Evaluation of Process and Economic Feasibility of Implementing a Topping Cycle Cogeneration System

Industrial applications that require steam for their end-uses generally utilize steam boilers that are at higher size than what is typically required. Similarly, gas turbine-based power plants corroborate the gas turbine system and eventually relieve the exhaust into the atmosphere. These facilities include food, paper, chemicals, refining, and primary metal manufacturing industries. This research focuses on the scope of a topping cycle combined heat and power (CHP) system by pushing the load on the boiler to a higher limit, or a gas turbine operation in place of a boiler system for a topping cycle CHP and its economic feasibility by utilizing the turbine exhaust to achieve the technological and economical evaluation of a CHP system. The excess steam is run through a condensing steam turbine to generate power that can offset the facility’s electricity usage cost and under favorable conditions, sell electricity back to the grid. Similarly, the steam turbine outlet water can be used to satisfy the plant’s heating needs in the form of comfort and district heating. A decision tool was developed to evaluate the technical and economic feasibility of a topping cycle CHP system, which can emulate a given facility’s steam or gas system and its operational parameters with steam turbines. It will help the user realize the point of breakeven (in terms of fuel cost incurred and overall cost savings) at the desired steam flow rate for a corresponding boiler system. Similarly, sensitive analysis of energy, power, cost savings, and payback of investment to boiler and steam parameters is also carried out. The research would provide necessary insights into the most appropriate parameters that will enable a CHP system to be advantageous in technical and economic aspects. The research determines that the fuel cost, electricity cost, and the steam quantity flowing through the turbines are the most important parameters for a desirable payback on the investment

The Optimization of Combined Power-Power Generation Cycles

An investigation into the performance of several combined gas-steam power generating plants’ cycles was undertaken at the School of Engineering and Technology at the University of Hertfordshire and it is predominantly analytical in nature. The investigation covered in principle the aspect of the fundamentals and the performance parameters of the following cycles: gas turbine, steam turbine, ammonia-water, partial oxidation and the absorption chiller. Complete thermal analysis of the individual cycles was undertaken initially. Subsequently, these were linked to generate a comprehensive computer model which was employed to predict the performance and characteristics of the optimized combination. The developed model was run using various input parameters to test the performance of the cycle’s combination with respect to the combined cycle’s efficiency, power output, specific fuel consumption and the temperature of the stack gases. In addition, the impact of the optimized cycles on the generation of CO2 and NOX was also investigated. This research goes over the thermal power stations of which most of the world electrical energy is currently generated by. Through which, to meet the increase in the electricity consumption and the environmental pollution associated with its production as well as the limitation of the natural hydrocarbon resources necessitated. By making use of the progressive increase of high temperature gases in recent decades, the advent of high temperature material and the use of large compression ratios and generating electricity from high temperature of gas turbine discharge, which is otherwise lost to the environment, a better electrical power is generated by such plant, which depends on a variety of influencing factors. This thesis deals with an investigation undertaken to optimize the performance of the combined Brayton-Rankine power cycles' performance. This work includes a comprehensive review of the previous work reported in the literature on the combined cycles is presented. An evaluation of the performance of combined cycle power plant and its enhancements is detailed to provide: A full understanding of the operational behaviour of the combined power plants, and demonstration of the relevance between power generations and environmental impact. A basic analytical model was constructed for the combined gas (Brayton) and the steam (Rankine) and used in a parametric study to reveal the optimization parameters, and its results were discussed. The role of the parameters of each cycle on the overall performance of the combined power cycle is revealed by assessing the effect of the operating parameters in each individual cycle on the performance of the CCPP. P impacts on the environment were assessed through changes in the fuel consumption and the temperature of stack gases. A comprehensive and detailed analytical model was created for the operation of hypothetical combined cycle power and power plant. Details of the operation of each component in the cycle was modelled and integrated in the overall all combined cycle/plant operation. The cycle/plant simulation and matching as well as the modelling results and their analysis were presented. Two advanced configurations of gas turbine cycle for the combined cycle power plants are selected, investigated, modelled and optimized as a part of combined cycle power plant. Both configurations work on fuel rich combustion, therefore, the combustor model for rich fuel atmosphere was established. Additionally, models were created for the other components of the turbine which work on the same gases. Another model was created for the components of two configurations of ammonia water mixture (kalina) cycle. As integrated to the combined cycle power plant, the optimization strategy considered for these configurations is for them to be powered by the exhaust gases from either the gas turbine or the gases leaving the Rankine boiler (HRSG). This included ChGT regarding its performance and its environmental characteristics. The previously considered combined configuration is integrated by as single and double effect configurations of an ammonia water absorption cooling system (AWACS) for compressor inlet air cooling. Both were investigated and designed for optimizing the triple combination power cycle described above. During this research, tens of functions were constructed using VBA to look up tables linked to either estimating fluids' thermodynamic properties, or to determine a number of parameters regarding the performance of several components. New and very interesting results were obtained, which show the impact of the input parameters of the individual cycles on the performance parameters of a certain combined plant’s cycle. The optimized parameters are of a great practical influence on the application and running condition of the real combined plants. Such influence manifested itself in higher rate of heat recovery, higher combined plant thermal efficiency from those of the individual plants, less harmful emission, better fuel economy and higher power output. Lastly, it could be claimed that various concluding remarks drawn from the current study could help to improve the understanding of the behaviour of the combined cycle and help power plant designers to reduce the time, effort and cost of prototyping

