23 research outputs found
Development of a solar cavity receiver with a short-term storage system
No full textThe technological progress carried out in the development of high-temperature materials has led to the design of new concentrated solar power plants, like Dish-Micro Gas Turbines (Dish-MGTs). This study proposes a novel cavity receiver for small-scale Dish-MGT plants with a phase-change material storage system integrated inside the receiver container. Such a storage system provides a proper thermal inertia to the component, to level the effects of short-term solar radiation fluctuations which can reduce plant performance and, in the worst cases, damage seriously the MGT. In the paper, results related to CFD steady-state and transient (charge and discharge storage phases) analyses are presented and discussed
Charge and Discharge Analyses of a PCM Storage System Integrated in a High-Temperature Solar Receiver
No full textSolar Dish Micro Gas Turbine (MGT) systems have the potential to become interesting small-scale power plants in off-grid or mini-grid contexts for electricity or poly-generation production. The main challenging component of such systems is the solar receiver which should operate at high temperatures with concentrated solar radiations, which strongly vary with time. This paper deals with the design and the analysis of a novel solar receiver integrated with a short-term storage system based on Phase Change Materials to prevent sudden variations in the maximum temperature of the MGT working fluid. Particularly, the charge and discharge behavior of the storage system was analyzed by means of Computational Fluid Dynamic methods to evaluate the potentiality of the concept and the component capabilities. Achieved results were highly satisfactory: the novel solar receiver has a good thermal inertia and can prevent relevant fluctuations in the working fluid temperature for 20–30 min
High-Temperature Cavity Receiver Integrated with a Short-Term Storage System for Solar MGTs: Heat Transfer Enhancement
No full textDish-Micro Gas Turbines (MGTs) can be promising systems for power production at small-scale by concentrated solar radiation. Several high-temperature solar receivers have been already designed for such plants, however, nowadays, none of them can assure the proper thermal inertia to level the effects of solar radiation fluctuations on engine performance and safety. In this paper, a solar receiver integrated with a short-term storage system based on high-temperature Phase-Change Materials (PCMs), is proposed. On the basis of a previous preliminary component design and analysis, the receiver geometry has been modified to improve storage capability and heat transfer to the working fluid, reducing temperatures on the irradiated surface making them compatible with material properties and reducing also temperature gradients inside the PCM. Six different geometries, varying length, opening and shape of a front cavity have been analyzed by means of CFD methods. All the configurations have shown a satisfactory behavior in terms of working fluid outlet temperature, storage capabilities and maximum temperatures reached on the surface and inside the receiver. In particular, among them, three geometries can be considered the most promising ones
Thermal analysis of Mg 2 Si and Fe 2 Si 5 phase change materials for Dish-MGT plants
No full textFor Concentrated Solar Power plants, the storage of thermal energy at high temperature is a critical issue. This paper deals with the application of a Phase Change Material integrated in the solar receiver of the Dish-Micro Gas Turbine (DMGT) for the mitigation of solar radiation fluctuation effects on DMGT performance. For this application, the PCM should have a melting temperature between 900 and 1200°C. Even if some promising materials are suggested in literature, the properties of most of them are not fully characterised in the working temperature range. Therefore, this paper presents the experimental results of the thermal analysis of two high-temperature metallic PCMs (Mg 2 Si and Fe 2 Si 5 ). Thermal diffusivity, specific heat capacity and thermal conductivity have been determined using Simultaneous Thermal Analysis (STA) and Laser Flash Analysis (LFA) apparatuses. The thermal expansion behaviour of the samples has been determined up to 1000°C. Furthermore, the compatibility of the PCM samples with the Silicon carbide (SiC) has been also studied up to 1000°C
High-temperature solar receiver integrated with a short-term storage system
No full textSmall-Scale Concentrated Solar Power Plants could have a potential market for off-grid applications in rural contexts with limited access to the electrical grid and favorable environmental characteristics. Some Small-Scale plants have already been developed, like the 25-30 kWe Dish-Stirling engine. Other ones are under development as, for example, plants based on Parabolic Trough Collectors coupled with Organic Rankine Cycles. Furthermore, the technological progress achieved in the development of new small high-temperature solar receiver, makes possible the development of interesting systems based on Micro Gas Turbines coupled with Dish collectors. Such systems could have several advantages in terms of costs, reliability and availability if compared with Dish-Stirling plants. In addition, Dish-Micro Gas Turbine systems are expected to have higher performance than Solar Organic Rankine Cycle plants. The present work focuses the attention on some challenging aspects related to the design of small high-temperature solar receivers for Dish-Micro Gas Turbine systems. Natural fluctuations in the solar radiation can reduce system performance and damage seriously the Micro Gas Turbine. To stabilize the system operation, the solar receiver has to assure a proper thermal inertia. Therefore, a solar receiver integrated with a short-term storage system based on high-temperature phase-change materials is proposed in this paper. Steady-state and transient analyses (for thermal storage charge and discharge phases) have been carried out using the commercial CFD code Ansys-Fluent. Results are presented and discussed
Deflection of coupled elasticity–electrostatic bimorph PVDF material: theoretical, FEM and experimental verification
No full textPiezoelectric materials have wide applications in the field of mechanical, aerospace and civil engineering because of its
voltage dependent actuation. Piezoelectric material goes through voltage generation whenever deflection is induced in it
and vice versa. Piezoelectric bimorph beam has been widely used for sensing and actuating. In the actuation mode, an
electric field is applied across the beam thickness, one layer contracts while the other expands. This results in the bending
