Higher Turbine Inlet Temperature Research Articles

Advanced Materials and Manufacturing Technology Developments for Extreme Environment Gas Turbine Applications

Abstract Electrical power generation is becoming increasingly reliant on gas turbines with multiple fuel capability, with research advances focusing on increased efficiency/power output and reduced emissions. Increasing gas turbine efficiency primarily requires higher operating temperatures and reduced coolant flow in the turbine flow path, which makes it challenging to increase component performance, as these will encounter high stresses and large temperature gradients. Current nickel-based alloys, which operate at operate at extreme environments, are exposed to stress caused by temperature or static/dynamic loading like creep and fatigue, oxidation and corrosion, wear, and damage due to vibrations. Higher turbine inlet temperatures are currently managed with internal/film cooling and thermal/environmental barrier coatings for hot section parts. Comprehensive solutions are needed to translate to achieve ultrahigh efficiencies, lower parts cost, reduced scrape rate, and life cycle savings. The paper discusses material developments coupled with innovative manufacturing approaches to be married with advanced design strategies to realize the needed improvements for hot gas path components. The case studies for combustion and turbine components will be presented to demonstrate the structure property relationships and improved component performance at lower cost.

Techno-economic analysis of supercritical carbon dioxide cycle integrated with coal-fired power plant

Supercritical carbon dioxide (sCO2) cycles can achieve higher efficiencies than an equivalent steam Rankine cycle at higher turbine inlet temperatures (>550 °C) with a compact footprint (tenfold). sCO2 cycles are low-pressure ratio cycles (~4–7), therefore recuperation is necessary, which reduces the heat-addition temperature range. Integration of sCO2 cycles with the boiler requires careful management of low-temperature heat to achieve higher plant efficiency. This study analyses four novel sCO2 cycle configurations which capture the low-temperature heat in an efficient way and the performance is benchmarked against the state-of-the-art steam Rankine cycle. The process parameters (13–16 variables) of all the cycle configurations are optimised using a genetic algorithm for two different turbine inlet temperatures (620 °C and 760 °C) and their techno-economic performance are compared against the advanced ultra-supercritical steam Rankine cycle. A sCO2 power cycle can achieve a higher efficiency than a steam Rankine cycle by about 3–4% points, which is correspond to a plant level efficiency of 2–3% points, leading to cost of electricity (COE) reduction. Although the cycle efficiency has increased when increasing turbine inlet temperature from 620 °C to 760 °C, the COE does not notably reduce owing to the increased capital cost. A detailed sensitivity study is performed for variations in compressor and turbine isentropic efficiency, pressure drop, recuperator approach temperature and capacity factor. The Monte-Carlo analysis shows that the COE can be reduced up to 6–8% compared to steam Rankine cycle, however, the uncertainty of the sCO2 cycle cost functions can diminish this to 0–3% at 95% percentile cumulative probability.

Gas turbine performance enhancement for naval ship propulsion using wave rotors

The propulsion demands of high-speed naval vessels often rely on gas turbines, producing significant amount of power achieving thus high performance requirements. Gas turbines can be used either to provide purely mechanical propulsion, or alternatively to generate electricity, which is subsequently used by electric drives to propel the ship. However, the thermal efficiencies of gas turbines are lower than those of Diesel engines of similar power. In the context of improving the performance of existing marine gas turbines, it is proposed to enhance engine’s performance by integrating a pressure wave supercharger (or wave rotor), while keeping the basic components of the baseline engine unchanged. This article is an application of a method developed by the author for marine gas turbines with and without recuperator, [Fatsis 2019]. It is found that important benefits are obtained for the topped engines in comparison to the self-standing baseline engines. The wave rotor integration is more appropriate for engines with low compression ratios and high turbine inlet temperatures. Application of wave rotor technology to recuperated marine gas turbines shows efficiency gain exceeding 19% for all the compression ratio and turbine inlet temperatures examined. Abbreviations: COGAS, Combined gas turbine and steam turbine; COGES, Combined gas turbine electric and steam; GTE, Gas turbine engines

