The effort in the adoption of energy efficient technologies and the attempt at reducing CO 2 emissions has brought a new wave in the diffusion of distributed generation and a renewed interested in CHP systems, especially in the case of industrial cogeneration applications. It is therefore of primary importance for prime movers ‘producers — as Baker Hughes — to develop fast and reliable simulation methods that are able to estimate the overall performances of the proposed plants in order to help the customer assessing the feasibility of the investment. The aim of this paper is to introduce a newly developed tool for the simulation of design and off-design conditions of gas turbine-based cogeneration systems, where heat is recovered through a Heat Recovery Steam Generator. The tool is meant to be driven by a small amount of inputs, making it possible to define sharp strategies for the design of such plants since the early phases of interaction with customers. Design points have been varied to assess their influence on the off-design working points of the plant and on the overall performances, which have been considered through the parameters of global efficiency and Primary Energy Saving. Results have highlighted the importance of considering the off-design effects in the simulation of CHP systems, both from a correct evaluation of plant’s critical operating parameters and from a correct estimation of plant’s performances.

Hydrogen-fired gas turbines have the potential to play an important role in decarbonized energy sectors. However, a demand-oriented supply of CO 2 -neutral hydrogen for the operation of gas turbines is technically and economically challenging. These challenges mainly arise due to various interdependencies between the volatility of renewable power generation, available hydrogen production capacities, available hydrogen storage capacities and the operational demands to be met by gas turbines. The present study aims to quantify these interdependencies by conducting a detailed model-based analysis of an exemplary combined heat and power system featuring a hydrogen-fired industrial gas turbine with on-site hydrogen production via electrolysis and on-site hydrogen storage in pressure vessels. In order to identify the sought-after interdependencies, simulation runs featuring various combinations of available hydrogen production and storage capacities are analyzed. If only local power surpluses are utilized for the electrolysis, the obtained results reveal a strong non-linear impact of both the hydrogen production capacity and the storage capacity on the ability to provide hydrogen for the gas turbine. Furthermore, the results indicate that an exclusive utilization of local power surpluses leads to very limited periods of hydrogen-based gas turbine operation and low utilization rates of the available hydrogen production and storage capacities. If additional power for the operation of electrolyzers is supplied by the grid, increased utilization rates and prolonged periods of hydrogen-based gas turbine operation can be achieved. However, in order to realize an overall reduction of CO 2 emissions, this mode of operation requires the supply of large quantities of renewable power by the grid. Furthermore, the results of an additional economic analysis reveal that both investigated operational modes are currently not economically viable within the considered economic framework.

Renewable energy penetration is growing, due to the target of greenhouse-gas-emission reduction, even though fossil fuel-based technologies are still necessary in the current energy market scenario to provide reliable back-up power to stabilize the grid. Nevertheless, currently, an investment in such a kind of power plant might not be profitable enough, since some energy policies have led to a general decrease of both the average price of electricity and its variability; moreover, in several countries negative prices are reached on some sunny or windy days. Within this context, Combined Heat and Power systems appear not just as a fuel-efficient way to fulfill local thermal demand, but also as a sustainable way to maintain installed capacity able to support electricity grid reliability. Innovative solutions to increase both the efficiency and flexibility of those power plants, as well as careful evaluations of the economic context, are essential to ensure the sustainability of the economic investment in a fast-paced changing energy field. This study aims to evaluate the economic viability and environmental impact of an integrated solution of a cogenerative combined cycle gas turbine power plant with a flue gas condensing heat pump. Considering capital expenditure, heat demand, electricity price and its fluctuations during the whole system life, the sustainability of the investment is evaluated taking into account the uncertainties of economic scenarios and benchmarked against the integration of a cogenerative combined cycle gas turbine power plant with a Heat-Only Boiler.

