bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Simulation and Optimization of an Experimental Micro-CSP Power Plant
Authors: Mitterhofer Matthias , Orosz Matthew
Published: October 2015

Small scale solar thermal systems are increasingly investigated in the context of decentralized energy supply, due to favorable costs of thermal energy storage (TES) in comparison with battery storage for otherwise economical PV generation. The present study provides the computational framework and results of a one year simulation of a low-cost pilot 3kWel micro-Concentrated Solar Power (micro-CSP) plant with TES. The modeling approach is based on a dynamic representation of the solar thermal loop and a steady state model of the Organic Rankine Cycle (ORC), and is validated to experimental data from a test site (Eckerd College, St. Petersburg, Florida). The simulation results predict an annual net electricity generation of 4.08 MWh/a. Based on the simulation, optimization studies focusing on the Organic Rankine Cycle (ORC) converter of the system are presented, including a control strategy allowing for a variable pinch point in the condenser that offers an annual improvement of 14.0% in comparison to a constant condensation pinch point. Absolute electricity output is increased to 4.65 MWh/a. Improvements are due to better matching to expander performance and lower condenser fan power because of higher pinch points. A method, incorporating this control strategy, is developed to economically optimize the ORC components. The process allows for optimization of the ORC subsystem in an arbitrary environment, e.g. as part of a micro-grid to minimize Levelized electricity costs (LEC). The air-cooled condenser is identified as the driving component for the ORC optimization as its influence on overall costs and performance is of major significance. Application of the optimization process to various locations in Africa illustrates economic benefits of the system in comparison to diesel generation.
Cost Analysis of Different Operation Strategies for Falling Particle Receivers
Authors: Gobereit Birgit , Amsbeck Lars , Buck Reiner , Singer Csaba
Published: October 2015

The potential for highly efficient and cost competitive solar energy collection at high temperatures drives the actual research and development activities for particle tower systems. One promising concept for particle receivers is the falling particle receiver. This paper is related to a particle receiver, in which falling ceramic particles form a particle curtain, which absorbs the concentrated solar radiation. Complex operation strategies will result in higher receiver costs, for both investment and operation. The objective of this paper is to assess the influence of the simultaneous variation of receiver costs and efficiency characteristics on levelized cost of heat (LCOH) and on levelized cost of electricity (LCOE).

Applying cost assumptions for the particle receiver and the particle transport system, the LCOE are estimated and compared for each considered concept. The power level of the compared concepts is 125 MWel output at design point. The sensitivity of the results on the specific cost assumptions is analyzed. No detailed evaluation is done for the thermal storage, but comparable storage utilization and costs are assumed for all cases.
Characterization of Particle Flow in a Free-Falling Solar Particle Receiver
Authors: Ho Clifford K. , Christian Joshua M. , Romano David , Yellowhair Julius , Siegel Nathan
Published: October 2015

Falling particle receivers are being evaluated as an alternative to conventional fluid-based solar receivers to enable higher temperatures and higher efficiency power cycles with direct storage for concentrating solar power applications. This paper presents studies of the particle mass flow rate, velocity, particle-curtain opacity and density, and other characteristics of free-falling ceramic particles as a function of different discharge slot apertures. The methods to characterize the particle flow are described, and results are compared to theoretical and numerical models for unheated conditions.
Cost and Performance Tradeoffs of Alternative Solar-Driven S-CO2 Brayton Cycle Configurations
Authors: Ho Clifford K. , Carlson Matthew , Garg Pardeep , Kumar Pramod
Published: October 2015

This paper evaluates cost and performance tradeoffs of alternative supercritical carbon dioxide (s-CO2) closed-loop Brayton cycle configurations with a concentrated solar heat source. Alternative s-CO2 power cycle configurations include simple, recompression, cascaded, and partial cooling cycles. Results show that the simple closed-loop Brayton cycle yielded the lowest power-block component costs while allowing variable temperature differentials across the s-CO2 heating source, depending on the level of recuperation. Lower temperature differentials led to higher sensible storage costs, but cycle configurations with lower temperature differentials (higher recuperation) yielded higher cycle efficiencies and lower solar collector and receiver costs. The cycles with higher efficiencies (simple recuperated, recompression, and partial cooling) yielded the lowest overall solar and power-block component costs for a prescribed power output.
Design and Characterization of a 7.2 KW Solar Simulator
Authors: Boubault Antoine , Yellowhair Julius , Ho Clifford K.
Published: October 2015

