Advanced storage concepts for solar and low energy buildings, IEA-SHC Task 32

Storage of heat is seen as a major issue for the large-scale and long-term development of solar energy for space heating and cooling under all climates.

Most combisystems (systems that produce heat for heating and domestic hot water from solar energy) on the market use water as the storage medium. Some are using the building structure (slabs) as a storage medium. Such systems are called direct floor heating.

Enhancing the storage performance is necessary to increase the solar fraction of combisystems. This can be done through either:

• densify the store content (same volume of storage but more energy can be stored and withdrawn)

or

• reduce the cost of the storage (there are 3 ways: reduce losses, use other materials, use other designs).

Task 32 was initiated to answer the following questions:

1. can we enhance existing water storage techniques for solar houses ?

2. can we beat water as a storage solution for a solar house in terms of performances ?

3. can we reach a factor 2 or 3 in the density of storage using chemical solutions?

4. can we combine solar and chemical heat pump to lead to a higher solar fraction for both heating and cooling of a building ?

Work is divided in four subtasks dealing with the following topics:

· Subtask A: Comparison of system concepts and dessimination of results

· Subtask B: Sorption and chemical storage

· Subtask C: Phase change materials

· Subtask D: Advanced water storage

In each subtask, laboratory tests and/or demonstration projects are performed. Finally, all concepts are compared based on simulations using the same boundary conditions for all storage concepts.

AEE INTEC is participating mainly in Subtask B dealing with sorption heat stores.

A handbook on the state of the art of heat storage technology was written by the task participants and can be ordered online (see link below).