About 75% of the electric power generated by centralized power plants feeds the energy needs from the residential and commercial sectors. These power plants waste about 67% of primary energy as heat emitting 2 billion tons of CO 2 per year in the process (∼ 38% of total US CO 2 generated per year) [1]. A study conducted by the United States Department of Energy indicated that developing small-scale combined heat and power systems to serve the commercial and residential sectors could have a significant impact on both energy savings and CO 2 emissions. However, systems of this scale historically suffer from low efficiencies for a variety of reasons. From a combustion perspective, at these small scales, few systems can achieve the balance between low emissions and high efficiencies due in part to the increasing sensitivity of the system to hydrodynamic and heat transfer effects. Addressing the hydrodynamic impact, the effects of downscaling on the flowfield evolution were studied on the low swirl burner (LSB) to understand if it could be adapted to systems at smaller scales. Utilizing particle image velocimetry (PIV), three different swirlers were studied ranging from 12 mm to 25.4 mm representing an output range of less than 1 kW to over 23 kW. Results have shown that the small-scale burners tested exhibited similar flowfield characteristics to their larger-scale counterparts in the non-reacting cases studied. Utilizing this data, as a proof of concept, a 14 mm diameter LSB with an output of 3.33 kW was developed for use in microturbine operating on a recuperated Brayton cycle. Emissions results from this burner proved the feasibility of the system at sufficiently lean mixtures. Furthermore, integration of the newly developed LSB into a can style combustor for a microturbine application was successfully completed and comfortably meet the stringent emissions targets. While the analysis of the non-reacting cases was successful, the reacting cases were less conclusive and further investigation is required to gain an understanding of the flowfield evolution which is the subject of future work.

Micro gas turbines (MGT) used as combined heat and power (CHP) systems present interesting advantages over conventional CHP systems. For low power MGTs (1–3 kW el ), a single stage jet-stabilized combustor is well suited to reach low emissions despite high preheat temperatures. Although several jet stabilized combustors in this power range have already been presented in literature, the influence of single design parameters was not described yet. Therefore this paper presents a design study with different combustor geometries. Besides the number of nozzles, also the diameter of air and fuel nozzles as well as the length of the mixing zone is varied. Experiments are performed in an atmospheric combustor test rig with preheat temperatures of 730°C. Additionally RANS-CFD simulations for selected conditions are carried out. The results indicate an inverse correlation between the number of nozzles (diameter adjusted for constant inlet velocities) and the emissions, where an increase in the number of nozzles leads to lower emissions and a shorter reaction zone. Changing the air nozzle diameter and therefore the jet velocity creates a different trend. As the pressure loss decreases with smaller inlet velocities, the CO- and NO x -emission levels increase. An extension of the mixing section as well as of the diameter of the fuel nozzles have only minor effects for the examined geometries. The knowledge acquired in this work helps to evaluate the influence of design parameter changes on the behavior of small scale jet-stabilized combustors and allows an optimization of the combustor design regarding flame length and emissions.

Residential buildings account for approximately one fifth of the total energy consumption and 12 % of the overall CO 2 emissions in the OECD countries. Replacing conventional boilers by a co-generation of heat and power in decentralized plants on site promises a great benefit. Especially, micro gas turbine (MGT) based combined heat and power systems are particularly suitable due to their low pollutant emissions without exhaust gas treatment. Hence, the overall aim of this work is the development of a recuperated inverted MGT as heat and power supply for a single family house with 1 kW el . First, an inverted MGT on a Brayton cycle MGT was developed and experimentally characterized, in previous work by the authors. This approach allows exploiting the potential of using the same components for both cycles. As a next step, the applicability of the Brayton cycle components operated in inverted mode needs to be evaluated and the requirements for a component optimization need to be defined, both, by pursuing thermodynamic cycle simulations. This paper presents a parametrization and validation of in-house 1D steady state simulation tool for an inverted MGT, based on experimental data from the inverted Brayton cycle test rig. Moreover, a sensitivity analysis is conducted to estimate the influence of every major component on the overall system and to identify the necessary optimizations. Finally, the component requirements for an optimized inverted MGT with 1 kW el and 16 % of electrical efficiency are defined. This work demonstrates the high potential of an inverted MGT for a decentralized heat and power generation when optimizing the system components.

Nowadays, the rising demand for energy and serious environmental pollution become the motive to improve the energy structure, saving energy and optimize energy utilization. Based on a gas turbine, a marine multistage gas turbine combined heat and power (CHP) structure is proposed. The CHP system includes the top gas turbine Brayton cycle, the intermediate water Rankine cycle (WRC) and the bottom organic Rankine cycle (ORC). According to the method of screening organic Rankine cycle refrigerant to select the appropriate organic working fluids, and their physical characteristics are described. Based on the modular modelling method, the 3-stage CHP system is established. In order to more effectively absorb low temperature waste heat, three different kinds of 3-stage CHP structures were designed to recover the heat in the exhaust gas from the heat recover steam generator (HRSG). The thermodynamic model of the combined heat and power system of marine multistage gas turbine was used to simulate the performance of three different types of 3-stage CHP structures, the optimal 3-stage CHP structure was selected by comparing and analyzing the simulation results. Based on the simulation results of the design point, it is found that the introduction of the optimal 3-stage CHP structure can increase the power output by about 8.5% and improve the cycle thermal efficiency by about 4.32% compared with a conventional 2-stage CHP cycle where only gas turbine topping cycle and water Rankine bottoming cycle are included.

