Open Cycle Gas Turbine Research Articles

Comparing least cost scenarios for 100% renewable electricity with low emission fossil fuel scenarios in the Australian National Electricity Market

Policy makers face difficult choices in planning to decarbonise their electricity industries in the face of significant technology and economic uncertainties. To this end we compare the projected costs in 2030 of one medium-carbon and two low-carbon fossil fuel scenarios for the Australian National Electricity Market (NEM) against the costs of a previously published scenario for 100% renewable electricity in 2030. The three new fossil fuel scenarios, based on the least cost mix of baseload and peak load power stations in 2010, are: (i) a medium-carbon scenario utilising only gas-fired combined cycle gas turbines (CCGTs) and open cycle gas turbines (OCGTs); (ii) coal with carbon capture and storage (CCS) plus peak load OCGT; and (iii) gas-fired CCGT with CCS plus peak load OCGT. We perform sensitivity analyses of the results to future carbon prices, gas prices, and CO2 transportation and storage costs which appear likely to be high in most of Australia. We find that only under a few, and seemingly unlikely, combinations of costs can any of the fossil fuel scenarios compete economically with 100% renewable electricity in a carbon constrained world. Our findings suggest that policies pursuing very high penetrations of renewable electricity based on commercially available technology offer a cost effective and low risk way to dramatically cut emissions in the electricity sector.

Effect of coolant injection angle and cooling hole dimensions on transpiration cooled gas turbine cycle performance

AbstractGas turbine cycles are extensively used in view of their capability of offering high specific work output with high thermal efficiency compared to steam turbine cycles. Studies are being carried out worldwide to further improve the gas turbine cycle performance. Among different options for improving cycle performance, the use of high turbine inlet temperature (TIT) along with efficient means and methods of turbine blade cooling is an attractive option. Studies show that transpiration cooling technique uses the coolant more effectively than the film and convection cooling techniques.The present study investigates the effects of varying coolant hole diameter, hole pitch/diameter ratio and coolant injection angles on the transpiration cooled (full coverage film cooled) gas turbine cycle performance. The results have been taken for a TIT of 1700 K and a cycle pressure ratio of 23, as used in the advanced ‘H’ class gas turbines. It is found that the coolant requirement increases with the increasing coo...

CO2 capture for gas turbines: an integrated energy-efficient process combining combustion in oxygen-enriched air, flue gas recirculation, and membrane separation

Carbon capture and storage for power generation systems is a major issue for achieving greenhouse gas emission reductions. Studies are usually dedicated to coal-fired power plants, but few efforts have addressed the challenge of CO2 capture for a gas turbine. In this paper, a recently reported hybrid process based on oxygen enriched air combustion, flue gas recycling and CO2 capture by membranes is explored for a 250MW open cycle gas turbine. An improved configuration based on an energy recovery system integrated with a heat exchanger offers superior performance compared to the reference gas turbine cycle. It is shown that an overall energy requirement below 2GJth/ton of CO2 captured (i.e. around 205kWhelectrical/ton CO2) can be achieved using a highly selective membrane (CO2/N2 selectivity of 200) operated under optimal process conditions.

Performance Evaluation of Gas-Steam Combined Cycle Having Transpiration Cooled Gas Turbine

In recent years improved gas turbine performance through developments in high temperature materials and blade cooling methods has made a positive impact on the combined cycle performance. Transpiration cooling technique has emerged as the most promising technique to improve the gas turbine cycle performance by allowing higher turbine inlet temperatures. This paper concentrates on improving the combined cycle performance by allowing higher turbine inlet temperatures (TIT) using transpiration cooling of gas turbine blades. A four-stage advanced gas turbine coupled with the dual pressure steam bottoming cycle is considered for the performance of combined cycle. Realistic input parameters used in current industrial practice have been considered for this study. The effects of variation of TIT on the performances of topping, bottoming and combined cycle are presented and discussed. For the combined cycle with transpiration cooled gas turbine an increase in TIT from 1600 K to 1800 K exhibits the combined cycle efficiency increase by 2.37 percent and the combined specific work increases by 185.42 kJ/kg. The results indicate that at a TIT of 1800 K the achievable efficiency of combined cycle with transpiration cooled gas turbine is 59.97 percent.

