Papers by Keyword: Energy Conversion

Abstract: I report a first-principles investigation of nickel-doped magnetite as a candidate for thermoelectric applications. Substituting Ni at the octahedral Fe sites preserves the inverse spinel framework while introducing Ni 3d impurity levels near the Fermi energy. Using Boltzmann transport theory in the constant-relaxation-time approximation, I calculate temperature and carrier-concentration-dependent transport properties, namely, electrical conductivity, the Seebeck coefficient, the power factor, and electronic thermal conductivity for both n-type and p-type doping. I find that conductivity increases significantly with increasing doping level, while the Seebeck coefficient shows large peaks and even changes sign at moderate carrier densities. Notably, I observed a very large power factor that exceeds that of the commonly used thermoelectric materials at higher temperatures. However, the accompanying rise in electronic thermal conductivity highlights the need for phonon engineering to limit total heat transport. These results demonstrate that Ni substitution provides an effective route to tune the electronic structure and optimize the thermoelectric performance of magnetite under realistic operating conditions.

Abstract: Improving the energy efficiency of thermal power plants through the thermodynamic analysis of their operational parameters in real time is a major issue in order to ensure rational and sustainable operation. An in-depth analysis has been conducted on the thermodynamic efficiency of three gas turbines in a gas/steam combined cycle power plant using real-time operational data. The presented work is part of the research that deals with operational parameters in order to maintain the performance of thermal power plants at the highest possible value. A combination of the first and second laws of thermodynamics has been developed to provide a model able of predicting the thermal efficiency of gas turbines in different operating modes in real-time. The results of our study indicate that each turbine demonstrated a thermal efficiency of around 33.5%. Additionally, the turbines produced an output power of 284 MW and had a specific fuel consumption rate of roughly 206 kg/MWh. The analysis not only verifies the durability of the turbines under various operating conditions, but also presents a verified method to monitor and improve energy efficiency in real time, which is crucial to optimize the power plant operations. Furthermore, this thermodynamic model can be used as a calculation program to be integrated into the display panel which will be used to provide operating indicators in real time. Keywords: Steam/Gas combined cycle, Gas turbine, Thermal performance, Energy conversion.

Abstract: The technology for converting energy from sunlight (photovoltaic) has entered the third generation. The Perovskite Solar Cell (PSC) can compete with the efficiency of current silicon solar cells. However, from the commercial side, there are still obstacles due to the high price of the hole transport material. This component prevents electrons from being transferred to the anode. It also extracts and transports active layer holes to the electrode. This material can be removed since perovskite material can play a dual role. Perovskite materials can be utilized as light harvesters and hole conductors. However, the absence of one component in the PSC structure certainly affects PSC performance. Therefore, in this review, several developments of hole-transport material-free PSC are discussed regarding the type of material used. It starts from the electron transport layer, perovskite layer, and counter electrode. The TiO₂ material is most often used for the electron transport layer because it can achieve a power conversion efficiency (PCE) of >12%. Moreover, with the addition of doping, the PCE value can reach 14.06%. In addition, for the perovskite layer, with a slight modification of the MAPbI₃ material, the PCE value is >16%.

Abstract: In this study, a device called a water vapour cell has been successfully fabricated. A water vapour cell consists of patterned silver on the top layer, chitosan film in the middle, titanium in the bottom layer and isolator substrate as the cover. Chitosan films utilized as a conversion material which works based on direct chemical interactions between chitosan film surface and water vapour to generate electrical current. The chitosan concentration was varied from 0%, 1%, 2%, 3%, 3.25%, 3.5%, 3.75%, 4%, 4.25% and 4.5% (w/v), respectively. The energy conversion properties of a water vapour cell were conducted by exposing water vapour into a water vapour cell. The water vapour was represented by a percentage of relative humidity (RH) which varied from 30% - 90% at 27 °C until 24 hours. It was proven that no electrical current was generated by water vapour cell with 0% chitosan film, while the other concentrations generated stable electrical current once exposed to ≤70% RH. However, the electrical current started to increase and achieved a stable state after 13-11 hours when exposed to ≥70% RH. The highest electrical current was generated 15.31 microampere (μA) achieved by 4% chitosan film under 90% RH exposure. The optical band gap and SEM characterization result indicated that the addition of chitosan concentration higher or equal to 4.25% showed the presence of aggregates which decreased chitosan film band gap into 3.22 and 3.53 eV. Therefore, the higher than 4% concentrations of chitosan have an effect on the physical structure which decreasing the band gap and electrical current.

