This paper presents the background, development and the validation of new analytical and numerical solutions for the
modeling of short-term response of borehole heat exchangers. The new analytical solution studies the borehole's heat
transfer and the related boundary conditions in the Laplace domain. A set of equations for the Laplace transforms for the
boundary temperatures and heat-fluxes is obtained. These equations are represented by a thermal network. The use of the
thermal network enables swift and precise evaluation of any thermal or physical setting of the borehole. Finally, very concise
formulas of the inversion integrals are developed to obtain the time-dependent solutions. The new analytical solution
considers the thermal capacities, the thermal resistances and the thermal properties of all the borehole elements and
provides a complete solution to the radial heat transfer problem in vertical boreholes. The numerical solution uses a special
coordinate transformation. The new solutions can either be used as autonomous models or easily be incorporated in any
building energy simulation software.