Net Power Generation Research Articles

Computational and experimental study of a complete heat dissipation system using water as heat carrier placed on a thermoelectric generator

The heat dissipation systems which have liquids as heat carriers outperform conventional dissipation systems at TEGs (thermoelectric generators). However, new elements need to be introduced such as pumps, secondary heat exchangers and piping.A predictive computational model of a dissipation system involving refrigerant liquids has been implemented. The accuracy of the model is 93% for all its outputs: the total thermal resistance, the hydraulic losses and the auxiliary power consumption. The validation of the model has been done with a prototype mainly composed by a multi-channel heat exchanger, a fan-coil, a pump and several sensors: temperature, pressure and flow meters.A study on the influence of the water and the air mass flow over the total thermal resistance has been conducted. The total resistance dependence on the air mass flow shows the importance of including the secondary heat exchanger into the thermal and hydraulic calculations. The smallest resistance does not always obtain the highest net power generation, the high demanding power of the auxiliary equipment needed to obtain this resistance influences negatively on the net power generation. Among the experimental points, the optimum scenario obtains a 40% additional power generation with respect to the smallest resistance point.

Off-design performance analysis of a closed-cycle ocean thermal energy conversion system with solar thermal preheating and superheating

This article reports the off-design performance analysis of a closed-cycle ocean thermal energy conversion (OTEC) system when a solar thermal collector is integrated as an add-on preheater or superheater. Design-point analysis of a simple OTEC system was numerically conducted to generate a gross power of 100 kW, representing a base OTEC system. In order to improve the power output of the OTEC system, two ways of utilizing solar energy are considered in this study: (1) preheating of surface seawater to increase its input temperature to the cycle and (2) direct superheating of the working fluid before it enters a turbine. Obtained results reveal that both preheating and superheating cases increase the net power generation by 20–25% from the design-point. However, the preheating case demands immense heat load on the solar collector due to the huge thermal mass of the seawater, being less efficient thermodynamically. The superheating case increases the thermal efficiency of the system from 1.9% to around 3%, about a 60% improvement, suggesting that this should be a better approach in improving the OTEC system. This research provides thermodynamic insight on the potential advantages and challenges of adding a solar thermal collection component to OTEC power plants.

A comprehensive measure of the energy resource: Wind power potential (WPP)

Currently, the quality of available wind energy at a site is assessed using wind power density (WPD). This paper proposes to use a more comprehensive metric: the wind power potential (WPP). While the former accounts for only wind speed information, the latter exploits the joint distribution of wind speed and wind direction and yields more credible estimates. The WPP investigates the effect of wind velocity distribution on the optimal net power generation of a farm. A joint distribution of wind speed and direction is used to characterize the stochastic variation of wind conditions. Two joint distribution methods are adopted in this paper: bivariate normal distribution and anisotropic lognormal method. The net power generation for a particular farmland size and installed capacity is maximized for different distributions of wind speed and wind direction, using the Unrestricted Wind Farm Layout Optimization (UWFLO) framework. A response surface is constructed to represent the computed maximum wind farm capacity factor as a function of the parameters of the wind distribution. Two different response surface methods are adopted in this paper: (i) the adaptive hybrid functions (AHF), and (ii) the quadratic response surface method (QRSM). Toward this end, for any farm site, we can (i) estimate the parameters of the joint distribution using recorded wind data (for bivariate normal or anisotropic lognormal distributions) and (ii) predict the maximum capacity factor for a specified farm size and capacity using this response surface. The WPP metric is illustrated using recorded wind data at four differing stations in the state of North Dakota. The results illustrate the variation of wind conditions and, subsequently, its influence on the quality of wind resources. A comparison of four sites in North Dakota shows that WPD and WPP follow different trends, and the ranking of candidate sites in terms of a realistic resource potential measure is not captured by WPD.