Abstract: Power consumption is becoming more expensive by the day. This is not far from the fact that power generation is facing a lot of challenges coupled with increasing demand. Industrial sector power demand shares a significant proportion of this generated power. It is therefore a necessary task to manage well industrial energy use through appropriate energy efficiency methods practice so as to minimise energy losses. In this study energy efficiency opportunities in pulp and paper (P&P) mill are identified and the saving potential is then quantified. An energy flow model with the help of an energy audit are used to quantify energy supply, generation, conversion and end use thereby exposing areas of energy losses of the mill. This analysis will serve as an eye opener to future and current P&P making operations in South Africa, and as a base case for stimulating changes toward more efficient energy utilization in the pulp and paper industry. Quite a reasonable energy losses avenues were identified, audited and options of improvements suggested. The results proved that quite a sensible amount of energy is lost in the P&P case study and a near future look into the opportunities and barriers have been noted.

Abstract: The trend of energy consumed growth all over the world demands to solve the problem of energy effectiveness of technological processes. Because of complexity of technological processes structure there is the main question to find a “worst link” in it. Effectiveness of technological process depends on type of process equipment and its links. There were formulated rules for choice most “weak” link of technological chain. Three strategic ways were learned for increasing of energy effectiveness: increasing productivity of the process equipment without increasing of its efficiency; increasing efficiency of the process equipment without increasing of its productivity; increasing both productivity and efficiency of the process equipment. Corresponding recommendations for growth of productivity or efficiency were given. There were proved that variation of average level of productivity of process equipment must be up to 50...60% and the variation of productivity relative to the average in duty cycle of process equipment operation must not be more than 10%.

Abstract: This paper proposed a novel micro wave energy converter which can convert irregular wave energy into rotating mechanical energy, then into electrical energy. The device consists of an energy absorption part and an energy conversion part. In details, the blades are installed on the absorber circumferentially and averagely, which are capable of converting the vertical motion of the surface body to continuous rotation of the absorber and leading to a great increase in efficiency. A physical prototype was built to test the performance of the novel generator and optimize the design parameters. In the experiment part, a linear motion electric cylinder was used as the drive power to provide the heaving motion for the device. And the experiment platform was built for modeling a marine environment. Also, a data acquisition program was edited in Labview. Thus, the experiment analyzed the influence of amplitude, frequency, blade angle and resistance value to the output power, and then obtained the optimum parameters combination which can maximize the value of the output power. The result will provide reference for the device’s further application.

Abstract: TiO₂ nanotubes were successfully synthesized by anodization method of Ti foils. The electrolyte was composed of ethylene glycol (EG), ammonium fluoride (0.3%wt NH₄F) and de-ionized water (2% vol H₂O). A constant DC power supply of 50 V was used during anodization with anodizing times of 1 hour, 2 hours, 4 hours and 6 hours. The samples were annealed at 450 °C for 2 hours. The TiO₂ nanotubes were studied by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Structural analysis revealed the presence of pure Ti, and the crystalline anatase phase due to transformation of amorphous TiO₂ after annealing. The morphology of TiO₂ nanotube sizes showed an increase in tube diameter with anodizing time from approximately 50 nm to 200 nm. However, the efficiency of dye-sensitized solar cells increased with anodizing times up to a maximum of 5.74 % for anodizing time of 4 hours.

Abstract: In order to prevent damage caused by instantaneous power failure to high-speed equipment, the thermoelectric energy conversion system for controller of magnetic bearing is studied. The heat source is used by the power loss of supply modules and the cold source is used by heat conduction aluminum block. The semiconductor thermoelectric generator produces direct-current working voltage between heat source and cold source. The overall design method of the energy conversion system is presented. The theory and design of circuits to thermoelectric energy generator, voltage regulator and charging for lithium polymer battery are analyzed. The experiment results show that this thermoelectric energy generator system is feasible and effective. The circuit can be adapted to change in output power due to temperature difference at both ends of the thermoelectric module. It achieves energy storage of the recovery from thermoelectric generator.

Abstract: Utilization of the waste toner in wasted print cartridge was beneficial to the environmental protection and resource recycling. Fe₃O₄ has been obtained from the waste toner via magnetic separation and heat-treatment in present study. XRD measurement revealed the recuperated sample has ferriferrous oxide structure without other crystalline impurity. The electrochemical performances of recuperated Fe₃O₄, as the electrode active material for supercapacitor, was conducted by cyclic voltammetry and charge-discharge process. The results showed that the specific capacitance of Fe₃O₄ achieved 76.5 F/g under 50 mA/g current density, which possessed typical capacitive behaviors and good cycling stabilities. Based on the preferable electrochemical performances, Fe₃O₄ recovered from waste toner may be a potential alternative as electrode material for supercapacitor.