Practical Development of Thermal Energy Storage Technology to Promote the Widespread Use of Renewable Energy

AICHI STEEL CORPORATION

Outline

At Aichi Steel, we recognize that the steel industry has a responsibility to reduce CO2 emissions, and are taking various measures to achieve this end. One of these measures is thermal energy storage technology.

Lime, an indispensable component in the steelmaking processes, is found in abundant quantities on earth, and is a familiar material known for its ability to absorb or release heat in reactions involving water. We aim to contribute to the realization of a low-carbon society that suppresses global heating by developing thermal energy storage technology using this material, and through the social implementation of a safe, reliable, and inexpensive thermal energy storage system.

Description

The rise in global temperatures in recent years is said to be the result of anthropogenic increases in concentrations of atmospheric CO2 attributed chiefly to the burning of fossil fuels. To therefore reduce the consumption of fossil fuels, we have been focusing our attention on thermal energy storage technology which effectively utilizes unused heat such as the high-temperature exhaust heat produced by industrial furnaces.

Calcium-based thermal energy storage material has long been known for its ability to harness the reaction between lime and water (water vapor). The problem with this material, however, is the decrease in thermal energy storage capacity which results from the agglomeration of lime powder that occurs during the reaction process. To suppress this agglomeration, we devised a new microstructure in which clay mineral is finely dispersed in lime powder and chemically bonded. In addition to this, we established a compression molding technology that achieves both water vapor diffusivity and densification. With this technology, we developed a thermal energy storage material superior to conventional technology with thermal energy storage capacity of 1.6 MJ/L, even following repeated use of the material over 1,000 times.

Using a thermal energy storage device equipped with this technology, we installed the world's first system at our company’s Kariya Plant to collect and store exhaust heat at temperatures of 400°C and higher generated by a heating furnace. The heat stored with this system can be used as steam for heating whenever it is required. When put into practical use, it is estimated that this system is capable of reducing CO2 emissions by approximately 80% compared to systems that use steam obtained from a combustion-type boiler.

In addition to effective utilization of exhaust heat from plants, we expect this thermal energy storage system to provide an energy source that is not dependent on the fluctuating absorption of renewable energy, or on social infrastructure, and we believe it will contribute to the realization of a low-carbon society that suppresses global heating through social implementation in a variety of fields.