Dynamic model of solar heating plant with seasonal thermal energy storage

The article focuses on existing technologies developed to harvest and store solar irradiance as a source of primary energy in district heating systems. In the study particular attention was given to solar collector systems cooperating with seasonal heat storage solutions. Motivating this work was the search for a tool to assess achievable solar fraction. the ratio of usable solar energy to total energy consumption. The outcomes of this work are: (i) a simplified dynamic model facilitating evaluation of the proposed solutions, and (ii) selection of optimal operating parameters of the proposed system. A brief review and discussion is made of the technical and legal limitations on possible investments. The ground rules of cooperation between solar based heat sources with seasonal storage systems and conventional industrial boilers and district heating network have been set out. The work touches on the physical components of the discussed systems. Commercially available solar collectors and heat exchangers are presented and their pros and cons discussed. Some in-depth analysis of seasonal heat storage solutions is provided, in particular on tank and pit thermal energy storage as well as storage solutions that use boreholes or aquifer layers. Examples are given of existing plants characterized by high solar fraction located in the EU region and outside of it. A simplified dynamic model developed in the Aspen Hysys software environment is described and the results discussed. Due to the high complexity of the primary problem, the model has been limited to a solar collector installation, seasonal heat storage system and auxiliary boiler. The results obtained from the model are discussed and future steps are presented in the last part of the article. These recommendations seek to further the development of an efficient way of analysis and commercial assessment of such systems. (c) 2019 Elsevier Ltd. All rights reserved.