Work Plan

Current seasonal thermal energy storage technologies still present several critical drawbacks. Therefore, the challenge is how to solve those problems, namely the high cost of the storage medium, the low density of thermal energy storage and significant thermal losses.

In this research, the development of a storage system capable to surpass such drawbacks is proposed. The system is based on the PI and team members previous works, which developed an adsorption based energy storage system to enhance the performance of conventional Domestic Hot Water (DHW) tanks. That system undergoes specific adaptations and enhancements for seasonal energy storage, encompassing the benefits of conventional and thermochemical seasonal storage systems, while adding several other advantages. Together, these represent the main ideas for the project and also its main challenges:

- Using both adsorption and sensible heat storage allows to maintain the simplicity of a conventional storage system and supplement it with the superior energy storage density of the sorption storage.

- Optimizing the quantity of adsorbent (more expensive solution) and water (cheaper solution) results in a high energy storage density and the minimization of the adsorbent costs.

- Keeping the heat stored as an adsorption potential and releasing it only at winter without losses maintains the water tank at minimum temperature and minimizes losses.

- The system is charged with solar energy (although it may be charged with any kind of renewable heat source) and operates to approach 100% solar fraction and to make unnecessary the use of other forms of energy for heating.

- Placing the adsorber inside the hot water tank allows reusing the adsorber’s thermal losses, which are reported in other projects as limiting the systems’ performance, to the water in the tank.

- Given its higher energy density, the inclusion of adsorption storage allows reducing the total size of the system, so the water tank presents less surface area, and thus lower thermal losses.

- In case of failure or loss of efficiency of the adsorption module, the system still operates as a sensible energy store.

- The system uses exclusively the excess of solar thermal energy (which is often wasted when the water in the tank reaches the maximum safe temperature), unlike some existing systems that use supplementary energy sources (e.g., electricity, natural gas). There is no additional energy consumption in the proposed system.

- By recovering the condensation heat while charging the adsorber, the mains water can be preheated. Other heating purposes may be defined.

- The energy from the surrounding environment is used to promote the adsorption process, during discharge. The induced vaporization process may be adapted for cooling processes (water, air) or integrated in geothermal processes, in radical new approaches.

- The addition of PCM materials may improve the storage density of the system and/or enhance the heat exchangers’ energy efficiency.

- The system can be used for domestic hot water or/and for space heating.

- It may be adapted for different scales (e.g., multi-family, hotels, office buildings).

The combination of these benefits makes for a groundbreaking approach to the seasonal thermal energy storage concept.

Therefore, the main goals of the research are:

1 – to develop the numerical model of a thermal energy storage system provided with an adsorption module for long-term storage;

2 – to construct an experimental prototype of the system;

3 – to explore different configurations for performance enhancement;

4 – to assess the employment of different energy storage materials;

5 – to explore the system’s adaptability in different scenarios.

The project team will reach these goals in five work packages (WP). Goal (1) is met in the first work package, goal (2) is completed in the second, goals (3) and (4) are concluded in the third, and, lastly, goal (5) is completed in the fourth work package. The remaining work package is dedicated to disseminating research findings and the management of the project.

In ‘WP1 – Simulation model’, led by ADAI, the configuration of the proposed seasonal storage system is defined to meet the concept presented above. The system will be defined according to the latest policies for long-term thermal energy storage, always prioritizing the strategy of minimizing thermal losses, reducing the costs and increasing the energy storage density. In accordance, its simulation model is specified, developed, and employed to evaluate the system operation in different case studies. The model will then be validated with experimental data from WP2. Meanwhile, the simulation results will be used to start the discussion on new configurations and purposes for the system, which will be implemented in WP3 and WP4.

In ‘WP2 – System prototype’, the CTCV team together with OCRAM Clima will construct, instrument, and perform the initial tests to the system’s prototype. This experimental model will be based on the prototype of the original short-term storage system, which will be used as groundwork for this task. The model will be properly instrumented with a set of sensors, actuators, and control software. In the end, the system will be assessed during thorough experimental test campaigns in distinct operation scenarios by the ADAI team. The outcomes will serve to validate de numerical model (WP1) and for the further development of the system (WP3 and WP4).

In ‘WP3 – Enhanced configurations’, the ADAI and TEMA teams with support from CTCV will develop the system according to four different numerical approaches. In the first development, the system will be adapted for space heating, to further take advantage of its operation process, thus covering most heating requirements: DHW and space heating. The second development will encompass new radical approaches for energy recovery. Different configurations and operation schemes of the system’s heat exchangers will be evaluated to promote their energy efficiency enhancement, by adopting the best engineering approaches for energy recovery. In the third development, different adsorption work pairs will be employed and assessed to improve the system’s performance. This approach will take advantage of the latest advances in adsorption materials in seasonal storage, as improved sorption materials already exist. And, in the last development, the integration of PCM materials will be assessed as a complement to increase the system’s energy density. The developed configurations will then be used in WP4 to assess the system’s operation in different scales and climates.

In ‘WP4 – Implementation', led by TEMA, the configurations developed in the previous work packages will be used to assess the system’s operation in different scales and climates. The system will be adapted to different usage levels in order to satisfy DHW and space heating requirements for muti-family buildings, hotels, and office buildings. In the follow-up, the system, in its different configurations, will be tested in different world climates to analyze where its operation may be more adequate. And, given the ADAI team members’ experience in future climate data generation, the system will also be assessed for future climate situations; namely for 2050 and 2080, according to climate change scenarios proposed by the Intergovernmental Panel on Climate Change.

ADAI will lead the last work package, the ‘WP5 – Dissemination and Management’, which will run throughout the entire project. The principal investigator will coordinate the project's human, material, and financial resources. The project team will implement three orientation plans: the dissemination and communication plan (DCP), the transfer-of-knowledge plan (TKP), and the data management plan (DMP). According to DCP, the projects’ results are disseminated through outreach activities among the general public, professionals, and students. These actions consist of the project media lab (website and social media pages) and the writing of scientific documents to be published in journals or communicated in international conferences. In the TKP plan, the projects’ results will be passed on to professionals, fellow investigators, and students. Having the consortium ADAI and TEMA as research units, CTCV as a technological centre, and OCRAM Clima as an industrial company, special attention will be given to the share of scientific and technological achievements between the partners. Relatively to DMP, the investigators will comply with the European Open Access policy on collecting, storing, sharing, and embargo periods of the datasets and scientific documents produced within the project. The outcomes are expected to expand the available solutions for thermal energy storage, following the current energy policies and supporting energy efficiency and sustainability on an international level. In this regard, this research plan is in line with two Sustainable Development Goals in the UN 2030 Agenda. Lastly, by developing new energy storage concepts, this research project opens development lines for new and more efficient storage technologies. This knowledge contributes to having safer and more sustainable systems and identifies development directions of novel approaches and solutions.