- Email: [email protected]
02511 Optimization of 60Co production using neutron flux trap in the Tehran research reactor
05 Nuclear fuels (economics, policy, supplies, forecasts) from solutions in the pH range 4.5-7.5, with very good specificity. The capacity of PANSIL is pH-dependent, increasing from about 0.4 g/kg at pH 4.5, to about 1 g/kg at pH 6, and 1.5 g/kg around pH 7.5. In neutral groundwater containing carbonate, both the anion exchange resin and PANSIL exhibit conditional distribution coefficients exceeding 1470 ml/g, which is about an order of magnitude higher than comparable reactive barrier materials reported in the literature.
05/02505 Proliferation resistance potential and burnup characteristics of an equilibrium core of novel natural uranium fueled nuclear research reactor Khan, M. J. et al. Annals of Nuclear Energy, 2005, 32, (6), 61~620. Standard reactor simulation codes WIMS-D/4 and CITATION were employed to analyse the proliferation resistance potential and burnup characteristics of a novel natural uranium fuelled nuclear research reactor. It was found that the proposed core, which provides twice the flux per unit core power compared to similar natural uranium fuelled, light water cooled, heavy water moderated and graphite reflected research reactors, NRX/CIR, is proliferation resistant almost by a factor of 2 as compared to NRX/CIR.
05/02506 RELAP5/MOD3.2 investigation of a VVER-1000 MCP switching on Benchmark problem Groudev, P. P. and Stefanova, A. E. Annals of Nuclear Energy, 2005, 32, (4), 399-416. This paper provides comparisons between experimental data of Kozloduy NPP 'MCP switching on when the other three MCP are in operation', with Relap5 calculations. The investigated thermal-hydraulic driven transient is characterized by spatially dependant nonsymmetric processes. RELAP5/MOD3.2 computer code has been used to simulate the investigated transient. Operational data from Kozloduy NPP have been used for the purpose of assessing how the RELAP5 model compares against plant data. During the plant-commissioning phase at Kozloduy NPP Unit 6 a number of experiments have been performed. One of them is switching on MCP when the other three MCPs are in operation. The event is characterized by rapid increase in the flow through the core resulting in a coolant temperature decrease, which leads to insertion of positive reactivity due to the modeled feedback mechanisms. The main purpose of this investigation was to improve the discrepancy between the calculations and the plant data. The sensitivity calculation investigates the mixing in reactor vessel and influence of heat structure on the hot legs temperature. The areas of improvements to the Relap5 model are: (1) the non-symmetrical mixing in downcomer and reactor vessel annular exit, (2) the influence of heat structure temperature on the time delay for equipments measurements and, (3) investigation of pressurizer water level - using the hot legs temperature correction. The RELAP5/MOD3.2 model of Kozloduy NPP VVER-I000 for investigation of operational occurrences, abnormal events, and design basis scenarios have been developed and validated in the Institute for Nuclear Research and Nuclear Energy - Bulgarian Academy of Sciences (INRNE-BAS) Sofia, and Kozloduy NPP. The model provides a significant analytical capability for the specialists working in the field of NPP safety. This investigation is a process that compares the analytical results obtained by the RELAP5 computer model of the VVER-1000 against the experimental transient data received from the Kozloduy NPP Unit 6. The comparisons indicate good agreement between the RELAP5 results and the experimental data. The sensitivity investigation improves the discrepancy between the calculation and the plant data. This investigation was possible through the participation of leading specialists from Kozloduy NPP and with the support of Argonne National Laboratory, under the International Nuclear Safety Program (INSP) of the United States Department of Energy.
methodology, subject to validation in two specific areas, and to sensitivity studies being undertaken on the effects of other related factors. The key areas requiring validation are: (a) the use of start-oflife yield strength and work hardening properties for estimating end-oflife constraint benefits, and (b) the transferability of local approach model parameters to situations of differing constraint. TAGSI has given consideration to circumstances in which the methodology could be used. In carrying out this review, it has been recognised that OUST is sensitive to constraint and attenuation adjustments and it can no longer be regarded as a material property. The value of OUST determined from highly constrained fracture toughness specimens should be regarded as a 'reference' value for a given material but will not necessarily represent the value of OUST for a service application.