A 7.2 kW radiative solar simulator was designed in order to perform accelerated testing on absorber materials for concentrating solar power (CSP) technologies. Computer-aided design (CAD) software integrating a ray-tracing tool was used to select appropriate components and optimize their positioning in order to achieve the desired concentration. The simulator comprises four identical units, each made out of an ellipsoidal reflector, a metal halide lamp and an adjustable holding system. A single unit was characterized and shows an experimental average irradiance of 257 kW m−2 on a 25.4 mm (1 inch) diameter spot. Shape, spot size and average irradiance are in good agreement with the model predictions. The innovative four-lamp solar simulator potentially demonstrates peak irradiance of 1140 kW m−2 and average irradiance of 878 kW m−2 over a 25.4 mm diameter spot. The costs per radiative and electric watt are calculated at $2.31 W−1 and $1.99 W−1, respectively.
Experimental Study on Test-Bed Vanadium Redox Flow Battery
Authors: Islam Rabiul , Eckerson Benjamin , Nolen Cameron , Jeong Kwangkook , McCann Roy
Published: October 2015

An experimental study has been conducted to develop a test-bed for advanced vanadium redox flow battery (VRFB) for renewable energy applications. Lab scale experimental setup has been designed based on enhanced geometry of mechanical components and reduced power consumption in terms of fluid mechanics and thermodynamics. Two tests have been conducted with variations of flowrate, concentration of electrolytes and electrical input power. The VRFB project has been collaborated between Arkansas State University Jonesboro (ASUJ) and University of Arkansas Fayetteville (UAF) to integrate VRFB with micro-grid at UAF. To obtain comparable experimental data, a test bed made of two half cells was constructed and joined together by a permeable membrane designed to facilitate ion transfer between two separate vanadium electrolytes. This research aims to better understand and demonstrate the transient characteristics of VRFB in order to refine the system in hopes of improving efficiency. This paper will focus on the steps taken to experimentally validate preliminary performance of the VRFB test bed. An analytical model has been performed to validate design and test of VRFB. Future work will be addressed to develop a pilot-scale multiple cell stacks with enhanced efficiency and temperature limits.
Dynamic Simulation of Performance and Cost of Hybrid PV-CSP-LPG Generator Micro Grids With Applications to Remote Communities in Developing Countries
Authors: Orosz Matthew S. , Mueller Amy V.
Published: October 2015

Energy infrastructure in rural areas of developing countries is currently deployed on an ad-hoc basis via grid extension, public and private sector solar home system (SHS) service using photovoltaic (PV) panels, and community distributed generation systems, also called mini or micro grids. Universal access to energy is increasingly pursued as a policy objective via e.g. the U.N. Millennium Develop Goals (MDG), Sustainable Energy for All (SE4All), and U.S. Power Africa initiatives. Rational allocation of energy infrastructure for 1.6b people currently lacking access requires a screening process to determine the economic break-even distance and consumer connection density favoring topologically diverse energy technology approaches. Previous efforts have developed approaches to determine grid-connection break-even distances, but work on micro-grid and SHS break-even distance and density is limited.

The present work develops an open access modeling platform with the ability to simulate various configurations of PV, Concentrating Solar Power (CSP), and fueled generator backup systems with exhaust waste heat recovery. Battery and thermal storage options are examined, and typical meteorological year (TMY) data is combined with probabilistic and empirical load curve data to represent the appropriate physical dynamics. Power flow control strategy and infrastructure is optimized for a minimum tariff (USD/kWh) for cost recovery. Cost functions derived from manufacturers’ data enable performance and economic assessment for a case study micro grid in Lesotho.
Fast Demand Response for Building Clusters
Authors: Srivastava Sanjeev , Song Zhen , Okunev Dmitriy
Published: October 2015

This paper describes an approach for performing fast demand response involving a cluster of buildings. This approach is adaptive as well as distributed in nature. The approach is adaptive in the sense that the amount of targeted demand reduction, in an interval, is adjusted based on the performance of demand response actions executed in the last interval. The approach is distributed because the demand reduction is performed in each building in such a way that a global demand reduction target is met while the costs of performing the demand reduction actions are minimized. The developed method was implemented on a cluster of three buildings situated at U.S. Air Force Academy in Colorado Springs, CO. The results show that the developed approach was able to meet the demand reduction target, which was based on the amount of actual load that were deemed controllable for the DR events.
Quantifying the Greenhouse Gas Impact of Pathways for Treatment of Secondary Resources Generated in the Food Supply Chain
Authors: Ebner Jacqueline , Williamson Anahita , Trabold Thomas
Published: October 2015

Food processors and retailers are under increasing regulatory and market pressure to manage their food waste in an environmentally responsible way. This study analyzes the climate change impacts of several alternatives available for the management of the several food wastes generated in this sector. Four food chain wastes are selected: whey, apple pomace, grease trap waste and bakery waste. Four treatment pathways were analyzed: landfill, anaerobic digestion, land application and animal feed. The results of the analysis showed significant differences among the pathways with climate change impact varying from −621 kgCO2e/t to 1924 kgCO2e/t. Landfilling of food waste resulted in the highest impacts and diversion to feed animals resulted in net benefits. The moisture content of the waste proved to be an important factor while the bio-degradability and nutrient value also had an influence. The combined impacts of diverting food waste from one disposal pathway to an alternative pathway were also considered and data is provided on the optimal pathways for each food waste alternatives.
Expansion Tank Structural Reconstruction for Central Heating Systems With Re-Engineering Consideration and Energetic Losses Minimization
Authors: Mohsenian Hamed , Ghadamian Hossein , Hamidi Ali Asghar , Alizad Karim
Published: October 2015

