Dual-Media High Temperature Thermal Storage for Industrial Waste Heat Recovery

Panel: 4. Technology, products and systems

Author:
Richard Gurtner, ZAE Bayern, Germany

Abstract

In energy-intensive industries (e.g. foundry industry, cement industry, etc.) the use of waste heat as process heat or general heating or cooling purposes reduces the consumption of primary energy and greenhouse gas emissions. Especially, the utilization of discontinuous waste heat (> 100 °C) by means of thermal energy storage has lately been discussed and has been theoretically considered. At the moment, only a few industrial applications can be found. The main reason for that are the high investment costs of commercially available storage technologies for temperatures above 100 °C. Another reason is the comparably low energy price for gas and electricity for energy-intensive industries. Low numbers of cycles (loading and unloading) of the thermal energy storage cause difficulties in achieving an economic operation. A suitable thermal energy storage in terms of performance, capacity, temperature, cycle stability and cost-effective availability has to be developed. At the ZAE Bayern, the development of such a thermal energy storage for temperatures up to 300°C includes material tests and storage experiments with a dual-media storage (solid filler material in direct contact with heat transfer oil). This non-pressurized design offers considerable advantages compared to alternative storage concepts (e.g. thermal oil only). Using a cost effective solid material (e.g. rocks) as a packed bed the costs for the storage material can be reduced by up to 60%. Additionally, the material storage capacity can be increased by up to 40%. In this collaboration project with Giesserei Heunisch, ZAE Bayern and Küttner GmbH & Co. KG as plant constructor an energy storage system for discontinuous industrial waste heat recovery will be developed and investigated in a pilot plant. The energy system stores the waste heat of a furnace at the foundry Heunisch. During the downtime of the furnace a continuous using of waste heat for process/space heating and process cooling is possible.

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