Thermal storage using zeolite pellets

Roughly half of the total energy content of the fuel is released as heat, which typically dissipates into the atmosphere unused.

The root of the problem lies in the fact that the heat is not generally used at the time it is generated – and options for storing it are limited.

Traditionally, water tanks have been used for this purpose, but they can only absorb a finite quantity of heat.

This new system can store three to four times the amount of heat that water can

Working together with industrial partners such as ZeoSys GmbH in Berlin, scientists from the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart are currently developing a new type of thermal storage system.

This new system can store three to four times the amount of heat that water can, so it only requires storage containers around a quarter the size of water tanks.

It is also able to store the heat loss-free over lengthy periods of time and can even operate at temperatures well in excess of 100 degrees Celsius.

The new system contains zeolite pellets, from the Greek ze?, meaning ‘boil’ and lithos, meaning ‘stone’.

Normally this material is used as an ion exchanger, for example to soften water.

Because zeolites are porous, they have a large surface area: A single gram of these pellets boasts a surface area of up to 1000 square meters.

When the material comes into contact with water vapour, it binds the steam within its pores by means of a physicochemical reaction, which generates heat.

A single gram of these pellets boasts a surface area of up to 1000 square meters

The water is in reverse removed from the material by the application of heat and the energy is stored, but not as a result of the material becoming palpably warm – as when water tanks are used.

What is stored is the potential to adsorb water and in the process release heat,

Provided the dried zeolite material is prevented from coming into contact with water, it can store the heat for an unlimited amount of time.

Although the basic principle has been widely understood for some time, it had never before been translated into a broad-based technical application for storage systems.

The Fraunhofer researchers will be using a model system to demonstrate the principles of sorptive thermal storage at Achema 2012 in Frankfurt from June 18 through 22 (Hall 9.2, Booth D64).