Gianni Bidini

Study of possible optimisation criteria for geothermal power plants

The possibility of exploiting low temperature liquid-dominated geothermal sources can considerably increase the use of this kind of renewable energy. Improvements in the performance of geothermal cycles are possible by using closed Rankine and Kalina cycles, whose working fluid may be a pure substance or a two-component mixture. In this paper three configurations of the Rankine cycle are examined and compared to conventional single and dual flash steam power plants. The Kalina cycle system no. 12 has also been studied. Results showed that there is a potential for optimisation of the performance, by modifying the main parameters, such as turbine inlet pressure and type of fluid.

Internal combustion engine combined heat and power plants: Case study of the University of Perugia power plant

Abstract A performance and economic analysis of an existing combined heat and power plant with an internal combustion engine and district heating for the Faculty of Engineering of the University of Perugia is presented. Results of the first 15 months of operation are shown and discussed with reference to daily performance of the combined heat and power plant, which shows how electric efficiency is only slightly affected by ambient temperature. A comparison of evaluation indexes for cogeneration plants is made with particular attention to the energy index ( EI ) which is used by Italian legislation as an evaluation parameter to decide if a combined heat and power plant can have access to financial benefits. A cost–benefits analysis based on the first year of operation was made to decide eventual changes in heat and power management, in order to reduce pay-back period and increase the internal rate of return of the investment.

Optimization of an integrated gas turbine–geothermal power plant

Abstract Geothermal resources represent an important renewable energy source for countries such as Italy, where steam dominated geothermal fields are present and have been exploited for decades. The main drawback in the direct use of geothermal steam is the low thermodynamic efficiency, due to its relatively low pressure and temperature. Steam from Italian steam dominated geothermal fields may be available up to 18 bar pressure and 207°C temperature, with a noncondensable gas content ranging from 4 to 10% by weight. In this paper the possibility to integrate geothermal power plants with a gas turbine is examined, in order to increase geothermal steam temperature through heat exchange with the gas turbine exhaust. The combination of ENEL standard sizes of geothermal power plants with commercially available gas turbines has been evaluated. In particular, an optimization of the gas turbine has been made in order to obtain the most suitable inlet conditions to the steam turbine and the highest overall efficiency.

Effect of turbine-blade cooling on the hat (humid air turbine) cycle

We discuss the effects of turbine-blade cooling on HAT-cycle performance. The performance depends on the location for cooling by air bleeding; four possible locations have been explored. A parametric analysis was performed to verify pressure-ratio and turbine-inlet-temperature (TIT) effects. An exergetic analysis was used to clarify the differences between bleed-air point options and cycle-configuration choices.

Experimental analysis of the actual behaviour of a natural gas fueled engine Caterpillar (CAT)-3516

Abstract In this work, first results are presented of the analysis of the behaviour, in actual, non-new operational conditions, of a lean burning, natural gas (NG) fueled, 1 MWe Caterpillar (CAT)-3516 engine, installed at the Engineering Faculty of Perugia University for the cogeneration of electrical and thermal energy. Data collected daily by the plant manager operators along 24 months of engine operation, which refer to power, electrical efficiency, NG flowrate, availability, and charge temperature, were analysed in connection with the recorded events of breakdown/defects and of maintenance/repair. An acquisition system for the continuous monitoring of several engine and plant quantities is described in detail.

Use of Artificial Neural Networks for the Simulation of Combined Cycle Transients

Due to techno-economic assets, the demand of combined cycles (CC) is currently growing. Nowadays, in a diversified electricity mix, these plants are often used on a load cycling duty or in the intermediate load range. The ability to start quickly and reliably may be a decisional criterion for the selection of the plant, in addition to the design performance, the cost and the pollutant emissions. Therefore, together with the simulation of CC transients, a proper monitoring system aimed at keeping high plant performance during the transients is required.With the help of advanced measurement and monitoring devices, artificial intelligence (AI) techniques as expert systems (ES) and neural networks (NN) can fulfill this duty.The goal of this paper is to show that a NN technique can be used reliably to obtain the response of a complex energetic system, such as CCs, during a slow transient and consequently as part of an on-line monitoring system.In this work, a CC power plant is simulated by dividing it into three blocks, which are representative of the three main elements of the CC: namely the gas turbine (GT), the heat recovery steam generator (HRSG) and the steam turbine (ST). To each of them a NN is associated. Once the training and testing of the NNs is carried out, the blocks are then arranged in a series cascade, the output of a block being the input of the subsequent one. With this solution, the NN-based system is able to produce the transient response of a CC plant when the input information are the GT inlet parameters.The transient data, not easy to obtain from measurements on existing plants, are provided by the CCDYN simulator (Dechamps, 1995). The performance obtained by the NN based system are observed to be in good agreement with those given by CCDYN, the latter being validated on the basis of measurements in an existing plant. The NN code, providing the departures of the measured data from the predicted ones, can be considered as a proper system for on-line monitoring and diagnosis.Copyright

Simulation of hydraulic power plant transients using neural networks

Abstract In this work the efficiency of the artificial neural network technology for evaluating the turbine speed and drain synchronous valve during the turn-off transient phase of an actual hydraulic power plant has been evaluated. These results have been achieved avoiding a detailed time consuming analysis of the power plant. Several net architectures have been set up and verified with regard to their response to this strongly non-linear problem.

Second-Law Analysis of Fluidized-Bed Steam Generators

Direct and indirect exergy balances are applied to a simplified fluidized bed combustor. The major losses are calculated, including exergy from chemical reactions (combustion, calcination, and sulfation), heat transfer, and sensible heat release to the environment (ash and solid residue flows). The analysis is applied to atmospheric and pressurized fluidized bed combustors.Copyright

External combustion engine with Stirling open cycle

An open-cycle engine approximating the Stirling cycle but retaining external combustion is being developed. The Stirling engine is being built on a motorcycle V-engine; however, the heat exchangers have been designed from scratch. Some thermodynamic considerations justifying the use of the open cycle are presented. A numerical simulation of the proposed open cycle is described. An optimization of the heat exchanging system, making the use of an entropic parameter, is attempted, and the results are presented. The design of the experimental motor has been completed and is waiting for experimental testing to verify the cycle effectiveness and the optimization criteria.<<ETX>>