Open expansion tanks are applied vastly in central heating and air-conditioning systems. Central heating systems are subjected to great deals of energy losses, owing to the lack of proper design. In this paper, the structure of Open Expansion Tanks is revised and some modifications for reducing energy and heat loss are made to their elements. Moreover, some common designs available in the market are studied in order to better recognize their defects and capabilities. To reach an efficient design, several scenarios are tested using Computational methods (CFD based). In order to validate the new design, an experimental model was created and heat and energy survey operations were performed. The results of energy auditing were analyzed to show the convergence of numerical and experimental models. Additionally, the proposed model was economically evaluated. The final presented model named “Optimized OET with twin containers” is capable of reducing the energy loss by 85 to 95 percent.
High-Temperature Heat Transport and Storage Using LBE Alloy for Concentrated Solar Power System
Authors: Kim Jin-Soo , Dawson Adrian , Wilson Robert , Venkatesan Kishore , Stein Wesley
Published: October 2015

Liquid metals have received growing attention as a potential replacement for more conventional heat transfer fluids in concentrated solar power (CSP) systems. Owing to liquid metals high thermal conductivity, an increase in solar receiver efficiency as well as higher serviceable temperatures could enable more advanced power cycles to be integrated to the CSP system. Recently, CSIRO carried out research on a solar air turbine system which includes a demonstration of a high-temperature pressurized air receiver combined with high-temperature thermal storage. Since the operation temperature of a solar air turbine system is much higher than that of conventional CSP systems, Lead-Bismuth Eutectic (LBE) alloy was chosen for its favorable high temperature heat transport properties and relative ease of storage. The heat test apparatus consisted of a LBE-air heat exchanger, storage tanks with internal heating elements and a pumping system developed by CSIRO. During the test, approximately 1,000 kg of LBE was successfully pumped while capturing and storing approximately 35MJ of solar energy. The test successfully transferred heat from the solar air receiver to the LBE, with the temperature of stored LBE reaching over 770 °C.

This paper will present the concept of the test system, design of its components, procedures and results of the test, and also lessons learnt.
Amino-Functionalized Silica Materials for Carbon Dioxide Capture
Authors: Abbo Hanna , Piet Marvin , Titinchi Salam , Schwieger Wilhelm , Bolland Olav
Published: October 2015

Amine-functionalized mesoporous silica has attracted much attention as a promising chemical sorbent for capturing carbon dioxide. It has the combination of several features viz., high adsorption capacity, high selectivity toward CO2, fast kinetics, mild conditions for desorption and should be stable under operating conditions.

In this study, a chemical grafting route has been developed to synthesize mesoporous adsorbents with amines functionalization for CO2 capture. The initial silylation step was achieved by grafting of different silane linkers (3-aminopropyl)-trimethoxysilane (APS) and 3-chloropropyl)-trimethoxysilane (CPS) via direct condensation and hydrolysis reaction. After silylation the CPS-supports was reacted with tris(2-aminoethyl)amine (TREN) to introduce the amine group to increase the adsorptive capabilities for these sorbents. The synthesized sorbents were characterized by N2 adsorption/desorption, XRD, FTIR and HR-SEM. The adsorption capacities of the modified solid sorbents show a significant enhancement in their adsorption capacity by 3–4 times higher than that of the parent materials which indicate the affirmative impact of amines for CO2 adsorption after grafting.
Sustainable Techniques for Public School in Florida: Application of the Sustainable Urban Drainage System (SUDS)
Authors: Abdulraheem Sahar , Nawari Nawari O.
Published: October 2015

Floods are among the most common natural hazards in Florida. They are threatening the safety and economic welfare of Floridians. Every year Florida spends millions of dollar to mitigate direct flood damages. Amongst the effective solutions to these flood damages is the control of urban drainage in school buildings and nearby grounds to conserve and preserve natural resources and to promote sustainable thinking.

This paper discusses how public schools in Florida can benefit from sustainable techniques by applying the sustainable urban drainage system (SUDS) to school designs. The article also illustrates how Florida can use school sites as double functions to provide an active educational environment and to manage storm water runoff at the same time. Construction costs estimation for sustainable techniques is calculated based on data available for the year 2011 and compared with the conventional construction methods for schools.

