Mobilized thermal energy storage (M-TES) system design for cooperation with geothermal energy sources.

[Display omitted] • Mobilized thermal energy storage system can be powered by heat from geothermal sources. • One of the main factors justifying the application of M-TES is the use of phase change materials (PCM) with the greatest possible heat accumulation capacity. This presents a large area for new research. • M-TES should be designed in detail and adapted to the available heat source and the needs of the recipient. It is possible to create a set of basic assumptions for M-TES (like: requirements for PCM and TES-tank construction, transport requirements, legal, economic and environmental aspects) which can be more widely used and applied for future systems. The main focus of this paper is the mobilized thermal energy storage system designed to be applied in the heating system of a single-family residential building. It has been investigated if it is possible to use geothermal heat as a heat source for M-TES based on PCMs. To analyze this possibility, tests were carried out under real conditions. The M-TES with 700 kg of Rubitherm RT70HC PCM filled into the tank equipped with internal heat exchanger was designed and experimentally tested in Szaflary and Zakopane, Poland. Conceptual and research work were carried out in cooperation with innogy Polska S.A., PEC Geotermia Podhalańska S.A. and the startup company Enetech sp. z o. o. The field tests were preceded by the series of laboratory experiments. On their basis and on the basis of literature research, a hypothesis was put forward that: it is possible to supply single-family buildings with the M-TES based on PCM, powered by geothermal sources. This has been confirmed in practice by observing the process of loading the storage in the heat source, its transport and heat collection at the user's location. The process was observed through the acquisition of the temperature data inside the tank. The appropriate distribution of sensors allowed the analysis of temperatures at the entrance, exit and located both centrally and at the walls of the tank. Results show that there can be indicated some important aspects that have a significant influence on the operation and justification of the application of the M-TES. Among them: proper selection of PCM, proper design of the heat exchanger, supply temperature and constancy of the heat source operating conditions, distance between charging and discharging points. An additional goal of this article is to present guidelines for the design of such systems, which were formulated on the basis of measurements and observations. The paper was designed to highlight the weakest points of the tests and areas for improvement. [ABSTRACT FROM AUTHOR]