Abstract
It is challenging to gain insight of a Compressed Air Energy Storage (CAES) system dynamic behaviour under various operation conditions due to its complexity with mixed mechanical, thermal, chemical and electrical processes in one. Although a number of studies are reported on CAES steady state and dynamic modelling to reveal its characteristics, few studies have been reported in whole CAES system dynamic modelling involving a radial turbine. This paper explores a new method to analyse the transient performance of the radial turbine while it is integrated with whole low temperature Adiabatic-CAES system. The proposed modelling method approximates the average air flow within single stator/rotor stage. By applying the principle of energy and torque balance on the transmission shaft, the dynamic speed-torque characteristics of the turbine is obtained with a “quasi dynamic iterative searching” process. The model is then integrated to a simulation platform, which is created to synchronise the wide range of time scale dynamic responses including heat transfer, mechanical and electrical energy conversion processes. As every component of the low temperature adiabatic CAES system is built on its fundamental physical and engineering principles, the model is capable of revealing the system transient characteristics. Based on the model, various simulation studies are conducted and the results are compared with the operation data from the literature. It provides a valuable tool for preliminary design of a radial turbine to test its suitability in full and partial load operation conditions, and analyse its transient behaviours.
Highlights
Energy storage recently attracts great attentions in addressing the issues associated with rapid growth of power generation from intermittent renewable energy sources
A new “quasi dynamic iterative searching” method for modelling turbine dynamic behaviours is proposed in this study, aiming to understand the dynamic characteristics of turbines in a LTA-Compressed Air Energy Storage (CAES) operation cycle
The exergy decreases of both the fluids considered in the LTACAES system discharging include air pressure drop in the air tank, water temperature reduction from the hot water tank to the normal water tank, heat dissipations to ambience of the both air and water tanks, throttling losses, flow losses in the turbines, and exhaust air loss
Summary
Energy storage recently attracts great attentions in addressing the issues associated with rapid growth of power generation from intermittent renewable energy sources. According to their analysis, advantages of the LTA-CAES include the fast start-up characteristics, wide-ranging part load, highly available thermal working fluid, low pressure drop of compressed air and potential plant profitability [1]. Sun et al developed a complete dynamic mathematical model of a hybrid CAES-wind turbine system, in which scroll expander is selected for storing the compressed air [4]. A new “quasi dynamic iterative searching” method for modelling turbine dynamic behaviours is proposed in this study, aiming to understand the dynamic characteristics of turbines in a LTA-CAES operation cycle. A new “quasi dynamic iterative searching” method is proposed to reflect both the off-design operative behaviours and dynamic characteristics of the radial turbine in the LTA-CAES system. A single shaft connects all the three stage turbines, which drives the generator through the gear box
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