Open Cycle Gas Turbine Research Articles

Energy and exergy analysis of biogas fired regenerative gas turbine cycle with CO2 recirculation for oxy-fuel combustion power generation

In this paper, thermodynamic performance of oxy-biogas regenerative gas turbine cycle with CO2 recirculation is evaluated. The CO2 stream is split into the primary and dilution zones. In the primary zone, chemical-equilibrium-model is applied for exergy analysis. Influences of relevant parameters—CO2-to-O2 molar ratio (CtO) in the primary zone and primary diluent ratio (PDR)—on the temperature of combustion chamber (CC) and turbine, net produced power, thermal efficiency, specific fuel consumption (SFC) and CO2 capturing mass flow rate are studied. Decreasing CtO and raising PDR result in high net produced power. Thermal efficiency has a maximum value in the range of CtO (1.5<CtO<4.0) and PDR (0.2<PDR<0.6) and by enhancing CtO, exergy destruction diminishes in both zones. With increasing the CtO in the range of 1.5–2.98, thermal efficiency is increased by 9.92% while variation of CtO in the range of 2.98–4 results in reduction of thermal efficiency by 1.3%. In the range of PDR, the minimum value of SFC is 388 g/kWh and in the range of CtO, the lowest achievable SFC is 387.4 g/kWh. Additionally, dilution zone exergy destruction and CC exergy efficiency increases with PDR and CtO. The two-zone model provided an appropriate control on the turbine inlet temperature.

Power Generation Prediction of an Open Cycle Gas Turbine Using Kalman Filter

The motivation for this paper is the enhanced role of power generation prediction in power plants and power systems in the smart grid paradigm. The proposed approach addresses the impact of the ambient temperature on the performance of an open cycle gas turbine when using the Kalman Filter (KF) technique and the power-temperature (P-T) characteristic of the turbine. Several Kalman Filtering techniques are tested to obtain improved temperature forecasts, which are then used to obtain output power predictions. A typical P-T curve of an open-cycle gas turbine is used to demonstrate the applicability of the proposed method. Nonlinear and linear discrete process models are studied. Extended Kalman Filters are proposed for the nonlinear model. The Time Varying, Time Invariant, and Steady State Kalman Filters are used with the linearized model. Simulation results show that the power generation prediction obtained using the Extended Kalman Filter with the piecewise linear model yields improved forecasts. The linear formulations, though less accurate, are a promising option when a power generation forecast for a small-term and short-term time window is required.

Transient CO2 capture for open-cycle gas turbines in future energy systems

In complex electricity systems with a varied generation mix, the security of supply is important, and the quick-response nature of gas turbines is invaluable in providing system flexibility. Accompanied with post-combustion capture (PCC) of CO2, gas turbines can support the transition to a future low-carbon electricity system. This study presents the development and validation of a dynamic rate-based model of the benchmark CO2 absorption process, using 30 wt% monoethanolamine (MEA). The model is scaled up from pilot-scale to match the flue gas output from a modern small-scale gas turbine operating in open-cycle configuration. Simulations of various flexible operating scenarios shows the rapid transitioning between full and partial load is beneficial in delivering higher time-averaged CO2 capture rates, compared to the Baseload scenario where the PCC system is operated at full load for 5 h. Maintaining a constant liquid/gas (L/G) ratio results in 90.01% CO2 capture; however, this increases the energy demand due to constant reboiler steam flowrate. To compensate, the steam flowrate is also ramped, resulting in a small decrease in reboiler duty compared to the Baseload scenario. Importantly, no negative energy or capture rate related issues to highly-transient PCC operation are found.

Highlighting and overcoming data barriers: creating open data for retrospective analysis of US electric power systems by consolidating publicly available sources

Studies of power system operation commonly draw from two key databases produced by the US Environmental Protection Agency: the Acid Rain Program’s Continuous Emission Monitoring System (CEMS) data, and the Emissions and Generation Resource Integrated Database (eGRID). Separate reporting requirements and heterogeneity in data aggregation between these two databases creates a barrier to systematic spatial and temporal retrospective power system analysis. This work describes the inherent challenges to this undertaking and documents a method for reconciling the two seemingly disparate data sources. While fundamental differences in data reporting and aggregation prevent us from achieving full coverage, this work represents an important initial step to aligning these two repositories of US power system data. We demonstrate the value of this linkage by computing relative unit-level, hourly utilization metrics for most thermal power plants in the US. Analysis of these metrics across time illustrates thermal generator cycling trends in California between 2011 and 2017. These unit-level results indicate that combined cycle units within California increased their part-load generation by 15% and resultant CO2 emissions by 17% and decreased their start/stop frequency over time by 8.5% and resultant emissions by 47%. Open cycle gas turbines overall increased their generation- number of start/stop cycles by 97% and resultant emissions by 85%, part-load generation by 120% and resultant emissions by 100%, and full load generation by 40% and resultant emissions 18%. We also observe a temporal shift in thermal generation from morning hours to evening in California.

