Abstract
This paper presents a detailed exergetic analysis of a novel high-temperature Solar Assisted Combined Cycle (SACC) power plant. The system includes a solar field consisting of innovative high-temperature flat plate evacuated solar thermal collectors, a double stage LiBr-H2O absorption chiller, pumps, heat exchangers, storage tanks, mixers, diverters, controllers and a simple single-pressure Combined Cycle (CC) power plant. Here, a high temperature solar cooling system is coupled with a conventional combined cycle, in order to pre-cool gas turbine inlet air in order to enhance system efficiency and electrical capacity. In this paper, the system is analyzed from an exergetic point of view, on the basis of an energy-economic model presented in a recent work, where the obtained main results show that SACC exhibits a higher electrical production and efficiency with respect to the conventional CC. The system performance is evaluated by a dynamic simulation, where detailed simulation models are implemented for all the components included in the system. In addition, for all the components and for the system as whole, energy and exergy balances are implemented in order to calculate the magnitude of the irreversibilities within the system. In fact, exergy analysis is used in order to assess: exergy destructions and exergetic efficiencies. Such parameters are used in order to evaluate the magnitude of the irreversibilities in the system and to identify the sources of such irreversibilities. Exergetic efficiencies and exergy destructions are dynamically calculated for the 1-year operation of the system. Similarly, exergetic results are also integrated on weekly and yearly bases in order to evaluate the corresponding irreversibilities. The results showed that the components of the Joule cycle (combustor, turbine and compressor) are the major sources of irreversibilities. System overall exergetic efficiency was around 48%. Average weekly solar collector exergetic efficiency ranged from 6.5% to 14.5%, significantly increasing during the summer season. Conversely, absorption chiller exergy efficiency varies from 7.7% to 20.2%, being higher during the winter season. Combustor exergy efficiency is stably close to 68%, whereas the exergy efficiencies of the remaining components are higher than 80%.
Highlights
In last few years, significant research efforts have devoted to improving the efficiency of CombinedCycle (CC) systems which have become the most common option for thermoelectric power plants.Different strategies have been implemented to this end
Note that in dynamic simulations, the time step corresponds to the controller sampling time: large time steps would determine an unrealistic operation of the controllers
This paper presented an exergetic model of a novel high-temperature solar assisted combined cycle, developed using dynamic simulations
Summary
Significant research efforts have devoted to improving the efficiency of CombinedCycle (CC) systems which have become the most common option for thermoelectric power plants.Different strategies have been implemented to this end. Cycle (CC) systems which have become the most common option for thermoelectric power plants. Solar energy is converted into high temperature thermal energy to drive a bottomed Rankine cycle, enhancing CCs power production. In this framework, the Integrated Solar Combined Cycle. Entropy 2016, 18, 356 common technology in the power generation sector [1]. This arrangement is very attractive since the highest power demand occurs when the incident solar radiation is maximum. According to the simulation results, the output capacity and the efficiency of ISCCs will be above the combined cycle regime by 17%
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