Subtasks

The task is divided into two subtasks:

• Subtask A: Materials
• Subtask B: Applications

The Operating Agent acting on behalf of the ECES Implementing Agreement will be Subtask A Leader, and the Operating Agent acting on behalf of the SHC Implementing Agreement will be Subtask B Leader.

Each subtask is further subdivided into working groups (see diagram). At the task kick-off meeting, selected task participants will be appointed as Working Group Leaders.

The division in working groups of Subtask B, Applications, can be changed if and when a need for this should arise during the task operation, e.g. because interest in a specific application has strongly increased or decreased.

To achieve the maximum amount of cross-fertilisation between the different backgrounds of the two Implementing Agreements and experts in this Joint Task, the Task is organised in a matrix-like structure (see diagram below).

One axis represents materials-related activities. It is divided into groups of similar activities:

• materials engineering,
• materials processing,
• tests and characterisation,
• numerical modelling, and
• system integration.

The other axis represents application-related activities, and is grouped into application categories:

• seasonal solar thermal storage,
• cogeneration and trigeneration (also including heat pumps),
• building cooling,
• district heating,
• industrial waste heat,
• concentrated solar power, and
• theoretical limits as a ‘special application’.

Each axis corresponds to a Subtask, and each category corresponds to a Working Group. The activities in each Working Group are described in more detail below. Because of the similarity between the activities in the various Application Working Groups, these are described under one heading.

Materials engineering

The activities in this Working Group focus on engineering new materials or composites, i.e. changing the properties of existing materials and developing new materials with better performance, lower cost, and improved stability. Eventually, this should lead to the ability to design new materials tailor-made to specification.

This Working Group includes the following activities:

• synthesis of new materials;
• determination of material characteristics such as phase diagrams;
• determination of the relation between material performance and material structure and composition, in order to direct the search for improved materials;
• create material safety data sheets;
• determination of the role and importance of material containers.

Materials processing

The activities in this Working Group focus on the processing of raw materials that is required to make these materials function in a realistic environment. In nearly all cases, storage material can not be used to store heat in its raw form, but e.g. needs to be processed into a slurry, encapsulated, or otherwise processed.

This Working Group includes the following activities:

• finding optimal methods for micro- and macro encapsulation of phase change materials;
• processing of phase-change slurries
• find new combinations of materials

Tests and characterisation

The performance characteristics of novel thermal energy storage materials, like phase-change materials or thermochemical materials, often cannot be determined as straightforward as with sensible heat storage materials. In order to have proper comparison possibilities appropriate testing and characterisation procedures should be developed and assessed. The activities of this Working Group are aimed at developing these new procedures and include:

• comparative testing of materials and their required methods
• long-term stability determination
• (pre-)standardisation of testing methods

Numerical modelling

The activities in this working group are aimed at developing and testing numerical models that help to understand and optimise the material behaviour and the dynamic behaviour of compact thermal energy storage systems and components. Ultimately, these numerical models could help to find ways to optimise the materials in combination with the system components. The activities in this working group can help lay the foundation for such models.

The Working Group includes the following activities:

• molecular dynamics
• multiscale modelling
• thermomechanical modelling
• storage (system) modelling

System integration

The storage system is composed of the storage material and the equipment necessary to charge and discharge the storage material in a controlled and optimal way. This includes heat and mass transfer equipment like heat exchangers and pumps or fans and (chemical) reactors. Methods for the design and optimisation of components and system should be developed, together with appropriate testing methods and procedures to assess the long-term behaviour of a system.

This Working Group includes the following activities:

• improve heat transfer from material to reactor wall or heat exchanger wall
• develop and apply test and validation methods for storages
• system performance assessment
• container and reactor design
• storage system design
• assessment of durability of components

Applications

There are several applications for compact thermal energy storage technologies, each with a different set of boundary conditions for the technology. The activities for every application, however, are similar and are given for all Application Working Groups. The activities are serving the underlying principle of guidance of the materials development within the limitations of the application. The materials development will be directed by the desired system performance. A constant assessment of performance criteria for a given application will be used to determine the chances for a given material/system combination. These criteria can come from economic, environmental, production technology or market considerations.

Activities in the Application Working Groups include:

• storage testing and validation
• performance assessment
• numerical modelling on application system level
• perform case studies
• economical modelling
• feasibility studies
• market potential evaluations

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