Global warming concerns have pushed coal-fired power plants to develop innovative solutions which reduce CO 2 emissions by increasing efficiency. While new ultra-supercritical units are built with extremely high efficiency, with Pingshan II approaching 50% LHV[1], subcritical units with much lower efficiency are a major source of installed capacity. The typical annual average net efficiency of subcritical units in China is about 37% LHV, and some are lower than 35% LHV. Since the total subcritical capacity in China is about 350GW and accounts for over one third of its total coal-fired power capacity, shutting all subcritical units down is not practical. Finding existing coal-fired plants a cost-effective solution which successfully combines advanced flexibility with high efficiency and low emissions, all while extending service lives, has challenged energy engineers worldwide. However, the (now proven) benefits a high temperature upgrade offers, compared to new construction options, made this an achievement worth pursuing. After many years of substantial incremental improvements to best-in-class technology, this first-of-its-kind subcritical high temperature retrofit successfully proves that a technically and economically feasible solution exists. It increases the main and reheat steam temperatures from 538°C (1000°F) to 600°C (1112°F), and the plant cycle and turbine internal efficiencies are greatly improved. This upgrade’s greatest efficiency gains occur at low loads, which is important as fossil plants respond to renewable energy’s increased grid contributions. These are combined with best-in-class flexibility, energy-savings, and technological advances, i.e., flue gas heat recovery technology and generalized regeneration technologies [4]. This project, the world’s first high-temperature subcritical coal-fired power plant retrofit, was initiated in April 2017 and finished in August 2019. Performance reports created by Siemens and GE record unit net efficiency at rated conditions improved from 38.6% to 43.5% LHV. The boiler’s lowest stable combustion load with operational SCR, without oil-firing support, was reduced from 55% to 19%. Substitution or upgrading of high-temperature components extended the lifetime of the unit by more than 30 years. At a third of the cost of new construction, this project set a high-water-mark for retrofitting subcritical units, and meets or supports the requisite attributes for Coal FIRST, Coal Plant of the Future, proposed by the United States Department of Energy (DOE) in 2019 [2].

An electrical generator is one of the most efficient large-scale machines. It converts mechanical to electrical energy with an efficiency coefficient of approximately 99%. The remaining 1% can mainly be contributed to heat losses. Direct cooling is only necessary for larger turbogenerators with more than 250 MVA where the cooling media is introduced via hollow conductors within the stator bars. Turbogenerators of approximately up to 700 MVA nowadays use exclusively hydrogen (H 2 ) gas as a cooling media. Even larger turbogenerators have to introduce direct water cooling. The water chemistry of the stator cooling water is typically of neutral pH and has a conductivity of less than 0.1 μS/cm. Two zones of the oxygen (O 2 ) concentration have been established through the last 50 years, one at low dissolved O 2 concentration with less than 20 ppb, the other with high concentrations of more than 2 ppm. The latter has to continuously inject CO 2 free air to ensure to always keep the oxygen concentration above 2 ppm. The first part of this publication shows several incidents with the air injection system in different Nuclear Power Plants in the US, resulting in unfavorable stator cooling water chemistry. This led to a reduced cooling efficiency, resulting in several chemical online cleanings being necessary. The second part of this work presents a technical solution to overcome the issues associated with the reduced stator cooling. It continuously injects and monitors the air injected into the system. Additionally, it also measures the hydrogen leakage rate.

