Sub-atmospheric disk generators for coal-fired MHD/steam combined cycle power plant

A coal fired MHD disk generator in a combined cycle MHD/steam power generation system with a diffuser operating at sub-atmospheric pressure is proposed. The effects of pressure on the performance of a radial outflow MHD disk generator and other systems components are analysed. Using a previous study as a reference case, preliminary calculations show that, in such a sub-atmospheric system, improved power station efficiency can be achieved. In addition, operation at reduced values of magnetic field strength would be feasible. Calculations have also been carried out for a 30 MW_th experimental disk generator operating at reduced pressure with a magnetic field strength of 2 T. Flow conditions at sub-atmospheric pressure would provide an improved simulation of a full-scale generator operating at normal pressures.     

High-temperature fuel cells for power generation

Hybrid systems consisting of series-connected high-temperature solid-electrolyte fuel cells (HTSEFCs) thermally coupled to coal gasifiers show great potential for overall efficiencies of nearly 60% for the production of electricity from coal. This paper describes a steady-state model for the prediction of HTSEFC voltage, current and power density. The HTSEFC model is essentially a distributed parameter electrical network that includes the effects of mass transfer resistance (concentration polarization), chemical kinetic resistance (activation polarization), as well as all relevant electrical resistances (ohmic losses). This electrical network representation leads to a finite-difference discretization which, in effect, divides the fuel cell into many simple current-flow sections. Furthermore, the model computes the fuel and oxidant stream compositions as functions of axial length from energy and mass balances performed on each fuel cell slice. The model yields results that compare favorably with the published experimental data from Westinhouse.     

Optimum size of base load generators for growing demand

The price per unit generated electrical energy decreases with increasing size of the generator, which implies longer transmission line and hence larger transmission losses. Considering both these facts the optimum size of thermal power station for growing demand has been obtained by using life-cycle costing analysis. The demand may be met by (1) a combination of base load and peak load generators (Sodha and Chandra, 1992) and (2) by a combination of base load generators only. The second option has been analysed in this paper. The dependence of investment ratio (the ratio of present worth of net income to the capital investment) on relevant parameters has been studied. It is seen that there exists a particular pattern (optimum combination) of base load generators. The effect of electricity price, coal price and escalation rates on the optimum configuration has also been investigated. The cost data from recent study in India have been used.     

A novel anti islanding detection method for grid connected fuel cell power generation systems

Renewable energy sources have been developed rapidly all around the world, and one of these green energy sources is hydrogen energy. The fuel cell systems have become prominent in renewable energy sources because of its minimal dimensions and energy conversion method. There have been developed, some applications, especially in domestic and automotive areas, and fuel cell systems are also have been started to use in grid connected systems. Fuel cell systems must have some electrical connection standards while they connected to an electrical grid. One of these electrical conditions and may be the most important one is unplanned islanding condition. Islanding is a very dangerous situation because it can damage to the fuel cell and related electrical systems and also working people have been at risk in islanding situation on the grid. In this study, a novel islanding detection method was introduced for grid connected fuel cell systems. 0.5 kW solid oxide fuel cell (SOFC) system used in developed experimental system and a novel anti islanding detection method was researched by using an effective method. The proposed method was also developed by using Matlab Simulink and its useful tools. The developed islanding detection method is robust, reliable and has a fast response time, according to present methods. The results confirm the suggested conditions, and it can be seen in this method, it can also be adapted easily to the grid connected fuel cell systems.     

Experimental evaluation of a passive fuel cell/battery hybrid power system for an unmanned ground vehicle

Unmanned vehicles are increasing the performance of monitoring and surveillance in several applications. Endurance is a key issue in these systems, in particular in electric vehicles, powered at present mainly by batteries. Hybrid power systems based on batteries and fuel cells have the potential to achieve high energy density and specific energy, increasing also the life time and safe operating conditions of the power system. The objective of this research is to analyze the performance of a passive hybrid power system, designed and developed to be integrated into an existing Unmanned Ground Vehicle (UGV). The proposed solution is based on six LiPo cells, connected in series, and a 200 W PEM fuel cell stack, directly connected in parallel to the battery without any limitation to its charge. The paper presents the characterization of the system behavior, and shows the main results in terms of performance and energy management.     