OFF-DESIGN OPERATION OF THE MULTI-FUEL CHP CYCLES

ABSTRACT The paper describes the problems when the operation regime of the CHP cycle is adjusted according to the user demands. The analysis concerns a multi-fuel system, which utilizes biomass, natural gas and coal. The analyzed system consists of a combined gas and steam cycles. The analysis presented here concerns off-design operation caused by part loading, varying ambient conditions and power demands. An appropriate division of the load between the subcycles increases the overall efficiency. The analysis concerns also various options of biomass supply to the system. The research regards mostly the effectiveness criterion as it has a direct influence on the costs of operation. INTRODUCTION Multi-fuel power cycles have become an significant alternative for conventional and combined heat and power plants. One main advantage is a fuel flexibility. Their design is usually fitted for specific user demands and in consequence the operation performs with optimized operation costs. The selection of the basic parameters (power output, amount of the generated heat) is strictly connected to the conditions under which a specified cycle is to operate. This strictly limited selection results in a very good efficiency of the operation in the design regime. However, the range of the off-design regime in which the operation is profitable may be very small. Therefore even the initial choice of the cycle components requires also an analysis of the offdesign operation. The issue of the off-design operation is well-known and studied for most of the machines, which are found in a typical combined cycle

Identifying opportunities for developing CSP and PV-CSP hybrid projects under current tender conditions and market perspectives in MENA – benchmarking with PV-CCGT