The result indicates a high initial cost that can easily be offset by considering the cost of conventional drainage structure, conserved storm water, flooding impact, storm water sewage disposal, and other measures.
Thermodynamic Investigation of Concentrating Solar Power With Thermochemical Storage
Authors: Gorman Brandon T. , Johnson Nathan G. , Miller James E. , Stechel Ellen B.
Published: October 2015

Concentrating solar power systems coupled to energy storage schemes, e.g. storage of sensible energy in a heat transfer fluid, are attractive options to reduce the transient effects of clouding on solar power output and to provide power after sunset and before sunrise. Common heat transfer fluids used to capture heat in a solar receiver include steam, oil, molten salt, and air. These high temperature fluids can be stored so that electric power can be produced on demand, limited primarily by the size of the capacity and the energy density of the storage mechanism. Phase changing fluids can increase the amount of stored energy relative to non-phase changing fluids due to the heat of vaporization or the heat of fusion. Reversible chemical reactions can also store heat; an endothermic reaction captures the heat, the chemical products are stored, and an exothermic reaction later releases the heat and returns the chemical compound to its initial state. Ongoing research is investigating the scientific and commercial potential of such reaction cycles with, for example, reduction (endothermic) and re-oxidation (exothermic) of metal oxide particles. This study includes thermodynamic analyses and considerations for component sizing of concentrating solar power towers with redox active metal oxide based thermochemical storage to reach target electrical output capacities of 0.1 MW to 100 MW. System-wide analyses here use one-dimensional energy and mass balances for the solar field, solar receiver reduction reactor, hot reduced particle storage, re-oxidizer reactor, power block, cold particle storage, and other components pertinent to the design. This work is part of a US Department of Energy (DOE) SunShot project entitled High Performance Reduction Oxidation of Metal Oxides for Thermochemical Energy Storage (PROMOTES).
Dependency of the Power of the Constant Phase Element to Operating Conditions in Proton Exchange Membrane Fuel Cells
Authors: Niya Seyed Mohammad Rezaei , Phillips Ryan , Hoorfar Mina
Published: October 2015

Despite the numerous studies conducted on the constant phase element (CPE) characteristics, they are not fully understood yet. In this paper, the constant phase element required for modeling the impedance characteristics of the proton exchange membrane fuel cells are studied in different operating conditions. The impedance of the cell is measured in different temperatures, anode and cathode relative humidities and potentials (current densities). Then, the powers of the constant phase elements required for modeling the most dominant arc in the measured Nyquist plots are determined, and the values are compared in different operating conditions using the analysis of variance method. It is shown that the CPE power is not related to the temperature and relative humidities; while it changes slightly when the potential or current density changes.
Performance of a High Temperature Proton Exchange Membrane Fuel Cell (HT-PEMFC) Operating on Simulated Reformate
Authors: Waller Michael G. , Walluk Mark R. , Trabold Thomas A.
Published: October 2015

Conventional proton exchange membrane (PEM) fuel cell systems suffer from requiring high purity hydrogen, necessitating a costly on-board hydrogen storage tank to be incorporated into the overall system design. One method to overcome this barrier is to use an on-board reforming system fueled by some sort of hydrocarbon. Unfortunately though, most fuel reforming processes generate significant amounts of impurities, such as CO and CO2, requiring a costly and complex upfront reforming system that is unwieldy for a practical system. High temperature PEM fuel cells based on acid doped polybenzimidazole (PBI), are capable of operating on lower quality reformed hydrogen, allowing for a simplified on-board fuel reforming system design to be envisioned. Advances in high temperature PEM fuel cells have progressed to the point where they are now a commercially viable technology. However, there remains a lack of published literature on the performance of HT-PEMFCs operating on common reformate effluent compositions consisting primarily of H2, CO, CO2, and N2. In this work, the performance of PBI-based HT-PEMFCs are evaluated under simulated reformate compositions.
A Novel Fuzzy Schema to Control the Temperature and Humidification of PEM Fuel Cell System
Authors: Jayakumar Arunkumar , Ramos Maximiano , Al-Jumaily Ahmed
Published: October 2015

The present paper proposes a simple yet effective technique to improve the performance of a practical PEM fuel cell system by tuning the two key operating parameters based on the expert’s rules derived from the literature. The fuzzy rule base is designed to optimally control the temperature and humidification of the two critical parameters governing the fuel cell system performance and dynamics. The modelling of the proposed methodology is presented through the Matlab/fuzzy logic toolbox.
Lessons Learned and Improvements in ANL Plant Dynamics Code Simulation of Experimental S-CO2 Loops
Authors: Moisseytsev Anton , Sienicki James J.
Published: October 2015

Validation of the ANL Plant Dynamics Code with the experimental data from integral S-CO2 cycle facilities has been continued. Several code modifications as well as modeling approaches and assumptions were introduced to improve both the code’s capabilities in modeling the experimental loops and the agreement of the code prediction with the experimental data. The lessons learned from the code improvement and modeling experience important for the validation of the codes with the experimental data from small-scale integral loops are presented.
Sensitivity Evaluation of the Daily Thermal Predictions of the AGR-2 Experiment in the Advanced Test Reactor
Authors: Hawkes Grant L. , Sterbentz James W. , Pham Binh T.
Published: October 2015