05•02508 Stochastic point-kinetics equations in nuclear reactor dynamics Hayes, J. G. and Allen, E. J. Annals of Nuclear Energy, 2005, 32, (6), 572-587. A system of It6 stochastic differential equations is derived that model the dynamics of the neutron density and the delayed neutron precursors in a point nuclear reactor. The stochastic model is tested against Monte CarIo calculations and experimental data. The results demonstrate that the stochastic differential equation model accurately describes the random behavior of the neutron density and the precursor concentrations in a point reactor.
05•02509 Time-dependent neutron transport in finite media using Pomraning-Eddington approximation E1-Wakil, S. A. et al. Annals of Nuclear Energy, 2005, 32, (3), 343-353. The time-dependent monoenergetic neutron transport equation in a finite plane-parallel medium with linear anisotropic scattering and with specular-reflecting boundaries is considered. The problem is solved using Pomraning-Eddington approximation and by using weight functions to force the boundary conditions to be fulfilled. Numerical calculations for the reflectivity and transmissivity of the proposed medium are calculated at different times and different thicknesses.
05/02510 Two-phase instability analysis in natural circulation loops of China advanced research reactor Yun, G. et al. Annals of Nuclear Energy, 2005, 32, (4), 379-397. In this paper, two-phase flow instability in natural circulation loops of China Advanced Research Reactor (CARR) has been investigated. C A R R is a low pressure and low power density research reactor. A natural circulation instability analysis model is developed for the natural circulation loop of CARR. The homogeneous flow model is used to establish the system control equations. The non-uniform heating and sub-cooled boiling heat transfer is included. The accumulation heat of the wall is also included. Numerical method of Gear is employed to solve the system equations documented in terms of ordinary differential equations. According to the calculation results, stability maps of the natural circulation loop, which confirm the presence of an instability region under the conditions of low equilibrium quality in the outlet and low pressure, are obtained. It is a special kind of density wave oscillation (DWO) that occurs in very low equilibrium quality region with the characteristics of geysering and 'Type-I' DWO at the same time. The calculation results show such oscillation course clearly. The variations of the mass flow rate, the pressure drop and the boiling boundary are analysed separately. Especially, the phase-space trajectory of the boiling boundary and the mass flow rate is discussed. Finally the oscillation frequency is discussed. The calculated results have important significance for the safety operation and accidental analysis of CARR.
05•02507 Review of a procedure for performing constraint and attenuation-corrected fracture mechanics safety case calculations for Magnox reactor steel pressure vessels Dolby, R. E. et al. International Journal of Pressure Vessels and Piping, 2005, 82, (6), 496-508. An assessment methodology put forward by BNFL Magnox Generation to take account of effects of constraint and dose attenuation in determining the margin between onset of upper shelf temperature (OUST) and normal steady state service temperature has been examined in detail by the U K Technical Advisory Group on Structural Integrity of Nuclear Plant (TAGSI). The standard methodology assumes that the constraint at a service flaw corresponds to that in a deeply notched three point bend or compact tension fracture toughness specimen. It also assumes that the maximum level of neutron and thermal ageing embrittlement at the vessel inner surface applies throughout the thickness. The revised procedure uses the local approach with detailed finite element analysis of specific defect geometries to determine constraint effects and aliows for attenuation of embrittlement effects through the thickness. Demonstration examples of the analysis procedures were provided by BNFL Magnox Generation and A E A Technology Ltd. TAGSI endorses the proposed
Economics, policy, supplies, forecasts 05/02511 Optimization of e°Co production using neutron flux trap in the Tehran research reactor Khalafi, H. and Gharib, M. Annals of Nuclear Energy, 2005, 32, (3), 331-341. Radioisotope production is one of the most important applications of research reactors. 6°Co has a wide application in industry and medicine. In this paper the efficient production of 6°Co by enhancing radiation systems is studied and developed by using neutron flux trap concept in the Tehran research reactor. Calculational methods were checked against experimental results.
