Thermal power generation systems have played an important role to adjust power supply and demand balance in power grid due to the high operational flexibility. It is required for next future thermal power generation systems to have higher thermal efficiency and operational flexibility, not only to reduce CO2 emission but also to cope with the increase of electricity generation by renewable energy sources which are changeable depending on the weather. The Advanced Humid Air Gas Turbine (AHAT) system is expected to meet these requirements and now proceeding with the development by Mitsubishi Hitachi Power Systems Ltd., Central Research Institute of Electric Power Industry (CRIEPI) and Sumitomo Precision Products Co., Ltd. So far, the system concept and cycle performance of the AHAT system were verified by operational tests of a 3MW-class pilot plant and a 40MW-class test facility. However, the characteristics of operational flexibility, such as load following capability and fast startup speed, have not been clarified sufficiently. It is considered that dynamic characteristics analysis is useful to evaluate and improve operational flexibility. On the other hand, CRIEPI is now developing the dynamic analysis tool for thermal power generation systems based on Modelica language using Dymola, in the aim of evaluating operational characteristics of both a new thermal power system and existing thermal power plant. The component models of this tool are basically developed based on mass and energy conservation equations. In this paper, we try to construct the dynamic model using this tool for the startup characteristics analysis and to investigate the possibility of shortening startup speed of AHAT system. First, the validity of the dynamic model of AHAT system was verified compared with the 3MW-class pilot plant operational data. As a result, the simulation result agrees almost well with the operational data and the validity of this dynamic model was confirmed. And next, the startup characteristics in the case of increasing startup load ratio by dynamic simulation were investigated. The simulation result show that it is difficult to achieve the rated power output only by changing startup load ratio because the humidification rate of humidification tower is rate-limiting and the gas turbine exhaust gas temperature reaches the limit value before achieving the rated power output. And it is found that the effects of the water valve operational speed of humidification tower and of the heat capacity of the recuperator are important to shorten the startup time of AHAT system.
Solar Thermal Power Generation Systems