Decentralized heat and power (CHP) production constitutes a promising solution to reduce the primary energy consumption and greenhouse gas emissions. Here, micro gas turbine (MGT) based CHP systems are particularly suitable due to their low pollutant emissions without exhaust gas treatment. Typically, the electrical power demand for single houses ranges from 1 to several kW el . However, downsizing turbocharger components of a conventional MGT CHP system can reduce electrical efficiencies since losses like seal and tip leakages, generally do not scale proportionally with size. By introducing an inverted Brayton Cycle (IBC) based MGT this potential can be exploited. The IBC keeps the volumetric flows constant while mass flow and thermodynamic work are scaled by the ratio of pressure level. Since the performance of turbocharger components is mainly driven by the volumetric flow they should be applicable for both cycles. Hence, smaller power outputs can be achieved. The overall aim of this work, is the development of a recuperated inverted MGT CHP unit for a single family house with 1 kW el . This paper presents an experimental study of the applicability and feasibility of a conventional MGT operated in IBC mode. The demonstrator was based on a single shaft, single stage conventional MGT. Reliable start up and stable operation within the entire operating range from 180 000 rpm to 240 000 rpm are demonstrated. The turbine outlet pressure varied between 0,5 bar (part load) and 0,3 bar absolute (full load). All relevant parameters such as pressure losses and efficiencies of the main components are investigated. Moreover, the power output and the mechanical and thermal losses were analyzed in detail. Although the results indicated that the mechanical and heat losses have a high influence on the performance and economic efficiency of the system, the prototype shows great potential for further development.

A promising technology solution to meet the demands for highly efficient and clean CHP systems with the highest load and fuel flexibility is the SOFC/MGT hybrid power plant concept (HPP). In this concept, a solid oxide fuel cell (SOFC) is combined with a micro gas turbine (MGT) to use the hot and low-caloric SOFC off-gases for further energy production. In this study, the focus is set on the development of a suitable single-stage jet-stabilized combustor which combines the functionality of a gas turbine combustor and a SOFC off-gas burner for low-caloric SOFC off-gases at combustor inlet temperatures up to 1073 K. To experimentally characterize the newly developed SOFC off-gas combustion system beyond the turbine operating conditions in the HPP, atmospheric tests were carried out. The anode and cathode flows within the test series are provided without the SOFC being in place. Reflecting the resulting SOFC off-gas conditions at different possible HPP operating points, the results from variations of the cathode and anode mass flow rates, the O 2 content and the LHV were carried out and are presented. The off-gas burner proves a wide operational stability of the combustion concept with CO emissions below 10 ppm and NO x emissions below 3 ppm. The shape and location of the flame is investigated using the OH* signal detected by an ICCD camera.

In the present work mathematical modeling of a CHP system based on Micro Gas Turbine (MGT) with Inverted Brayton Cycle (IBC) (also known as subatmospheric) is provided. Nominal electric power of the facility is 10 kW. Engineering calculation based modeling is conducted to determine optimal parameters of each component, electrical and total efficiency at full load. Further dynamic modeling is provided for the components with determined optimal parameters. With chosen optimal parameters of the scheme components and coolant temperature the dynamic (time-dependent) modeling of disturbance from the nominal state with no control, ramp down and ramp up of power load (a) and heat load (b) with the activated control system was provided. An iteration based approach of MGT modeling is suggested. The difficulties in the system control under reduction of heat consumption are revealed and challenged. The final objectives of the research are comparison of the IBC with the conventional Brayton cycle for MGT application from the electric efficiency, dynamic behavior and controllability points of view, creation of the control system for such a facility.