Over the past decades there has been a dramatic increase in natural gas burning as the benign fossil fuel, offering far lower emissions than oil or coal. Its place had been established in a clean, or at least, cleaner energy future. Today, the national and international energy policy has been shifted to carbon neutrality — achieving net zero carbon emissions — and as result has moved natural gas from the “benign” to the “menace” category At present, there are chiefly two alternatives for fuel carbon neutrality under discussion: power-to-gas (PtG) producing methane (or synthetic natural gas, SNG, hydrogen etc.) and power-to-liquid, which stores electric power in the form of methanol. In opposite to other synthetic or fossil fuels, like synthetic methane, NG or hydrogen, methanol burning leads to significant reductions in emissions of nitrogen oxides without any substantial firing system design change. Burning of synthetic methane or hydrogen requires significant effort for NOx reduction. Hydrogen as a fuel offers many advantages in power production. It is a carbon-free fuel that can decarbonize power and heat generation, and transportation, to help meet long-term CO 2 emission-reduction targets. However, things are different for NOx emissions are a different matter. The more hydrogen is added to a NG, the higher the NOx is anticipated. Dry Low NOx (DLN) combustor has traditionally mixed NG with sufficient air upstream the combustor, so burning can take place in a lean atmosphere to maintain a relatively cool flame and thus keep NOx down. That approach does not work so well when more hydrogen enters the picture due to auto ignition occurring in the premix zone. Some companies already have diffusion-type combustor technology where fuel and air are supplied separately. Combustion of hydrogen, specifically in diffusion mode, implies combustion with a hotter flame, leading to higher combustion temperatures and the formation of local hot spots. These, in turn, can cause NOx to increase. The generalized solution is to cool the flame using diluents, such as demineralized water, steam or nitrogen. However, reducing NOx, by dilution reduces efficiency compared to a DLN combustor. Another option of providing wide load range of GT operation, while maintaining low NOx emissions is fuel dilution with flue gas being recirculated from the exhaust (FGR - Flue gas recirculation). The present paper discusses the effect of burning renewable fuels produced from carbon dioxide and hydrogen which are being diluted with a flow of FGR on GT performance and emissions reduction in diffusion combustors. For the prediction of the combustion behavior a methodology that combines experimental work and computational simulations was used. Given the fact that due to the increase in renewable energy introduction into the grid, addition of renewable fuel-based energy produced from carbon dioxide becomes very significant. Hence, the development of enhanced firing systems burning synthetic clean fuels with low emissions is challenging and should be promoted. Using renewable fuels for energy supply would reduce the unfavorable impact of CO 2 and allow meeting the targets established in the Kyoto and Paris Protocols.

Many parts of the world are facing the triple challenge of providing secure energy to fuel economic growth at an affordable cost while minimizing the impact of energy production on the environment. Island nations especially struggle to address this trilemma, as renewable resources are usually limited and fossil fuels imported. Traditionally such distributed power plants have relied on liquid fuels and multiple open cycle reciprocating engines to provide both redundancy and the ability to load follow across a broad load range to maximize efficiency. This approach has created high electricity prices and significant negative environmental impact, especially that attributed to CO 2 , NO x , and SO x . With increasing natural gas production, the availability of Liquefied Petroleum Gas (LPG) has grown, and costs have fallen, allowing the potential to switch from fuel oils to LPG to reduce environmental impacts. Energy costs and environmental impact can be further reduced by using high efficiency Gas Turbine Combined Cycle plants with dry low emissions combustion technology. However, a further hurdle facing many locations is lack of the fresh water required for combined cycle operations. LPG-fuelled Gas Turbine Combined Cycle using Organic Rankine Cycle (ORC) technology can address all aspects of this energy trilemma. This paper reviews the conceptual design of a proposed 100MW distributed power plant for an island location, based on multiple LPG-fuelled gas turbines to follow load demand, with an ORC bottoming cycle to maximize efficiency.

