G. Negri di Montenegro

Inverted Brayton cycle employment for low-temperature cogenerative applications

The employment of cogeneration plants for thermal and electric power production is constantly increasing especially for low power requirements. In most cases, to match these low power needs, the cogeneration plant is built up with diesel or gasoline engine or with gas turbine units. In this paper, the performance, in terms of the most utilized cogenerative indexes, of an inverted Brayton cycle working with the gas exhausted by the open power plant have been evaluated. Subsequently, the analysis of a cogenerative gas turbine equipped with IBC was carried out and the benefits numerically calculated. It resulted that the IBC employment may increase of about five percentage points the plant electric efficiency, making this solution particularly attractive for cogenerative applications.

Thermo-Economic Analysis of an Intercooled, Reheat and Recuperated Gas Turbine for Cogeneration Applications–Part I: Base Load Operation

The knowledge of off-design performance for a given gas turbine system is critical particularly in applications where considerable operation at low load setting is required. This information allows designers to ensure safe operation of the system and determine in advance thermoeconomic penalty due to performance loss while operating under part-load conditions. In this paper, thermoeconomic analysis results for the intercooled reheat (ICRH) and recuperated gas turbine, at the part-load conditions in cogeneration applications, have been presented. Thermodynamically, a recuperated ICRH gas turbine-based cogeneration system showed lower penalty in terms of electric efficiency and Energy Saving Index over the entire part-load range in comparison to the other cycles (nonrecuperated ICRH, recuperated Brayton and simple Brayton cycles) investigated. Based on the comprehensive economic analysis for the assumed values of economic parameters, this study shows that a midsize (electric power capacity 20 MW) cogeneration system utilizing nonrecuperated ICRH cycle provides higher return on investment both at full-load and part-load conditions, compared to the other same size cycles, over the entire range of fuel cost, electric sale, and steam sale values examined. The plausible reasons for the observed trends in thermodynamic and economic performance parameters for four cycles and three sizes of cogeneration systems under full-load and part-load conditions have been presented in this paper.

Gas Turbine Based Power Cycles - A State-of-the-Art Review

Gas turbines have been used in wide ranging applications since their world’s first use in aviation and power generation in the jet engine powered flight of Heinkel aircraft (model He-178) and Brown Boveri & Cie’s (BBC) 4 MW power generation plant in Neuchatel, Switzerland, respectively during 1939. This paper provides the historical evolution of the gas turbine (GT) based power cycles. A detailed parametric thermodynamic cycle analysis is presented for various GT cycles (mostly, which have been implemented). In addition, a comparative performance evaluation of various cycles is presented clearly showing ranges within which a particular arrangement can be beneficial. The simulation results are compared with the performance of existing machines with similar design conditions. A discussion is presented to show limitations and advantages of each GT cycle and the associated technological advancements made. To complete the review, modified Brayton cycles under development by the gas turbine manufacturers, researchers, etc. have also been identified.

A Feasibility Study of Inverted Brayton Cycle for Gas Turbine Repowering

In the paper a feasibility study of inverted Brayton cycle (IBC) engines, for the repowering of existing gas turbines, is presented. The following main phases have been carried out: (i) identification of the more suitable gas turbines to be repowered by means of an IBC engine; (ii) designing of the IBC components. Once the IBC engines for the candidate gas turbines were designed, an analysis has been developed to check the possibility to match these engines with other gas turbines, similar to those for which the IBC engines have been designed. In all the analyzed cases the evaluated performance result only slightly worse than that obtainable by repowering the same gas turbine with IBC engines ad hoc designed.

Cogenerative Below Ambient Gas Turbine (BAGT) Performance With Variable Thermal Power

The use of gas turbine and combined cycle power plants for thermal and electric power generation is, nowadays, a consolidated technology. Moreover, the employment of combined heat and power production, especially for low power requirements, is constantly increasing. In this scenario, below ambient pressure discharge gas turbine (BAGT) is an innovative and interesting application; the hot gases discharged from a gas turbine may be expanded below ambient pressure to obtain an increase in electric power generation. The gases are then cooled to supply heat to the thermal utility and finally recompressed to the ambient pressure. The power plant cogenerative performance depends on the heat and electric demand that usually varies during the year (for residential heating the heat to electric power ratio may range from 0.3 to 9). In this paper the thermal load variation influence on the BAGT performance will be investigated and compared with those of gas turbine and combined cycle power plants.

