Performance modelling of an open volumetric receiver CSP plant incorporating rock bed thermal storage

[摘要] ENGLISH ABSTRACT: Open volumetric receiver (OVR) concentrating solar power (CSP) plant technology utilises air as a heat transfer fluid, which enables higher peak power cycle temperatures in comparison to conventional heat transfer fluids. This creates the potential for improvements in solar-electric conversion efficiency and reduced electricity generation costs. Despite the promise of the technology, it still faces appreciable technical challenges that have inhibited its commercial adoption.R&D activities have enabled progress in overcoming these challenges. However, a deeper understanding of plant behaviour is required to improve the competitiveness of the technology. In this regard, computational performance modelling at a system and plant level has served as a powerful tool for the exploration of new concepts and the evaluation of improved plant arrangements. Yet little attention has been paid to performance optimisation, and there is still a fairly limited understanding of plant performance characteristics.The objective of this work is to develop a comprehensive plant modelling capability to enable further investigation of key aspects of OVR CSP plant operational behaviour. Of particular interest is the investigation of component inter-dependencies and the sensitivity of plant performance to variations in design parameters at a system and plant level.Firstly, a comprehensive review of performance modelling studies associated with OVR CSP plant technology is presented, detailing recent developments in the simulation of open volumetric receivers, packed bed thermal energy storage systems and OVR CSP plants. The review establishes the state-of-the-art in modelling methodologies, evaluates the extent to which system and plant performance have been investigated, and identifies aspects of plant design and behaviour that require further attention.A design-point model of a 100 MWe OVR CSP plant is then developed and applied to parametrically study the sensitivity of plant performance to heat recovery steam generator (HRSG) configuration and design parameters. The study provides novel insight into the thermodynamic interaction that exists between OVR and HRSG, and identifies the HRSG characteristics that permit the best utilisation of solar energy.The effectiveness of the local thermal equilibrium (LTE) assumption in the long-term performance modelling of rock bed thermal energy storage systems is then evaluated. A one-dimensional LTE performance model is formulated and validated, and applied to simulate the annual performance of a CSP rock bed. Predictions are compared to those associated with an analogous two-phase model to establish, for the first time, the applicability of the LTE assumption for the conditions typically associated with air-rock CSP packed beds.Finally, a detailed OVR CSP plant model with off-design fidelity is developed and applied to parametrically study the long-term performance of a 100 MWe plant, incorporating rock bed thermal energy storage and operating in a peaking role. In this manner, the annual performance of a plant of this configuration is predicted for the first time. Furthermore, the relationships between plant solar-electric efficiency, energy yield, heliostat field size and thermal energy storage capacity are detailed.

[发布机构] Stellenbosch University