Rising atmospheric CO 2 levels from significant imbalance between carbon emissions from fossil fuel utilization, especially for energy and chemicals, and natural carbon sequestration rates is known to drive-up the global temperatures and associated catastrophic climate changes, such as rising mean sea level, glacial melting, and extinction of ecosystems. Carbon capture and utilization techniques are necessary for transition from fossil fuel infrastructure to renewable energy resources to help delay the dangers of reaching to the point of positive feedback between carbon emissions and climate change which can drive terrestrial conditions to uninhabitable levels. CO 2 captured from the atmosphere directly or from flue gases of a power plant can be recycled and transformed to CO and syngas for use as energy and value-added chemicals. Utilizing renewable energy resources to drive CO 2 conversion to CO via thermochemical redox looping can provide a carbon negative renewable energy conversion pathway for sustainable energy production as well as value-added products. Substituted ferrites such as Co-ferrite, Mnferrite were found to be promising materials to aid the conversion of CO 2 to CO at lower reduction temperatures. Furthermore, the conversion of these materials in the presence of Al 2 O 3 provided hercynite cycling, which further lowered the reduction temperature. In this paper, Co-ferrite and Co-ferrite-alumina prepared via co-precipitation were investigated to understand their potential as oxygen carriers for CO 2 conversion under isothermal redox looping. Isothermal reduction looping provided improved feasibility in redox conversion since it avoids the need for temperature swinging which improves thermal efficiency. These efforts alleviates the energy losses in heat recovery while also reducing thermal stresses on both the materials and the reactor. Lab-scale testing was carried out at 1673 K on these materials for extended periods and multiple cycles to gain insights into cyclic performance and the feasibility of sintering, which is a common issue in iron-oxide-based oxygen carriers. Cobalt doping provided with lowering of reduction temperature requirement at the cost of oxidation thermodynamic spontaneity that required increased oxidation temperature. At the concentrations examined, these opposing phenomenon made isothermal redox operation feasible by providing high CO yields comparable to oxygen carriers in the literature, which were operated at different temperatures for reduction and oxidation. Significantly high CO yields (∼ 750 μmol/g) were obtained from Co-ferrite isothermal redox looping. Co-ferrite-alumina provided lower CO yields compared to Co-ferrite. The oxygen storage was similar to those reported in the literature on isothermal H 2 O splitting, but with improved morphological stability at high temperature, especially compared to ferrite. This pathway of oxygen carrier development is considered suitable with further requirement in optimization for scaling of renewable CO 2 conversion into valuable products.

High intensity colorless distributed combustion has been a promising combustion technique as it enables much reduced pollutant emissions such as NO and CO, as well as more thermal uniformity, flame stability and combustion efficiency. The main requirement for achieving distributed conditions is to provide controlled entrainment of reactive hot product gases into the fresh mixture prior to ignition. In this way, the oxygen concentration is reduced, which results in lower reaction rates, promoting longer mixing times and volumetric distribution of the reaction zones. Though distributed combustion has been extensively studied for various heat loads and intensities, fuels, geometries, there is limited information related to fuel flexibility. Therefore, it is of interest to investigate hydrogen enriched gaseous fuels for greater understanding of low calorific high flame speed fuels in a distributed combustion system. Three various hydrogen content gaseous fuel (40–60% by volume) were investigated in a swirl-stabilized burner for this study, through the use of either N 2 or CO 2 as the diluent in order to achieve distributed conditions. The OH* chemiluminescence flame signatures were obtained in the flame front and emissions were measured from the combustor exit. The results showed that both the hydrogen concentration and diluent type considerably impacted the oxygen concentration at which transition to CDC occurred. Distributed conditions were achieved at oxygen concentrations of 10–12% with entrained N 2 and 13–15% with entrained CO 2 for various gaseous fuels consumed. It was determined that the transition to CDC occurred at a lower oxygen concentration for high hydrogen content fuels due to the higher flame speed of hydrogen. The flame images demonstrated that the flashback propensity of the gaseous fuels were eliminated and enhanced flame stability was achieved under the favorable CDC conditions. For NO pollutant emission, ultra-low NO level was achieved under CDC (less than 1 ppm) while CO pollutant emission decreased gradually with condition approaching distributed conditions, and then increased slightly due to the lower flammability limit and dissociation of CO 2 .