Design and Analysis of a Combined Rankine Cycle for Waste Heat Recovery of a Coal Power Plant Using LNG Cryogenic Exergy

In this study, a combined Rankine cycle was modeled and optimized. This process consists of a coal combustion unit, a steam cycle, a CO2 capture process, a gas conditioning process, and a CO2 organic Rankine cycle (ORC). This process is able to extract additional power without consuming additional fossil fuel by integrating the CO2-ORC with the steam cycle and a liquefied natural gas (LNG) evaporation process. Unlike conventional ORC, the CO2-ORC utilizes the low grade waste heat only for super heating of working fluid, while the main evaporation process is achieved by seawater. The CO2 condensation process in the ORC takes place at a temperature lower than the ambient temperature by coupling with the LNG evaporation system as a cold sink. Furthermore, a fraction of liquefied CO2 is purged for the sequestration. Therefore, CO2 liquefaction can be achieved without an additional refrigeration cycle. This process not only produces more power with the same fuel consumption but also reduces CO2 removal energy. The gross power is increased from 42.21 to 90.54 MWe compared with the conventional power plant, and total CO2 removal energy is decreased about 9%. The optimum design and operating conditions were also obtained through parameter sensitivity analysis. The power reduction of the proposed process resulting due to the CO2 capture process installation was identified as 19.3%. However, the net power generation is about 73% higher than that of the conventional power cycle even without CO2 capture.

Process Evaluation of Carbon Dioxide Capture for Coal-Fired Power Plants

Carbon capture is a promising technology for carbon dioxide (CO2) removal from large stationary CO2 sources. The effects of carbon dioxide capture process on output efficiency of fossil power plants were investigated. Supercritical pulverized coal and integrated coal gasification combined cycle (IGCC) were assumed as model coal-fired power plants for this investigation. Heat-driven and pressure-driven CO2 capture processes such as chemical absorption and physical adsorption were assumed for CO2 capture process. In this study, these technologies were evaluated and compared under the unified basis and conditions by using the commercial process simulator. For IGCC plant, the efficiency penalty by installing water-gas shift reaction was also investigated. Gross and net power generation, efficiency and the efficiency penalty by CO2 capture process were calculated. Heat duty for CO2 capture process and CO2 compression conditions were varied, and those effects on the efficiency penalty were obtained. The results provide a guideline for development of CO2 capture process of power plants.

Study of Complete Thermoelectric Generator Behavior Including Water-to-Ambient Heat Dissipation on the Cold Side

Reduction of the thermal resistances of the heat exchangers of a thermoelectric generation (TEG) system leads to a significant increase in TEG efficiency. For the cold side of a thermoelectric module (TEM), a wide range of heat exchangers have been studied, from simple finned dissipators to more complex water (water–glycol) heat exchangers. As the Nusselt number is much higher in water heat exchangers than in conventional air finned dissipators, the convective thermal resistances are better. However, to conclude which heat exchanger leads to higher efficiencies, it is necessary to include the whole system involved in the heat dissipation, i.e., the TEM-to-water heat exchanger, the water-to-ambient heat exchanger, as well as the required pumps and fans. This paper presents a dynamic computational model able to simulate the complete behavior of a TEG, including both heat exchangers. The model uses the heat transfer and hydraulic equations to compute the TEM-to-water and water-to-ambient thermal resistances, along with the resistance of the hot-side heat exchanger at different operating conditions. Likewise, the model includes all the thermoelectric effects with temperature-dependent properties. The model calculates the net power generation for different configurations, providing a methodology to design and optimize the heat exchange in order to maximize the net power generation for a wide variety of TEGs.

Feasibility study and performance assessment for the integration of a steam-injected gas turbine and thermal desalination system

This study proposes a systematic approach for retrofitting a steam-injection gas turbine (SIGT) with a multi-effect thermal vapor compression (METVC) desalination system. The retrofitted unit's product cost of the fresh water (RUPC) was used as a performance criterion, which comprises the thermodynamic, economic, and environmental attributes when calculating the total annual cost of the SIGT–METVC system. For the feasibility study of retrofitting the SIGT plant with the METVC desalination system, the effects of two key parameters were analyzed using response surface methodology (RSM) based on a central composite design (CCD): the steam air ratio (SR) and the temperature difference between the effects of the METVC system (∆TMETVC) on the fresh water production (Qfreshwater) and the net power generation (Wnet) of the SIGT–METVC system. Multi-objective optimization (MOO) which minimizes the modified total annual cost (MTAC) and maximizes the fresh water flow rate was performed to optimize the RUPC of the SIGT–METVC system. The best Pareto optimal solution showed that the SIGT–METVC system with five effects is the best one among the systems with 4–6 effects. This system under optimal operating conditions can save 21.07% and 9.54% of the RUPC, compared to the systems with four and six effects, respectively.