Concentrating solar power (CSP) is one of the promising renewable energy technologies provided the fact that it is equipped with a cost-efficient storage system, thermal energy storage (TES). This solves the issue of intermittency of other renewable energy technologies and gives the advantage of achieving higher capacity factors and lower levelized costs of electricity (LCOE). This is the main reason why solar tower power plants (STPP) with molten salts and integrated TES are considered one of the most promising CSP technologies in the short term [1]. On the other hand, solar photovoltaic (PV) is a technology whose costs have been decreasing and are expected to continue doing so thus providing competitive LCOE values, but with relatively low capacity factors as electrical storage systems remain not cost-effective. Combining advantages and eliminating drawbacks of both technologies (CSP and PV), Hybridized PV-CSP power plants can be deemed as a competitive economic solution to offer firm output power when CSP is operated smartly so that its load is regulated in response to the PV output. Indeed previous works, have identified that it would allow achieving lower LCOEs than stand-alone CSP plants by means of allowing it to better utilize the solar field for storing energy during the daytime while PV is used [1]. On the fossil-based generation side, the gas turbine combined cycle (CCGT) occupies an outstanding position among power generation technologies. This is due to the fact that it is considered the most efficient fossil fuel-to-electricity converter, in addition to the maturity of such technology, high flexibility, and the generally low LCOE, which is largely dominated by fuel cost and varies depending on the natural gas price at a specific location. Obviously, the main drawback is the generated carbon emissions. In countries rich in natural gas resources and with vast potential for renewable energies implementation, such as the United Arab Emirates (UAE), abandoning a low LCOE technology with competitively low emissions – compared to coal or oil - and heading to costly pure renewable generation, seems like an aggressive plan. Therefore, hybridizing CCGT with renewable generation can be considered an attractive option for reducing emissions at reasonable costs. This is the case of the UAE with vast resources of both natural gas and solar energy. Previous work have shown the advantages of hybrid PV-CCGT and hybrid PV-CSP plants separately [1][2]. In this thesis, CSP and the two hybrid systems are compared on the basis of LCOE and CO2 emissions for a same firm-power capacity factor when considering a location in the UAE. The results are compared against each other to highlight the benefits of each technology from both environmental and economic standpoints and provide recommendations for future work in the field. The techno-economic analysis of CSP (STPP with TES), PV-CSP(STPP with TES) and PV-CCGT power plants have been performed by DYESOPT, an in-house tool developed in KTH, which runs techno-economic performance evaluation of power plants through multi-objective optimization for specific locations[1]. For this thesis, a convenient location in the UAE was chosen for simulating the performance of the plants. The UAE is endowed by the seventh-largest proven natural gas reserves and average to high global horizontal irradiation (GHI) and direct normal irradiation (DNI) values all year round, values considered to be lower than other countries in the MENA region due to its high aerosol concentrations and sand storms. The plants were designed to provide firm power in two cases, first as baseload, and second as intermediate load of 15 hours from 6:00 until 21:00. The hours of production were selected based on a typical average daily load profile. CSP and PV-CSP model previously developed by [3][1] were used. Ideally in the PV-CSP model, during daytime hours the PV generation is used for electricity production, covering the desired load, while CSP is used partly for electricity production and the rest for storing energy in the TES. Energy in the TES system is then used to supply firm power during both periods of low Irradiance and night hours or according to need. A PV-CCGT model has been developed which operates simultaneously, prioritizing the availability of PV while the CCGT fulfils the remaining requirement. There is a minimum loading for the CCGT plant which is determined by the minimum possible partial loading of the gas turbine restricted by the emission constraints. Accordingly, in some cases during operation PV is chosen to be curtailed due to this limitation. The main results of the techno-economic analysis are concluded in the comparative analysis of the 3 proposed power plant configurations, where the PV-CCGT plant is the most economic with minimum LCOE of 86 USD/MWh, yet, the least preferable option in terms of carbon emissions. CSP and PV-CSP provided higher LCOE, while the PV-CSP plant configuration met the same capacity factor with 11% reduction in LCOE, compared to CSP

Topcycle: A novel high performance and fuel flexible gas turbine cycle

High pressure humidified cycles can combine high operational flexibility and high thermal efficiency. The current work introduces such a cycle, namely TopCycle, which provides the necessary combustion infrastructure to operate on a wide fuel variety in a steam-rich atmosphere. The cycle configuration is presented in detail, and its operation is exemplified on the basis of simulation results. Operation at design condition results in electric efficiencies higher than 50% (lower heating value (LHV)) and power densities higher than 2100 kW/kgair (referred to intake air flow). A sensitivity analysis identifies the cycle performance as a function of representative parameters, which provide the basis for future operation and design improvements. As for any gas turbine cycle, TopCycle’s electric efficiency can be effectively improved by increasing the turbine inlet temperature, optimizing the economizer heat recovery, as well as elevating the working pressure. Finally, TopCycle’s performance is compared to a state-of-the-art combined cycle (CC) at equivalent operation parameters. The TopCycle operates at an elevated electric efficiency and considerably higher power density, which can be transferred into smaller plant footprint and dimensions and thus lower investment costs at equal power output in comparison to a C

Case study of an Organic Rankine Cycle (ORC) for waste heat recovery from an Electric Arc Furnace (EAF)

The organic Rankine cycle (ORC) is a mature technology for the conversion of waste heat to electricity. Although many energy intensive industries could benefit significantly from the integration of ORC technology, its current adoption rate is limited. One important reason for this arises from the difficulty of prospective investors and end-users to recognize and, ultimately, realise the potential energy savings from such deployment. In recent years, electric arc furnaces (EAF) have been identified as particularly interesting candidates for the implementation of waste heat recovery projects. Therefore, in this work, the integration of an ORC system into a 100 MWe EAF is investigated. The effect of evaluations based on averaged heat profiles, a steam buffer and optimized ORC architectures is investigated. The results show that it is crucial to take into account the heat profile variations for the typical batch process of an EAF. An optimized subcritical ORC system is found capable of generating a net electrical output of 752 kWe with a steam buffer working at 25 bar. If combined heating is considered, the ORC system can be optimized to generate 521 kWe of electricity, while also delivering 4.52 MW of heat. Finally, an increased power output (by 26% with combined heating, and by 39% without combined heating) can be achieved by using high temperature thermal oil for buffering instead of a steam loop; however, the use of thermal oil in these applications has been until now typically discouraged due to flammability concerns

