18-05-2012, 05:05 PM
An energy and exergy analysis of a microturbine CHP system
An energy and exergy analysis of a microturbine CHP system.pdf (Size: 271.51 KB / Downloads: 76)
Introduction
Microturbines are small components of modern electricity generators that burn gaseous and liquid fuels, creating high-speed rotation which in turn operates the generators. Working in small stationary and automotive gas turbine has very much benefited from recent developments in the microturbine process [1]. The vast majority of gas turbines today are jet engines, turboprops or turbo shaft engines. A separate class of industrial gas turbine is used in power generation and other heavy-duty applications [2].
Organic Rankine Cycle (ORC)
The use of an Organic Rankine power cycle to recover low grade thermal energy is becoming widely recognised as a major technology in power engineering [13]. The simple Rankine Cycle contains four components: a heat supplier (evaporator), power turbine, condenser and pump. The cycle begins when the refrigerant is heated in the boiler (heat
exchanger) to a high temperature, and then transferred to the turbine where it is expanded to produce electrical energy.
Tools
The proposed model of this study has been modelled by using the IPSEpro software. This software is a complete set of modules used to create process models, and the life cycle of a process plant can be simulated and investigated according to the given thermodynamic properties. Firstly, PES, which is IPSEpro’s process simulation environment, and the system of equations, is solved by using two-phases: firstly, checking the model for errors in the process conditions and then calculating the optimum solution method; secondly, PSExcel, which can be installed in Microsoft Excel (MS-Excel), allows the data in the PSE project to be put together with an MS-Excel worksheet. Thus, the result from IPSEpro simulations can be transferred to the Ms-Excel in order to investigate the process situation at many picked points, such as carrying out a parametric study. Besides, the proposed model has been created by using two libraries:
Model configuration, result and discussions
Microturbine stand-alone
the base model of a microturbine stand alone. A microturbine power generation cycle essentially consists of a compressor, a combustion chamber and a reciprocator. The real data of a 200kW microturbine was collected from product number C200 that manufactured by the Capstone Company. This microturbine, produces 1.3 kg/s of exhaust gas flow at a temperature of 280°C. The isentropic efficiencies of the turbine and compressor are 98% and 90%, respectively. On entering the compressor, air is compressed to 8 bar and mixed with 0.011 kg/s of fuel in the combustion chamber. Next, the air expands in the turbine and generates 200 kW of electricity. From the second law of thermodynamics, the energy balance showed that the overall electrical efficiency of this cycle is 34%, while its carbon emission rate is 663 kg of CO2/kW.