Thermoeconomic analysis and off-design performance of an organic Rankine cycle powered by medium-temperature heat sources

This paper presents the performance of an organic Rankine cycle (ORC) powered by medium-temperature heat sources. A simulation model, developed by the authors, has been improved to this scope. The model is based on zero-dimensional energy and mass balances for all the components of the system. It is also strictly related to the geometrical and design parameters of its components, especially in case of heat exchangers. The model evaluates the energetic and economic performance of the system, for different operating conditions and design criteria. In particular, the model allows one to set the geometrical parameters of heat exchanger and evaluate the off-design performance of the system. Hence, it could be an useful tool in the preliminary design of the plant. The n-butane has been used as working fluid according to results of the previous authors’ work.Two types of simulations have been performed. The first simulation aims at selecting a design optimization criterion of some geometrical parameters of the shell and tube heat exchangers. The total cost of ORC plant has been selected as objective function. The parametrical analysis has been performed in steady-state regime.The second simulation evaluates the off-design performance of the ORC power plant. The thermal input of the cycle, i.e. diathermic oil coming from the heat source, has been varied in terms of mass flow rate and temperature to analyze the plant response to variations of boundary conditions starting from the design point.With respect to the total cost minimization, as objective function, the simulation results show that for all heat exchangers the higher the heat transfer area, the higher the net power generated and income. Instead, the evaporator shows different trends, hence it represents a key element in ORC design. The geometric optimization of heat exchangers allows the ORC to increase the economic benefit, the net power generated and the global efficiency of about 21.06%, 20.01% and 33.60% respectively.The results of the off-design analysis show that the heat source mass flow rate is a key parameter in net power generation. Fixed the heat source temperature on the upper bound of its variation range (185°C), the net power generation shows both the maximum and minimum value, 335.4kW and 269.3kW, in correspondence of the lowest and the highest value of heat source mass flow rate respectively. Moreover, the results show that the plant efficiency decreases as both heat source mass flow rate and temperature increase. Its maximum value, 14.7%, is achieved for heat source temperature and mass flow rate equal to 155°C and 18kg/s, while its minimum value, 9.54%, is reached for heat source temperature and mass flow rate equal to 185°C and 24kg/s.

Recent Progress of SOFC Combined Cycle System with Segmented-In-Series Tubular Type Cell Stack at MHI

Solid oxide fuel cell (SOFC) triple combined cycle system, integrated with gas turbine (GT) and steam turbine (ST), is an ultimate fossil fuel electric power generation system with very high efficiency. In 2008, Mitsubishi Heavy Industries, Ltd. (MHI) operated the 200 kW-class SOFC micro gas turbine (MGT) hybrid system under commission of New Energy and Industrial Technology Development Organization (NEDO) and we could demonstrate 52.1%-LHV net power generation efficiency. Based on the successful achievement, MHI developed a more compact 250 kW-class SOFC-MGT hybrid system for the purpose of utilization of a hybrid system in the NEDO project scheduled from fiscal 2011 to 2012. Furthermore, we have started a development of fundamental technologies of SOFC-GT-ST triple combined cycle system that aims to achieve more than 70% of power generation efficiency. In this paper, latest results on the development of SOFC and the systems are described.