Comprehensive Review on Leading Edge Turbine Blade Cooling Technologies

Developments in the gas turbine technology have caused widespread usage of the Turbomachines for power generation. With increase in the power demand and a drop in the availability of fuel, usage of turbines with higher efficiencies has become imperative. This is only possible with an increase in the turbine inlet temperature (TIT) of the gas. However, the higher limit of TIT is governed by the metallurgical boundary conditions set by the material used to manufacture the turbine blades. Hence, turbine blade cooling helps in drastically controlling the blade temperature of the turbine and allows a higher turbine inlet temperature. The blade could be cooled from the leading edge, from the entire surface of the blade or from the trailing edge. The various methods of blade cooling from leading edge and its comparative study were reviewed and summarized along with their advantages and disadvantages.

A Benchmark for Compact CO2 Capture Plant Designs by Monoethanolamine Solvent Testing at Technology Centre Mongstad

Technology Centre Mongstad (TCM) is a large and flexible demonstration site for post-combustion CO2 capture. It is located next to the Equinor refinery at Mongstad (Norway) which is the source of the flue gases supplied to TCM. It has been used for testing CO2 capture with MEA solvent and a compact design, providing a benchmark for compact CO2 capture technologies.. The absorber was used with its lowest possible packing height of 12m, and only one of two water washes was used (3m height). The plant was operated with a high flue gas flow rate (67,000 Sm3/h) and 35 wt% MEA with a sensitivity down to 30 wt%. The CO2 inlet concentration was 6% mimicking some industrial exhausts, small turbines with exhaust gas recycle or modern turbines with high turbine inlet temperatures. The tests demonstrated that such a low absorber can capture more than 80% of the CO2 with only a slightly higher steam demand than conventional applications with higher packing heights of 18-24m. The low absorber gave 3.9 MJ/kg CO2 for the specific reboiler duty, while previous tests at other conditions and with higher absorbers gave 3.5-3.7. Acceptable emissions were observed, while degradation was higher than earlier TCM campaigns due to the choice of running with 35 w% MEA. Overall, a benchmark has been provided for future improved compact capture technologies.

Gas Turbine Blade Heat Transfer and Internal Swirl Cooling Flow Experimental Study Using Liquid Crystals and Three-Dimensional Stereo-Particle Imaging Velocimetry

Abstract The challenging engineering intricacies related to improving efficiency of a gas turbine engine come with the need to maximize the internal cooling of the turbine blade to withstand the high turbine inlet temperature. Understanding the fluid mechanics and heat transfer of internal blade cooling is, therefore, of paramount importance. This paper presents the impact of swirl cooling flow on the heat transfer of a gas turbine chamber to understand the mechanics of internal blade cooling. The focus is the continuous swirl flow that must be maintained via nonstop injection of tangential flow, whereby swirl flow is generated. The impact of swirl flow considers the velocity fields measured using stereo particle image velocimetry, the wall temperature and the convective heat transfer coefficient measured by liquid crystals. Flow behavior and heat transfer at three Reynolds numbers ranging from 7000 to 21,000 and the average profiles of axial and radial, magnitudes of velocity, and Nusselt numbers are given to research the direct effects of the circular chamber shape. Heat transfer results are measured in a second circular chamber and collected continuously after the system is heat soaked to the required temperature. As part of the results relatively low heat transfer rates were observed near the upstream end of the circular chamber, resulting from a low momentum swirl flow as well as crossflow effects. The thermochromic liquid crystal heat transfer results exemplify how the Nu measured favorably at the midstream of the chamber and values decline downstream.