An Analysis of Support Mechanisms for New CHPs: The Case of Poland

The increasing demand for energy on a global scale, as well as the social pressure related to counteracting the effects of climate change, has created favourable conditions for the transformation of energy sectors towards the possession of low-emission generation sources. This situation, however, requires investment actions in order to modernise the existing power and CHP (Combined Heat and Power) plants and construct new units. These issues, together with the climate and energy policy pursued by the European Union, are the main reasons for the emergence of various governmental mechanisms supporting the replacement of old coal power units with highly efficient cogeneration units based on gas turbines and other units. The support may take different forms. This article discusses two examples of mechanisms available on the Polish market, i.e., (i) the capacity market and (ii) promoting electricity from high-efficiency cogeneration in the form of individual cogeneration premium. The purpose and novelty of the analysis was to identify the pros and cons and the key parameters which determine the advantage of a given mechanism. Both these mechanisms have been characterised and then compared via the example of a planned cogeneration gas unit (an open cycle gas turbine—OCGT). This assessment was made using discount methods based on the FCFF (free cashflow to company) approach. The analysis did not bring forward an unequivocal answer as to the absolute advantage of any of the solutions, but it was able to point out significant problems related to their practical use.

Development and performance assessment power generating systems using clean hydrogen

In this study, three possible reactions of aluminum - water are considered for clean hydrogen production. The utilization of this clean hydrogen through the two concepts of power generation is investigated thermodynamically. The evaluated first power generation facility based on Al - water reaction has an open cycle gas turbine, steam turbine, boiler, reactor and grinder. The second power generation facility has a fuel cell, a reactor and a grinder. The hydrogen generation resulting from the reactions then the conversion of this hydrogen into energy using turbines or fuel cell and the total exergy destruction are examined comparatively. A thermodynamic analysis is performed with the help of EES (Engineering Equation Solver) software based on the equilibrium reactions in steady state regime. The amount of water required for the hydrogen production is investigated and it is found that the energy efficiencies for the three methods are directly proportional to the amount of water. The energy efficiency for the method 1 based on Bayerite reaction is 38%, the energy efficiency for the method 2 based on boehmite reaction is 56% and the method 3 based on aluminum oxide reaction is 73%. The exergy efficiencies for all methods are calculated at around 41%. When two different power generation concepts are examined, it is observed that combustion-based energy production is more efficient in terms of both energy efficiency and exergy efficiencies.

Role of modeling approach on the results of thermodynamic analysis: Concept presentation via thermoeconomic comparison of biomass gasification-fueled open and closed cycle gas turbines

Thermodynamic analysis of various cycles (for single- or multi-generation systems) is a major topic on which lots of attention is paid in recent years. In such research activities, setting up an experimental rig is very time and money consuming, thus many of research works are conducted theoretically and the results are verified using the available data in literature. However, details of cycle modeling in component level has received little attention, albeit it has crucial effects on the obtained results from theoretical modeling and simulation. To demonstrate this issue in this paper, two different modeling approaches, which have been commonly used in previous literature to model the heat exchangers in thermodynamic cycles, are compared. To attain this goal, a biomass-fueled externally fired closed cycle gas turbine is proposed and its performance is compared with that of conventional open cycle gas turbine. To model the Intermediate Heat Exchanger (IHE), two approaches are considered: Approach (a): assuming a proper value for cold end temperature difference, and Approach (b): assuming a proper value for heat exchanger effectiveness. A comprehensive thermoeconomic analysis is conducted to evaluate the two considered systems’ performance via applying the two modeling approaches. The results revealed that, applying different modeling approaches brings about attaining conflicting outcomes, a conclusion which is not desirable from engineering perspective and reveals the crucial importance of applying appropriate modeling approach. It is found that, via applying approach (b) as the more rational approach, the closed cycle gas turbine yields a lower value of LCOE by 16.3% and a higher value of net output power by 13.5% than the conventional open cycle system.