Exergy analysis and parametric optimization of three power and fresh water cogeneration systems using refrigeration chillers

Three power and fresh water cogeneration systems that combine a GT (gas turbine) power plant and a RO (reverse osmosis) desalination system were compared based on the exergy viewpoint. In the first system, the GT and RO systems were coupled mechanically to form a base system. In the second and third systems, a VCR (vapor-compression refrigeration) cycle and a single-effect ACWater–LiBr (water/lithium bromide absorption chiller) were used, respectively, to cool the compressor inlet air and preheat the RO intake seawater via waste heat recovery in the VCR condenser and ACWater–LiBr absorber. A parametric analysis-based exergy was conducted to evaluate the effects of the key thermodynamic parameters including the compressor inlet air temperature and the fuel-mass flow rate on the system exergy efficiency. Parameter optimization was achieved using a GA (genetic algorithm) to reach the maximum exergy efficiency, where the thermodynamic improvement potentials of the systems were identified. The optimum values of performance for the three cogeneration systems were compared under the same conditions. The results showed that the cogeneration system with the AC is the best system among the three systems, since it can increase exergy and energy efficiencies as well as net power generation by 3.79%, 4.21%, and 38%, respectively, compared to the base system.

DESIGN AND PARAMETRIC OPTIMIZATION OF AN ORGANIC RANKINE CYCLE POWERED BY SOLAR ENERGY

This study presents the simulation and performance analysis of a regenerative and superheated Organic Rankine Cycle (ORC). To this scope, anew simulation model has been developed. The model is based on zero-dimensional energy and mass balances for all the components of the system. Shell and tube heat expanders with single shell and double tube pass have been chosen. Pump and expander have been considered only form a thermodynamic point of view, with constant compressor and expansion efficiency. The simulations have been carried out in order to find different optimization criteria to use as preliminary design tools, especially for the organic fluid choice and the heat exchanger design. Firstly, the ORC performances have been evaluated for different organic medium, varying the temperature of the heat source. The global efficiency of the plant, the net electric power generation and the volumetric expansion ratio has been considered as evaluation parameters. The simulation results show that two hydrocarbons demonstrate good performance for low, medium and high heat source, namely Isobutene, n-Butene; R245fa can add to them for the exploitation of heat source up to 170°C. Additional simulations have been carried out to discover an optimization criterion for the heat exchanger design. The plant performances have been first evaluated varying one by one the following parameters: tube length, tube number and shell diameter. Then a global optimization was also performed using the Golden Search technique. The total cost of the plant has been considered as objective functions. With respect to the objective function, higher the boiling heat transfer area higher the electric power generation and the economical benefit. The optimal configuration, compared to the initial one, shows an increase of incomes and mechanical power equal to 60.1 and 48.2% respectively, against a decrease of global efficiency equal to 10.9%.

Regulatory Compliance and Environmental Benefit Analysis of Combined Heat and Power (CHP) Systems in Taiwan

The energy conservation achieved by utilizing waste heat in the energy and industrial sectors has became more and more important after the energy crisis in the 1970s because it plays a vital role in the potential energy-efficiency improvement. In this regard, cogeneration (combined heat and power, CHP) systems are thus becoming attractive due to the energy, economic, and environmental policies for pursuing stable electricity supply, sustainable development and environmental pollution mitigation in Taiwan. The objective of this paper is to present an updated analysis of CHP systems in Taiwan during the period from 1990 to 2010. The description in the paper is thus based on an analysis of electricity supply/consumption and its sources from CHP systems during the past two decades, and centered on two important regulations in compliance with CHP systems (i.e., Energy Management Law and Environmental Impact Assessment Act). Based on the total net power generation from CHP systems (i.e., 35,626 GWh) in 2011, it was found that the carbon dioxide reduction benefits were estimated to be around 20,000 Gg.