Degradation characteristics of thermal barrier coatings for hot corrosion and CaO–MgO–Al2O3–SiO2

Hot corrosion and CaO–MgO–Al 2 O 3 –SiO 2 (CMAS) resistance of thermal barrier coatings (TBCs) are required in an industrial gas turbine employed with impure fuels and high turbine inlet temperatures . Therefore, various TBC systems with different structural combinations were investigated in thermochemical aspects of hot corrosion and CMAS causing the degradation of TBCs. Four types of 8 wt% yttria-stabilized zirconia (8YSZ), namely dense microstructure (8YSZ), porous microstructure (C–8YSZ), no monoclinic phase (NoM–8YSZ), and low thermal conductivity (low-k), were employed to prepare topcoats using an atmospheric plasma spray on the two bondcoats coated by a vacuum plasma spray with feedstocks of NiCoCrAlY and NiCoCrAlY+Hf + Si. Hot corrosion components penetrated through the whole topcoat layer at 1000 °C however did not infiltrate to the bondcoat layers because of the thermally grown oxide layer formed between the topcoat and the bondcoat. In addition, the elements Hf and Si contained in the bondcoat composition suppressed diffusion of β phase aluminum. In the visual inspection after the hot corrosion at 1000 °C and CMAS test at 1250 °C, the TBC system with the NoM–YSZ topcoat layer showed a sound condition without failure unlike other TBCs, and no monoclinic phase after hot corrosion and the CMAS test, indicating that the phase stability plays a critical role in TBCs' lifetime in the hot corrosion and CMAS environments. • Superiority of Hf and Si elements in MCrAlY bondcoat was observed through hot corrosion test. • Conventional and advanced TBCs failed with a similar trend independent of chemicals and porosity. • low-k TBCs showed a negative dependency on both hot corrosion and CMAS • Phase stability of topcoat layer can also be proposed to have more life time under the environment of hot corrosion and CMAS.

Energy and exergy analyses of novel supercritical CO2 Brayton cycles driven by direct oxy-fuel combustor

This study addresses major research gaps related to supercritical carbon dioxide (sCO2) power cycles including the shortcomings due to adding extra components, the high operating temperatures and the lack of studies on using direct oxy-combustion for sCO2 power cycles. Energy and exergy analyses for five novel sCO2 Brayton cycles with direct oxy-fuel combustion are introduced. The studied cycle configurations are the simple recuperator cycle (SRC), dual recuperator cycle (DRC), intercooling cycle (ICC), reheating cycle (RHC) and partial intercooling cycle (PIC). A numerical model was developed for the detailed calculations of the recuperators that considers variations in the properties of sCO2 as a function of temperature. Comprehensive studies and optimization are performed for the major parameters including the pressure ratio (rc), intermediate pressure ratio (RPR), turbine inlet temperature (TIT) and compressor inlet temperature (CIT). Optimum rc and RPR values have been obtained at which the maximum efficiencies of the cycles occur. Results show that the partial intercooling cycle (PIC) has superior performance compared to the other configurations at higher TIT and lower PRR. The maximum thermal efficiency of 52% is achieved by the PIC at rc of 5, RPR of 0.45, TIT of 750 °C, high pressure of 20 MPa, and CIT of 50 °C. Furthermore, the reheating cycle has the highest second law efficiency with marginal improvement in the thermal efficiency compared to the dual recuperator cycle (DRC).

Thermo-economic optimization of an air driven supercritical CO2 Brayton power cycle for concentrating solar power plant with packed bed thermal energy storage

This work presents an innovative indirect supercritical CO2 – air driven concentrated solar power plant with a packed bed thermal energy storage. High supercritical CO2 turbine inlet temperature can be achieved, avoiding the temperature limitations set by the use of solar molten salts as primary heat transfer fluid. The packed bed thermal energy storage enables the decoupling between solar irradiation collection and electricity production, and it grants operational flexibility while enhancing the plant capacity factor. A quasi steady state thermo-economic model of the integrated concentrating solar power plant has been developed. The thermo-economic performance of the proposed plant design has been evaluated via multi-objective optimizations and sensitivity analyses. Results show that a Levelized Cost of Electricity of 100 $/MWhe and a capacity factor higher than 50% can be achieved already at a 10 MWe nominal size. Such limited plant size bounds the capital investment and leads to more bankable and easily installable plants. Results also show that larger plants benefit from economy of scale, with a 65 $/MWhe cost identified for a 50 MWe plant. The receiver efficiency is found to be the most influential assumption. A 20% decrease of receiver efficiency would lead to an increase of more than 15% of the Levelized Cost of Electricity. These results show the potential of indirect supercritical CO2 – air driven concentrated solar power plant and highlight the importance of further air receiver development. More validations and verification tests are needed to ensure the system operation during long lifetime.

