describes a study of the relative influences of different system design decisions upon the performance of an organic Rankine cycle (ORC) used to generate electricity from foundry waste heat. The design choices included concern the working fluid, whether to use a regenerator and the type of condenser. The novelty of the research lies in its inclusion of the influence of both the ORC location and the auxiliary electricity used by the pumps and fans in the ORC power system. Working fluids suitable for high temperature applications are compared, including three cyclic siloxanes, four linear siloxanes and three aromatic fluids. The ORC is modelled from first principles and simulation runs carried out using weather data for 106 European locations and a heat input profile that was derived from empirical data. The impact of design decisions upon ORC nominal efficiency is reported followed by the impact upon annual system efficiency in which variations in heat input and the condition of outdoor air over a year are considered. The main conclusion is that the location can have a significant impact upon the efficiency of ORC systems due to the influence of climate upon the condenser and auxiliary electricity requirements.

Mini passive direct methanol fuel cells (mpDMFCs) appear to be a promising alternative for powering portable devices, since they use a liquid fuel, have a fast refuelling time, have a high efficiency and have a low environmental impact. However, some issues need to be solved before their commercialization, such as methanol crossover, short lifetime and high costs. The present work studies the effect of reducing the anode and cathode catalyst loading on the performance of a mpDMFC towards a reduction in the system costs and the characterization of the system losses. The undesirable losses that affect the fuel cell performance were identified and quantified using the electrochemical impedance spectroscopy (EIS) technique. Accordingly, a novel equivalent electric circuit (EEC) was proposed, accurately reproducing the mini pDMFC. In this work, a maximum power density of 7.07 mW cm−2 was obtained, with a methanol concentration of 5 M, using 2 mg cm−2 Pt-RuB and 4 mg cm−2 PtB. The mpDMFC allowed the cell to work with high methanol concentrations and reduced anode catalyst loadings.

The combustion instability and ash agglomeration in a wood pellet boiler were investigated in this study. The tests were conducted using the Taguchi method of orthogonal array L27(133). Several parameters are applied, including grate area (GA), primary to secondary air split ratio (SR), excess air (EA), and fuel power (P). Pine wood pellets were used, and the boiler’s nominal load was 20 kW. The results show that instability during combustion occurs since the fuel bed rises as the accumulation of the unburned wood pellets on the grate causes a slow combustion rate and pressure drop, which creates noise and disturbances. A good combination of the parameters applied to TN9 and TN20 can be useful in obtaining stable combustion. In addition, the ash agglomerations were influenced by the duration of the combustion and the temperature of the fuel bed. The largest size of the ash agglomeration was referred to as test number-TN26 (P: 16 kW, EA: 110%, SR: 30/70, and GA: 115 mm × 75 mm), which is 59 mm, and the duration time is 14,400 s (≈4 h).