Two-Stage Flash for CO2 Regeneration: Dynamic Modeling and Pilot Plant Validation

High operating cost and significant decrease in net power generation are major barriers to the implementation of post- combustion amine scrubbing for CO2 capture from coal-fired power plants. To improve efficiency and make the process more attractive economically, alternative process configurations and second generation solvents are being investigated. Dynamic modeling can be a useful tool in understanding the optimal operating conditions and control strategies for a proposed modified process; however, there are limited examples of dynamic model development for amine scrubbing. The Separations Research Program (SRP) at the University of Texas at Austin has completed a pilot plant campaign using a two-stage flash for CO2 regeneration as an alternative to a simple stripper, and piperazine solvent as an alternative to the baseline standard of monoethanolamine. This work develops a dynamic model for the alternative SRP configuration using first principles material and energy balances assuming an equilibrium stage process, and the model is validated with steady state SRP data. The model output was reasonably well matched to pilot plant measurements, with average temperature deviations of ≤1.7°C and average pressure errors of ≤ 3.4%.

Myosin Heavy Chain Isoforms Influence the Magnitude of Stretch Activation in Drosophila Muscles

The stretch activation (SA) mechanism, a general property of all muscle types, is most prominent in muscles that generate power through cyclical contractions, such as insect indirect flight muscles (IFM) and vertebrate cardiac muscles. SA is defined as phase 3, a delayed tension increase, of the tension transient following a muscle stretch. We are testing our hypothesis that myosin heavy chain isoforms help set SA magnitude and hence power generating ability in different muscle types. The Drosophila thorax contains two muscle types, IFMs and jump muscles. In IFMs, the magnitude of SA is great enough to enable net positive power generation when it is fully calcium activated. In contrast, jump muscles display very little stretch activation and cannot generate net positive power when fully activated. We found that when an embryonic myosin isoform (EMB) is transgenically expressed in the jump muscle, the muscle is transformed and behaves like a moderately stretch-activatable muscle. The transformed muscle can now generate positive power and SA magnitude is increased by ∼60% at 0mM Pi and ∼350% at 16mM Pi. This shows that SA magnitude is influenced by myosin isoforms. We found that power generation is [Pi] dependent as ≥ 2mM Pi is required for power production in jump muscles expressing the EMB isoform. Expressing the IFM isoform in jump muscles did not enable positive power generation or increase SA magnitude. To further test our hypothesis, we are expressing the jump myosin isoform in IFMs to determine if this reduces IFM SA magnitude. We conclude that myosin isoforms can influence the magnitude of SA, but are not the only mechanism responsible for natural differences in SA magnitude.

Power generation from waste heat in a food processing application

In this paper, the potential of recovering waste heat from the fryer section and exhaust stream sent to the stack of a typical potato crisps or chips manufacturing plant and using the heat to drive an Organic Rankine Cycle (ORC) system for power generation has been presented. Five different ORC system Options (A, B, C, D and E) were considered. The first two options (A and B) make use of the waste heat from the foul gas and exhaust to stack respectively for power generation using a single ORC system each while the third option (option C) makes use of a novel dual heat source single ORC system where the low temperature waste heat from the foul gas is used to provide preheating and the high temperature waste from the exhaust to the stack used to provide the evaporation. Option D also shows a dual heat source ORC system where the high temperature waste heat to the exhaust stack is used to provide the preheating while the lower temperature foul gas is used for the evaporation (reverse of option C in terms of waste heat usage) while option E makes use of a reheat cycle where the waste heat from the foul gas is used to provide the reheating of the working fluid exiting the turbine. In terms of waste heat usage, the combination of options A and B can be compared with options C, D and E. The simulation result shows that in terms of net power generation, cooling water requirement, and working fluid (R245fa) requirement, the combination of Options A and B gives the best power generation result and this is similar as the result produced by Option C. Following option C is option E which gave a better result than option D. The entropy generation analysis showed that the entropy generation is inversely proportional to the power output. It was also observed that the net power generation for the ORC configuration adopted in this paper (option C) meets the average daily power requirement of the crisps manufacturing process as well as 98.58% of the daily peak power requirement. ► We model and optimised different ORC configurations for power generation from waste heat in crisps manufacturing plant. ► We carried out second law analysis of the different configurations. ► We selected the configuration which will be most economical for power generation from waste heat in crisps manufacturing plant.

