AbstractAssessment of the practical implementation of systems for subsurface inter-seasonal storage and recovery of solar energy requires a modelling capability which can represent heat transfer processes at the soil surface, at depth in the soil profile, and within the energy collector system itself. This study presents initial findings related to the development of both analytical and numerical tools to represent various components of such inter-seasonal heat storage facilities. In particular two aspects are considered; firstly the use of widely available averaged meteorological data to be employed in an analytical solution of a simplified version of the problem and secondly the use of a more comprehensive finite element solution to explore the detailed thermal response of the ground in terms of seasonal energy storage. Initial comparisons against field measurements from a large scale demonstration project (undertaken by others) are presented and preliminary conclusions related to the key factors affecting the representation of the surface boundary condition made. The analytical approach developed appears to offer a representative and practical way of estimating initial conditions for both initial assessment of potential for energy collection and storage and for use in defining initial conditions in any subsequent numerical analysis of a detailed inter-seasonal heat storage facility.