Performance Evaluation of Gas-Steam Combined Cycle Having Transpiration Cooled Gas Turbine

In recent years improved gas turbine performance throughdevelopments in high temperature materials and blade cooling methodshas made a positive impact on the combined cycle performance.Transpiration cooling technique has emerged as the most promisingtechnique to improve the gas turbine cycle performance by allowinghigher turbine inlet temperatures. This paper concentrates on improvingthe combined cycle performance by allowing higher turbine inlettemperatures (TIT) using transpiration cooling of gas turbine blades. Afour-stage advanced gas turbine coupled with the dual pressure steambottoming cycle is considered for the performance of combined cycle.Realistic input parameters used in current industrial practice havebeen considered for this study. The effects of variation of TIT on theperformances of topping, bottoming and combined cycle are presentedand discussed. For the combined cycle with transpiration cooled gasturbine an increase in TIT from 1600 K to 1800 K exhibits the combinedcycle efficiency increase by 2.37 percent and the combined specific workincreases by 185.42 kJ/kg. The results indicate that at a TIT of 1800 K theachievable efficiency of combined cycle with transpiration cooled gasturbine is 59.97 percent.

Analytical Investigation of Parameters Affecting the Performance of Cooled Gas Turbine Cycle with Evaporative Cooling of Inlet Air

The article investigates the effect of compressor pressure ratio, turbine inlet temperature, ambient relative humidity and ambient temperature on the performance parameters of an air-cooled gas turbine cycle with evaporative cooling of inlet air. Air-film cooling has been adopted as the cooling technique for gas turbine blades. The mass of coolant required for turbine blade cooling is calculated for a selected range of ambient conditions and found to vary with temperature drop achieved in the evaporator. The effect of ambient temperature and ambient relative humidity on plant efficiency and plant-specific work is computed at different TIT and r p,c and it was found that the rate of increase in these performance parameters are more pronounced at higher TIT and r p,c. The results indicate that a maximum temperature drop of 21 °C is achieved in the evaporator. The inlet cooling is found to increase the efficiency by 4.1% and specific work by 9.44 %.

Energy-Saving and Economical Evaluations of a Ceramic Gas Turbine Cogeneration Plant

A ceramic gas turbine can save energy because of its high thermal efficiency at high turbine inlet temperatures. This paper deals with the thermodynamic and economic aspects of a ceramic gas turbine cogeneration system. Here cogeneration means the simultaneous production of electrical en-ergy and useful thermal energy from the same facility. The thermodynamic performance of a ceramic gas turbine cycle is assessed using a computer model. This model is used in parametric studies of performance under partial loads and at various inlet air temperatures. The computed performance is compared to the measured performance of a conventional gas turbine cycle. Then, an economic evaluation of a ceramic gas turbine cogeneration system is investigated. Energy savings provided by this system are estimated on the basis of the distributions of heat/power ratios. The computed economic evaluation is compared to the actual economic performance of a conventional system in which boilers produce the required thermal energy and electricity is purchased from a utility.

The Role of CCS in Power Systems with High Levels of Renewables Penetration

Past studies have used power plant dispatch models with fixed plant portfolios to demonstrate that flexible capture systems may allow operators to increase profits in current electricity markets by increasing plant output at times of high demand. Some of these studies have also speculated that flexible capture systems may be valuable in future electricity systems with high shares of renewable energy as they could allow fossil fuel plants with capture to rapidly respond to changes in residual load. However, few studies have actually examined the role that plants with flexible capture could play in future power systems. Thus, this study examines the role that power generation with flexible capture systems could play in a future European power system where 80% of generation (by energy) is supplied by renewables. The results show that conventional base- and mid-load capacity decreases while the peak-load capacity (i.e., open cycle gas turbines) increases. In European regions with high shares of renewables, the residual load duration curve become steeper, and hourly changes in residual load increase significantly and happen more frequently at low load levels. The shift towards peak capacity and general decrease in load factors places technologies with high capital costs at a relative disadvantage. In the scenario in which CO2 prices reach 650 per tonne CO2 in 2050, approximately one-fifth of the CCS capacity deployed is equipped with flexible capture. However, in a scenario in which CO2 prices reach € 100 per tonne CO2 in 2050, very little capacity is equipped with flexible capture systems as the cost of emitting CO2 offsets the value of flexibility.

