Introduction
In the year 2015 the Paris Agreement was signed, which established a landmark in
combating climate change effects, with international consensus to reduce global
temperatures to 2
C with a goal of 1.5
C reduction by 2100 (UNFCCC 2015).
Although the 2
C goal was deemed sufficiently aggressive by the IPCC to avoid
catastrophic climate changes, the current trend points to rising temperatures of as
much as 3
C by 2100 (Masson-Delmotte et al. 2018). It is clear to the research
community that greater efforts are needed. The production of electricity is at the
forefront of attention as it is the greatest source of greenhouse gases and thus can cut
carbon emissions almost entirely and faster than other manufacturing sectors.
Through the development of arresting climate change, renewables are expected to
have a major effect on greenhouse gas (GHG) emission, and geothermal energy has
significant advantages over other renewables. This energy source is basically omnipresent (in the subsurface of the Earth, the temperature of formation rises by depths
created by the environmental geothermal gradient), it is independent of global
climate transition and thus a means of electricity production, and it is affordable
(with an increased mean power cost as minimal as USD 0.07/kWh) (IRENA 2019).
The important aspect is that it uses well-known thermodynamic methods to produce
electricity.
As with other techniques, geothermal resources have been harnessed from highcaliber and less obvious potentials (Schechinger and Kissling 2015). Geothermal
system technology pumps heated geothermal fluid from deep aquifers at depths
between 1 and 4 kilometers (km). With increase in enthalpy of water, the consistency
of an aquifer improves, basically from liquid reservoirs to steam reservoirs by
improving water vapour concentrations. In comparison, petrothermal system technology seeks to provide geothermal water where traditional reserves do not occur by
the development of an “engineered reservoir.” These types of systems, also referred
to as enhanced geothermal systems (EGS), are drawing considerable interest as this
theoretically enables geothermal resources to be harnessed anywhere, although the
technology is financially viable only in the case of significant geothermal gradients.
In the year 2018 geothermal power production was calculated as about
630 petajoules, with approximately half of this in electricity generation
(89.3 TWh) and half as other applications in the form of heat. However, the overall
capacity is projected to be nearly 21 GWe from 2015 to 2020 (Bertani 2016). Single
flash systems currently account for nearly 40% of the global installed capacity; dry
steam and double flash plants follow with almost 30%, whereas binary technologies
used in petrothermal and hydrothermal techniques add around 14% (Bertani 2016).
In recent decades, considerable attempts have been made to identify the ecological consequences of enhanced geothermal energy systems for the reduction of GHG
emissions and to assess the life cycle of geothermal plants (Frick et al. 2010;
Lacirignola and Blanc 2013; Pratiwi et al. 2018; Sullivan et al. 2010, 2011; Treyer
et al. 2015). However, geothermal resources still dominate the current generation of
electricity and are expected to grow in future.
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K. Yadav et al.
In the year 2015 the Paris Agreement was signed, which established a landmark in
combating climate change effects, with international consensus to reduce global
temperatures to 2
C with a goal of 1.5
C reduction by 2100 (UNFCCC 2015).
Although the 2
C goal was deemed sufficiently aggressive by the IPCC to avoid
catastrophic climate changes, the current trend points to rising temperatures of as
much as 3
C by 2100 (Masson-Delmotte et al. 2018). It is clear to the research
community that greater efforts are needed. The production of electricity is at the
forefront of attention as it is the greatest source of greenhouse gases and thus can cut
carbon emissions almost entirely and faster than other manufacturing sectors.
Through the development of arresting climate change, renewables are expected to
have a major effect on greenhouse gas (GHG) emission, and geothermal energy has
significant advantages over other renewables. This energy source is basically omnipresent (in the subsurface of the Earth, the temperature of formation rises by depths
created by the environmental geothermal gradient), it is independent of global
climate transition and thus a means of electricity production, and it is affordable
(with an increased mean power cost as minimal as USD 0.07/kWh) (IRENA 2019).
The important aspect is that it uses well-known thermodynamic methods to produce
electricity.
As with other techniques, geothermal resources have been harnessed from highcaliber and less obvious potentials (Schechinger and Kissling 2015). Geothermal
system technology pumps heated geothermal fluid from deep aquifers at depths
between 1 and 4 kilometers (km). With increase in enthalpy of water, the consistency
of an aquifer improves, basically from liquid reservoirs to steam reservoirs by
improving water vapour concentrations. In comparison, petrothermal system technology seeks to provide geothermal water where traditional reserves do not occur by
the development of an “engineered reservoir.” These types of systems, also referred
to as enhanced geothermal systems (EGS), are drawing considerable interest as this
theoretically enables geothermal resources to be harnessed anywhere, although the
technology is financially viable only in the case of significant geothermal gradients.
In the year 2018 geothermal power production was calculated as about
630 petajoules, with approximately half of this in electricity generation
(89.3 TWh) and half as other applications in the form of heat. However, the overall
capacity is projected to be nearly 21 GWe from 2015 to 2020 (Bertani 2016). Single
flash systems currently account for nearly 40% of the global installed capacity; dry
steam and double flash plants follow with almost 30%, whereas binary technologies
used in petrothermal and hydrothermal techniques add around 14% (Bertani 2016).
In recent decades, considerable attempts have been made to identify the ecological consequences of enhanced geothermal energy systems for the reduction of GHG
emissions and to assess the life cycle of geothermal plants (Frick et al. 2010;
Lacirignola and Blanc 2013; Pratiwi et al. 2018; Sullivan et al. 2010, 2011; Treyer
et al. 2015). However, geothermal resources still dominate the current generation of
electricity and are expected to grow in future.
244
K. Yadav et al.