Fuel and Energy Abstracts
November 2005
369
06 Electrical power supply and utilization (scientific, technical)
06
ELECTRICAL POWER SUPPLY A N D UTILIZATION
Scientific, technical 05102512 A comparative study of adaptive load frequency controller designs in a power system with dynamic neural network models Oysal, Y. Energy Conversion and Management, 2005, 46, (15-16), 2656 2668. This paper investigates applications of dynamic neural network (DNN) models for adaptive load frequency controller designs in power systems. The proposed dynamic neural network models have lag dynamics and dynamical elements such as delayers or integrators in their processing units. They only differ in activation functions. The first uses sigmoid functions, the second uses standard fuzzy systems and the third uses non-orthogonal mother wavelets as activation functions. Each DNN model is connected between two area power systems. The input signals of the DNN models are the area control errors (ACE). The outputs are the control signals for two area load frequency control. Adaptation is based on adjusting the parameters of each for load frequency control. This is done by minimizing the cost functional of load frequency deviations. In simulations for each DNN model, comparative results are obtained for damping the frequency due to a load disturbance effect applied to a two area power system.
05102513 A new control scheme of a cascaded transformer type multilevel PWM inverter for a residential photovoltaic power conditioning system Kang, F.-S. et al. Solar Energy, 2005, 78, (6), 727-738. From the viewpoint of high quality output voltage generation in a residential photovoltaic system, a multilevel inverter employing cascaded transformers can become a good substitute for the conventional pulse width modulated inverters and other multilevel counterparts. However, to obtain more sinusoidal output voltage waves, it should increase the number of switching devices and transformers resulting in a cost increase. To alleviate this problem, an efficient switching pattern is proposed and applied to a multilevel inverter equipped with two cascaded transformers, which have a seriesconnected secondary. Operational principle and analysis are illustrated focusing on a change of the switching pattern. High-performance of the proposed multilevel scheme embedded in a photovoltaic power conditioning system is verified by computer-aided simulations and experimental results.
05/02514 A robust damping controller for SMES using loop-shaping technique Rahim, A. H. M. A. and Nowicki, E. P. International Journal of Electrical Power & Energy Systems, 2005, 27, (5 6), 465-471. A robust damping controller for a power system installed with superconducting magnetic energy storage (SMES) has been designed using a simple graphical loop-shaping technique. The graphical method starts by selection of a nominal plant function satisfying the robust stability and performance criterion. The variations in operating conditions from the nominal values are modelled as multiplicative structured uncertainty. The generator-SMES system has been represented with a detailed dynamic model for the control design. The robust design, with generator speed variation as the controller input, was tested for a range of operating points considering various disturbances. It is observed that the fixed parameter robust controller provides very good damping for a wide range of operating conditions.
05102515 Combination of thermochemical recuperative coal gasification cycle and fuel cell for power generation Kuchonthara, P. et al. Fuel, 2005, 84, (7-8), 1019-1021. An integrated power generation cycle combining thermochemical recuperation, brown coal gasification and a solid oxide fuel cell (SOFC) was proposed based on the concept of thermochemical recuperative energy. Process simulation combining the coal gasifier, gas turbine cycle, and SOFC module was conducted using the ASPEN Plus process simulation tool. The simulation indicated that the cycle efficiency increases from 39.5% (HHV) without the SOFC to about 45% (HHV) with the SOFC.
370
Fuel and Energy Abstracts
November 2005
05•02516 Design optimization of a large scale rooftop photovoltaic system Gong, X. and Kulkarni, M. Solar Energy, 2005, 78, (3), 362 374. This paper presents the optimization process of a grid connected photovoltaic (PV) system, which is intended to replace a large-scale thermal solar system on the rooftop of a Federal office building. A PV energy conversion model is described. Based on this model, array surface tilt angle and array size are optimized. The optimization method is based on maximizing the utilization of the array output energy, and, at the same time, minimizing the electricity power sold to grid. An effectiveness factor is introduced that takes into account both of these parameters. The array configuration and the output parameters are determined by comparing several PV modules. A 43.2 kW PV system is designed and operational problems such as harmonic effects and anti-islanding are discussed. Finally, the system performance is simulated and through economic analysis it has shown that the cost of PV system can be recouped in 13 years under the current renewable energy incentive program by the state of Illinois.
05102517 Detection of inrush current in distribution transformer using wavelet transform Sedighi, A.-R. and Haghifam, M.-R. International Journal of Electrical Power & Energy Systems, 2005, 27, (5-6), 361-370. Inrush currents in transformers are non-sinusoidal, high magnitude currents generated due to flux saturation in the core during energization. For protection purpose, in this paper an efficient method for detection of inrush current in distribution transformer based on wavelet transform is presented. Using this method inrush current can be discriminated from the other switching transients such as: load switching, capacitor switching and single phase to ground fault. Inrush current and other events for feature extraction and discrimination are simulated using an electromagnetic transient programme. Results in all cases show the effectiveness of proposed procedure in identifying inrush current from other transients.