Energy saving and environment become important issues in power and propulsion generation industry. One of such examples is the marine transportation where a lot of energy from consumed fuel is wasted in exhaust and emissions are produced in vessel propulsion systems. The focus of this research is to look at a typical marine propulsion system where gas turbines are the prime movers and to investigate the potentials of a novel 3-stage gas turbine combined heat and power (CHP) system for marine applications. Such a CHP system may include a topping gas turbine Brayton cycle, an intermediate water Rankine cycle (WRC), and a bottoming organic Rankine cycle (ORC). In the system, gas turbine is connected with a generator to produce electricity, water Rankine cycle produces superheated steam driving steam turbine for electricity generation and/or for heating, and organic Rankine cycle is used to produce electricity by recycling low temperature energy. A thermodynamic model for the 3-stage CHP system is established to simulate the performance of the system at different power demand operating conditions. The developed performance simulation system has been applied to a typical model vessel propulsion system application. Based on the simulated results, it is evident that compared with a conventional 2-stage CHP cycle where only gas turbine topping cycle and water Rankine bottoming cycle are included, the introduction of the organic Rankine cycle can increase the power output by about 7% and improve the cycle thermal efficiency by about 3.52%.

A laboratory based undergraduate course focused on energy systems and energy efficiency was developed at the Lucerne University of Applied Sciences. The course is a practice-oriented introduction to fluid / energy systems, turbomachinery, and energy production. It is offered to the mechanical engineering as well as to the “Energy Systems” program students in the first semester. Main parts of the course are experiments and mini projects carried out in the fluid mechanics, thermodynamics, and turbomachinery laboratories. After an introduction of (1) the basic theory of the mass- and energy conservation equations as main governing laws for energy systems and (2) measurement techniques during the first two weeks, the students carry out experiments in small groups on different test rigs with the help of an instructor for about four weeks (each week a different test). The experiments and test rigs are selected considering different aspects of turbomachinery and energy systems. They cover hydraulic turbines, small wind turbines, a water pump, compressor, heat pump, combined heat and power system, fuel cell, solar energy, and combustion engine. Following a two weeks theory wrap up, the students start with mini projects again in small groups in the laboratory. The students are requested to do a new design or to carry out a design change or modification at an existing machine or test rig. They also need to test their new design or design modification. At the end the students have to do a presentation about the mini project results and write a short report. The objectives of the course are first to introduce the laboratory environment to the students from the beginning of the curriculum. Further the experimental investigations on laboratory test rigs make the students familiar with the fundamentals, working principles, characteristics, operation, and application of turbomachinery and energy systems. They also learn the basics of energy conversion, conservation, and the importance of relevant performance parameters such as efficiency. The mini projects have direct practical relevance to real world problems and applications. From an educational viewpoint the students are introduced to team-work during the projects, project planning with execution, and they are learning by doing or by experiential learning. The students are actively involved in the mini projects and they can reflect their experience at the end of the course during the presentations. The implementation of the course is time consuming and costly but the feedback from the students is very positive although they are challenged by confronting real world energy systems and problems in the first semester.

This paper presents a comprehensive experimental investigation of a newly designed single-stage combustion system based on the flameless oxidation (FLOX ® ) technology for a small scale micro gas turbine (MGT). It is used for a combined heat and power plant (CHP) with an electrical power output of 3 kW, using natural gas as fuel. Flameless oxidation is characterized by a flame distributed over a large volume and a high internal recirculation of flue gas. Considering the high combustor inlet temperatures up to 1000 K as required for this application, the FLOX ® -combustion concept offers various advantages compared to swirl-stabilized combustion systems in terms of flashback risk and exhaust gas emissions. This paper describes the detailed characterization of the jet-stabilized combustor. Two versions of the combustor were tested, one generic and one modified version suitable for the integration into the micro gas turbine at an atmospheric test rig with optical access. The stable operating range, including lean blow out (LBO) limits, was determined for varying equivalence ratios, thermal powers and preheat temperatures. The influence of these parameters on the combustion characteristics is discussed. Furthermore, the shape and location of the heat release zone is investigated with OH*-chemiluminescence (OH* CL). The exhaust gas emissions NO x , CO and unburned hydrocarbon (UHC) were also measured. The results demonstrate that the developed combustor design ensures stable and reliable performance. It also offers a high operational flexibility and low pressure loss with NO x , CO and UHC emissions far below regulation limits for all relevant engine conditions.

Cogeneration systems capable of utilizing our abundant coal resources are now especially attractive, as petroleum products are relatively expensive. However, coal-fired systems must inevitably cope with the abrasive and fouling character of the noncombustible ash content of all coals. This paper discusses the characteristics and cogeneration potential of the coal-fired, closed-cycle, gas turbine system (in which the working fluid is isolated from the products of coal combustion). Many closed-cycle, gas turbine thermodynamic cycles may be adapted to cogeneration. Parametric performance data are presented. The advantages of closed-cycle, gas turbine system/cogeneration cycles are explored, and comparisons are made between such systems and the more conventional steam-turbine based cogeneration cycles. The technology of closed-cycle fired heaters, including pulverized coal and fluidized bed firing is discussed. The key technical features of the fired heaters are discussed.

