Maximum potential for geothermal power in Germany based on engineered geothermal systems

Charitra Jain,Christian Vogt,Christoph Clauser

doi:10.1186/s40517-015-0033-5

Charitra Jain, Christian Vogt + Show 1 more

Open Access

https://doi.org/10.1186/s40517-015-0033-5

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Abstract

We estimate the maximum geothermal potential in Germany available for exploitation by operated engineered geothermal systems (EGS). To this end, we assume that (a) capabilities for creating sufficient permeability in engineered deep heat exchange systems will become available in the future and (b) it will become possible to implement multiple wells in the reservoir for extending the rock volume accessible by water circulation for increasing the heat yield. While these assumptions may be challenged as far too optimistic, they allow for testing the potential of EGS, given the required properties, in countries lacking natural steam reservoirs. With this aim, we model numerically the thermal and electric energies which may be delivered by such systems by solving coupled partial differential equations governing fluid flow and heat transport in a porous medium. Thus, our model does not represent the engineered fractures in their proper physical dimension but rather distributes their flow volume in a small region of enhanced permeability around them. By varying parameters in the subsurface, such as flow rates and well separations, we analyze the long-term performance of this engineered reservoir. For estimating the maximum achievable potential for EGS in Germany, we assume the most optimistic conditions, realizing that these are unlikely to prevail. Considering the available crystalline landmass and accounting for the competing land uses, we evaluate the overall EGS potential and compare it with that of other renewables used in Germany. Under most optimistic assumptions, the land surface available for emplacing EGS would support a maximum of 13,450 EGS plants each comprising 18 wells and delivering an average electric power of 35.3 MW e . When operated at full capacity, these systems collectively may supply 4155 TWh of electric energy in 1 year which would be roughly seven times the electric energy produced in Germany in the year 2011. Thus, our study suggests that major scientific, engineering, and financial efforts are justified for developing the drilling and stimulation technologies required for creating the permeabilities required for successful EGS. Then, EGS will have great potential for contributing towards national power production in a future powered by sustainable, decentralized energy systems.

Highlights

Geothermal energy is renewable, environmentally friendly, and ubiquitous
Considering the available crystalline landmass and accounting for the competing land uses, we evaluate the overall engineered geothermal systems (EGS) potential and compare it with that of other renewables used in Germany
Heat extraction from EGS reservoirs is a challenging task owing to limited subsurface knowledge and inaccessibility to rock volume (Pettitt et al 2011)

Summary

Introduction

Geothermal energy is renewable, environmentally friendly, and ubiquitous. Yet, only a tiny fraction of it is harnessed commercially for space heating or for electricity by conversion at some expense (Clauser 2006). In the presence of natural steam or hot water reservoirs, electricity can be produced by forcing high-pressure steam or organic vapor to drive the turbines. In their absence and when the reservoirs lack sufficient permeability for effective heat transfer, engineered geothermal systems (EGS) may be employed for electricity production by engineering the reservoir (Clauser 2006). They cogenerate heat and power and can be used for large-scale applications like district heating or base-load power supply with capacity factors above 90 % (Bertani 2009). The process of heat extraction from the subsurface using EGS needs optimization

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