05•02518 Development and testing of a domestic woodstove thermoelectric generator with natural convection cooling Nuwayhid, R. Y. et al. Energy Conversion and Management, 2005, 46, (9 10), 1631-1643. A thermoelectric generator was fitted to the side of a domestic woodstove. The generator was driven using one or more thermoelectric modules designed to give significant power at a reasonable cost. The thermoelectric generator was air cooled by natural convection using a commercially available heat sink. Testing was undertaken under a controlled woodstove firing rate and temperatures, and open circuit voltages were monitored over extended periods. The maximum steady state matched load power was 4.2 W using a single module. The use of multiple modules with a single heat sink was found to reduce the total power output relative to the single module case as a result of reduced hot to cold surface temperature differences.
05/02519 Distributed grid-connected photovoitaic power system emission offset assessment: statistical test of simulated- and measured-based data Spiegel, R. J. et al. Solar Energy, 2005, 78, (6), 717-726. This study assesses the pollutant emission offset potential of distributed grid-connected photovoltaic (PV) power systems. Computer-simulated performance results were utilized for 214 PV systems located across the US. The PV systems' monthly electrical energy outputs were based on a performance calculator called PVWATTS. Offset emissions of sulfur dioxide (SO2), carbon dioxide (CO2), and nitrogen oxides (NO y) were determined from PV system outputs and average utility emissions data from each state. For validation, the simulated monthly results were statistically compared with measurement-based data (both production and corresponding emissions data) from 29 PV systems installed at different sites across the US. While the data shows high (geographic) variability, the substantial number of measurements allows reliable statistical analysis. The methods are found to give consistent results in spite of the necessity to employ some even quite crude input approximations - such as the use of statewide rather than specific emissions data for the systems. No significant differences between simulated and measured monthly means for any of the pollutants were noted on the basis of individual monthly analyses, though the results for NOx suggest the possible existence of some difference in that case. A more detailed statistical modelling using all monthly data in one combined analysis (allowing improved variability estimation) confirms these conclusions. Even the shorter confidence intervals for expected offsets obtained through the combined analysis show no significant differences between simulated and measured methods for SO2 and CO2. The differences for NOx are statistically significant but consistent-suggesting useful prediction by the simulations via a constant correction factor. As expected, significant differences between months are evident for both simulated and measured offsets.
05/02505 Proliferation resistance potential and burnup characteristics of an equilibrium core of novel natural uranium fueled nuclear research reactor Khan, M. J. et al. Annals of Nuclear Energy, 2005, 32, (6), 61~620. Standard reactor simulation codes WIMS-D/4 and CITATION were employed to analyse the proliferation resistance potential and burnup characteristics of a novel natural uranium fuelled nuclear research reactor. It was found that the proposed core, which provides twice the flux per unit core power compared to similar natural uranium fuelled, light water cooled, heavy water moderated and graphite reflected research reactors, NRX/CIR, is proliferation resistant almost by a factor of 2 as compared to NRX/CIR.
05/02506 RELAP5/MOD3.2 investigation of a VVER-1000 MCP switching on Benchmark problem Groudev, P. P. and Stefanova, A. E. Annals of Nuclear Energy, 2005, 32, (4), 399-416. This paper provides comparisons between experimental data of Kozloduy NPP 'MCP switching on when the other three MCP are in operation', with Relap5 calculations. The investigated thermal-hydraulic driven transient is characterized by spatially dependant nonsymmetric processes. RELAP5/MOD3.2 computer code has been used to simulate the investigated transient. Operational data from Kozloduy NPP have been used for the purpose of assessing how the RELAP5 model compares against plant data. During the plant-commissioning phase at Kozloduy NPP Unit 6 a number of experiments have been performed. One of them is switching on MCP when the other three MCPs are in operation. The event is characterized by rapid increase in the flow through the core resulting in a coolant temperature decrease, which leads to insertion of positive reactivity due to the modeled feedback mechanisms. The main purpose of this investigation was to improve the discrepancy between the calculations and the plant data. The sensitivity calculation investigates the mixing in reactor vessel and influence of heat structure on the hot legs temperature. The areas of improvements to the Relap5 model are: (1) the non-symmetrical mixing in downcomer and reactor vessel annular exit, (2) the influence of heat structure temperature on the time delay for equipments measurements and, (3) investigation of pressurizer water level - using the hot legs temperature correction. The RELAP5/MOD3.2 model of Kozloduy NPP VVER-I000 for investigation of operational occurrences, abnormal events, and design basis scenarios have been developed and validated in the Institute for Nuclear Research and Nuclear Energy - Bulgarian Academy of Sciences (INRNE-BAS) Sofia, and Kozloduy NPP. The model provides a significant analytical capability for the specialists working in the field of NPP safety. This investigation is a process that compares the analytical results obtained by the RELAP5 computer model of the VVER-1000 against the experimental transient data received from the Kozloduy NPP Unit 6. The comparisons indicate good agreement between the RELAP5 results and the experimental data. The sensitivity investigation improves the discrepancy between the calculation and the plant data. This investigation was possible through the participation of leading specialists from Kozloduy NPP and with the support of Argonne National Laboratory, under the International Nuclear Safety Program (INSP) of the United States Department of Energy.