A temperature sensitivity evaluation has been performed for an individual test capsule in the AGR-2 TRISO particle fuel experiment. The AGR-2 experiment is the second in a series of fueled test experiments for TRISO coated fuel particles run in the Advanced Test Reactor at the Idaho National Laboratory. A series of cases were compared to a base case by varying different input parameters in an ABAQUS finite element thermal model. Most input parameters were varied by ±10%, with one parameter ±20%, to show the temperature sensitivity to each parameter. The most sensitive parameters were the outer control gap distance, heat rate in the fuel compacts, and neon gas fraction. The thermal conductivity of the fuel compacts and thermal conductivity of the graphite holder were of moderate sensitivity. The least sensitive parameters were the emissivities of the stainless steel and graphite, along with gamma heat rate in the non-fueled components. Sensitivity calculations were also performed for the fast neutron fluence, which showed a general, but minimal, temperature rise with increasing fluence.
Efficient Cogeneration Design Applying New Rules in Mexico
Authors: Vega-Galaz Jose Ramon , Sañudo-López Daniel
Published: October 2015

At the end of 2011, the Mexican Regulatory Energy Commission (CRE) has issued new rules to comply as efficient cogeneration plant. At this moment, there are some cogeneration plants under construction trying to accomplish these rules consisting in minimal design and operation parameters to overcome the current public power system efficiency. These rules can also be applied to those cogeneration plants currently operating. The approved efficient cogeneration plant can be considered as green energy in order to receive incentives to improve economic behavior of these kinds of plants. Basically, the wheeling cost is reduced compared to conventional power plants, the energy bank may be applied to swap energy and match production with demand. Also, interconnection services with public utility are offered cheaper. From the point of view of taxes the efficient cogeneration plant may be depreciated 100% the first year. However these incentives are not clear for the energy reform just signed by the Congress. This paper explains how these new rules from 2013 were applied in the design and construction of a new cogeneration plant.
Technical/Technological Advances for Optimizing Heat Rate
Authors: Raj Komandur Sunder
Published: October 2015

Heat rate in a power plant cycle is a calculated value expressed as the ratio of the amount of heat supplied to the cycle divided by the amount of power that is generated. It is directly affected by the heat source and associated auxiliaries, the prime mover, the regenerative feedwater heating cycle and, the heat sink.

Heat rate computations also suffer from imprecision/time lags associated with fuel flow measurements, difficulties/uncertainties in determination of the actual amount of heat supplied to the power plant cycle and, measurement of the power that is generated. Consequently, many power plant owners and operators have reservations as to the intrinsic value of heat rate as a performance metric, since detailed analysis and evaluation of the underlying causes and issues are essential to account for deviations from predicted or expected values.

Several innovations and advances have paved the way for real-time monitoring, trending, analyzing, evaluating, diagnosing and optimizing power generating asset performance. Using a coal-fired unit as a representative case study, this paper provides an overview of how technical/technological advances in optimizing power generating asset performance facilitate concomitant optimization of heat rate.
The Impact of Qualified Bolting Specialists on the Safe, Reliable Assembly and Operation of Bolted Flanged Connections
Authors: Waterland A. Fitzgerald (Jerry) , Lay David , Dodge Michael
Published: October 2015

Why do we certify welders but require no evidence of training or competence from those performing the critical bolted flanged joint assembly of pressure vessels and piping throughout the same industries? To remedy this situation ASME has recently released the first comprehensive standard in ASME PCC-1-2013 Appendix A that establishes uniform criteria, not just for the quality of the bolted joints but for the workers who assemble them. To support this critical training and qualification standard, ASME Training & Development has created a unique blended learning program for pipe fitters and mechanics to become Qualified Bolting Specialists (QBS), per the requirements outlined in PCC-1-2013 Appendix A.

The purpose of this technical presentation is to explain the opportunities presented by this new standard and how industry can benefit from a better-trained work force in this critical area of bolted joint assembly. The authors have been integrally involved in the development of both the PCC-1 guideline document, and the ASME qualification program, and can authoritatively answer industry’s questions.
Modeling Power Generation Water Usage
Authors: Peck Jaron J. , Smith Amanda D.
Published: October 2015