Experimental investigation of effusion and transpiration air cooling for single turbine blade

A great number of studies have been conducted on a film cooling for turbine blades, which is to prevent thermal damage on blades originated from high turbine inlet temperature. However, film cooling with several rows of cooling-holes results in lifting-off of coolant film and limited cooling on a restricted area due to flow reattachment. In this study, effusion and transpiration cooling were applied to the single C3X blade. A multiple hole-array with a diameter of 0.5 mm was fabricated by the electric discharging machining, and a porous structure with an equivalent pore diameter of 40 μm was manufactured by the 3-D metal additive manufacturing. Experiments were performed in the high-temperature subsonic wind tunnel, which has a freestream temperature of 100 °C and a velocity of 20 m/s. The surface temperature of blades was measured using infrared thermometry with a specially designed protocol to eliminate background radiation errors from the surroundings. Also, the outflow of coolant from blades was investigated with smoke-laser sheet visualization. The overall cooling effectiveness was quantitatively analyzed on the pressure-side, suction-side, and leading-edge of blades. Due to the enhancement of convective cooling through porous media, transpiration cooling achieves 34% and 25% higher cooling effectiveness than effusion and internal cooling each.

Efficiency Enhancement of Solar Thermal Power Systems Introduction of Secondary Brayton Cycle with Supercritical CO2/C2H6

An improvement of supercritical carbon dioxide Brayton cycle with regeneration coupled with a (carbon dioxide/ethane) shielded as a second cycle before starting the cooling phase in a solar tower installation was carried out. The power block unit in the cycle, as mentioned above designed to produce 160 MWe in the Ouarzazate region, where a gigantic solar project conducted in Morocco with a design point DNI evaluated as 823 W/m2. So, the aim to compare the performance of the s-ethane against the s-CO2, operating in the secondary cycle, two critical parameters studied are, the first one is the effect of turbine inlet temperature on net power. And the second one is the effect of secondary Brayton cycle pressure on the system efficiency. The cycle efficiency, founded to be 58% at high turbine inlet temperature by including an aided s-ethane cycle. The research work is in progress. In perspectives, specific other possible configurations and other trans-critical fluids will address in the secondary Brayton cycle.

Full coverage film cooling on a non-axisymmetric contoured endwall and the baseline endwall

Full coverage film cooling arrangement is widely needed in nozzle guide vanes (NGVs) to keep the turbine surfaces from melting due to the unprecedented high turbine inlet temperature. Meanwhile, to reduce the passage aerodynamic losses, non-axisymmetric endwall contouring are widely applied. The employment of endwall contouring will impact the full coverage film cooling performance, thus changing the turbine durability. Thus, it is important to deeper know the effect of non-axisymmetric endwall contouring on endwall full coverage film cooling performance. In this study, Pressure Sensitivity Paint (PSP) technique is used to measure the full coverage film cooling effectiveness (η) distributions on a non-axisymmetric contoured endwall (CE) and the corresponding baseline endwall (BE) with several coolant mass flow ratios (MFRs). Meanwhile, cases with the corresponding experimental conditions by computational fluid dynamics (CFD) are done to calculate the blowing ratio (BR) and MFR distributions of the film cooling holes. The η distributions on the CE and the BE are compared, and the effect of MFR on the CE full coverage film cooling performance are documented. In addition, different turbulence models are evaluated on the ability to model the endwall film cooling problems by comparing the CFD results with the experimental results. With small MFR values, the film cooling performance are worse on the CE in the near-hole regions at the fore part of the passage but better on the CE in the far-hole regions and at the aft part of the passage than that on the BE. While with large MFRvalues, the CE perform better than the BE throughout the endwall surface.