Performance analysis in near-critical conditions of organic Rankine cycle

According to fluid critical temperature and heat source temperature, organic Rankine cycle (ORC) is recognized in two categories: subcritical ORC and supercritical ORC. For a given heat source, some organic fluids not only can be used in subcritical ORC, but also can be used in supercritical ORC. For heat source with temperature of 90 °C, HFC125, HFC143a and HF218 can be used in both ORCs. Performance of the three substances in both cycles, especially in near-critical conditions is studied with expander inlet temperature of 85 °C and hot water mass flow rate of 1 kg/s. The results show that when fluids go in supercritical ORC from subcritical ORC, cycle thermal efficiency varies continuously, while mass flow rate and net power generation vary discontinuously. Maximum net power generation in near-critical conditions of subcritical ORC is higher than that of supercritical ORC. For HFC125 and HFC143a, outlet temperature of hot water decreases with the increase of heating pressure ratio. For HF218, outlet temperature of hot water increases firstly and decreases secondly with the increase of heating pressure ratio, which leads to an increase of net power generation with the increase of heating pressure ratio in high heating pressure ratio conditions.

Gasification as an optimum alternative for the sludge management

Assimilate sludge to a fuel is not new. Sludge incineration and Combined Heat and Power (CHP) engines powered with sludge-derived anaerobic digestion gas (ADG) are operations widely used. However, they have a room of improvement to reach simultaneously a positive net power generation and a significant level of waste reduction and stabilization. Gasification has been used in other realms for the conversion of any negative-value carbon-based materials, that would otherwise be disposed as waste, to a gaseous product with a usable heating value for power generation . In fact, the produced gas, the so-called synthetic gas (or syngas), could be suitable for combined heat and power motors. Within this framework gasification could be seen as an optimum alternative for the sludge management that would allow the highest waste reduction yield (similar to incineration) with a high power generation. Although gasification remains a promising route for sewage sludge valorisation, campaigns of measurements show that is not a simple operation and there are still several technical issues to resolve before that gasification was considered to be fully applied in the sludge management. Fluidised bed was chosen by certain technology developers because it is an easy and well known process for solid combustion, and very suitable for non-conventional fuels. However, our tests showed a poor reliable process for gasification of sludge giving a low quality gas production with a significant amount of tars to be treated. The cleaning system that was proposed shows a very limited removal performance and difficulties to be operated. Within the sizes of more common WWTP, an alternative solution to the fluidised bed reactor would be the downdraft bed gasifier that was also audited. Most relevant data of this audit suggest that the technology is more adapted to the idea of sludge gasification presented in the beginning of this paper where a maximum waste reduction is achieved with a great electricity generation thanks to the use of a “good” quality syngas in a CHP engine. Audit show also that there is still some work to do in order to push sludge gasification to a more industrial stage. Regardless what solution would be preferred, the resulting gasification system would involve a more complex scenario compared to Anaerobic Digestion and Incineration, characterised by a thermal dryer and gasifier with a complete gas cleaning system. At the end, economics, reliability and mass and energy yields should be carefully analysed in order to set the place that gasification would play in the forthcoming processing of sewage sludge.

Unrestricted wind farm layout optimization (UWFLO): Investigating key factors influencing the maximum power generation

A new methodology, the Unrestricted Wind Farm Layout Optimization (UWFLO), that addresses critical aspects of optimal wind farm planning is presented in this paper. This methodology simultaneously determines the optimum farm layout and the appropriate selection of turbines (in terms of their rotor diameters) that maximizes the net power generation. The farm layout model obviates traditional restrictions imposed on the location of turbines. A standard analytical wake model has been used to account for the velocity deficits in the wakes created by individual turbines. The wind farm power generation model is validated against data from a wind tunnel experiment on a scaled down wind farm. Reasonable agreement between the model and experimental results is obtained. The complex nonlinear optimization problem presented by the wind farm model is effectively solved using constrained Particle Swarm Optimization (PSO). It is found that an optimal combination of wind turbines with differing rotor diameters can appreciably improve the farm efficiency. A preliminary wind farm cost analysis is performed to express the cost in terms of the turbine rotor diameters and the number of turbines in the farm. Subsequent exploration of the influences of (i) the number of turbines, and (ii) the farm land size, on the cost per Kilowatt of power produced, yields important observations.