Across the world, many people, especially in rural communities, still lack access to secure, affordable electricity supplies. Many countries also lack or have under-developed indigenous fossil fuel resources, or rely on environmentally unfriendly fuels such as coal or Heavy Fuel Oil. Many under-developed regions though are blessed with considerable agricultural resources, and well-suited to Distributed Power Generation, where smaller decentralized power plants are located close to the actual energy consumers. Distributed Power eliminates the need for an electricity transmission grid, or reduces the investment costs necessary to strengthen the grid system, and helps ensure stable, secure electricity to support local economic growth. Agricultural wastes can be used as a locally available feedstock to produce the energy required to electrify regions and stimulate economic growth. This paper examines the benefits of applying Poly-generation — the production of multiple products at a single location — and examines a proposed bio-refinery scheme to produce ethanol from agricultural waste. The ethanol production process produces a waste biogas, which can then be used in a high efficiency Cogeneration (or Combined Heat and Power) plant as a fuel for gas turbines to generate electricity and steam (heat), not just for the bio-refinery but also local industry and businesses. By creating a high value product (ethanol) along with a free fuel, the bio-refinery acts as an anchor plant to provide reliable, affordable electricity to the local community. As well as providing economic benefits, such a concept has multiple environmental benefits as regions and nations try to combine growth in energy demand with reduction in global greenhouse gas emissions: agricultural residues that would otherwise have decayed emitting methane and CO 2 into the atmosphere are used to create a high value product in ethanol, while using the biogas as a fuel displaces combustion of fossil fuels, reducing both combustion emissions and those associated with transportation of the fuel to the point of use.

Traditional carbon capture technology has been shown to effectively capture emissions, but at a cost of reducing power plant output. Molten carbonate fuel cell technology (MCFC) has the potential to be able to concentrate plant carbon emissions into a gas stream that is suitable for storage while boosting total plant power output. When considering this type of technology, the original purpose and function of the power plant must be considered. In particular, gas turbines (GT) based natural gas combined cycle (NGCC), which are capable of dynamic load following operation, are likely to need to maintain operational flexibility. This work explores the retrofit of an existing GT with MCFC technology for carbon capture when the plant is operated at part load. Physical models for major plant components are built and used to select optimal operating set points such that operating cost is minimized. Special attention is given to ensuring feasible operation across all engine components. The results show MCFC operational parameters that minimize change in fuel cell operating conditions when the gas turbine is operated at part load.

Development of alternative carbonaceous sources for energy production is essential to alleviate the dependence on depleting fossil fuels which led to increasing atmospheric CO 2 and thus global warming. While biomass utilization for energy and chemical production has been extensively studied in the literature, such studies on municipal solid wastes is difficult to interpret due to the heterogeneous nature of the waste. Understanding of the influence of individual components is necessary for comprehensive development of waste-to-energy pathway. One such waste that is complicated and has often been ignored in the literature is composite polymer absorbent material waste which can also be considered as a potential feedstock for thermochemical pathway of energy production. Composite polymer absorbent materials are ubiquitously used these days in the form of sanitary napkins, diapers, water blockers, fire blockers and surgical pads due to their high water-absorptive nature. Pyrolysis and CO 2 gasification is ideal for such materials due to its versatile feedstock intake and uniform product output in the form of syngas with adjustable composition. CO 2 gasification also provides the added benefit of CO 2 utilization which provides carbon offset to this process. In the present study, a mixture of cellulose, absorbent material (sodium polyacrylate), polypropylene and polystyrene in a fixed proportion, to model approximate composition of a diaper, was examined for its pyrolysis and CO 2 gasification capability for viable syngas production. The influence of individual components into the syngas yield from the composite waste gasification was also investigated. A fixed-bed, semi-batch reactor facility along with gas chromatography was employed to analyse the syngas yield and compositional evolution. Pyrolysis was done under nitrogen atmosphere and gasification was done under CO 2 atmosphere. CO 2 gasification provided net CO 2 consumption which means a net reduction in carbon emissions per joule of energy produced. The sample was tested under four isothermal conditions of 973, 1073, and 1173 K to understand the impact of operational conditions on the syngas yield. Influence of individual component of the composite absorbent waste on the syngas yield and composition was also analyzed by comparing these syngas characteristics with that of the yield from gasification of its individual components separately at 1173 K. These investigations provided us with novel results on the behavior and capabilities of these composite polymer absorbent wastes and which opens up a new avenue towards efficient utilization of solid waste resources for sustainable energy production in the form of syngas which can also be used for various chemicals production such as methanol, gasoline and other petrochemical products.