Integration of gas switching combustion and membrane reactors for exceeding 50% efficiency in flexible IGCC plants with near-zero CO2 emissions

• Gas switching combustion and membrane reactors are integrated in an IGCC plant. • The proposed plants produce flexible electricity/H 2 with CCS to balance renewables. • IGCC benchmarks with/without CCS incorporate hot gas clean-up and H-class turbines. • Electric/H 2 LHV efficiencies up to 50.3%/62.4% with >98% CO 2 capture are achieved. • The energy penalty is less than 2%-points relative to the unabated IGCC plant. Thermal power plants face substantial challenges to remain competitive in energy systems with high shares of variable renewables, especially inflexible integrated gasification combined cycles (IGCC). This study addresses this challenge through the integration of Gas Switching Combustion (GSC) and Membrane Assisted Water Gas Shift (MAWGS) reactors in an IGCC plant for flexible electricity and/or H 2 production with inherent CO 2 capture. When electricity prices are high, H 2 from the MAWGS reactor is used for added firing after the GSC reactors to reach the high turbine inlet temperature of the H-class gas turbine. In periods of low electricity prices, the turbine operates at 10% of its rated power to satisfy the internal electricity demand, while a large portion of the syngas heating value is extracted as H 2 in the MAWGS reactor and sold to the market. This product flexibility allows the inflexible process units such as gasification, gas treating, air separation unit and CO 2 compression, transport, and storage to operate continuously, while the plant supplies variable power output. Two configurations of the GSC-MAWGS plant are presented. The base configuration achieves 47.2% electric efficiency and 56.6% equivalent hydrogen production efficiency with 94.8–95.6% CO 2 capture. An advanced scheme using the GSC reduction gases for coal-water slurry preheating and pre-gasification reached an electric efficiency of 50.3%, hydrogen efficiency of 62.4%, and CO 2 capture ratio of 98.1–99.5%. The efficiency is 8.4%-points higher than the pre-combustion CO 2 capture benchmark and only 1.9%-points below the unabated IGCC benchmark.

Experimental study of the effects of spark timing and water injection on combustion and emissions of a heavy-duty natural gas engine

The growing concern over global warming and stricter emissions regulations (EURO 6 standards) have led to natural gas engines being operated in stoichiometric combustion conditions with three-way catalytic (TWC) and exhaust gas recirculation (EGR) equipment. However, natural gas engines suffer from high thermal load, knock onset, and high turbine inlet temperatures at stoichiometric combustion conditions. Water injection is a promising approach to reduce thermal load and NOx emissions and suppress knock onset. In this study, the effects of water injection on the combustion and performance characteristics of a heavy-duty natural gas engine were experimentally studied. The experiments were conducted with four water to natural gas mass ratios (WNMRs) and various spark timings. The results showed that water injection decreased the burning velocity of natural gas, leading to a decrease in peak in-cylinder pressure, peak heat release rate, and combustion temperature. The flame development period (CA0-10) and the flame propagation period (CA10-90) increased with an increase in WNMR. Compared to pure natural gas, the brake thermal efficiency at the optimum spark timing increased from 27.8% to 28.2% at WNMR = 0.35. BSNOx emissions consistently decreased with an increase in WNMR, while BSTHC emissions and BSCO emissions increased slightly.

Parametrized Analysis and Multi-Objective Optimization of Supercritical CO2 (S-CO2) Power Cycles Coupled with Parabolic Trough Collectors

Supercritical CO2 (S-CO2) Brayton cycles have become an effective way in utilizing solar energy, considering their advantages. The presented research discusses a parametrized analysis and systematic comparison of three S-CO2 power cycles coupled with parabolic trough collectors. The effects of turbine inlet temperature and pressure, compressor inlet temperature, and pressure on specific work, overall efficiency, and cost of core equipment of different S-CO2 Brayton cycles are discussed. Then, the two performance criteria, including specific work and cost of core equipment, are compared, simultaneously, between different S-CO2 cycle layouts after gaining the Pareto sets from multi-objective optimizations using genetic algorithm. The results suggest that the simple recuperation cycle layout shows more excellent performance than the intercooling cycle layout and the recompression cycle layout in terms of cost, while the advantage in specific work of the intercooling cycle layout and the recompression cycle layout is not obvious. This study can be useful in selecting cycle layout using solar energy by the parabolic trough solar collector when there are requirements for the specific work and the cost of core equipment. Moreover, high turbine inlet temperature is recommended for the S-CO2 Brayton cycle using solar energy.