The deployment of an advanced gasification technology in the treatment of household and other waste streams

The Gasplasma® process developed by APP is an advanced thermal conversion (ATC) technology which has been developed for the treatment of household and trade wastes and has also been successfully applied to the handling of wastes derived from landfill and would be capable of achieving effective energy conversion when utilised as an integrated part of the Enhanced Landfill Mining (ELFM) concept.The core Gasplasma® technology comprises a two-stage thermal treatment system—firstly, a fluidizing bed gasifier which converts the wastes to a crude syngas using oxy-steam and, secondly, a plasma converter that efficiently cracks problematic tars in the raw syngas to produce a reformed and clean syngas suitable for generating electrical power in gas engines and also recovering an environmentally stable vitrified product for use as a secondary aggregate material. The utilization of oxy-steam as a gasifying agent greatly reduces the syngas volume compared to other ATC processes and incineration and hence reduces the cost of the gas cleaning system while improving the efficiency of the process. By adopting this two-stage approach, high energy conversion (74–90%) and carbon conversion (95±1.6%) efficiencies were achieved with the Gasplasma® plant that compare favourably with published efficiencies data. The calculated net exportable power generation efficiency for a commercial scale plant is significantly in excess of 25%. This compares well with the published figures of 17.7–23% for fluidized bed technologies processing MSW.

Optimal design and integration of an air separation unit (ASU) for an integrated gasification combined cycle (IGCC) power plant with CO 2 capture

The air separation unit (ASU) plays a key role in improving the efficiency, availability, and operability of an oxygen-fed integrated gasification combined cycle (IGCC) power plant. An optimal integration between the ASU and the balance of the plant, especially the gasifier and the gas turbine (GT), has significant potential for enhancing the overall plant efficiency. Considering the higher operating pressure of the GT, an elevated-pressure air separation unit (EP-ASU) is usually favored instead of the conventional low-pressure air separation units (LP-ASU). In addition, a pumped liquid oxygen (PLOX) cycle is usually chosen if the operating pressure of the gasifier is high. A PLOX cycle helps to improve plant safety and availability and to decrease the capital cost by reducing the size of the oxygen compressor or by eliminating it completely. However, the refrigeration lost in withdrawn liquid oxygen must be efficiently recovered. This paper considers five different configurations of an ASU with PLOX cycle and compares their power consumptions with an EP-ASU with a traditional gaseous oxygen (GOX) cycle. The study shows that an optimally designed EP-ASU with a PLOX cycle can have similar power consumption to that of an EP-ASU with GOX cycle in the case of 100% nitrogen integration. In the case of an IGCC with pre-combustion CO 2 capture, the lower heating value (LHV) of the shifted syngas, both on a mass and volumetric basis, is in between the LHV of the unshifted syngas from an IGCC plant and the LHV of natural gas, for which the GTs are generally designed. The optimal air integration in the case of a shifted syngas is found to be much lower than that of an unshifted syngas. This paper concurs with the existing literature that the optimal integration occurs when air extracted from the GT can be replaced with the nitrogen from the ASU without exceeding mass/volumetric flow limitations of the GT. Considering nitrogen and air integration between the ASU and the GT, this paper compares the power savings in an LP-ASU with a PLOX cycle to the power savings in an EP-ASU with GOX cycle and EP-ASU with PLOX cycle. The results show that an LP-ASU with a PLOX cycle has less power consumption if the nitrogen integration levels are less than 50–60%. In addition, a study is carried out by varying the concentration of nitrogen and steam in the fuel diluents to the GT while the NOx level was maintained constant. The study shows that when the nitrogen injection rate exceeds 50%, an EP-ASU with a PLOX cycle is a better option than an LP-ASU with a PLOX cycle. This paper shows that an optimal design and integration of an ASU with the balance of the plant can help to increase the net power generation from an IGCC plant with CO 2 capture.