Comparative analysis of thermal energy storage technologies
- January 10, 2019
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The importance of Thermal Energy Storage (TES) inside efficient and renewables-driven systems is growing. While different technologies from traditional sensible TES are entering the market or moving towards commercialisation, a common basis for fair comparison and evaluation of these systems is lacking.
Three main competing technologies are available: sensible energy storage, commonly present in our homes in the form of water or ice storage for domestic hot water or for heating/cooling purposes, but also used for large CSP plants using molten salts, rock or sand. Latent heat storage makes use of Phase Change Materials, exploiting the heat of solidification of melting for industrial or residential purposes. Finally, thermochemical storage is based on reversible reactions, allowing to store energy with a high density.
The maturity of these technologies, their fields of applications and costs are extremely variables: how to assess whether a certain system is suitable for our applications? The easiest approach is the definition of Key Performance Indicators, a set of parameters able to describe the technological, environmental and economical aspect of a technology.
The main requirements, for a parameter to become a Performance Indicator, are:
- Simplicity, in order to be understood not only by technicians or researchers specialized in the field, but also by stakeholders of interconnected sectors.
- Clear and unique definition, in order not to misunderstand or evaluate wrongly the parameter when applying it to different technologies.
- Meaningfulness, which means that the selected parameter should be of relevance not only to one stakeholder (e.g. the academia, or the designer), but to several entities involved in the storage design/realization/operation/evaluation process.
In order to be of interest to the maximum number of stakeholders possible, we selected the Key Performance Indicators by comparing the values and parameters in the scientific literature with the goals indicated in different national and international roadmaps.
Starting from such a methodology, a simplified set of Key Performance Indicators, covering all the abovementioned aspects was defined, as shown in the picture.
The developed approach was then used to evaluate some examples of TESs, both at commercial and under development level. Most of the KPIs were easily evaluated from literature and technical data, confirming the potentiality of the methodology. The comparative evaluation of the KPIs can then drive both the design and optimization of energy systems as well as the needed development activities to bring novel TES technology to high TRL.
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