Optimum sub-megawatt electric-hybrid power source selection

PurposeThe limited energy density of batteries generates the need for high-performance power sources for emerging eVTOL applications with radical operational improvement potential over traditional aircraft. This paper aims to evaluate on-design and off-design recuperated turbogenerator performances based on newly developed compression loaded ceramic turbines, the Inside-out Ceramic Turbine (ICT), in order to select the optimum engine configuration for sub-megawatt systems.Design/methodology/approachSystem-level thermal engine modeling is combined with electric generators and power electronics performance predictions to obtain the Pareto front between efficiency and power density for a variety of engine designs, both for recuperated and simple cycle turbines. Part load efficiency for those engines are evaluated, and the results are used for an engine selection based on a simplified eVTOL mission capability.FindingsBy operating with high turbine inlet temperature, variable output speed and adequately sized recuperator, a turbogenerator provides exceptional efficiency at both nominal power and part load operation for a turbomachine, while maintaining the high power density required for aircraft. In application with a high peak-to-cruise power ratio, such power source would provide eight times the range of battery-electric power pack and an 80% improvement over the state-of-the-art simple cycle turbogenerator.Practical implicationsThe implementation of a recuperator would provide additional gains especially important for military and on-demand mobility applications, notably reducing the heat signature and noise of the system. The engine low-pressure ratio reduces its complexity and combined with the fuel savings, the system could significantly reduce operational cost.Originality/valueImplementation of radically new ICT architecture provides the key element to make a sub-megawatt recuperated turbogenerator viable in terms of power density. The synergetic combination of a recuperator, high temperature turbine and variable speed electric generator provides drastic improvement over simple-cycle turbines, making such a system highly relevant as the power source for future eVTOL applications.

Experimental Study on the Emissions Characteristics of a Premixed Axial-Fuel-Staged Model Combustor

Abstract Axial-fuel-staged combustion is a promising technology to reduce NOx emission at high turbine inlet temperatures and provide extended gas turbine operational flexibility. To investigate the emissions characteristics of the axial-fuel-staged combustion, a staged model combustor was constructed and a parametric study was performed at atmospheric pressure. Fuel distribution, equivalence ratio, and jet velocity effects on the emissions characteristics have been studied in the present research. Results show that the influence of fuel distribution on emissions is depending on the combustor outlet temperature. The NOx emissions increase with secondary fuel fraction when the combustor outlet temperature is low but decrease when the combustor outlet temperature is high. Investigation of the equivalence ratio on each stage shows that a lower relative NOx increase in secondary combustion zone is achieved at higher first-stage equivalence ratio. Moreover, the secondary stage jet velocity was varied to study the jet mixing influence on the emissions. The results show that a higher jet velocity will enhance the mixing between the secondary jet and the upstream first-stage burnt gases, producing lower NOx emissions. Finally, a simplified axial-fuel-staged combustion chemical reactors network (CRN) model was established to study the mixing of the secondary fresh fuel/air mixture and the first-stage burnt gases. The CRN modeling results show that a poor mixing in the secondary stage will significantly increase the NOx emission, which means that the mixing enhancement at the secondary stage is important for the axial-fuel-staged combustor design.

