A consortium that comprises Vast Solar, CyD, Solar Dynamics, Alia Energy Consulting and Critical Engineering, has jointly developed Flexitank, a novel design for high temperature molten salt thermal energy storage tanks used in CSP and standalone thermal energy storage.
The Flexitank solves a serious issue in the CSP industry. Due to the impacts of thermal cycling and fatigue, the molten storage tanks at two operating CSP plants developed major leaks, causing catastrophic business loss. Flexitank has been shown to prevent hot salt tank failure and is scalable to all sizes of tanks. The consortium has filed to patent the innovative solution.
Other than CSP with storage, no other solar resource can operate like a conventional power plant. Solar PV and direct steam CSP have the disadvantage of not being able to generate electricity when there is no sunlight.
Vast Solar will use the novel Flexitank design in their 50 MW 14 hours storage project.
The consortium developed the Flexitank solution by replicating the failure points in traditional storage tanks and with that insight, developing a design which has been shown to survive the FEA model.
The design increases the flexibility of the floor of the tank and mitigates the risk of failure associated with thermal cycles by absorbing the repeated expansion and contraction typically encountered in such tanks.
The Advanced Materials Team at the Australian Solar Thermal Research Institute (ASTRI), led by the Queensland University of Technology and Flinders University, worked collaboratively with Vast Solar and the consortium to examine the operation of thermal energy storage tasks.
Dominic Zaal, ASTRI Director, stated that “The daily cycling of thermal energy storage systems requires careful management of materials to ensure that the system can operate reliably over the 30-year plant life. In close collaboration with Vast Solar and its consortium partners, ASTRI has examined the material challenges associated with existing tank systems, and this has assisted Vast Solar and its consortium partners to develop a design to address these challenges and substantially mitigate the risk of tank failures. We are confident that the new design will substantially improve the operation performance of CSP systems moving forward.”
Reliable thermal energy storage through improved hot salt tank design
The Concentrating Solar Power Best Practices Study published by NREL and others in June 2020 stated that “the reliability and design of…the hot tank…and foundation are the key issues identified…Leaks have occurred in the floors of hot salt tanks at two operating plants [and] there is also some concern about friction forces between the tank floor and the foundations…Tank specifications should accommodate all potential combinations of cyclic temperature and cyclic salt levels.”
Mark Mehos, NREL CSP Program Manager, has previously said “it’s not endemic of all plants [and] to improve reliability, CSP designers and operators must fully understand the impact of sudden or short-lived operating conditions on all components, including the thermal energy storage tanks.”
Craig Wood, Vast Solar CEO, said “The economics of thermal storage are compelling, and we are delighted that our work will now deliver much needed reliability. Once we understood the tank failure modes and started testing the physical properties of the incumbent materials, we realised that flexibility is the key to overcoming thermal cycling and fatigue”.
“We were amazed by the accurate correlation and, once we understood the science, the solution followed soon afterwards”, commented Sergio Davila, Business Director for CyD.
ast Solar – modular tower solar thermal generation and storage
Vast Solar is an Australian company that, with support from the Australian Renewable Energy Agency (ARENA), has developed world-leading solar thermal generation and storage technology to deliver low-cost renewable energy that is reliable, controllable and dispatchable. Vast Solar’s CSP system is smart, modular and highly cost effective to construct and operate. Vast Solar’s significant contribution to the progress of CSP globally has been recognised by the international CSP community through it receiving the International Energy Agency’s SolarPACES 2019 Technical Innovation Award.
CyD (Contratos y Diseños Industriales, S.A) – industrial project development
CyD is a company experienced in the development of industrial projects in the machinery, boiler, piping and structural sectors. CyD is dedicated to industrial assembly, to detailed engineering using its own technical department and to realising turn-key projects, from technical studies, design, calculations, supply, assembly, technical advice, pre-fabrication, commissioning and certification of installations. CyD also undertakes modification, repair and expansion of existing plants, piping and other equipment.
Solar Dynamics – CSP consulting
Solar Dynamics is a team of experienced CSP professionals that deliver products, services and projects that enable the U.S. and the world to move to a sustainable and reliable carbon free power sector to help address climate change in an economic manner. Its proprietary technology focus is molten salt tower technology, molten salt trough technology and developing advanced heliostat and trough collector designs to make these systems more cost-effective.
Alia Energy Consulting – engineering and consulting for power plants
Alia Energy Consulting is a Spanish company offering services on six continents in the field of engineering and consulting for power plants. Its team has worked for many years as engineers and technical advisors for developers, EPC contractors and owners, providing support in all project stages. The Alia Energy team has been involved in the development of international generation as well as research, development and innovative projects that have allowed them to develop deep knowledge and excellent relationships with National Centres, suppliers and owners.
Critical Engineering – thermal and mechanical designs
Critical Engineering advises on advanced thermal and mechanical designs that require high performance in terms of reliability. It is staffed by experienced and practical engineers with deep fabrication and operating experience.