Performance and Water Consumption of the Solar Steam-Injection Gas Turbine Cycle

Solar heat at moderate temperatures around 200 °C can be utilized for augmentation of conventional steam-injection gas turbine power plants. Solar concentrating collectors for such an application can be simpler and less expensive than collectors used for current solar power plants. We perform a thermodynamic analysis of this hybrid cycle, focusing on improved modeling of the combustor and the water recovery condenser. The cycle's water consumption is derived and compared to other power plant technologies. The analysis shows that the performance of the hybrid cycle under the improved model is similar to the results of the previous simplified analysis. The water consumption of the cycle is negative due to water production by combustion, in contrast to other solar power plants that have positive water consumption. The size of the needed condenser is large, and a very low-cost condenser technology is required to make water recovery in the solar STIG cycle technically and economically feasible.

Assessing the value of wind generation in future carbon constrained electricity industries

This paper employs a novel Monte-Carlo based generation portfolio assessment tool to explore the implications of increasing wind penetration and carbon prices within future electricity generation portfolios under considerable uncertainty. This tool combines optimal generation mix techniques with Monte Carlo simulation and portfolio analysis methods to determine expected overall generation costs, associated cost uncertainty and expected CO2 emissions for different possible generation portfolios. A case study of an electricity industry with coal, Combined Cycle Gas Turbines (CCGT), Open Cycle Gas Turbines (OCGT) and wind generation options that faces uncertain future fossil-fuel prices, carbon pricing, electricity demand and plant construction costs is presented to illustrate some of the key issues associated with growing wind penetrations. The case study uses half-hourly demand and wind generation data from South Eastern Australia, and regional estimates of new-build plant costs and characteristics. Results suggest that although wind generation generally increases overall industry costs, it reduces associated cost uncertainties and CO2 emissions. However, there are some cases in which wind generation can reduce the overall costs of generation portfolios. The extent to which wind penetration affects industry expected costs and uncertainties depends on the level of carbon price and the conventional technology mix in the portfolios.

Effects of Wet Compression on Performance of Regenerative Gas Turbine Cycle with Turbine Blade Cooling

When water is injected at an inlet of compressor, wet compression occurs due to evaporation of water droplets. In this work, the effects of wet compression on the performance of regenerative gas turbine cycle with turbine blade cooling are analytically investigated. For various pressure ratios and water injection ratios, the important system variables such as ratio of coolant flow for turbine blade cooling, fuel consumption, specific power and thermal efficiency are estimated. Parametric studies show that wet compression leads to significant enhancement in both specific power and thermal efficiency in gas turbine systems with turbine blade cooling.

Life Cycle Greenhouse Gas Emissions from Electricity Generation: A Comparative Analysis of Australian Energy Sources