The interaction between upstream and downstream film cooling rows in flow field and heat transfer

Towards a higher turbine inlet temperature, full coverage film cooling or effusion cooling is an effective way to cool the hot cascade. The interaction between upstream and downstream film cooling rows becomes more and more important for the evaluation of cooling effectiveness. In this paper, film cooling effectiveness distributions and aero-thermal fields of one film cooling row and two in-line film cooling rows with spacing ratio S/D = 6 are compared and investigated to reveal the row-to-row interaction. The LES model is first validated by a flat plate experiment in which the mainstream velocity equal to 25 m/s, then the LES model is used to analyze the flow field and heat transfer. The results show that the upstream ejection would thickens the downstream boundary layer, making the downstream coolant flow penetrate deeper into the main flow, thus causing poor coolant coverage of the rear film cooling ejection. On the other hand, the lifted kidney vortices of the second row ejection entrain first row ejection to the wall, making the coolant flow from the first row contribute significantly to the coolant coverage on the wall downstream of the second row. The turbulence intensity has great impact on the film cooling effectiveness after the first row, but very small influence on the second row.

Investigation into a Combined Inverted Brayton and Rankine Cycle

Abstract Waste heat recovery is a vitally important technology to address increasingly stringent emissions legislation and environmental concerns over CO2. One such means of recovering thermal energy is the inverted Brayton cycle (IBC). This paper presents an experimental study of a novel combination of the IBC with a Rankine cycle for the first time. The IBC requires cooling of the exhaust gases after expansion. If the gases contain water vapor, as is the case for hydrocarbon combustion, and cold enough coolant is available, the water can be condensed, pressurized, and reboiled for expansion in a Rankine cycle. The steam produced from the cycle can be utilized in a number of ways. In this study, steam is injected through a series of de Laval nozzles directed into the main turbine to produce additional shaft power in a compact arrangement. To minimize the size of the system, additive manufacturing was used for the heat exchangers, giving high performance per unit volume. The study demonstrates the feasibility of the cycle in producing power from waste heat using humid gas that already is present in most applications. The experimental results show that the system is able to generate power at very low exhaust temperatures where the standard IBC would cease to operate. With an IBC inlet temperature of 370 °C, approximately 5 kJ/kg of specific shaft work was produced with 5 g/s of steam flowrate. At higher exhaust temperatures, the IBC and the Rankine cycle started to work together to increase the shaft power resulting in much higher specific work. At 620 °C, a specific shaft work of 41 kJ/kg was generated at a steam flow of 9 g/s. For the present turbomachinery sizes, this corresponded to 1933 W of power at 47 g/s of main exhaust flow. A model of the thermodynamic system was created in order to study the sensitivity of the system to parameters such as the steam expander pressure ratio and efficiency. Higher steam pressure and higher steam expander efficiency both led to greater power generated for the same operating point, particularly at high IBC turbine inlet temperatures. The peak specific work for the range of parameters explored in the paper was 68 kJ/kg with a steam expander efficiency of 70% and exhaust conditions of 600 °C and 50 g/s. The plots produced in this study can be used as a guide for others considering this system to understand the expected power generated under a range of conditions.

New parametric performance maps for a novel sizing and selection methodology of a Liquid Air Energy Storage system

Liquid Air Energy Storage is one of the most promising novel energy storage concept that guarantees at the same time viable capital cost, high energy density and no geographical/geological constrains. Considering the complexity of the plant, composed by three different phases (charge, discharge and storage), thermodynamic modelling could be a challenging undertaking. Making use of the strong similitude with gas turbine technology, this paper aims to deliver new generalized performance maps for Liquid Air Energy Storage system. The performance maps, validated against the experimental results of Highview Power pilot plant, have been modelled by means of a comprehensive sensitivity analysis carried out considering three macro-scenarios imposing the storage pressures and the turbomachinery performance (design/off-design conditions). By means of the performance maps, the impact of the main LAES operative parameters, as well as the effect of the cold/warm thermal energy storage utilization factor, over the key performance indicators has been assessed and analysed. The analysis shows that at design condition the higher is the value of the high grade cold thermal energy storage utilization factor, the lower is the positive impact of charge pressure over the specific consumption. For off-design condition of the main turbomachinery, the negative effect of lower isentropic efficiency of the main turbomachinery on the round trip efficiency is amplified by the choice of the charge pressure. At high value of the warm energy storage utilization factor, this negative effect can be partially offset by the higher Turbine Inlet Temperature available for the expansion process of the discharge phase.