Carbon capture from natural gas combined cycle power plants: Solvent performance comparison at an industrial scale

Natural gas is an important source of energy. This article addresses the problem of integrating an existing natural gas combined cycle (NGCC) power plant with a carbon capture process using various solvents. The power plant and capture process have mutual interactions in terms of the flue gas flow rate and composition vs. the extracted steam required for solvent regeneration. Therefore, evaluating solvent performance at a single (nominal) operating point is not indicative and solvent performance should be considered subject to the overall process operability and over a wide range of operating conditions. In the present research, a novel optimization framework was developed in which design and operation of the capture process are optimized simultaneously and their interactions with the upstream power plant are fully captured. The developed framework was applied for solvent comparison which demonstrated that GCCmax, a newly developed solvent, features superior performances compared to the monoethanolamine baseline solvent

A technical evaluation, performance analysis and risk assessment of multiple novel oxy-turbine power cycles with complete CO2 capture

In recent years there has been growing concern about greenhouse gas emissions (particularly CO2 emissions) and global warming. Oxyfuel combustion is one of the key technologies for tackling CO2 emissions in the power industry and reducing their contribution to global warming. The technology involves burning fuel with high-purity oxygen to generate mainly CO2 and steam, enabling easy CO2 separation from the flue gases by steam condensation. In fact, 100% CO2 capture and near-zero NOx emissions can be achieved with this technology. This study examines nineteen different oxy-turbine cycles, identifying the main parameters regarding their operation and development. It also analyses the use of advanced natural gas combustion cycles from the point of view of the carbon capture and storage (CCS) and considering political, legislative and social aspects of deploying this technology. Six oxy-turbine cycles which are at the most advanced stages of development (NetPower, CES, Modified Graz, E-MATIANT, AZEP100% and SCOC-CC), were chosen to conduct a Political, Environmental, Social, Technological, Legislative and Economic (PESTLE) risk analysis. This compares each technology with a conventional combined cycle gas turbine (CCGT) power plant without carbon capture as the base-case scenario. Overall, the net efficiency of the different oxy-turbine cycles ranges between 43.6% and 65%, comparable to a CCGT power plant, while providing the extra benefits of CO2 capture and lower emissions. A multi-criteria analysis carried out using DECERNS (Decision Evaluation in Complex Risk Network Systems) software determined that, depending on the specific criterion considered, one can draw different conclusions. However, in terms of technology, environment and social opinion, the most promising cycles are the NetPower and CES cycles, whereas from an economic point of view, E-MATIANT is more competitive in the energy market. Giving each factor equal importance, the NetPower cycle must be considered to be the best oxy-turbine cycle based on our analysis. Most of the oxy-turbine cycles are still under development and only a few cycles (e.g., CES and NetPower) are progressing to the demonstration phase. In consequence, political measures such as CO2 tax and emission allowances need to be implemented for oxy-turbine technologies to become the preferred option for fossil fuel power plants burning natural gas. Key Words: Carbon capture and storage, oxy-turbine power cycle, air separation unit, combined cycle gas turbine, techno-economic analysis, PESTLE risk analysi

Desalination Processes’ Efficiency and Future Roadmap

For future sustainable seawater desalination, the importance of achieving better energy efficiency of the existing 19,500 commercial-scale desalination plants cannot be over emphasized. The major concern of the desalination industry is the inadequate approach to energy efficiency evaluation of diverse seawater desalination processes by omitting the grade of energy supplied. These conventional approaches would suffice if the efficacy comparison were to be conducted for the same energy input processes. The misconception of considering all derived energies as equivalent in the desalination industry has severe economic and environmental consequences. In the realms of the energy and desalination system planners, serious judgmental errors in the process selection of green installations are made unconsciously as the efficacy data are either flawed or inaccurate. Inferior efficacy technologies' implementation decisions were observed in many water-stressed countries that can burden a country's economy immediately with higher unit energy cost as well as cause more undesirable environmental effects on the surroundings. In this article, a standard primary energy-based thermodynamic framework is presented that addresses energy efficacy fairly and accurately. It shows clearly that a thermally driven process consumes 2.5-3% of standard primary energy (SPE) when combined with power plants. A standard universal performance ratio-based evaluation method has been proposed that showed all desalination processes performance varies from 10-14% of the thermodynamic limit. To achieve 2030 sustainability goals, innovative processes are required to meet 25-30% of the thermodynamic limit