Climate change can have a large effect on thermoelectric power generation. Typical thermoelectric power plants rely on water to cool steam in the condenser in order to produce electricity. Increasing global temperatures can increase average water temperatures as well as decrease the amount of water available for cooling due to evaporation. It is important to know how these parameters can affect power generation and efficiency of power systems, especially when assessing the water needs of a plant for a desired power output and whether a site can fulfill those needs. This paper explains the development of a model that shows how power and efficiency are affected due to changing water temperature and water availability for plants operating on a Rankine cycle. Both a general model of the simple Rankine cycle as well as modifications for regeneration and feedwater heating are presented. Power plants are analyzed for two different types of cooling systems: once-through cooling and closed circuit cooling with a cooling tower. Generally, rising temperatures in cooling water have been found to lower power generation and efficiency. Here, we present a method for quantifying power output and efficiency reductions due to changes in cooling water flow rates or water temperatures. Using specified plant parameters, such as boiler temperature and pressure, power and efficiency are modeled over a 5°C temperature range of inlet cooling water. It was found that over this temperature range, power decrease ranged from 2–3.5% for once through cooling systems, depending on the power system, and 0.7% for plants with closed circuit cooling. This shows that once-through systems are more vulnerable to changing temperatures than cooling tower systems. The model is also applied to Carbon Plant, a coal fired power plant in Utah that withdraws water from the Price River, to show how power and efficiency change as the temperature of the water changes using USGS data obtained for the Price River. The model can be applied to other thermoelectric power stations, whether actual or proposed, to investigate the effects of water conditions on projected power output and plant efficiency.
Analysis of a Solar Updraft Tower Utilizing Compost Waste Heat
Authors: Anderson Kevin R. , Shafahi Maryam , McNamara Chris , Schroeder Wesley , Owen David , Castillo Ivan
Published: October 2015

This paper presents the results for a feasibility study of a solar chimney which uses low-grade waste heat from compost in conjunction with solar energy transmitted via a transparent roof top. The feasibility study shows that the solar chimney’s turbine power increases with pressure ratio, the height of the chimney as well as the differential temperature in the chamber. This paper also outlines the thermodynamic modeling related to using waste heat from composting to increase the air temperature in the inlet chamber of a solar chimney. It is found that from this analysis that the average temperature in the chamber increases as a function of the chimney inlet chamber axial length. For a chimney 1150 ft (350 m) high and 24 ft (7.3 m) in diameter processing 8000 tons of composting material it is found that a power output of 38 kW can be harnessed at the turbine.
PIV Characterization of the Air Flow in a Scale Model of a Hydrogenerator
Authors: Bach Emmanuel , Mydlarski Laurent , Torriano Federico , Charest-Fournier Jean-Philippe , Sirois Hubert , Morissette Jean-François , Hudon Claude
Published: October 2015

In hydroelectric power plants, generators are essential components and, like all machines, generate heat due to losses. The most common way to evacuate this heat is by circulating a cooling fluid (generally air) through the generator’s components. Due to the geometrical complexity, it is quite challenging to simulate the flow to predict the cooling in a generator, and in-situ measurements are costly and difficult to perform due to the limited access. For this reason, a 1:4 scale model of a hydroelectric generator was built at the research institute of Hydro-Québec (IREQ). In this paper, particle image velocimetry (PIV) measurements of the flow in the opening of the generator scale model pit, in the space between the enclosure wall and the cooler exit, at the cooler exit, in the covers, in the air gap and in the interpole region are presented. Experimental aspects pertaining to the seeding of the flow, calibration targets, and experimental method are also discussed. Furthermore, a comparison of the experimental data with CFD (Computational Fluid Dynamics) simulation results using ANSYS-CFX is given.
Auto-Mapping of Tactical Grid Topology Through the Use of a Power Beacon
Authors: Miller Michael A. , Gibbons Greg , Curtiss Peter S.
Published: October 2015

The world of intelligent microgrids and smart grids is rapidly evolving, with new technologies frequently emerging. Integrating “smart” controls into tactical or mobile grids is critical for remote locations that may not have access to utility power. This paper describes research on a process by which a power network topology can be automatically mapped, allowing the control system to identify which equipment is powered by a specific generator. Called the power beacon, this technology is designed to be used in cases where electric subgrids can be joined or split to accommodate power sharing for tactical or emergency power grids.

The power beacon operates by issuing a brief current that can be measured at the generation source. Each load in the power grid is retrofitted with the simple and inexpensive circuitry to create this signal. If the grid configuration changes, an iterative process is used so that the location of each load with respect to its power source can be automatically and rapidly determined.

Research and development of the power beacon evaluated various methods for generating the current pulses. Initial testing of the concept included shaping of the pulse to reduce noise, as well as testing open and closed loop pulse generation with and without feedback. The development also addressed pulse frequency to help mitigate the negative effect the load inductance will have on power beacon operations.