of the entire structure and tip deflection. In the sensing mode, the bimorph is used to measure an external load by
monitoring the piezoelectric induced electrode voltages. In this research work, a 2D bimorph piezoelectric actuator model
having two layers made of polyvinylidene fluoride (PVDF) material was developed to examine the inverse piezoelectric
effect. Finite element analysis (FEA) was carried out on specially designed actuator model by using MATLAB Partial
Differential Equation (PDE) ToolboxTM. Theoretical analysis has been carried out to measure the tip deflection under
applied electric field. The laboratory test was performed to investigate the deformation behavior of piezoelectric actuator. It
is observed that, more the electric field applied, more the material would be deformed in a particular direction. The
experimental results are in good agreement with numerical results
Design of the Power Group for a 15 MW Supercritical Carbon Dioxide Plant
No full textFor the last years, several power cycles which consider supercritical CO2 as working fluid have been analyzed in detail. Due to their potential thermodynamic efficiency, their compactness and their expected operational flexibility if compared with conventional Rankine cycles, they are attracting the R&D Community interests worldwide. The paper deals with the layout arrangement and machinery design of a 15 MW power group for a supercritical recompressed cycle. Starting from a conventional twin-shaft layout, the final one was arranged on three shafts at different speed. Moreover, all the components have been iteratively designed using preliminary 1-D and 2-D models and, then, they have been modelled in detail by means of the commercial Ansys-CFX software. Finally, a power group with a nominal output power of 13 MW and an overall efficiency of about 57% (taking all kind of losses into account) was achieved
Nexus Between Equity Pricing Models and Equity Price Fragility: Empirical Insights From Pakistan
No full textPurpose: The study tests conventional and behavioral pricing multifactor impact on price fragility from the equity market of Pakistan. Methodology: The positivist approach is used to deduct study rationale via probability sampling. At the same time, systematic sampling for data collection of PSX is tested in parallel to mean-variance random walk theory. Findings: The impact of conventional factors is significant on price fragility in the short run and vice versa in the long run. Specifically, herd behavior and disposition effects are found to be insignificant. But size, value, illiquidity, and price earning had a significant impact on price fragility in the short run. Limitations: The current research has not covered the desired scope of the topic due to time limitations, lack of harmony in corporate data on databases, and literature on price fragility being very scarce. Implication: In PSX, there is a need to develop a corporate culture to promote the standard modern financial practice to enhance financial productivity and sustainability. For corporate culture to be established, corporate governance boards should be established, and family governance systems should be replaced by an independent democratic board. Mispricing and arbitragers need serious control. Originality: The value of the research is that little research currently exists on about pricing multifactor impact on price fragility. Copyright © 2022 Anser, Yusop, Abbas, Ali and Ahmad.APC will be provided by the corresponding author
Thermal performance of a phase change material-based heat sink in presence of nanoparticles and metal-foam to enhance cooling performance of electronics
No full textThe present study explores the parametric investigation of a heat sink filled with composite of pure phase change material (PCM), nanocomposite phase change material (NCPCM), metal-foam (MF) by employing the numerical approach for effective passive thermal management of electronics. The combinations of heat sink are varied by filling PCM, NCPCM, MF+PCM and NCPCM+MF. Different parameters such as MF materials, porosities, pore densities (PPI-pores per inch), volume fractions of nanoparticles in NCPCM, power levels and combination of MF+NCPCM by varying different porosities and nanoparticles volume fractions. Copper (Cu) nanoparticles of 1%, 3% and 5% volume fraction were dispersed in RT-35HC, used as a PCM, and copper, aluminium (Al) and nickel (Ni) MFs were embedded inside the heat sink. Transient simulations with conjugate heat transfer and melting/solidification schemes were formulated using finite-volume-method (FVM). The thermal performance and melting process of the NCPCM filled heat sink were evaluated through melting time, heat storage capacity, heat storage density, rate of heat transfer and rate of heat transfer density. The results showed that with the addition of Cu nanoparticles and MF, the rate of heat transfer was increased and melting time was reduced. The melting time was reduced by 1.25%, 1.87% and 2.34%; and rate of heat storage is enhanced by 1.35%, 0.76%, and 0.19% with the addition of 1%, 3% and 5% volume fraction of Cu nanoparticles, respectively. The composite of MF+NCPCM showed the lower heat sink temperature and higher liquid-fraction were obtained. The latent-heating phase duration was decreased with the increase of Cu nanoparticles volume fraction. Additionally, the lower reduction in melting time of 18.10% and higher rate of heat transfer of 8.12% were obtained with 1% Cu nanoparticles, 95% porosity and 10 PPI Cu MF based heat sink
Outdoor testing of photovoltaic modules during summer in Taxila, Pakistan
No full textAn experimental study has been carried out to measure the performance of commercially available photovoltaic modules during summer months in the climate of Taxila, near the capital of Pakistan. The modules used in the study are monocrystalline silicon (c-Si), polycrystalline silicon (p-Si) and single junction amorphous silicon (a-Si). The analysis has been focused on the measurement of module efficiency, performance ratio and temperature of each module at actual operating conditions using outdoor monitoring facility. The measured results are compared with the already published data of peak winter month at the same site. Overall, the monocrystalline module showed high average module efficiency while amorphous silicon module was better in term of average performance ratio. Furthermore, the module efficiency and performance ratio has shown decreasing trend with increase of module temperature. It was found that modules have much higher temperature in summer months (about 20°C higher) and showed low efficiency and performance ratio than peak winter month. The average ambient temperature varied from 18.1°C to 38.6°C from winter to summer
