Unified Methodology to Identify the Potential Application of Seasonal Sorption Storage Technology

Abstract

In this study, the definition of a new methodology for a preliminary evaluation of the working boundary conditions under which a seasonal thermal energy storage (STES) system operates is described. The approach starts by considering the building features as well as the reference heating system in terms of solar thermal collectors’ technology, ambient heat sinks/source, and space heating distribution systems employed. Furthermore, it is based on a deep climatic analysis of the place where the STES needs to be installed, to identify both winter and summer operating conditions. In particular, the STES energy density is evaluated considering different space heating demands covered by the STES (ranging from 10% up to 60%). The obtained results demonstrate that this approach allows for the careful estimation of the achievable STES density, which is varies significantly both with the space heating coverage guaranteed by the STES as well as with the ambient heat source/sink that is employed in the system. This confirms the need for careful preliminary analysis to avoid the overestimation of the STES material volume. The proposed approach was then applied for different climatic conditions (e.g., Germany and Sweden) and the volume of one of the most attractive composite sorbent materials reported in the literature, i.e., multi-wall carbon nanotubes (MWCNT)-LiCl, using water as the working fluid, needed for covering the variable space heating demand in a Nearly Zero Energy Building (NZEB) was calculated. In the case of Swedish buildings, it ranges from about 3.5 m3 when 10% of the space heating demand is provided by the STES, up to 11.1 m3 when 30% of the space heating demand is provided by the STES.

Static Temperature Guideline for Comparative Testing of Sorption Heat Storage Systems for Building Application

“…Figure 1 and the accompanied text explains the required process temperatures and Table 1 provides a glimpse of the great dispersion of operating temperatures for the building application reported in literature. This is an issue also pointed to by authors such as Courbon et al [27], Palomba and Frazzica [18] and Scapino et al [55], Hauer et al [57] and Frazzica et al [54]. In this proposition for uniform testing conditions with a crosscomparison of current practice reported in literature, effort has been undertaken to show that a single static guideline is applicable for all sorption process types and able to provide simple remedy to this dilemma.…”

“…They stated that solar thermal charging at temperatures above 100 • C are not practicable. Palomba and Frazzica [18] and again Frazzica et al [54], point to the huge inhomogeneity among prototype testing results and call for the definition of common testing methods and key performance indicators in order to make the prototype characterization comparable. Scapino et al [55] stated that, to make research on sorption heat storage comparable, common key performance indicators should be adopted by the research community, emphasizing the need for common reference temperatures.…”

“…Additionally, their proposition focuses on the material level and not the system, thus excluding HTF temperatures. HTF temperatures are considered by Frazzica et al [54]. In their unified methology to sorption heat storage testing, they clearly point to the need for eight individual HTF temperatures.…”

Experimental Comparison of Innovative Composite Sorbents for Space Heating and Domestic Hot Water Storage

“…This technology can be based either on chemical reactions, usually suitable for high temperature storage [13] or on physical interactions, characterized by lower heat and operating temperature [14]. This technology has gained a lot of attention thanks to the higher storage density achievable through the occurring reaction, as well as the possibility of keeping the energy stored almost indefinitely, as long as the two components are kept separated and no re-combination reaction is allowed (i.e., seasonal storage [15]). On the contrary, some of the main barriers towards its diffusion are represented by the highest system complexity, slow kinetic reaction, and issues in the long-term stability of the materials.…”

Seasonal Energy Flexibility Through Integration of Liquid Sorption Storage in Buildings

“…This fact is very often overlooked even in the research field of sorption energy storage. For a cross comparison of different thermochemical storage types, materials, and processes, thus a common reference framework as suggested, e.g., for the building application, in [9], is needed. A generalized metric provided in [10] can be used for performance comparison across different storage processes reported in literature but does not replace performance metrics such as volumetric energy density, asking for a uniform basis for evaluation.…”