methodology, subject to validation in two specific areas, and to sensitivity studies being undertaken on the effects of other related factors. The key areas requiring validation are: (a) the use of start-oflife yield strength and work hardening properties for estimating end-oflife constraint benefits, and (b) the transferability of local approach model parameters to situations of differing constraint. TAGSI has given consideration to circumstances in which the methodology could be used. In carrying out this review, it has been recognised that OUST is sensitive to constraint and attenuation adjustments and it can no longer be regarded as a material property. The value of OUST determined from highly constrained fracture toughness specimens should be regarded as a 'reference' value for a given material but will not necessarily represent the value of OUST for a service application.
05•02508 Stochastic point-kinetics equations in nuclear reactor dynamics Hayes, J. G. and Allen, E. J. Annals of Nuclear Energy, 2005, 32, (6), 572-587. A system of It6 stochastic differential equations is derived that model the dynamics of the neutron density and the delayed neutron precursors in a point nuclear reactor. The stochastic model is tested against Monte CarIo calculations and experimental data. The results demonstrate that the stochastic differential equation model accurately describes the random behavior of the neutron density and the precursor concentrations in a point reactor.
05•02509 Time-dependent neutron transport in finite media using Pomraning-Eddington approximation E1-Wakil, S. A. et al. Annals of Nuclear Energy, 2005, 32, (3), 343-353. The time-dependent monoenergetic neutron transport equation in a finite plane-parallel medium with linear anisotropic scattering and with specular-reflecting boundaries is considered. The problem is solved using Pomraning-Eddington approximation and by using weight functions to force the boundary conditions to be fulfilled. Numerical calculations for the reflectivity and transmissivity of the proposed medium are calculated at different times and different thicknesses.
05/02510 Two-phase instability analysis in natural circulation loops of China advanced research reactor Yun, G. et al. Annals of Nuclear Energy, 2005, 32, (4), 379-397. In this paper, two-phase flow instability in natural circulation loops of China Advanced Research Reactor (CARR) has been investigated. C A R R is a low pressure and low power density research reactor. A natural circulation instability analysis model is developed for the natural circulation loop of CARR. The homogeneous flow model is used to establish the system control equations. The non-uniform heating and sub-cooled boiling heat transfer is included. The accumulation heat of the wall is also included. Numerical method of Gear is employed to solve the system equations documented in terms of ordinary differential equations. According to the calculation results, stability maps of the natural circulation loop, which confirm the presence of an instability region under the conditions of low equilibrium quality in the outlet and low pressure, are obtained. It is a special kind of density wave oscillation (DWO) that occurs in very low equilibrium quality region with the characteristics of geysering and 'Type-I' DWO at the same time. The calculation results show such oscillation course clearly. The variations of the mass flow rate, the pressure drop and the boiling boundary are analysed separately. Especially, the phase-space trajectory of the boiling boundary and the mass flow rate is discussed. Finally the oscillation frequency is discussed. The calculated results have important significance for the safety operation and accidental analysis of CARR.
