South Africa's geothermal energy hotspots inferred from subsurface temperature and geology

Taufeeq Dhansay,Luc Chevallier,Chiedza Musekiwa,Maarten J De Wit,Thakane Ntholi,Doug Cole

doi:10.17159/sajs.2017/20170092

Abstract

   South Africa intends to mitigate its carbon emissions by developing renewable energy from solar, wind and hydro, and investigating alternative energy sources such as natural gas and nuclear. Low-enthalpy geothermal energy is becoming increasingly popular around the world, largely as a result of technological advances that have enabled energy to be harnessed from relatively low temperature sources. However, geothermal energy does not form part of South Africa’s future renewable energy scenario. This omission may be related to insufficient regional analysis of potentially viable geothermal zones across the country. We considered existing subsurface temperature and heat flow measurements and performed solute-based hydrochemical geothermometry to determine potentially anomalous geothermal gradients that could signify underlying low-enthalpy geothermal energy resources. We correlated these findings against hydro/geological and tectonic controls to find prospective target regions for investigating geothermal energy development. Our results show a significant link between tectonic features, including those on-craton, and the development of geothermal potential regions. In addition, potential regions in South Africa share similarities with other locations that have successfully harnessed low-enthalpy geothermal energy. South Africa may therefore have a realistic chance of developing geothermal energy, but will still need additional research and development, including new temperature measurements, and structural, hydrogeological and economic investigations.     Significance:     The regional low-enthalpy geothermal energy potential of South Africa should be further researched for consideration of low-enthalpy geothermal energy as a renewable energy option.   

Highlights

South Africa is the leading carbon emitter in Africa and has one of the highest rates of emissions of nations in the world.[1]
South Africa does not have any active or recent volcanism and is situated far from any active continental and/or oceanic plate boundaries, but does have anomalously high heat flow regions that could meet the requirements for low-enthalpy geothermal energy development.[3,4,5]
We considered existing heat flow, heat productivity, downhole temperature and hot spring data to conduct estimates of the geothermal gradient across South Africa

Summary

Introduction

South Africa is the leading carbon emitter in Africa and has one of the highest rates of emissions of nations in the world.[1]. Low-enthalpy geothermal energy is becoming increasingly popular around the world.[2] This popularity is largely because it requires geothermal gradients as low as ca 40 °C/km, which may be found in many global settings. South Africa does not have any active or recent volcanism and is situated far from any active continental and/or oceanic plate boundaries, but does have anomalously high heat flow regions that could meet the requirements for low-enthalpy geothermal energy development.[3,4,5]

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Findings

Discussion

Conclusion