Electricity generation is one of the major contributors to global greenhouse gas emissions. Transitioning the World’s energy economy to a lower carbon future will require significant investment in a variety of cleaner technologies, including renewables and nuclear power. In the short term, improving the efficiency of fossil fuel combustion in energy generation can provide an important contribution. Availability of life cycle GHG intensity data will allow decision-makers to move away from overly simplistic assertions about the relative merits of certain fuels, and focus on the complete picture, especially the critical roles of technology selection and application of best practice. This analysis compares the life-cycle greenhouse gas (GHG) intensities per megawatt-hour (MWh) of electricity produced for a range of Australian and other energy sources, including coal, conventional liquefied natural gas (LNG), coal seam gas LNG, nuclear and renewables, for the Australian export market. When Australian fossil fuels are exported to China, life cycle greenhouse gas emission intensity in electricity production depends to a significant degree on the technology used in combustion. LNG in general is less GHG intensive than black coal, but the gap is smaller for gas combusted in open cycle gas turbine plant (OCGT) and for LNG derived from coal seam gas (CSG). On average, conventional LNG burned in a conventional OCGT plant is approximately 38% less GHG intensive over its life cycle than black coal burned in a sub-critical plant, per MWh of electricity produced. However, if OCGT LNG combustion is compared to the most efficient new ultra-supercritical coal power, the GHG intensity gap narrows considerably. Coal seam gas LNG is approximately 13–20% more GHG intensive across its life cycle, on a like-for like basis, than conventional LNG. Upstream fugitive emissions from CSG (assuming best practice gas extraction techniques) do not materially alter the life cycle GHG intensity rankings, such is the dominance of end-use combustion, but application of the most recent estimates of the 20-year global warming potential (GWP) increases the contribution of fugitives considerably if best practice fugitives management is not assumed. However, if methane leakage approaches the elevated levels recently reported in some US gas fields (circa 4% of gas production) and assuming a 20-year methane GWP, the GHG intensity of CSG-LNG generation is on a par with sub-critical coal-fired generation. The importance of applying best practice to fugitives management in Australia’s emerging natural gas industry is evident. When exported to China for electricity production, LNG was found to be 22–36 times more GHG intensive than wind and concentrated solar thermal (CST) power and 13–21 times more GHG intensive than nuclear power which, even in the post-Fukushima world, continues to be a key option for global GHG reduction.

The Expansion-Cycle Evaporation Turbine

This paper investigates a continuous-flow heat engine based on evaporative cooling of hot air at reduced pressure. In this device, hot air is expanded in an expansion turbine, spray-cooled to saturation and re-compressed to ambient pressure in several stages with evaporative cooling between each stage. More work is available in expansion than is required during re-compression, so the device is a heat engine. The device provides a relatively cheap way to boost the power output of open-cycle gas turbines. The principal assumptions for the theoretical model developed herein are that air and water vapor are regarded as ideal gases with constant specific heat capacities. In the absence of losses associated with expansion and compression, the engine produces more power as the inlet temperature and the pressure ratio increase. The effects of irreversibilities are subsequently included in the expansion and compression stages, with realistic values used for the adiabatic efficiencies of turbine and fans. Purification and injection of water are also considered in the overall energy budget. As a typical result for the new engine, if the inlet air is the exhaust of a 56 MW open-cycle gas turbine, the adiabatic efficiencies of turbine and fan are 0.9, the pressure ratio is 6.5 and there is four-stage re-compression, then the power output is 20.5% that of the gas turbine. The power output is sensitive to the adiabatic efficiencies of turbine and fans.

Overview: Asset Management – Gas Turbine Power Stations

This overview was written primarily with graduates, engineers and electrical, mechanical, chemical, instrumentation and control and computer technicians in mind who wish to enter the power generation industry at large and gas turbine power generating plants in particular, since combined cycle gas turbine power plants constitute the largest output and most efficient turbine power generation stations operating today. This Part 4 of a four part overview focuses on the salient asset management (O&M) aspects of generator and exciter plant in both open cycle and combined cycle gas turbine power stations.

Understanding and improving energy conversion systems with the aid of exergy-based methods

Exergy–based methods are powerful tools for developing, evaluating and improving an energy conversion system. Conventional exergy–based analyses have limitations, which are significantly reduced by the so–called advanced analyses. The latter evaluate: (a) the interactions among components of the overall system, and (b) the real potential for improving a system component. The main objective of advanced exergy–based analyses is to provide additional information that is useful improving the design and operation of energy conversion systems. This paper deals with integrated conventional and advanced exergetic, exergoeconomic and exergoenvironmental analyses. The advantages of these analyses are demonstrated using an academic example, an open–cycle gas turbine power system.

Performance evaluation of a transpiration-cooled gas turbine for different coolants and permissible blade temperatures considering the effect of radiation

Successful gas turbine technology is based significantly upon the introduction of new blade materials with increased permissible temperature for gas turbine blades and/or the use of efficient means and methods of turbine blade cooling in order to achieve the highest possible turbine inlet temperature. The gas turbine blade cooling models found in literature indicate that the effect of radiation from elevated temperature gases is generally not considered. However, the radiative heat transfer always occurs owing to the presence of mainly carbon dioxide and water vapour in the combustion products. The present paper deals with the comparative study of transpiration-cooled gas turbine cycle performance with and without taking radiation effect for different coolants and permissible blade temperature. The thermodynamic evaluation shows that, with consideration of the radiation effect, the theoretical coolant requirement increases so as to be close to the actual requirement and hence the cycle performance is affected accordingly. The transpiration-cooled gas turbine cycle performance parameter variations are presented to exemplify the role of cooling technology, cooling means, and material development, taking the radiation effect into account.