Design of compact methanol reformer for hydrogen with low CO for the fuel cell power generation

The effect of the heat transfer area and the thermal conductivity of the reactor materials are evaluated with three identical structured reactors having multiple columned-catalyst bed and using three different reactor materials, aluminum alloy, brass and stainless steel. A series of compact methanol reformers are then designed and fabricated with the use of large reactor surface area in catalyst beds and high heat transfer constant to produce hydrogen fuel with 2–4 ppm of CO for the fuel cell (FC) power generation. The same design principle is successfully used for easy scale up of the reactor capacity from 250 L/h to 10,000 L/h. This low CO hydrogen (68–70%) used as the fuel for the fuel cell power generation provides a very competitive cost of hydrogen and electric power, $0.20–0.23/m³ of H₂ and $0.196/KWh, respectively.     

An enhanced microfluidic control system for improving power density of a hydride-based micro fuel cell

Microfuel cells (MFCs) can potentially power emerging technologies that require power sources in the microliter size range. The recent development of a microfluidic mechanism for self-regulated generation of hydrogen has enabled fabrication of MFCs orders of magnitude smaller than previously possible. In this study, we report an order of magnitude enhancement in the power density of a microliter-scale fuel cell incorporating a new microfluidic design. The microfluidic mechanism is part of an on-board hydrogen generator that uses a reaction between a metal hydride, LiAlH₄, and water vapor to generate hydrogen. The hydrogen generated exits the hydride reactor through a porous silicon wall to reach a Nafion-based membrane electrode assembly (MEA). The microfluidic design increased the water vapor release rate to the hydride reactor by one order of magnitude over a previous design. A 9 μL device incorporating the enhanced microfluidic design delivered a power density of 92 W L⁻¹. Details of a parametric study conducted to improve the water vapor release rate of the microfluidic mechanism and performance analysis of the integrated device are presented in this paper.     

Environmental impact associated with the substitution of internal combustion vehicles by fuel cell vehicles refueled with hydrogen generated by electrolysis using the power grid. An estimation focused on the Autonomous Region of Murcia (Spain)

This article explores the possibilities of substituting internal combustion vehicles (ICV) by fuel cell vehicles (FCV) refueled with hydrogen generated by electrolysis during the hours of low demand in the electrical grid, having been estimated that this substitution ratio would be below 25% of the total number of vehicles existing today, against the 100% in the case of using electric vehicles. Furthermore, a network of 322 hydrogen stations would be necessary for refueling the maximum number of fuel cell vehicles, given the actual limitations of the electrical grid for hydrogen generation. Thus, considering that hydrogen used for refueling would be generated by electrolysis using the electrical grid, fuel cell vehicles would only be a 4% less polluting than an internal combustion vehicle. However, if we could achieve a substitution ratio of 25% of the total ICV by FCV, the Autonomous Region of Murcia could avoid the emission of up to 24,500 metric Tons of CO₂ to the atmosphere every year. This value contrasts with the 2.2 millions of metric tons of CO₂ that could be avoided using electric vehicles.     

Optimum size of thermal power stations

It is well known that the price per unit of generated electrical energy decreases with increasing size of the generator, which implies longer transmission lines and hence larger transmission losses. Considering both these facts, the optimum size of a thermal power station has been obtained by using life-cycle costing analysis; the demand is proposed to be met by a base load generator and a peak load generator. The dependence of the investment ratio (the ratio of present worth of net income to the capital investment) on relevant parameters has been studied. It is seen that there exist optimum sizes of base load generator and peak load generator of a power station, for a given load density. The effect of electricity price, coal price and escalation rates on the optimum sizes has also been investigated. The analysis has been made for constant demand as well as for growing demand. The effect of the ratio of base load to peak load on the economics has also been investigated. The cost data from a recent study in India have been used.     

Validation of measured data on F/A ratio and turbine inlet temperature with optimal estimation to enhance the reliability on a full-scale gas turbine combustion test for IGCC

This study is aimed at verifying the reliability and reproducibility of combustion tests, including ignition, load change and fuel changeover, conducted at a well-resourced full-scale gas turbine syngas combustion test facility. The 10 MWth, single-can, syngas-fired combustion test facility was equipped with analytical equipment to measure air and fuel flow rates to the combustor, the metal/gas temperature in the combustor, and exhaust gas composition and temperature distribution at the combustor's outlet.To confirm the test facility's reliability, the repeatability of the fuel changeover test from natural gas to syngas was evaluated. Reliability was also verified by cross-validating the theoretical and measured values for fuel/air (F/A) ratio and Turbine Inlet Temperature (TIT). In this study, the deviation between the averaged F/A ratio based on O₂ and CO emission data and the F/A ratio based on the mass flow rate was under 2% at most, when the F/A ratio exceeded 20%. And, the calculated TIT for syngas, taking thermal dissociation and heat loss into consideration, correlates well with the experimental result which is the corrected TIT value based on heat balance at the temperature sensor tip.