Renewable energy has a significant role to play in helping the world achieve the greenhouse gas emission reduction necessary to achieve the pathway to a 2°C increase in global temperature. Electricity generation from wind and solar resources can contribute immensely to the decarbonization of power generation, but these resources are intermittent. High penetration of intermittent renewable power generation can cause grid stability and control issues for network operators, with fast response fossil fuel power plant necessary to provide security of supply and maintain grid stability. Increasingly natural gas-fueled distributed power generation is being installed to provide the necessary grid support. However, hybrid power plants comprised of a fossil fuel power generating system, a renewable power generation system and energy storage can provide both the low CO 2 electricity required to meet environmental constraints, and the despatchability and stability required by grid operators. Integrated Solar Combined Cycle Power Plants (ISCCs), comprising a Concentrated Solar Power plant and a natural gas fired combined cycle plant, have the potential to simultaneously reduce fossil fuel consumption, provide secure, highly predictable electricity generation, and reduce the cost of integrating renewable energy into a power system. While a number of ISCCs have been built at a larger scale (above 150MW power output), the concept has rarely been adopted for smaller scale distributed power applications. In addition, the traditional ISCC concept uses a steam bottoming cycle, which consumes water, and often locations where distributed ISCC could be utilized suffer from a scarcity of fresh water. This paper evaluates whether replacing the steam bottoming cycle with an Organic Rankine Cycle (ORC) alternative can provide a simpler, lower cost distributed ISCC solution that can be utilized on smaller and island grid systems, or mini- and micro-grids, to provide an affordable, water-free, low carbon power generation system.

In order to pursue superior cycle efficiency and lower power generation cost for the CSP plants, two S-CO 2 –Brayton–cycle–based power cycles with different utilization methods of the residual heat recover of the top S-CO 2 Brayton cycle (SCBC) are investigated to seek alternatives to the stand-alone S-CO 2 cycle as the power block of concentrated solar power plants. The residual heat released by the top S-CO 2 cycle are either utilized to drive a LiBr absorption chiller (AC) for further chilling of the CO 2 fluids exiting the precooler before entering the main compressor inlet temperature or recovered by an organic rankine cycle (ORC) for generating electricity. Thermo-economic analysis and optimization are performed for the SCBC–AC and SCBC–ORC, respectively. The results show that the thermal and exergetic efficiencies of the SCBC–AC are comparable with those of the SCBC–ORC in low pressure ratio conditions ( PR <2.7) but are apparently lower than SCBC–ORC when PR is over 2.7. The LCOE of the CSP plant integrated with SCBC–AC is more sensitive to the change of PR . The optimal PR to maximum the cycle efficiency or minimize the plant LCOE for the SCBC–ORC is higher than that for the SCBC–AC, while the optimal recuperator effectiveness to minimize the LCOE of CSP plant integrated with SCBC–ORC is lower than that of SCBC–AC. The optimization results show that the thermo-economic performance of the SCBC–AC is comparable to that of the SCBC–ORC. Significant η ex improvement and LCOE reduction can be obtained by both the two combined cycles relative to the stand-alone S-CO 2 cycle. The maximal η ex improvements obtained by the SCBC–ORC and SCBC–AC are 6.83% and 4.12%, respectively. The maximal LCOE reduction obtained by the SCBC-ORC and SCBC–AC are 0.70 ȼ / (kW·h) and 0.60 ȼ / (kW·h), respectively.

Over the past decade, several technical developments (such as hydraulic fracturing) have led to an exponential increase in discovering new domestic natural gas reserves. Raw natural gas composition can vary substantially from source to source. Typically, methane accounts for 75% to 95% of the total gas, with the rest of the gas containing ethane, propane, butane, other higher hydrocarbons, and impurities, with the most common including H 2 O, CO 2 , N 2 , and H 2 S. All natural gas requires some treatment, if only to remove H 2 O; however, the composition of natural gas delivered to the commercial pipeline grids is tightly controlled. Sub-quality natural gas reserves, which are defined as fields containing more than 2% CO 2 , 4% N 2 , or 4 ppm H 2 S, make up nearly half of the world’s natural gas volume. The development of sub-quality, remote, and unconventional fields (i.e. landfill gas) can present new challenges to gas separation and purification methods. Adsorbent technologies, such as the use of activated carbons, zeolites, or metal-organic frameworks (MOFs), may hold the key to more efficient and economically viable separation methods. This work proposes to prove the applicability of the multi-component potential theory of adsorption (MPTA) to a real world natural gas adsorbent system to properly characterize the adsorbent’s selectivity for an individual gas component using only the single component isotherms. Thus, the real-world gas separation/purification application of a specific adsorbent for a given gas stream can be obtained simply and effectively without the need for large experimental efforts or costly system modifications until after an initial computational screening of perspective materials has been completed. While the current research effort will use natural gas, which is the world’s largest industrial gas separations application, to validate the MPTA, the tools gained through this effort can be applied to other gas separation effort.

