A novel heat exchanger concept for latent heat thermal energy storage in solar power towers: Modelling and performance comparison

Abstract

Highlights• Study introduces spray crystallization as phase change heat recovery option.• Can be directly incorporated into tower of central power tower designs.• Particle diameter found to be largest single influence of tower height.• Prilling feed system identified as critical for further investigation.• Best case result indicates a 20% reduction in plant capital cost is achievable. AbstractThis study presents an innovative new alternative for utilizing phase change materials as energy storage media in solar power towers. The solar power tower prilling or granulation concept combines the existing molten salt design with a prilling tower incorporated into the central receiver. In this way heat transfer limitations normally associated with these systems can be overcome since only very small particles (diameter 1-2 mm) are utilized. Three design cases were considered and a detailed model of the process was developed. The model demonstrates the design dependence on several key variables including particle diameter and the necessity of considering the system in conjunction with the steam generation cycle. Pinch considerations within this cycle and the tower itself determine the operational feasibility. It was found that the receiver design and prilling feed systems are crucial aspects which must be investigated further to refine the concept design and complete a full techno-economic assessment and optimization. The "best case scenario" resulted in a reduction of the circulating salt flow by one third compared to the base case. Preliminary indications are that this would result in a 20% reduction of the * Corresponding author. Tel: +27 12 420 4989. Fax: +27 12 420 2516. E-mail: carbon@up.ac.za 2 overall plant capital cost, but additional costs such as solids handling and a complex receiver design have to be taken into account.

Enthalpy of fusion prediction for the economic optimisation of salt based latent heat thermal energy stores

“…From a power generation perspective it would be preferred if the stored energy could be recovered at a roughly constant temperature, thereby mitigating complex heat integration and pinch considerations [9]. The required temperature will vary widely depending on the power block requirements, as influenced by the type and configuration of the turbine.…”

Performance enhancement with inorganic phase change materials for the application of thermal energy storage: A critical review

“…Zhao et al 33 studied the influence of Ca(NO 3 ) 2 by mixing with LiNO 3 ‐KNO 3 mixture that showed increase of phase change temperature by increasing concentration whereas the use of NaNO 3 34 showed enhanced performance in terms of thermal stability, energy density maximum at the ratio of 3:7. Heinrich Badenhorst et al 35 used KF‐KCl combination that was found to be feasible with elevated thermal performance by enhancing the efficiency of the power plants and lead to cost saving of 20% though a corrosive nature was found inside the container. To provide long‐term stability, study on corrosion characteristics was carried out by Gomez‐Vidal et al 36 using NaCl‐LiCl mixture and the study showed nickel as corrosion inhibitor (refer Figure 3).…”

A mobile thermal battery resembling a solar receiver: Innovative design and performance assessment

“…A model study of a high‐temperature receiver utilized in a CSP system was carried out by Przenzak et al They introduced an optimization approach for the selection of concentrator‐receiver geometry and the appropriate optical system configurations. The latent heat thermal energy storage system in solar power towers was examined by Badenhorst . He indicated that the receiver design and prilling feed systems were crucial aspects, which should be investigated further to refine the design concept, and complete a full techno‐economic assessment and optimization.…”

“…The latent heat thermal energy storage system in solar power towers was examined by Badenhorst. 16 He indicated that the receiver design and prilling feed systems were crucial aspects, which should be investigated further to refine the design concept, and complete a full techno-economic assessment and optimization. A high-temperature solar thermal energy storage unit based on the molten soda lime silica glass was examined by Cárdenas et al 17 They demonstrated that the overall performance of the thermal energy storage unit was satisfactory and the unit was capable of supplying the required 4 kW output throughout the 16-hour discharge while it reached its fully charged state during the subsequent 8-hour recharge.…”