05•02507 Review of a procedure for performing constraint and attenuation-corrected fracture mechanics safety case calculations for Magnox reactor steel pressure vessels Dolby, R. E. et al. International Journal of Pressure Vessels and Piping, 2005, 82, (6), 496-508. An assessment methodology put forward by BNFL Magnox Generation to take account of effects of constraint and dose attenuation in determining the margin between onset of upper shelf temperature (OUST) and normal steady state service temperature has been examined in detail by the U K Technical Advisory Group on Structural Integrity of Nuclear Plant (TAGSI). The standard methodology assumes that the constraint at a service flaw corresponds to that in a deeply notched three point bend or compact tension fracture toughness specimen. It also assumes that the maximum level of neutron and thermal ageing embrittlement at the vessel inner surface applies throughout the thickness. The revised procedure uses the local approach with detailed finite element analysis of specific defect geometries to determine constraint effects and aliows for attenuation of embrittlement effects through the thickness. Demonstration examples of the analysis procedures were provided by BNFL Magnox Generation and A E A Technology Ltd. TAGSI endorses the proposed
Economics, policy, supplies, forecasts 05/02511 Optimization of e°Co production using neutron flux trap in the Tehran research reactor Khalafi, H. and Gharib, M. Annals of Nuclear Energy, 2005, 32, (3), 331-341. Radioisotope production is one of the most important applications of research reactors. 6°Co has a wide application in industry and medicine. In this paper the efficient production of 6°Co by enhancing radiation systems is studied and developed by using neutron flux trap concept in the Tehran research reactor. Calculational methods were checked against experimental results.
Fuel and Energy Abstracts
November 2005
369
06 Electrical power supply and utilization (scientific, technical)
06
ELECTRICAL POWER SUPPLY A N D UTILIZATION
Scientific, technical 05102512 A comparative study of adaptive load frequency controller designs in a power system with dynamic neural network models Oysal, Y. Energy Conversion and Management, 2005, 46, (15-16), 2656 2668. This paper investigates applications of dynamic neural network (DNN) models for adaptive load frequency controller designs in power systems. The proposed dynamic neural network models have lag dynamics and dynamical elements such as delayers or integrators in their processing units. They only differ in activation functions. The first uses sigmoid functions, the second uses standard fuzzy systems and the third uses non-orthogonal mother wavelets as activation functions. Each DNN model is connected between two area power systems. The input signals of the DNN models are the area control errors (ACE). The outputs are the control signals for two area load frequency control. Adaptation is based on adjusting the parameters of each for load frequency control. This is done by minimizing the cost functional of load frequency deviations. In simulations for each DNN model, comparative results are obtained for damping the frequency due to a load disturbance effect applied to a two area power system.
05102513 A new control scheme of a cascaded transformer type multilevel PWM inverter for a residential photovoltaic power conditioning system Kang, F.-S. et al. Solar Energy, 2005, 78, (6), 727-738. From the viewpoint of high quality output voltage generation in a residential photovoltaic system, a multilevel inverter employing cascaded transformers can become a good substitute for the conventional pulse width modulated inverters and other multilevel counterparts. However, to obtain more sinusoidal output voltage waves, it should increase the number of switching devices and transformers resulting in a cost increase. To alleviate this problem, an efficient switching pattern is proposed and applied to a multilevel inverter equipped with two cascaded transformers, which have a seriesconnected secondary. Operational principle and analysis are illustrated focusing on a change of the switching pattern. High-performance of the proposed multilevel scheme embedded in a photovoltaic power conditioning system is verified by computer-aided simulations and experimental results.
05/02514 A robust damping controller for SMES using loop-shaping technique Rahim, A. H. M. A. and Nowicki, E. P. International Journal of Electrical Power & Energy Systems, 2005, 27, (5 6), 465-471. A robust damping controller for a power system installed with superconducting magnetic energy storage (SMES) has been designed using a simple graphical loop-shaping technique. The graphical method starts by selection of a nominal plant function satisfying the robust stability and performance criterion. The variations in operating conditions from the nominal values are modelled as multiplicative structured uncertainty. The generator-SMES system has been represented with a detailed dynamic model for the control design. The robust design, with generator speed variation as the controller input, was tested for a range of operating points considering various disturbances. It is observed that the fixed parameter robust controller provides very good damping for a wide range of operating conditions.