Starting up rapid-start units for reserve contributions in a system with interruptible loads

This study presents the effect of starting reliability of rapid-start units (RSUs), such as open-cycle gas turbines (OCGTs) and hydro generators, for energy scheduling and reserve allocation. A method that explicitly integrates unit starting reliability into the expected energy not served (EENS) formulation for non-spinning reserve (NR) contribution is proposed. A unit commitment objective function is used to incorporate the various types of energy/reserve providers and to schedule energy and reserve simultaneously. These providers are conventional thermal units, OCGTs, hydro units and interruptible loads. An EENS model that considers these energy/reserve providers and accounts for their response times is presented pictorially. A penalty cost formulation for RSUs that failed to start up for NR contribution is proposed. This work emphasises the importance of modelling units of varying starting reliability. These results could be used to assist independent system operators and generation companies when selecting energy/reserve sources for power generation and reserve contribution.

Flexible CCS plants–A key to near-zero emission electricity systems

Abstract Power generation processes with CCS that are capable of operating at variable load will be needed to achieve deep reductions in emissions of CO 2 to the atmosphere. This paper assesses the effects of operating load factor on costs of coal and gas fired power generation processes with CCS and analyses the emissions and costs of fossil fuel fired plants in an electricity system that includes 35% wind and 25% nuclear generation. The paper shows how the costs of generation increase at an increasing rate as the emissions are reduced using power plants with integrated CCS such as post combustion capture, because many of the CCS plants have to operate at low load factors. This could be avoided by using coal gasification plants with CCS which feed hydrogen to underground buffer storage and then to flexible combined and open cycle gas turbines. The gasification, CO 2 capture and storage equipment would operate at base load which would avoid potential practical difficulties of flexible operation and reduce costs. Emissions from the fossil fuel plants in the system with wind and nuclear generation could be reduced to 16 g/kWh at electricity costs competitive with coal-based post combustion capture with emissions of 140 g/kWh. Emissions from the overall electricity system including the wind and nuclear would be 6 g/kWh.

Study on the effective parameter of gas turbine model with intercooled compression process

In this paper parametric study of a gas turbine cycle model power plant with intercooler compression process was proposed. The power output and the efficiency are simulating with respect to the cycle temperatures and pressure ratio for a typical set of operating conditions. Simple gas turbine cycle calculations with realistic parameters are made and confirm that increasing the turbine inlet temperature no longer means an increase in cycle efficiency, but increases the work done. The analytical study is done to investigate the performance improvement by intercooling. The analytical formula for specific work and efficiency are derived and analyzed. The simulation results shows that increasing turbine inlet temperature and pressure ratio can still improve the performance of the intercooled gas turbine cycle. Key words: Gas turbine, power plant, performance, intercooler.

Ecological performance optimisation for an open-cycle ICR gas turbine power plant Part 1 - thermodynamic modelling

Abstract Considering the flow processes of the working fluid with the pressure drops, a thermodynamic model for open cycle intercooled and regenerated gas turbine power plant is established using finite time thermodynamics in Part 1 of this article. The flow processes of the working fluid with the pressure drops of the working fluid and the size constraints of the real power plant are modelled. There are 19 flow resistances encountered by the working fluid for the cycle model. Five of these, the frictions through the blades, vanes of the compressors and the turbines, are related to the isentropic efficiencies. Three of these, the frictions through the intercooler and the regenerator, are related to the effectiveness of the heat exchangers. The remaining flow resistances are always present because of the changes in the flow cross-section at the compressor inlets and outlets, the intercooler inlet and outlet, the regenerator inlet and outlet, the combustion chamber inlet and outlet, and the turbine i...