Overview

We are currently experiencing a drastic energy transition from fossil fuels to renewable energy sources. This transition is due, on the one hand, to the progressive decrease in fossil-based energy resources and, on the other hand, to the environmental consequences of their use, namely high greenhouse gas emissions. In this transition, there are some problems for which it is urgent to find efficient solutions, such as intermittency and the variable availability throughout the year, which often do not match the thermal energy needs, particularly for space heating and domestic hot water in buildings.

Regarding solar thermal energy, the solution to solve the intrinsic intermittency and the mismatch between availability and need is to develop long-term storage solutions that, although they have been studied in several aspects, still present problems that greatly limit the storage and use of solar thermal energy. Thus, it is urgent to find solutions that solve these limitations, namely through (i) the maximization of the storage density, (ii) the minimization of thermal losses during storage, and (iii) the development of configurations that allow more efficient charging and discharging processes.

The AdsorSeason project aims to contribute to solving this need for long-term storage with the following significant contributions. Based on the know-how of the research team, a new configuration of a long-term solar thermal energy storage system with high energy density and reduced thermal losses will be studied, defined, and optimized, combining an adsorption module with a conventional hot water storage system. In this sense, based on previous studies of the research team, a new numerical model will be specified and developed to evaluate and optimize the operation of the proposed system, in different applications. Following that, a laboratory prototype will be built and instrumented, to be evaluated in experimental tests with different scenarios and operation modes.

Taking the experimental results as a reference, the numerical model will be validated and extensively used to define and study new development paths: different configurations and operation schemes of the adsorption module’s heat exchangers, looking for the most efficient solutions; different working pairs for the adsorption cycle, identifying the advantages and disadvantages and the most suitable and efficient solutions; configurations with the integration of phase change materials to evaluate the effect on increasing the efficiency and energy storage density of the system.

Finally, the new numerical model will be used to evaluate the performance in different climatic conditions, and dimensional scales and profiles of thermal energy use (space heating and domestic hot water) in buildings of various typologies. The evaluation of the system performance in terms of climate variability will also be assessed in a future perspective, based on the experience of the research team, since it is essential to understand how these systems will behave in the future in face of the enormity of problems imposed by climate change.

The project is a co-promotion partnership between the research units ADAI (leader) and TEMA, the industrial company Vieira&Lopes, and the technology centre CTCV. The team covers the critical areas of scientific and technical knowledge of the project, in the development and in the experimental and numerical study of energy production and storage systems (ADAI and TEMA), in the design and manufacture of HVAC equipment (Vieira&Lopes), and in carrying out characterization tests for certification of thermal systems (CTCV). The proposed research combines the experience of different researchers, and also of engineers with great expertise and knowledge, allowing us to find the most appropriate guidelines for the development of better long-term thermal energy storage systems. In the project team, besides new elements in the research teams (ADAI and TEMA), new researchers will also be integrated to increase the R&D capacity of the industrial company (Vieira&Lopes).

Previous results from the research team have shown 16% energy savings for a conventional solar thermal system when the adsorption storage module is attached, which is why the project will certainly identify promising solutions and new paths for the development of long-term thermal energy storage systems. Finally, the project is in line with two Sustainable Development Goals in the UN 2030 Agenda (SDGs 7 and 11).