Effects of thermophysical and thermochemical recuperation on the performance of combined gas turbine and organic rankine cycle power generation system: Thermoeconomic comparison and multi-objective optimization

In this paper, effects on the performance of a combined gas turbine and organic Rankine cycle (GT/ORC) system of using thermophysical and thermochemical recuperation based on methane steam reforming (MSR) process is investigated from the viewpoint of thermoeconomics. For this purpose, three power generation systems consisting of simple GT/ORC, GT/ORC with thermophysical recuperators (TPR) and GT/ORC with thermophysical and thermochemical recuperators (TPCR) are proposed and compared thermodynamically and economically. In addition, the multi-objective optimization using genetic algorithm is conducted for the systems and the systems characteristics at the final optimum design points are compared. Resultsreveals that the thermodynamic, economic and environmental performance of all three proposed power generation systems are enhanced as the combustion temperature raises. In addition, the power generation system with TPR shows the best performance from the thermodynamic perspective with the 22.86% and 27.52% improvement in the exergy efficiency compared to the simple GT/ORC and GT/ORC with TPCR, respectively. However, under the operating thermodynamic conations obtained by the multi-objective optimization approach, the product cost associated with the system using TPCR is less than that of the other configurations.

Performance improvement of biomass-fueled closed cycle gas turbine via compressor inlet cooling using absorption refrigeration; thermoeconomic analysis and multi-objective optimization

Compressor inlet air cooling is a practical and applied methodology to enhance the conventional open cycle gas turbine power plants. This methodology in this paper, is proposed to be applied on an innovative biomass-fueled Closed Cycle Gas Turbine (CCGT), in which the exhaust gas waste heat is utilized to run an ammonia-water absorption refrigeration cycle for compressor inlet cooling. Thermoeconomic analysis is presented to investigate the two systems (with and without inlet cooling) and multi-objective optimization is conducted to compare their performances at optimal operating conditions. Levelized Cost of Electricity (LCOE) and exergy efficiency are selected as the two rational objectives. The results indicated that, for all the practical range of operating conditions, compressor inlet cooling significantly improves the system performance in terms of both thermodynamics and economics, despite the additional costs imposed on the overall system by adding the absorption refrigeration cycle. It is found that, under the optimal operating conditions, incorporation of compressor inlet cooling results in an improvement of net power and exergy efficiency by 30.1%, meanwhile the LCOE would be reduced by 22.5% when inlet cooling is employed.

On Entry Cost Dynamics in Australia’s National Electricity Market

In theory, well designed electricity markets should deliver an efficient mix of technologies at least-cost. But energy market theories and energy market modelling are based upon equilibrium analysis and in practice electricity markets can be off-equilibrium for extended periods. Near-term spot and forward contract prices can and do fall well below, or substantially exceed, relevant entry cost benchmarks and associated long run equilibrium prices. However, given sufficient time higher prices, on average or during certain periods, create incentives for new entrant plant which in turn has the effect of capping longer-dated average spot price expectations at the estimated cost of the relevant new entrant technologies. In this article, we trace generalised new entrant benchmarks and their relationship to spot price outcomes in Australia’s National Electricity Market over the 20-year period to 2018; from coal, to gas and more recently to variable renewables plus firming, notionally provided by—or shadow priced at—the carrying cost of an Open Cycle Gas Turbine. This latest entry benchmark relies implicitly, but critically, on the gains from exchange in organised spot markets, using existing spare capacity. As aging coal plant exit, gains from exchange may gradually diminish with ‘notional firming’ increasingly and necessarily being met by physical firming. At this point, the benchmark must once again move to a new technology set...

Influence of the working fluid thermophysical parameters variation on the gas turbine cycle performance

The thermodynamic analysis of effect of the syngas combustion products (working fluid) thermophysical parameters variation on the economic and energy parameters of the gas turbine cycle is described. The thermodynamic analysis of Brayton cycle performance on various compositions of working fluid within a selected range of control parameters variation is presented. A gas turbine working fluid database was generated based on the analysis of flow diagram and operating regime of the production and design alternative gas-fired CCPP. The relationship between the cycle thermodynamic (pressure and temperature) and thermophysical parameters of the working fluid, which ensures gas turbine cycle maximum work, is derived analytically and supported by the well-known actual data.