The design process and results from initial testing acted as a proof of concept. Based on the initial results of system testing, modifications were made to handle electrical “noise” coming from the sample power distribution system. The new design integrated a digital filter for noise rejection and increased the current pulse amplitude. These adjustments were tested and indicated significant improvement. The updated power beacon has been installed in a demonstration power distribution system to continue evaluation of viability.
A Novel Boiler Design for High-Sodium Coal in Power Generation
Authors: Wu Song , Bai Wengang , Tang Chunli , Tan Xiaowen , Wang Chang’an , Che Defu
Published: October 2015

Considering the severe fouling of high temperature convection pass in the boilers using high-sodium coals, a novel boiler design with a furnace exit gas temperature (FEGT) below 800 °C was proposed. The design was evaluated in different kinds of boilers with various capacities by examining thermal system arrangement, heat transfer, ignition and combustion, and steel consumption. The results indicate that, more radiation heating surface should be used in the thermal system arrangement of the novel boiler besides the volume-enlarged furnace. A marked decrease in the converted coefficient of radiation heat transfer is found in a volume-enlarged furnace due to the reduction in the average temperature of the flame. Moreover, the volume-enlarged furnace can adversely affect ignition and combustion. The cyclone-fired boiler is considered to be the most appropriate application for the novel design, for its combustion and heat transfer in furnace are carried out in divided chambers. A comparison of steel consumption demonstrates the expense of the novel boiler is approximately increased by 10% relative to the conventional one. In addition, an improved application with flue gas recirculation is described in detail, owing to its advantages of controlling FEGT and maintaining the level of convection heat transfer capability of the boiler.
Identification of Energy Storage Capacities Within Large-Scale Power Plants and Development of Control Strategies to Increase Marketable Grid Services
Authors: Huebel Moritz , Nocke Juergen , Meinke Sebastian , Hassel Egon
Published: October 2015

In order to meet future demands, existing and new plants need to be optimized to offer additional control reserves to stabilize an electrical grid, which is highly penetrated by fluctuating renewables. Since this requires a dynamic investigation, transient physical based models of different power plants have been developed to evaluate effects of increased flexibility as well as to develop optimization strategies. The approach has been tested for a specific 500 MW lignite-fired power plant. It includes detailed modeling of the incorporated sub-systems and their interactions as well as the implementation of the power plant’s control system. The dynamic simulation model is used for the identification of energy storage potentials within the process and for testing and developing control strategies in order to increase flexibility and marketable output of the process. The strategies are benchmarked and evaluated based on the consideration of exergetic efficiency and lifetime-consumption of critical components.
Design of an Ammonia Synthesis System for Producing Supercritical Steam in the Context of Thermochemical Energy Storage
Authors: Chen Chen , Lovegrove Keith , Kavehpour H. Pirouz , Lavine Adrienne S.
Published: October 2015

Concentrating solar power plants typically incorporate thermal energy storage, e.g. molten salt tanks. The broad category of thermochemical energy storage, in which energy is stored in chemical bonds, has the advantage of higher energy density as compared to sensible energy storage. In the ammonia-based thermal energy storage system, ammonia is dissociated endothermically as it absorbs solar energy during the daytime. The stored energy can be released on demand (for electricity generation) when the supercritical hydrogen and nitrogen react exothermically to synthesize ammonia. Using ammonia as a thermochemical storage system was validated at Australian National University (ANU), but ammonia synthesis has not yet been shown to reach temperatures consistent with the highest performance modern power blocks such as a supercritical steam Rankine cycle requiring steam to be heated to ∼650°C. This paper explores the preliminary design of an ammonia synthesis system that is intended to heat steam from 350°C to 650°C under pressure of 26 MPa. A two-dimensional pseudo-homogeneous model for packed bed reactors previously used at ANU is adopted to simulate the ammonia synthesis reactor. The reaction kinetics are modeled using the Temkin-Pyzhev reaction rate equation. The model is extended by accounting for convection in the steam to predict the behavior of the proposed synthesis reactor. A parametric investigation is performed and the results show that heat transfer plays the predominant role in improving reactor performance.
A Comparative Study of Different Methods of Correcting Combined Cycle Thermal Performance
Authors: Nanjappa Jagadish
Published: October 2015

The power output and heat rate (or efficiency) of a combined cycle power plant are expressed in the Power Industry at a specified set of “reference conditions”. Some of these reference conditions pertain to the test boundary (eg. ambient air temperature, barometric pressure etc.) while some others pertain to the operating condition (eg. baseload, evaporative cooler status, etc.) within the plant boundary. The process of measuring the actual thermal performance of a combined cycle plant involves conducting a test wherein the plant is operated at the pre-determined set of operating conditions that enable minimizing deviations from the “reference conditions”. It is a well-known fact that despite all efforts made during such a test, the actual boundary and operating conditions that prevail at the time of the test will not necessarily be identical to the pre-defined set of “reference conditions”. Hence, in order to evaluate the performance levels of the plant, one of the essential steps in the testing process is to “correct” the measured power output and heat consumption (or heat rate) for differences that persist between the actual test conditions and the corresponding set of “reference conditions”. This “correction” can be performed by using either a correction curve-based approach or a model-based approach.

When a correction curve-based approach is used, the effects of the boundary conditions on the relevant performance parameter (output, heat consumption or heat rate) can be depicted as an additive correction term or as a multiplicative correction term. As such, the corrections to the boundary conditions can be applied as either a) additive or b) multiplicative or c) a combination of additive and multiplicative referred to as “hybrid”. The prevailing industry code for testing combined cycle power plants, ASME PTC 46, has adopted the “hybrid” method while the codes for testing individual equipment (such as PTC 22, PTC 6.2, PTC 6) have adopted either the additive philosophy or the multiplicative philosophy or a “hybrid” philosophy similar to PTC 46.

