Analysis of particle based thermal storage solutions for gas turbine applications

Abstract

The growth of installed renewable energy sources as a reaction to the rising interest in a low-carbon energy production has an impact on the load activity of conventional power plants. The generated power from wind parks and photovoltaic power stations is fluctuating based on the local weather conditions, which are often unpredictable and change in a short amount of time. This behavior results in many load changes of conventional power plants to provide a stable frequency in the electricity grid. The lifespan of these power plants, which are often thermal power plants, will be reduced due to the load changes and that the operating point is not the design case. This leads to higher maintenance costs, reduced efficiency and often to a higher carbon output. To maintain a constant load on conventional power plants, the fluctuating share of the electricity fed into the grid needs to be stored when the supply exceeds the demand, or the produced energy from a conventional power plant needs to be stored to enable a flexible supply. The aim of this thesis is to develop a sensible particle-based heat storage system that allows the load flexibility of combined cycle power plants (CCPP) to be increased by diverting the exhaust gas from a gas turbine, which is normally used in a steam generator to drive a steam turbine. Two systems are envisioned for this task, a fluidized bed heat exchanger (HEX) and a plate type moving bed HEX. For the first system the exhaust gas from a gas turbine will be used to fluidize a sand bed and heat the particles. With the exhaust gas fluidizing the solid bulk, additional components are reduced to bulk conveying systems which transport the heat storage material from the HEX to storage tanks and back. The second system consists of several channels arranged in parallel, which are traversed by air. The heat storage material falls between these channels, reducing the auxiliary energy to bulk conveying systems. Both systems will be analyzed numerical to gain information about viable operating conditions and the physical values of both streams. In a second step computational fluid dynamic (CFD) systems are used to optimize the proposed systems.