Assessment and Public Reporting of Geothermal Resources in Germany: Review and Outlook

Abstract

Any geothermal resource assessment requires consistent and widely accepted terminology, methods, and reporting schemes that facilitate the comparison of geothermal resource estimates. This paper reviews common resource assessment methods, as well as reporting codes and terminology. Based on a rigorous analysis of the portrayed concepts and methods, it discusses the appropriateness of the existing reporting codes for sustainable utilization of geothermal resources in Germany. Since the last quantitative geothermal resource assessment in Germany was done 15 years ago, a revised report is overdue. Unlike fossil energy commodities, geothermal energy replenishes naturally and heat recuperation increases in created heat sinks. This replenishment process offers the opportunity for sustainable reservoir management in the case of moderate production rates or cyclic operation. Existing reporting codes, however, regard geothermal resources in a similar way to fossil resources or focus too much on field development rather than on the whole assessment process. In order to emphasize the renewability of geothermal energy, we propose the reporting of geothermal capacities (per doublet or per km 2 ) instead of recoverable heat energy which depends very much on project lifetime and other factors. As a first step, a new classification scheme for geothermal resources and reserves is outlined.

Assessing the contribution of simultaneous heat and power generation from geothermal plants in off-grid municipalities

“…However, the relative growth from 7 MW el to 39 MW el (+450%) in geothermal power generation in Germany between 2010 and 2017 is one of the highest in the world (Bertani 2016). The currently (2017) installed 30 GTPs in Germany generate about 155 GWh of electricity (UBA 2018a) and 1.3 TWh of heat (Agemar et al 2018) annually, which is generally used for district heating (DH) applications (Weber et al 2016). The locations of the 30 GTPs are shown in Figure 2.…”

Energy Pile Field Simulation in Large Buildings: Validation of Surface Boundary Assumptions

“…where q = −k∇T is the heat flux through each layer of the medium. According to the large simulation scale, the mesh was defined as follows 3 : maximum and minimum element sizes respectively 2.67m and 0.481m, maximum element grow rate 1.5, curvature factor 0.6 and resolution of narrow regions 0.5. The actual pile temperatures were measured with sensors placed in soil on the edge of the structure, at depths listed in Table 1.…”

“…Even though the above setup is rather simple and the physical phenomenon investigated is straightforward, involving a relatively small amount of degrees of freedom, reproducing the measurements accurately was not trivial. This is due to the inherent inhomogeneity of the soil 3 A few tests performed with finer meshes showed a negligible impact of the resolution on the temperature profiles. layers, whose composition and thermophysical properties might well be approximated by Table 2 globally, but on a smaller scale this lack of accuracy becomes relevant.…”

“…Such a requirement clearly demands an extensive use of renewable sources. A recent review [2] on the utilization of geothermal energy [3,4] revealed that, by 2015, 49 countries invested over 20 billion USD in geothermal plants, which resulted in energy savings of ca 52.5 million tonnes of equivalent oil. This prevented respectively 46 and 148 million tonnes of carbon and CO2 from being released into the atmosphere every year.…”

Energy Pile Field Simulation in Large Buildings: Validation of Surface Boundary Assumptions

“…A recent review [2] on the utilization of geothermal energy [3,4] revealed that, by 2015, 49 countries invested over 20 billion USD in geothermal plants, which resulted in energy savings of ca 52.5 million tonnes of equivalent oil. This prevented respectively 46 and 148 million tonnes of carbon and CO 2 from being released into the atmosphere every year.…”