The purpose of this paper is to present the outcome of a study that compares the three different correction methods utilizing the correction curve approach for a combined cycle power plant. The studies were based on thermodynamic simulations performed on different plant configurations. A key result will be the quantification of the errors associated with the different methods, which are primarily a function of the ability of the different methods to inherently capture the interactions between the various boundary parameters in the correction process and are a representation of the uncertainty associated with the particular correction method. Furthermore, the paper will introduce a new calculation method and provide recommendations that will help improve the accuracies of test results.
Analysis and Comparison Between Fixed and Variable Volume Ratio Expander for Micro-Scale ORC
Authors: Gusev Sergei , van den Broek Martijn
Published: October 2015

Waste heat recovery has become very important in the last decennia. The Organic Rankine Cycle is the most popular technology to transform waste heat into mechanical work or electricity. While large and medium scale installations are widely available on the market for various temperature and power levels, small scale ORCs are still in a pre-commercial phase because of a relatively high specific price.

To make small scale ORCs more attractive for potential customers, the price has to be drastically reduced which means reducing the manufacturing and assembling operations, the number of parts in assemblies and unification of these assemblies. In addition, the performance has to be increased by using advanced cycle architectures and the right fluids. Not only the right choice of the working fluid is important but also the expander built-in volume ratio (BVR) has to be optimal or improved. Neither a fixed volume ratio expander, nor a turbine can provide an optimal expansion of a working fluid in a wide range of operating conditions [1]. In automotive applications, for instance, a strongly fluctuating heat input will be introduced to an ORC unit.

To estimate losses caused by non-optimal operation, a model of a volumetric expander has been developed and verified using the result of extensive test campaigns with a screw expander. The volume ratio of the expander mentioned cannot be physically changed, so under widely changing pressure ratio, caused by varying inlet waste heat and ambient temperatures, it operates mostly far from its design point. The model gives a possibility to vary the BVR in order to compare a fixed-volume ratio expander with a variable one. Benefits from replacement of this expander by an adaptive one are studied. Only steady states are taken into account since there is no dynamic model of this expander developed yet. As a consequence of the results obtained, a concept of a variable volume ratio expander is proposed.
Effect of Inlet Steam Temperature on the HP Section Efficiency of a Steam Turbine
Authors: Fu Yiping , Winterberger Thomas
Published: October 2015

Steam turbines for modern fossil and combined cycle power plants typically utilize a reheat cycle with High Pressure (HP), Intermediate Pressure (IP), and Low Pressure (LP) turbine sections. For an HP turbine section operating entirely in the superheat region, section efficiency can be calculated based on pressure and temperature measurements at the inlet and exhaust. For this case HP section efficiency is normally assumed to be a constant value over a load range if inlet control valve position and section pressure ratio remain constant.

It has been observed that changes in inlet steam temperature impact HP section efficiency. K.C. Cotton stated that ‘the effect of throttle temperature on HP turbine efficiency is significant’ in his book ‘Evaluating and Improving Steam Turbine Performance’ (2nd Edition, 1998). The information and conclusions provided by K.C. Cotton are based on test results for large fossil units calculated with 1967 ASME steam tables. Since the time of Mr. Cotton’s observations, turbine configurations have evolved, more accurate 1997 ASME steam tables have been released, and our ability to quickly analyze large quantities of data has greatly increased.

This paper studies the relationship between inlet steam temperature and HP section efficiency based on both 1967 and 1997 ASME steam tables and recent test data, which is analyzed computationally to reveal patterns and trends. With the efficiencies of various inlet pressure class HP section turbines being calculated with both 1967 and 1997 ASME steam tables, a comparison reveals different characteristics in the relationship between inlet steam temperature and HP section efficiency. Recommendations are made on how the results may be used to improve accuracy when testing and trending HP section performance.
Impact of Plant Cycling on Availability
Authors: Kumar Nikhil , Ouellette Maria , Miller Kurt , Liu Michael C.
Published: October 2015

Evidence is mounting that power plant cycling is causing significant additional wear and tear on the units. However, the effects of this additional wear and tear on future maintenance costs, production cost, and equivalent forced outage rate (EFOR) are not accurately quantified at the present time. For example, units that were originally designed for base load operation are now being cycled by many utilities. Typically, such units experience long-term decreases in availability and significantly increased maintenance and capital equipment expenditures because several materials degradation phenomena (creep, fatigue, creep-fatigue interaction, etc.) are accelerated by increased cycling.

The authors will present results of several hundred studies, which highlight the impacts of plant cycling events on short and long term plant availability. The paper will also show the impact of plant cycling design, annual capital and operating expenses which can have a direct impact on plant availability.