Exergy assessment and energy integration of advanced gas turbine cycles on an offshore petroleum production platform

On offshore platform applications, power and heat are normally supplied by simple open cycle gas turbine (OCGT) and heat recovery steam generators (HRSG) at lower efficiencies if compared to onshore combined cycle systems. Certainly, due to the reduced available space and the weight constraints, combined cycles are not commonly considered as cogeneration systems on conventional offshore petroleum platforms. However, more stringent environmental policies for the natural gas and oil production activities have motivated the integration assessment of advanced technological solutions that aim to mitigate the environmental impact that conventional offshore platforms are responsible for. Accordingly, in this paper, the effect of the integration of a low emission, oxyfuel gas turbine cycle is analyzed and compared against an amines-based post-combustion system and a conventional offshore petroleum platform operation in terms of its exergy efficiency and reduced atmospheric CO2 emissions. Indeed, although the conventional configuration is the most efficient, the oxyfuel powered platform configuration presents close power cycle efficiency of 27.10% and the lowest specific CO2 emissions of 0.014 kgCO2/toil, whereas the amines-based layout provides the best cogeneration efficiency (55.34%) of the advanced configurations. Moreover, an energy integration analysis is performed to identify the heat recovery potential, while the exergy method is used to evaluate and quantify the most critical components that lead to the largest irreversibilities along the primary separation, cogeneration and gas compression systems. As a result, the study points to ways of decarbonizing offshore applications in the oil and gas sector.

A thermodynamic optimization of a gas turbine cycle with a supplementary regenerator

International concern regarding pollution related to maritime transport sector and energy efficiency desiderate have determined specialists to search for more suitable alternatives to internal combustion engines. Due to their advantages, gas turbine systems are met in different marine propulsion applications, such as passenger ships or military vessels. Gas turbines will be even more intensively used in the future, an outcome of this reality being the need of their performance increment. A direction to be followed, considered in this study, is the combination between the improvement of the gas turbine efficiency by including a regenerator in the layout of the plant and, also, the rise of the temperature at the inlet of the turbine (TIT). Will be considered an open cycle gas turbine. The thermodynamic analysis is about the assessment of different influences such as: regenerative effectiveness versus the heat added in the combustor, regenerative effectiveness versus the work consumed by the compressor, regenerative effectiveness versus the thermal efficiency, regenerative effectiveness versus the specific fuel consumption, temperature at inlet of the turbine (TIT) versus the thermal efficiency. The results obtained will indicate the fact that both actions will lead to a gain in the performance of this technology.

CCS and the energy trilemma

Carbon capture and storage (CCS) is an emissions reduction technology that can be applied to all fuel sources for energy production (gas, coal and biofuel). In addition, it is the only available option to reduce emissions from industrial processes. It has enormous potential for global impact by capturing more than 90% of CO2 and other emissions from power plants and industry. It is recognised by the Intergovernmental Panel on Climate Change as a critical tool in the move to a low‐emission future.

Feasibility of Using sCO2 Turbines to Balance Load in Power Grids with a High Deployment of Solar Generation

Solar photovoltaic power generation capacity is growing rapidly, increasing the need for dynamic load balancing when solar production dips. This balancing might be delivered using energy storage and/or advanced power generation cycles, that are compact, dynamic, and highly efficient, such as supercritical carbon dioxide (sCO2) cycles. Here, the load balancing capability of a sCO2 combined cycle plant was compared to open cycle and steam combined cycle gas turbines. A characteristic-based transient model was developed to evaluate the impact of machinery ramp rates, minimum part loads, and cycle efficiencies. High resolution demand and solar irradiance data from the University of Virginia campus, before and after installation of a major solar project, was used to represent low and high levels of solar deployment in the grid. The results suggest that under high deployment of solar power, sCO2 cycles and steam combined cycle systems with ramp rates greater than 5.75%/minute can balance load and provide comparable levelized costs of electricity ($0.057/kWh). Solar curtailment was driven by the minimum part load capabilities. A sCO2 cycle with a minimum part load of 30% was predicted to have a curtailment of 15% in the high solar scenario without a battery, and 4% with a 30 MWh battery.

The effects of the ideal gas model with constant heat capacities on fuel efficiency optimization of the open-cycle gas turbine

