Performance of a solar aided power plant in fuel saving mode

Integrating solar energy into conventional fossil-fuel fired power plant has been proven to be an efficient way to use solar energy for power generation purpose. In a solar-aided power generation (SAPG) system without storage system, owing to the instability of solar radiation, the turbine and the boiler work under off-design conditions most of time. In this paper, a modified simulation model is established to analyze the off-design performance of SAPG system. In order to speed up the calculations of the model, improved Matrix Thermal Balance Equation (MTBE) approach is used. A solar-aided feedwater heating of a 330 MW coal-fired power generation unit in fuel-saving operation mode is discussed as a case study. The results show that, in a SAPG system, when HP extraction steam is partly replaced, with the increasing solar energy being introduced, the temperature of exhaust flue gas decreases; boiler efficiency improves and standard coal consumption rate decreases. With more solar heat introduced the temperature of superheated and reheated steam keep constant at first and then decrease rapidly. However, in real project, the temperature drop should be no more the permissible limits, which should be considered. The results obtained in the current study could provide a promising approach to find the balance between coal saving and safe operation of the SAPG system.