Thermo-Economic Optimization of a Cogeneration Plant With Below Ambient Pressure Discharge Gas Turbine

The gas turbine use in cogeneration plants for thermal and electric power production is constantly increasing especially for low power requirements.In this paper, firstly a thermodynamic analysis of a Below Ambient pressure discharge Gas Turbine (BAGT) has been evaluated and the BAGT cogenerative performance compared with those of a Brayton Cycle (BC) cogenerative power plant.Subsequently, an economic investigation of BAGT is carried out and the benefits, with respect to BC, evaluated.It resulted that the BAGT presents a higher electric efficiency and its employment may strongly increase the budget at disposal for the cogenerative plant investment.© 2001 ASME

COMBINED-CYCLE POWER PLANTS FROM GAS TURBINES AND GEOTHERMAL SOURCE INTEGRATION

Geothermal power plants have difficulties due to the low conversion efficiencies achievable.Geothermal integrated combined cycle proposed and analyzed in this paper is a way to achieve high efficiency.In the proposed cycle the geothermal fluid energy is added, through suitable heat ecxhangers, to that of exhaust gases for generating a steam cycle.The proposed cycle maintains the geothermal fluid segregated from ambient and this can be positive on the environmental point of view.Many systems configurations, based on this possibility, can be taken into account to get the best thermodynamic result.The perfomed analysis examines different possible sharings between the heat coming from geothermal and exhaust gases, and gives the resulting system efficiencies.Various pressures of the geothermal steam and water dominated sources are also taken into account.As a result the analysis shows that the integrated plant power output is largely greater than the total power obtained by summing the gas turbine and the traditional geothermal plant power output, considered separately.Copyright

Micro Gas Turbine Repowering With Inverted Brayton Cycle

Micro gas turbine may represent a successful energy system for distributed combined heat and power generation, if its energetic and economic performances become competitive, especially in cogenerative application. Furthermore, in the last years, the Inverted Brayton Cycle gas turbine has been reconsidered as a potential solution for the simple cycle gas turbine performance increase. In the present paper, the employment of an Inverted Brayton Cycle at the micro gas turbines discharge is investigated. The results obtained show that the electric and thermal performances of the energy system increase; moreover, the reduction of the maximum hot gas temperature in the recuperator (usually micro gas turbines are recuperated), due to the below ambient pressure expansion, may reduce the recuperator thermal stress problems. The economic impact of the repowering of simple cycle micro gas turbines with the Inverted Brayton Cycle is also investigated in the present study; the carried out analysis shows that the benefit of the Inverted Brayton Cycle depends on the fuel price and the electric energy tariff and the turbine discharge pressure can be optimized to maximize the economic performance.Copyright

Inverted Brayton Cycle Employment for Low Temperature Cogenerative Applications

The employment of cogeneration plants for thermal and electric power production is constantly increasing especially for low power requirements. In most cases, to match these low power needs, the cogeneration plant is built up with diesel or gasoline engine or with gas turbine units.In this paper, the performance, in terms of the most utilized cogenerative indexes, of an Inverted Brayton Cycle working with the gas exhausted by the open power plant have been evaluated.Subsequently, the analysis of a cogenerative gas turbine equipped with IBC was carried out and the benefits numerically calculated.It resulted that the IBC employment may increase of about 5 percentage points the plant electric efficiency, making this solution particularly attractive for cogenerative applications.© 2000 ASME

Sensitivity Analysis on Brayton Cycle Gas Turbine Performance

This paper evaluates the performance of a Brayton cycle gas turbine, in terms of power output and conversion efficiency. Sensitivity of this performance to the realistic value of each input variable considered is analyzed. Sensitivity is evaluated by introducing a parameter, defined as the ratio between the logarithmic differential of the power output or efficiency, functions and the logarithmic differential of each variable considered. These analytical functions and their derivatives correspond to a gas turbine model developed by the authors. The above-mentioned sensitivity parameter can be also evaluated by means of a numerical procedure utilizing a common gas turbine power plant computational model. The values calculated with the two procedures turn out to be substantially the same. Finally, the present analysis permits the determination of the weight of the input variable and of its value on the obtainable numerical performance. Such weights are found to be less important for some variables, while they are of marked significance for others, thus indicating those input parameters requiring a very precise verification of their numerical values.