Thermodynamic and Economic Analysis of an Integrated Solar Combined Cycle System
Integrating solar thermal energy into the conventional Combined Cycle Power Plant (CCPP) has been proved to be an efficient way to use solar energy and improve the generation efficiency of CCPP. In this paper, the energy, exergy, and economic (3E) methods were applied to the models of the Integrated Solar Combined Cycle System (ISCCS). The performances of the proposed system were not only assessed by energy and exergy efficiency, as well as exergy destruction, but also through varied thermodynamic parameters such as DNI and Ta. Besides, to better understand the real potentials for improving the components, exergy destruction was split into endogenous/exogenous and avoidable/unavoidable parts. Results indicate that the combustion chamber of the gas turbine has the largest endogenous and unavoidable exergy destruction values of 202.23 MW and 197.63 MW, and the values of the parabolic trough solar collector are 51.77 MW and 50.01 MW. For the overall power plant, the exogenous and avoidable exergy destruction rates resulted in 17.61% and 17.78%, respectively. In addition, the proposed system can save a fuel cost of 1.86 $/MW·h per year accompanied by reducing CO2 emissions of about 88.40 kg/MW·h, further highlighting the great potential of ISCCS.
Thermodynamic analysis of a compressed carbon dioxide energy storage system using two saline aquifers at different depths as storage reservoirs
Abstract Compressed air energy storage (CAES) is one of the leading large-scale energy storage technologies. However, low thermal efficiency and low energy storage density restrict its application. To improve the energy storage density, we propose a two-reservoir compressed CO2 energy storage system. We present here thermodynamic and parametric analyses of the performance of an idealized two-reservoir CO2 energy storage system under supercritical and transcritical conditions using a steady-state mathematical model. Results show that the transcritical compressed CO2 energy storage system has higher round-trip efficiency and exergy efficiency, and larger energy storage density than the supercritical compressed CO2 energy storage. However, the configuration of supercritical compressed CO2 energy storage is simpler, and the energy storage densities of the two systems are both higher than that of CAES, which is advantageous in terms of storage volume for a given power rating.
Approche de conception et d’optimisation de centrale solaire intégrée à cycle combiné inspirée de la méthode du pincement (partie II: réseau d’échangeurs de chaleur)
Steam production units (HRSG and HSSG) of ISCCS include several heat exchangers (economizers, evaporator, superheater, reheaters, etc.). The knowledge of the extended composites as a function of the solar input, allows the determination of the most critical zones for heat transfer but does not allow, in itself, the full knowledge of the real streams needed to be able to design an optimum heat exchanger network. The procedure proposed in this paper permits, from so called interaction factors which characterize the interdependancy between streams, the determination of the massflows in each stream. The choice of the best heat exchanger network must respect, for each operational conditions, the optimum evaporation levels (including pressures et temperatures) determined in part I, as well as the particular practical operational factors (independance or not between the various heat recovery units, etc.). The network design is done using the standard guidelines of pinch technology (respect of the minimum pinch DTmin for each heat exchanger close to the pinch temperature, separate design of the zone above and below the pinch temperature, etc.). The respect of the DTmin in the critical zones of heat transfer requires the use of stream splitting and the network includes heat exchanger tubes which are interlaced at the same level of the stack. One example of the best performing power plant designed on the basis of this approach is given.