The optimization of a gas power cycle can be thermodynamical, techno-economical, thermo-economical and so on but, in general, the thermodynamic modeling is mandatory to solve the problem. Once the thermodynamic model is established the properties of the gases present in the cycle must be evaluated and the simplifications made for this evaluation could lead to inaccurate and even misleading results. In this paper the effect of using the perfect gas model in the optimization of the Specific Fuel Consumption (SFC) of the open simple cycle gas turbine has been analyzed. The results are obtained for compressor and turbine inlet temperatures (CIT and TIT) between 260 K–320 K and 1200 K–1800 K respectively. The optimization yields the minimum of SFC but also the corresponding values of compressor pressure ratio and specific power. In this work the optimization is first performed with a highly accurate ideal gas modeling approach in order to generate benchmark results. Afterward, the optimization is performed with a perfect gas modeling approach using four different methods (named A, B, C and D) to evaluate the constant value needed of the isobaric heat capacity. It is found that the optimization results can depend strongly on the method or rule used to evaluate the heat capacity. As an example, the uncertainty in the optimal value of SFC is between 8.5% and 14.9% with method C and below 3.2% with method D. In general, huge deviations in the compressor pressure ratio are found. Values higher than 16% for CIT below 300 K regardless the TIT value are found with methods A, B and C. In the worst case this deviation can be even higher than 100%. In general, this uncertainty gives rise to higher deviations in the specific power than in optimal SFC values. For example, with the method B and a TIT of 1800 K the ranges of the relative error are 56%–112%, 4.9%–6.2% and 17.8%–26.7% in the compressor pressure ratio, optimal SFC and specific power respectively. With respect to the CIT and TIT dependence the deviations in the compressor pressure ratio and specific power increase for high TIT and low CIT.This work is an extension of a previous paper publish by the author where the detailed development of the modeling approaches used in this work can be consulted.

Competitiveness of open-cycle gas turbine and its potential in the future Korean electricity market with high renewable energy mix

In this paper, we analyzed the competitiveness of an open-cycle gas turbine (OCGT) in the Korean electricity market and found reasons why OCGT has not been constructed since 2001, when the market opened. Through the analysis, we found that OCGT was weak in the Korean electricity market due to 3 factors: high load factor, high price of liquefied natural gas, and existing inefficient power plants. Using the conformity theory of the optimum in resource planning and the equilibrium in market dynamics, we verified the reasons by implementing resource planning using the Wien Automatic System Planning (WASP)-Ⅳ package with actual market data for the 16 years from 2001 to 2016. In addition, considering the new energy policy of Korea, shifting main sources of electricity generation from nuclear and coal to clean renewable energies and natural gas, we analyzed the competitiveness of OCGT in the future Korean electricity market. We identified the factors unfavorable for OCGT in the current market and suggested what should be changed to cope with high renewable energy penetration.

New approach for enhancing the performance of gas turbine cycle: A comparative study

Abstract In order to achieve higher performance of combined cycle power plant and reducing greenhouse gas emission, recently different technical approaches have been used based on the choice of higher efficiency of pure mechanical components nonetheless these solution remain very expensive. Though, including original combinations of two or more systems are not well treated previously. In this paper a comparative study has been performed for three combined gas turbine cycle configurations S3, S4 and S5 including innovative combinations for both simple gas turbine cycle S1 and regenerative gas turbine cycle S2. The evaluations of these proposed configurations are executed according to the thermodynamics conventional energy and exergy analysis. The effects of the new configurations on the performance and the exergy destruction of the combined cycle plant are investigated. The results indicate that the third configuration S5 is the most beneficial for the industrialists. The analysis method is used to recognize and identify the most substantial system configuration with less exergy destruction. Models that were used in the present study give a novel alternative approach to increases not only the thermal efficiency and net output of power plant by using the same amount of fuel rate but also to reduce exergy losses.

Effect of mixing Mach number and mixing efficiency on the preliminary cycle design of mixed high-BPR turbofans

This article presents the implementation of an updated analytical flow mixing model in a state-of-the-art, non-dimensional gas turbine cycle performance simulation and optimisation tool. The model considers three separate streams in the mixer, each expanding through its own ‘virtual’ nozzle. The use of three streams, compared to one single stream, allows for a more realistic simulation of a mixed exhaust gas turbine. This approach is used in a parametric study to assess the effect of the choice of mixing efficiency and mixer inlet Mach number on the preliminary design of mixed-exhaust, high-bypass ratio turbofan engines. It was found that in terms of best thermal performance, a trade-off exists between mixer inlet Mach number and mixer effectiveness. The findings of this research establish some useful guidelines for the accurate selection of these two parameters to achieve robust cycle designs.

Thermodynamic evaluation of open cycle gas turbines with carbon-free fuels H&lt;sub&gt;2&lt;/sub&gt; and NH&lt;sub&gt;3&lt;/sub&gt; at high temperatures

Thermodynamic evaluation of open cycle gas turbines with carbon-free fuels H&lt;sub&gt;2&lt;/sub&gt; and NH&lt;sub&gt;3&lt;/sub&gt; at high temperatures