A study of thermal exchange in a thermophotovoltaic (Tpv) system at moderate temperature

A numerical simulation study is reported on the thermal exchange in an evacuated parallel-plate system consisting of an emitter and a photovoltaic (PV) material with the emitter temperature between 350K and 550K. Although higher temperature (and thus higher power output) thermophotovoltaic systems have been of interest previously, the focus here is on systems that can not achieve high temperatures, like micromachines. The study examines the electrical power output and power generation efficiency for four kinds of emissivity variations for the heat source coupled with three different compounds of {dollar}\rm In\sb{(x)}Ga\sb{(1-x)}As{dollar} PV materials. The results show that a 25% Ho YAG thin film selective emitter coupled with an In(0.72)Ga(0.28)As material has the highest power generation efficiency for actual materials. These values are between 28% and 34%, depending upon the temperature. Also, the ideal cases that yield the potential maximum electrical power output and power generation efficiency for this temperature range are discussed

Improving the efficiency of a steam power plant cycle by integrating a rotary indirect dryer

This article deals with the integration of a rotary indirect dryer, heated by low pressure extraction steam, into the Rankine cycle. The article evaluates the power generation efficiency of a steam power plant, with an integrated indirect dryer, which combusts waste biomass with a high moisture content and is further compared to the same plant without the dryer. The benefits of the dryer’s integration are analysed in respect to various moisture contents of biomass before and after the drying. The evaluation of the power generation efficiency is based on parameters evaluated from experiments carried out on the steam-heated rotary indirect dryer, such as specific energy consumption and evaporation capacity. The dryer’s integration improves the efficiency of the cycle in comparison to a cycle without a dryer, where moist biomass is directly combusted. This improvement increases along with the difference between the moisture content before and after the drying. For the reference state, a fuel with a moisture content of 50% was dried to 20% and the efficiency rised by 4.38 %. When the fuel with a moisture content of 60% is dried to 10 %, the power generation efficiency increases by a further 10.1 %. However, the required dryer surface for drying the fuel with a moisture content of 60% to 10% is 1.9 times greater as compared to the reference state. The results of the work can be used both for the prediction of the power generation efficiency in a power plant with this type of dryer based on the moisture content in the fuel and the biomass indirect dryer design

The Shape of the Blade with the highest power generation efficiency

The purpose of our wind turbine blade design research is to find the most efficient blade shape for power production. Our plan was to first study the size and structure of existing blades, then use the AutoDesk Inventor 3D program to design a suitable blade profile. After 3D printing the desired blade profile it would be tested using the existing wind turbine simulation equipment in the lab. The Inventor software allowed us to model, and repeatedly debug, to ensure that it our mount fit into the hub of the turbine holding the fixed blade. After repeated changes, the printer finally produced three sets of fan blades of different shapes. The wind simulation equipment still must be used be to complete our testing. By adjusting the wind speed and measuring the recorded output power, it will eventually be converted into an experimental model: a certain shape of blade generates higher electrical power

Enhancing the photomixing efficiency of optoelectronic devices in the terahertz regime

A method to reduce the transit time of majority of carriers in photomixers and photo detectors to $< 1$ ps is proposed. Enhanced optical fields associated with surface plasmon polaritons, coupled with velocity overshoot phenomenon results in net decrease of transit time of carriers. As an example, model calculations demonstrating $> 280\times$ (or $\sim$2800 and 31.8 $\mu$W at 1 and 5 THz respectively) improvement in THz power generation efficiency of a photomixer based on Low Temperature grown GaAs are presented. Due to minimal dependence on the carrier recombination time, it is anticipated that the proposed method paves the way for enhancing the speed and efficiency of photomixers and detectors covering UV to far infrared communications wavelengths (300 to 1600 nm).Comment: 5 pages, 4 figure

An investigation of arc discharging on negatively biased dielectric conductor samples in a plasma

Proposals are now being developed for the construction of high-power photovoltaic systems for operation in low Earth orbit, where the plasma number density is about 1,000 to 1,000,000 per cubic cm. Existing data indicate that interactions between the plasma and high-voltage surfaces of an orbiting power system will occur. In ground tests, where the applied voltage is increased negatively from ground, the array current collection shows an approximately linear rise until it terminates in arcing at greater than several hundred volts negative. This arcing may reduce the power generation efficiency and could possibly affect the low-level logic circuits of the spacecraft. Therefore it is important that the arcing phenomenon be well understood. This study is a survey of the behavior of different dielectric-conductor samples, including a solar cell module, that were biased negatively in a low-density plasma environment with the intent of defining arc discharge conditions and characteristics. Procedures and results are discussed

Overview for improving steam turbine power generation efficiency

Electricity is an integral part of every society for which demand is growing continuously, whereas the production is still based on limited sources of energy derived mainly from steam and gas turbines, the turbomachinery. This paper presents an overview for preliminary study on the optimization of the design of the steam turbine. This was done with a special focus on the last stage low pressure turbine blades, for the reason that the design parameters of this component exhibit influence on the efficiency of power generation from the steam turbine electric power generating system. For supporting the study, a practical overview of the Egbin thermal power station, Nigeria, was included in the study with the parameters from the last stage low pressure turbine blade for this energy generation installation. By these, suggestions that could be undertaken for improving efficiency of the steam power plant for enhancing sustainability of electric power generation were also detailed in the pape

A Reusable Calcium-Based Sorbent for Desulfurizing Hot Coal Gas

There is a continuing need for an inexpensive, regenerable sorbent for desulfurizing hot coal gas. Such a material is needed especially for advanced power generating systems including integrated gasification combined-cycle (IGCC) systems and other systems which employ various topping cycles. Maximum power generation efficiency can be achieved by cleaning the gas at nearly gasifier outlet temperatures which can range up to 1200 K or more

Comparative turbulent three-dimensional Navier-Stokes hydrodynamic analysis and performance assessment of oscillating wings for renewable energy applications

Oscillating wings can extract energy from an oncoming water or air stream, and first large-scale marine demonstrators are being tested. Oscillating wing hydrodynamics is highly unsteady, may feature dynamic stall and leading edge vortex shedding, and is significantly three-dimensional due to finite-wing effects. Understanding the interaction of these phenomena is essential for maximizing power generation efficiency. Much of the knowledge on oscillating wing hydrodynamics stemmed from two-dimensional low-Reynolds number computational fluid dynamics studies and laboratory testing; real installations, however, will feature Reynolds numbers higher than 1 million and unavoidable finite-wing-induced losses. This study investigates the impact of flow three-dimensionality on the hydrodynamics and the efficiency of a realistic aspect ratio 10 device in a stream with Reynolds number of 1.5 million. The improvements achievable by using endplates to reduce finite-wing-induced losses are also analyzed. Three-dimensional time-dependent Navier-Stokes simulations using the shear stress transport turbulence model and a 30 million-cell grid are performed. Detailed comparative hydrodynamic analyses of the finite and the infinite wings reveal that flow three-dimensionality reduces the power generation efficiency of the finite wing with sharp tips and that with endplates by about 17% and 12% respectively. Presented analyses suggest approaches to further reducing these power losses

The Efficiency Improvement of the Stand-alone Photovoltaic Power Systems

An automated solar tracking system was developed to improve the power generation efficiency of standalone photovoltaic systems. In the system, the discrete-continuous tracking with the adjustable discrete pitch was implemented. In addition, the technique and the algorithm of the standalone photovoltaic power system controlwas developed for the positioning. The technique provides the minimization of the power consumption when tracking and controlling and supports tracking accuracy adopting it to actual illumination changes