Investigation of the Role and Design of Thermal Insulation in the Envelope of Buried Large-Scale Thermal Energy Storage
Abstract
In an urban context, the size of large thermal energy storage (LTES) is limited by space availability and by high land costs, so deep LTES systems with insulated vertical walls are a promising alternative to the state-of-the-art shallow pit TES. The design of buried LTES envelope is investigated using a finite-element (FE) based numerical model. The focus is a detailed thermophysical representation of its envelope with thermal insulation. This geometric representation allows to investigate the envelope design and its influence on LTES performance as well as on the surrounding ground temperature. Additionally, the influence of the envelope modelling approach (i.e., detailed geometric/thermophysical vs. resistive) is investigated. Purely resistive models are sensitive to insulation quality, but are not able to model the effects of insulation location or 2D heat flux. For the same insulation quality, cases with external insulation show lower performance than cases with internal insulation. In particular, the energy efficiency is about 2% lower and the exergy efficiency is 5% lower with external insulation than with internal insulation.
Keywords
large-scale thermal energy storage, envelope, numerical modelling, thermal insulation, energy, exergy