05102515 Combination of thermochemical recuperative coal gasification cycle and fuel cell for power generation Kuchonthara, P. et al. Fuel, 2005, 84, (7-8), 1019-1021. An integrated power generation cycle combining thermochemical recuperation, brown coal gasification and a solid oxide fuel cell (SOFC) was proposed based on the concept of thermochemical recuperative energy. Process simulation combining the coal gasifier, gas turbine cycle, and SOFC module was conducted using the ASPEN Plus process simulation tool. The simulation indicated that the cycle efficiency increases from 39.5% (HHV) without the SOFC to about 45% (HHV) with the SOFC.
370
Fuel and Energy Abstracts
November 2005
05•02516 Design optimization of a large scale rooftop photovoltaic system Gong, X. and Kulkarni, M. Solar Energy, 2005, 78, (3), 362 374. This paper presents the optimization process of a grid connected photovoltaic (PV) system, which is intended to replace a large-scale thermal solar system on the rooftop of a Federal office building. A PV energy conversion model is described. Based on this model, array surface tilt angle and array size are optimized. The optimization method is based on maximizing the utilization of the array output energy, and, at the same time, minimizing the electricity power sold to grid. An effectiveness factor is introduced that takes into account both of these parameters. The array configuration and the output parameters are determined by comparing several PV modules. A 43.2 kW PV system is designed and operational problems such as harmonic effects and anti-islanding are discussed. Finally, the system performance is simulated and through economic analysis it has shown that the cost of PV system can be recouped in 13 years under the current renewable energy incentive program by the state of Illinois.
05102517 Detection of inrush current in distribution transformer using wavelet transform Sedighi, A.-R. and Haghifam, M.-R. International Journal of Electrical Power & Energy Systems, 2005, 27, (5-6), 361-370. Inrush currents in transformers are non-sinusoidal, high magnitude currents generated due to flux saturation in the core during energization. For protection purpose, in this paper an efficient method for detection of inrush current in distribution transformer based on wavelet transform is presented. Using this method inrush current can be discriminated from the other switching transients such as: load switching, capacitor switching and single phase to ground fault. Inrush current and other events for feature extraction and discrimination are simulated using an electromagnetic transient programme. Results in all cases show the effectiveness of proposed procedure in identifying inrush current from other transients.
05•02518 Development and testing of a domestic woodstove thermoelectric generator with natural convection cooling Nuwayhid, R. Y. et al. Energy Conversion and Management, 2005, 46, (9 10), 1631-1643. A thermoelectric generator was fitted to the side of a domestic woodstove. The generator was driven using one or more thermoelectric modules designed to give significant power at a reasonable cost. The thermoelectric generator was air cooled by natural convection using a commercially available heat sink. Testing was undertaken under a controlled woodstove firing rate and temperatures, and open circuit voltages were monitored over extended periods. The maximum steady state matched load power was 4.2 W using a single module. The use of multiple modules with a single heat sink was found to reduce the total power output relative to the single module case as a result of reduced hot to cold surface temperature differences.
05/02519 Distributed grid-connected photovoitaic power system emission offset assessment: statistical test of simulated- and measured-based data Spiegel, R. J. et al. Solar Energy, 2005, 78, (6), 717-726. This study assesses the pollutant emission offset potential of distributed grid-connected photovoltaic (PV) power systems. Computer-simulated performance results were utilized for 214 PV systems located across the US. The PV systems' monthly electrical energy outputs were based on a performance calculator called PVWATTS. Offset emissions of sulfur dioxide (SO2), carbon dioxide (CO2), and nitrogen oxides (NO y) were determined from PV system outputs and average utility emissions data from each state. For validation, the simulated monthly results were statistically compared with measurement-based data (both production and corresponding emissions data) from 29 PV systems installed at different sites across the US. While the data shows high (geographic) variability, the substantial number of measurements allows reliable statistical analysis. The methods are found to give consistent results in spite of the necessity to employ some even quite crude input approximations - such as the use of statewide rather than specific emissions data for the systems. No significant differences between simulated and measured monthly means for any of the pollutants were noted on the basis of individual monthly analyses, though the results for NOx suggest the possible existence of some difference in that case. A more detailed statistical modelling using all monthly data in one combined analysis (allowing improved variability estimation) confirms these conclusions. Even the shorter confidence intervals for expected offsets obtained through the combined analysis show no significant differences between simulated and measured methods for SO2 and CO2. The differences for NOx are statistically significant but consistent-suggesting useful prediction by the simulations via a constant correction factor. As expected, significant differences between months are evident for both simulated and measured offsets.