In a parabolic trough solar power plant, the steam generation system is the junction of the heat transfer fluid circuit and the water/steam circuit. Due to the discontinuous nature of solar radiation, the dynamic characteristics of working fluid physical parameters, such as mass flow rate, temperature, and pressure, are more evident in the steam generation system in this kind of plant, increasing the complexity of system operation. In this paper, a zero-dimension dynamic model of an oil/water steam generation system was developed based on the lumped parameter method. Based on the developed model, four typical single-parameter disturbance processes were simulated, and then the control strategy was obtained. System-level simulations on different days (clear and cloudy) and in different seasons (spring, summer, autumn, and winter) were also conducted on a STAR-90 simulation platform using real meteorological data. The simulation results show that PI control can be used to adjust the water level, that system operation on cloudy days should be avoided, and that the system can continue to generate steam after the sun sets. The simulation results can provide a useful reference for plant operators.

Introduction

In recent years, the massive use of fossil fuels, including coal, oil, and gas, has led to environmental pollution and energy shortages. It is increasingly important to find alternative fuels. Solar energy has been emphasized by most countries in the world due to its abundance, wide distribution, and low carbon emission. There are many kinds of solar energy utilization technologies, one of which is the concentrating solar power (CSP) technology. CSP technology captures the sun’s direct normal irradiation (DNI), concentrates it onto a receiving surface and transforms the absorbed heat into mechanical work and subsequently electricity, by using state-of-the-art thermodynamic power cycles [1, 2]. The CSP technology is an environmental-friendly renewable energy approach that can greatly contribute to energy conservation and environmental protection [3]. This technology has two advantages, its amenability to hybridization and the ability to readily store energy via thermal energy storage [4]. Therefore, the CSP technology is gradually gaining recognition and acceptance by many countries. According to the International Energy Agency (IEA), the installed capacity of CSP plants will reach 20 GW by 2020 and 800 GW by 2050 [5].