Homogeneous charge compression ignition (HCCI) is a combustion technology which has received increased attention of researchers in the combustion field for its potential in achieving low oxides of nitrogen (NO x ) and soot emission in internal combustion (IC) engines. HCCI engines have advantages of higher thermal efficiency and reduced emissions in comparison to conventional internal combustion engines. In HCCI engines, ignition is controlled by the chemical kinetics, which leads to significant variation in ignition time with changes in the operating conditions. This variation limits the practical range of operation of the engine. Additionally, since HCCI engine operation combines the operating principles of both spark ignition (SI) and compression ignition (CI) engines, HCCI engine parameters such as compression ratio and injection timing may vary significantly depending on operating conditions, including the type of fuel used. As such, considerable research efforts have been focused on establishing optimal conditions for HCCI operation with both conventional and alternative fuels. In this study, numerical simulation is used to investigate the effect of compression ratio on combustion and emission characteristics of an HCCI engine fueled by pure biodiesel. Using a zero-dimensional (0-D) reactor model and a detailed reaction mechanism for biodiesel, the influence of compression ratio on the combustion and emission characteristics are studied in Chemkin-Pro. Simulation results are validated with available experimental data in terms of incylinder pressure and heat release rate to demonstrate the accuracy of the simulation model in predicting the performance of the actual engine. Analysis shows that an increase in compression ratio leads to advanced and higher peak incylinder pressure. The results also reveal that an increase in compression ratio produces advanced ignition and increased heat release rates for biodiesel combustion. Emission of NO x is observed to increase with increase in compression ratio while the effect of compression ratio on emissions of CO, CO 2 and unburned hydrocarbon (UHC) is only marginal.

Reduced mechanisms are needed for use with computational fluid dynamic codes (CFD) utilized in the design of combustors. Typically, the reduced mechanisms are created from the detailed mechanisms which contain numerous species and reactions that are computationally difficult to handle using most CFD codes. Recently, it has been shown that the detailed Aramco 2.0 mechanism well predicted the available experimental data at high pressures and in high-CO 2 diluted methane mixtures. Further, a 23-species gas-phase mechanism is derived from the detailed Aramco 2.0 mechanism by path-flux-analysis method (PFA) by using CHEM-RC. It is identified that the reaction CH 4 +HO 2 ⇔ CH 3 +H 2 O 2 is very crucial in predicting the ignition delay times under current conditions. Further, it is inferred that species C 2 H 3 and CH 3 OH are very important in predicting the ignition delay time of lean sCO 2 methane mixtures. Also, the 23-species mechanism presented in this work is performing on par with the detailed Aramco 2.0 mechanism in-terms of simulating ignition delay times, perfectly-stirred-reactor estimates under various CO 2 dilutions and equivalence ratios, and prediction of turbulence chemistry interactions. It is observed that the choice of equation-of-state has no significant impact on the ignition delay times of supercritical CH 4 /O 2 /CO 2 mixtures but it influences supercritical H 2 /O 2 /CO 2 mixtures considered in this work.