General characteristics equations for cogeneration cycle thermodynamic performance were derived and expressed as functions of the power-to-heat ratio. Based on these equations, design point performance of indirect-fired open-cycle and closed-cycle gas turbine/cogeneration systems were analyzed and compared with those of steam turbine/cogeneration system. Effects of gas turbine pressure ratio and inlet temperature on design point performance were evaluated. Off-design partial load performances of the three cogeneration systems using various control modes were also investigated. Results indicated significant efficiency advantage of the closed-cycle gas turbine/cogeneration system over the others for both design and off-design operations.

Heat recovery boilers utilizing the exhaust from gas turbines continue to be viable as industrial cogeneration systems. This paper outlines the types of heat recovery boilers available for use with gas turbines (1–100 MW). It discusses the design and performance criteria for both unfired and supplementary fired gas turbine exhaust heat recovery boilers of single and multiple pressure levels. Equations to assist in energy balances are included along with design features of heat recovery system components. The economic incentive to achieve the maximum practical heat recovery versus the impact on boiler design and capital cost are examined and discussed. It is intended that the information presented in this paper will be of use to individuals who are not intimately familiar with gas turbine heat recovery systems so that they can better specify and evaluate potential systems.

This paper will describe a co-generation system using a conventional boiler or process heater and applying a gas turbine to provide preheated combustion air to the boiler or furnace. A number of design considerations such as applicable type and size of the gas turbine, expected energy savings and control and safety aspects are discussed. These design considerations should be taken into account when retrofitting a conventional plant into a co-generation system. The paper will also describe such a type of co-generation system with a process heater which is in operation at the Chevron/Texaco Refinery in The Netherlands.

While present energy needs can be met with available supplies of fossil fuels, the need to plan for the eventual elimination of dependence on premium fuels in utility and industrial applications remains urgent. Along with continuing awareness of the need for non-petroleum-based power and heat production is the renewed interest in cogeneration systems, for reasons of both energy conservation and the economies possible in meeting industrial/commercial process and space heat needs. One of the most promising power conversion technologies for these needs is the closed cycle gas turbine (CCGT) configured for power and heat production. The CCGT offers the ability to operate with a wide range of fuel types and qualities and to provide congenerated heat and power over a wide range of power-to-heat ratios. Additionally, the CCGT has the unique advantage of operating over a wide capacity range at no significant compromise in efficiency. Closed cycle gas turbines have been in commercial use, principally in Europe, for over four decades. That experience base, combined with emerging awareness of potential CCGT applications, could lead to the operation of coal-fired CCGT cogeneration systems in the U.S. within the next decade. This paper discusses the multi-fuel capability of the CCGT and compares its performance as a flexible cogeneration system with that of a more conventional steam turbine system.

Samples of thermal and electric loads for four hospitals were used to evaluate cogeneration potential. The size range was one-half to three MWe, and the units were assumed free-standing in the sense that surplus power buyback by utilities was not considered. Discounted cash flow analysis was applied to calculate Return on Investment (ROI). Using typical values for the installed equipment cost, fuel cost and financing variables ROI was found to range from 25% to 90%. The sensitivity of ROI to eight system and pricing variables and five financing variables is reported. The ROI was found to be most sensitive to electricity price. The sensitivity to thermal efficiency of the engine was low provided that the efficiency was in the 20%–30% range. This suggests that moderate-performance high reliability gas turbines are the most suitable for this application.

This paper discusses a current research and development program whose object is to advance the technical readiness of large, coal-fired heaters to supply the input to closed-cycle gas turbine cogeneration systems. Such closed-cycle systems become increasingly attractive as energy cost increase. The gas turbine working fluid is completely isolated from the products of coal combustion, thus avoiding corrosion and erosion of the gas turbine system. Additionally, the nature of the thermodynamic cycles is frequently such as to afford substantial savings in coal input requirements as compared to steam turbine based systems producing equivalent process heat and power. This paper describes three fired heater concepts that are under development for CCGT service. The organization of the research and development program, and the development needs of the fired heaters that are to be satisfied by the R&D program, are discussed.