Material and system development for high temperature thermal energy storage

EnergyNest has developed, and demonstrated, a novel technology for storing thermal energy in solid-state medium that has many advantages and enhanced performance over prior art. Thermal energy is stored in a state-of-the-art concrete-based storage medium denoted HEATCRETE. A thermal energy storage (TES) system is made by combining a large number of individual thermal "battery elements", connected together efficiently to provide the total thermal battery solution. Each thermal element consists of HEATCRETE with integrated heat exchanger tubes contained inside a steel casing. A heat-transfer fluid flows within the heat exchanger tubes (water, steam, oil, gas etc) to transport the energy into, and out of the TES. Multiple elements are stacked inside a steel frame to provide a module; these modules can be stacked and combined vertically and horizontally, as in a "Lego-like" system to form a fully scalable, complete TES system in accordance with the specific needs. The project has strong ambitions for advances in material research as well as technological innovation. In the proposed project, the goal is to research new cement and geomaterial based mixtures suitable for TES systems operating at temperatures up to 600 degrees C, and higher. Different new material mixtures have been evaluated, and the thermal and mechanical properties tested. Heat exchanger elements cast with two of materials developed has been tested at high temperatures in a controlled lab environment. The final results are being compared with simulated performance models. An analytical model for thermal properties has been developed and compared to results for heterogeneous, granular materials to predict the overall thermal properties. The project also develops, tests, demonstrates, and enables to optimize new TES system designs which will utilize these new materials at high temperatures.

The project has led to increased knowledge and competence on thermal concretes for the company and partners related to the following results: 1) New calcium-aluminate and new geopolymer concretes for high thermal energy storage (TES) applications. Developed, characterized, fabricated and tested using high-temperature cycling. 2) New TES system designs for operation with superheated steam for conventional power plants and energy intensive industries (patent filed). It is hoped that the results will have a significant impact on Europe's energy-intensive industry and thermal power plants, which share a common challenge: they waste large amounts of valuable, high-temperature heat/energy into the atmosphere. The developed Thermal Battery system provides an efficient solution to recover, store, and reuse such wasted energy. This will significantly reduce energy costs, carbon emissions to the atmosphere and provides increased operational flexibility and better use of renewable power sources.

EnergyNest has developed, and demonstrated, a novel technology for storing thermal energy in solid-state medium that has many advantages over prior art. Thermal energy is stored in a state-of-the-art solid-state concrete based storage medium; Heatcrete. A thermal energy storage (TES) system is made of a large number of individual thermal "battery" elements, connected through pipes in series and parallel. An element consists of Heatcrete with integrated heat exchanger tubes contained inside a steel casing. A heat-transfer fluid flows inside the heat exchanger tubes, where the majority of heat transfer is convective. Heat transfer through the solid media is conductive. Multiple elements are stacked inside a steel frame, termed Module, and Modules are stacked vertically and horizontally to form a complete TES system. The fundamental idea is to develop a robust, large-scale high temperature TES technology that is competitive on the international market and that will have a major impact in three strategic areas of the energy system: 1) Concentrating solar power (CSP); 2) Electric power system and 3) Waste heat from industries and thermal power plants. The project has strong ambitions for advances in material research as well as technological innovation. In the proposed project, the major new elements of the planned innovation are to: 1) Realize new cement mixtures and 2) develop and characterize new solid-state materials based on geopolymers and calcium-aluminates (new materials) as solid-state materials for TES systems operating at temperatures up to 600C and higher, and 3) Demonstrate, test, develop and optimize new TES system designs which will utilize these new materials.