High-temperature Gas-cooled Reactor Pebble-bed Module (HTR-PM) is under construction in Shidao Bay, Shandong of China. It is supposed to be the world’s first pebble-bed modular commercial demonstration plant for High Temperature Gas-cooled Reactor (HTGR). In HTR-PM project, water-Rankine cycles have been used in the power conversion system. Meanwhile, supercritical carbon dioxide (S-CO2) Brayton cycle has shown great potentials for future HTGR technology. Comparing with typical helium Brayton cycle, in S-CO2 cycle where critical properties of carbon dioxide are utilized, compressor work may reduce significantly and thermal efficiency may improve greatly. Furthermore, the general sizes of S-CO2 cycle equipment, such as heat exchanger and turbine, would be orders of magnitude smaller than water-Rankine system at similar power output. Therefore, parameters study of S-CO2 were conducted in this paper for future HTGR. Firstly, a physical model of S-CO2 Brayton cycles was built and the performance of cycles were analyzed. Secondly, compression ratio, temperature ratio, the inlet temperature of turbine, inlet parameters of compressor, and recuperated effectiveness were discussed as key cycle parameters. For heat capacities of CO2 are significantly different as a function of temperature and pressure, flow recompression was considered. Calculation was based on a split-flow cycle configuration. The split flow ratio was also analyzed. Finally, the parameters of S-CO2 cycle were optimized for HTGR. In conclusion, S-CO2 Brayton cycle will be a good option for future HTGR.

As a promising approach for sustainable development, the distributed energy system receives increasing attention worldwide and has become a key topic explored by researchers in the areas of building energy systems and smart grid. In line with this research trend, this paper presents a case study of designing an integrated distributed energy system including photovoltaics (PV), combined cooling heating and power (CCHP) and electric and thermal energy storage for commercial buildings (i.e., a hospital and a large hotel). The subsystems are modeled individually and integrated based on a proposed control strategy to meet the electric and thermal energy demand of a building. A multi-objective particle swarm optimization (PSO) is performed to determine the optimal size of each subsystem with objectives to minimize carbon dioxide emissions and payback period. The results demonstrate that the proposed method can be effectively utilized to obtain an optimized design of distributed energy systems that can minimize environmental and economic impacts for different buildings.

Combined Cycle Gas Turbine (CCGT) power plant offer operators both environmental and economic benefits. The high efficiency achievable across a wide load range reduces both fuel costs and CO 2 emissions to atmosphere. However, the scale of the power generation plays a major role in determining both cost and efficiency: a modern large centralized CCGT of 600MW output or more will have a full load efficiency in excess of 60% and a very competitive installed cost on a US$/kW basis. The smaller gas turbines required for distributed power applications are not optimized for combined cycle operation, with potential full load efficiencies of a combined cycle scheme ranging from a little over 40% to the high 50s depending on the power output of the gas turbine, the exhaust gas conditions and the plant configuration, while the installed cost is around twice that of a large centralized CCGT on a US$/kW basis. The drawback of a conventional combined cycle plant design is the need for water, which is a scarce commodity in some regions. Air cooling of the CCGT plant can be used to reduce water consumption, but make-up water will still be required for the steam system to compensate for steam losses, blowdown etc. While the lower exhaust gas temperatures of the smaller gas turbines impact the combined cycle efficiencies achievable, they do allow Organic Rankine Cycle (ORC) technology to be considered for an alternative combined cycle configuration. This paper compares both the capital and operating costs and performance of combined cycle power plants for distributed power applications in the 30MW to 250MW power range based on conventional steam and various different ORC configurations.

The Kemper County Project has demonstrated Transport Integrated Gasification (TRIG™) at a 2-on-1 Integrated Gasification Combined-Cycle (IGCC) facility located in Kemper County, Mississippi. Kemper is the largest IGCC project in the world, the first to use lignite as fuel, the first to capture and sell CO 2 , and the first to produce multiple byproducts from initial startup. The facility features two Siemens SGT6-5000F gas turbines, each capable of operating on a high-hydrogen syngas produced in the Transport Gasifiers from locally mined lignite. Using high-hydrogen syngas requires unique modifications to the combustion turbine design. Flame-diffusion combustors, rather than dry low-NO X designs, prevent flashback caused by the high hydrogen content of the syngas. Also, ports added to the turbine compressor casing allow air to be extracted from the compressor and used elsewhere in the plant, supplying up to one half of the air required by the gasifier. The Kemper facility has achieved the integrated operation of both gasifiers, including the production of electricity from syngas by both combustion turbines. Turbine operation on the high hydrogen syngas was smooth both during normal operations and during transitions, with efficiencies meeting or exceeding expectations. This paper describes the Kemper plant design, focusing on the combustion turbine design unique to Kemper. The paper also discusses turbine design challenges specific to Kemper, provides an overview of the robust control scheme used on both syngas and natural gas co-firing operations, and provides preliminary operational and performance results, including inspection findings.

