Dynamic response characteristics and economic analyses of two solar-assisted multi-generation systems

Abstract

Efficient use of solar energy can alleviate the depletion of fossil energy and global warming. In this paper, two solar-aided combined cooling, heating and power systems are proposed and dynamically modeled. The main difference between the two systems is whether the solar energy is stored. A rotor speed-temperature-fuel control system is established, which is suitable for both systems. A control system for solar heat collection process is developed. Energy, exergy and techno-economic analyses are carried out to evaluate the thermodynamic and economic performances. The dynamic responses under direct normal irradiation perturbation and load perturbation are also investigated. The result shows that compared with the system without energy storage, the system with energy storage has higher primary energy utilization rate, exergy efficiency and fuel saving rate, but the economic performance is poorer. The rotor speed-temperature-fuel control system can guarantee a short equilibrium time and a small overshoot for power generation process. When electrical load disturbance occurs, the stabilization times of the output power, cooling energy supply and thermal energy supply are 30 s, 675 s and 770 s, respectively. Under the regulation of the solar heat collection control system, the maximum overshoot of the outlet thermal oil temperature of the parabolic trough solar collector is 2.6 % with a stabilization time of 83 s when the direct normal irradiation step disturbance occurs.