Incredible untapped potential for the direct use of geothermal heat globally

Screenshot of paper (source: Elsevier/ ScienceDirect)
Alexander Richter 20 Nov 2017

Direct use of geothermal energy for heating and cooling purposes represents an incredible large and untapped potential globally, so a recent paper by scientists.

A paper recently published in Renewable and Sustainable Energy Reviews, provides a global assessment of the resource base for direct heat utilization.

The authors present results of a global resource assessment for geothermal energy within deep aquifers for direct heat utilization. Greenhouse heating, spatial heating, and spatial cooling are considered in this assessment.

Subsurface temperatures were derived from geophysical data and apply a volumetric heat-in-place method to improve current global geothermal resource base estimates for direct heat applications. The amount of thermal energy stored within aquifers depends on the Earth’s heat flow, aquifer volume, and thermal properties. The authors assess the thermal energy available by estimating subsurface temperatures up to a depth of three kilometer depending on aquifer thickness.

In 2016, so the document, the installed geothermal capacity for direct heat was 20.6 GW (equivalent electric power) and about 13.4 GW for electricity generation. In the overall energy mix worldwide, geothermal only represents about 0.15% of the world final energy consumption in 2015. Excluding ground-source heat pumps, direct use applications represent about 50% thereof.

The paper aims to estimate the geothermal resource base for direct heat in deep aquifers, basing this on the heat demand by different applications, such as spatial cooling, greenhouse and spatial heating. The authors define the geothermal resource base as the aquifer volume with temperatures sufficiently high to meet requirements for direct heat applications.

In Conclusion, the authors describe that only limited areas in the world have sufficiently high geothermal gradients and suitable reservoirs for geothermal electricity generation and it was important to focus on low-enthalpy geothermal heat applications.

Based on the research, the paper states a global geothermal resource base ranging between 125 and 1,793 EJ year. With suitable aquifers underlaying 16% of the Earth’s land surface could theoretically be used for direct use. Even if one would be setting a rather conservative 1% recovery factor and and an assumed lifetime of 30 years, “the annual recoverable geothermal energy is in the same order as the world final energy consumption of 363.5 EJ/ yr.

Paper & Source:

“Geothermal energy in deep aquifers: A global assessment of the resource base for direct heat utilization”

Authors: Jon Limbergera Thijs Boxem, Maarten Pluymaekers, David Bruhn, Adele Manzellae, Philippe Calcagno, Fred Beekman, Sierd Cloetingh, Jan-Diederik van Wees.