In order to reduce CO 2 emission from thermal power stations with keeping high thermal efficiency, a new concept of IGCC system, namely oxy-fuel IGCC, has been recently proposed. Hence CO 2 is recycled in the system, the effect of CO 2 recycle on each equipments should be clarified. In this study, the effect of recycled CO 2 injection on coal gasifier performance was investigated by means of three-dimensional RANS-based numerical simulation. For estimating of coal gasifier performance, coal gasification and water-gas shift reaction are key phenomena. Therefore, the partially active site sharing coal gasification model and detailed chemistry of water-gas shift reaction model were implemented. Calculated gasifier was a commercial scale entrained flow coal gasifier whose coal feeding rate is 70 tons per hour. The gasifier consists of a lower combustor part and an upper reductor part. The effect of coal feeding rate into the reductor, R/T, was investigated. The results show that temperature in the combustor decreases with decreasing R/T. In the lower R/T condition, hence air ratio in the combustor decreases, the reducing atmosphere becomes stronger. As a result, coal gasification which is endothermic reaction in the combustor is promoted. Although coal gasification is occurred in the reductor in higher R/T condition, total coal gasification rate is not so promoted compared with lower R/T condition. Due to the above mechanism, the gasification performance becomes higher with decreasing R/T. The results obtained in this study indicate that it is important that how much the higher gasification reactivity in a gasifier is exploited by optimizing local heat balance.

In recent years, global warming and climate change caused by the greenhouse gas emissions has given rise to widespread concerns. CO 2 has been considered as the principal greenhouse gas of interest, and fossil-fuel-fired power plants have been deemed as the largest stationary sources of CO 2 emission. It is imperative to capture CO 2 from these sources to reduce the global CO 2 emissions. Lately, capturing CO 2 from flue gas using solid absorbents shows promising for CO 2 abatement. For the cost-effective CO 2 capture process and the recycling of environmental pollutants, deprecated resources have been utilized for CO 2 capture from flue gas. In this work, fly ashes derived from different raw materials were tried as solid CO 2 sorbents for flue gas treatment. To improve their CO 2 capture capacities, the ashes were modified by different polyamines. An experimental demonstration on CO 2 capture behaviors of fresh ashes and modified sorbents in simulated flue gas atmosphere of 40°C, 15% CO 2 + 15% H 2 O and balanced N 2 was presented in detail with a fixed-bed reactor system. CO 2 capture capacities of fresh ashes were calculated as 0.56 mmolCO 2 /g, 0.32 mmolCO 2 /g, 0.44 mmolCO 2 /g and 0.83 mmolCO 2 /g, respectively. By contrast, CO 2 capture capacities of amine-modified samples had been enhanced as 0.38 mmolCO 2 /g, 0.65 mmolCO 2 /g, 1.07 mmolCO 2 /g, 0.85 mmolCO 2 /g and 1.17 mmolCO 2 /g. The optimal sample of TEPA-modified biomass ash (TEPA-BA) with CO 2 capture capacity of 1.17mmolCO 2 /g was screened. The optimal candidate was then selected for further investigation of the effects of temperature, CO 2 concentration and H 2 O concentration on its CO 2 capture behaviors. The results indicated that CO 2 capture capacity would increase with the increase of temperature in the range of 30 to 40 °C and decrease with the increase of temperature in the range of 40 to 60°C, increase with the increase of CO 2 concentration in the range of 5% to 20%, increase with the increase of H 2 O concentration in the range of 0% to 15% and decrease with the increase of H 2 O concentration in the range of 15% to 20%. The results in this work could provide basic data as a guidance for further applying the sorbents in practical operations.