Geothermal energy

Web-based Application for the Investigation of thermally activated Tunnels

Quelle/credit: IGS

Overview of the distribution of renewable energy sources 1^st–4^th quarter 2017 from [1], WtE = waste to energy

Quelle/credit: IGS

Influences and boundary conditions, under which a tunnel geothermal plant extracts heating and cooling energy from the subsoil

Quelle/credit: IGS

System sketch of the calculation model, BC = boundary condition

Quelle/credit: IGS

Isometric display of the Stuttgart-Fasanenhof calculation model: ground stratification (left), absorber circuits (right)

Quelle/credit: IGS

Comparison of the measured and simulated return temperatures of absorber circuit 1

Quelle/credit: IGS

Characteristic curve of the activated heat flux density of the investigated tunnel geothermal plant; here: radial variation of the location of the absorber pipes in the tunnel lining

Quelle/credit: IGS

Screenshot of an input window of the web-based simulation application

Quelle/credit: IGS

The equipment of infrastructure tunnels with absorbers for the extraction of heating or cooling energy is a consistent further development of the shallow geothermal hybrid systems in the field of ground engineering. The heat fluxes acting on a tunnel geothermal plant result from a complex interaction of the climatic conditions at the surface and inside the tunnel, the subsoil conditions and the operation of the geothermal plant. A prediction of possible heat extraction rates is thus only possible on the basis of transient simulations. In this article, a simulation application for the investigation of tunnel geothermal plants developed at the Institute of Geotechnical Engineering of the University of Stuttgart is presented, and the results of parameter studies regarding the heat extraction performance from a shallow urban transit tunnel are discussed.

1 Introduction

About 32 % of the German energy consumption is used for the provision of heating and hot water in buildings, which corresponds to 40 % of all CO2 emissions. The share of renewable energy in primary energy consumption was 13.1 % in 2017; an increase of 6 % over the figure for 2016 [2]. Within the renewable energies, geothermal energy has a share of about 3 %, only a small part of total energy consumption (Fig. 1). Considering that geothermal energy provides an inexhaustible energy reserve for human dimensions [4], this share should be increased.

Construction elements in ground...