**4. Economic and environmental impacts of geothermal energy**

In addition of being harnessed for the production of electrical energy, geothermal energy can also be utilized for various thermal applications including industrial heat input and space heating. Geothermal waters are highly beneficial for health and well-being, treat arthritis and skin diseases. Production of freshwater and minerals exploiting the hot reinjected brine of geothermal resource is also a viable and economic option [4]. Furthermore, geothermal energy resources improve the security and defense of the country through their exploitation in military facilities such as heating of runways and heliports and wide range applications of heat pumps [48]. For the above-mentioned advantages, many countries offer incentives for the use of the technology. For instance, Switzerland raised its geothermal power Feed-in Tariff (FiT) from USD 0.48 to USD 0.54 per kWh [44].

Nevertheless, the main barriers for the development of geothermal industry include high resource and exploration risk, overall high development cost particularly drilling, economic risk associated with long project lead-times and inadequate financing and grant support, as well as lack of clear policy and regulatory frameworks. Indonesia, for example, did not meet its 2018 targets for investment acceleration in geothermal due largely to drilling delays by developers. The economic recession stemming from COVID-19 crisis has enormously affected the technology progress even for the pioneered geothermal energy users such as Italy, the United States and New Zealand that have not witnessed significant growth in recent years [44]. The global crisis has caused deferrals of strategic decisions such as financing and disruptions to the global supply chain for materials and machinery. On the other hand, it is reported that the availability of better data about geothermal resources facilitates attracting new investors and developing new projects [49].

The per MW cost of geothermal power unit hits USD 7 million [44]. Global range of electricity cost and its weighted average of various technologies are tabulated in **Table 5**. As can be seen, renewable technologies are competing with fossil fuels, while geothermal projects are not far behind (at USD 72/MWh). Because of its adequacy for relatively low-temperature resources and applicability for both power and heat, among the key players of geothermal binary technology are Exergy (Italy), Ormat Technologies (United States), and Turboden (Italy, a subsidiary of Mitsubishi Heavy Industries of Japan) [44].

An economic analysis performed by [23] indicated that the economic performance of the Rankine cycle depends greatly upon the type of working fluid and cycle configuration. The results also showed that a standard Rankine cycle with a 2-stage turbine using n-pentane is the most thermo-economic design for the particular brine resource and re-injection conditions. For binary ORC plants, the simple ORC offers the lowest total capital investment and the shortest payback period as compared to the regenerative and the one with internal heat exchanger [22]. An economic assessment of double-flash geothermal power cycle and single-flash-ORC combined cycles showed that the former configuration attains the minimum unit cost of produced power [37]. In another economic analysis


#### **Table 5.**

*Global electricity cost of different technologies as of 2018 [44, 50].*

of a hybrid CSP-binary geothermal power plant showed that the levelized cost of electricity can be reduced by 2% for the hybrid system in comparison to the stand-alone geothermal system [51].

Land requirement of geothermal power plant is relatively much lower than other technologies. For example, a single-flash geothermal unit needs approximately 1200 m<sup>2</sup> per MW installation as compared to coal-fired facility which requires 40,000 m<sup>2</sup> /MW and a photovoltaic plant requirements of 66,000 m<sup>2</sup> /MW [9]. On the contrary, this economic advantage in land aspect is challenged with other environmental concerns such as water usage and its pollution, visual and noise pollution, greenhouse gas emissions, and loss of natural beauty. However, methods to alleviate these environmental concerns include reinjection for surface water pollution, the use of silencers for noise pollution and air-cooled condensers for water usage [52].

The great benefits of increased implementation of geothermal technology include the high reliability and the feasible functionality over 7000 h per year, which is a crucial issue for electrical utility grids. If the reservoir is appropriately managed i.e., the reservoir water balance, then the sustainability of geothermal power plants is guaranteed [53]. However, the release of NCGs to the environment has become a critical factor for a geothermal power plant. NCGs are naturally found in geothermal reservoirs and can contain several types of pollutants, dominantly carbon dioxide (CO2), in addition to ammonia (NH3), hydrogen sulfide (H2S) and heavy metals. Although CO2 production of the geothermal power plants is much lower than fossil fuel generation units, they still emit averagely 400 g CO2/kWh and may be higher depending upon the chemical composition of the reservoir and the conversion technology [54].

Treatment of NCGs has been a hot topic in the industry world and research community. After segregation of the NCGs, geothermal fluids are reinjected into the reservoir. This is a demonstrated design in geothermal power plants. The Sinem ORC geothermal power plant rated at 24 MW and located in Aydın province, Turkey re-injects about 70% of the heat drawn fluid, after being condensed at 70°C, into re-injection well whereas the remaining 30% is emitted to atmosphere as NCGs [55]. However, an emerging technology based on reinjection of NCGs is still under development intending to minimize the environmental footprint, handling the emissions of H2S and CO2 [53]. It is confirmed that complete reinjection of NCGs using binary ORC geothermal power plant assures the sustainability of geothermal

#### *Geothermal Power Generation DOI: http://dx.doi.org/10.5772/intechopen.97423*

resource [56]; in this regard, some advancements have been achieved in Iceland geothermal plants [57]. More funds are dedicated for eliminating the environmental effect of geothermal industry. The European Commission, for example, awarded the Geothermal Emission Control (GECO) project, USD 18.3 million to advance research on reinjection of harmful gases such as CO2 and H2S from open-loop geothermal plants [44].

Feasibility of hydrogen production by means of geothermal resource has been also explored. In [58] the authors conducted a thermo-economic cost assessment of electrolysis based hydrogen production powered via a binary geothermal unit. The analysis argues that for a geothermal heat of 160°C and a flow rate of 100 kg/s, hydrogen can be obtained at a level of 0.253 g per kilogram of geothermal water. It was also found that unit exergetic costs of electricity and hydrogen are 0.0234 \$/ kWh 2.366 \$/kg H2, respectively. Koroneos et al., [59] demonstrated the technical feasibility (based on efficiencies and exergy indicators) of installing a 2.1 MW binary geothermal power plant at in Nisyros Island, Greece. The proposed facility could reach up to 10 MW of total installed capacity in the future and capable of supplying a substantial amount of electricity thereby reducing the reliance of the island to the diesel power generation thus the gain from an environmental point of view is guaranteed.

Energy savings from utilizing Direct Use geothermal energy amounts to 81 million tonnes (596 million barrels) of equivalent oil yearly. This eventually prevented 78.1 million tonnes of carbon and 252.6 million tonnes of CO2 from being released to the atmosphere [4]. Geothermal technology based freshwater production is one of the most economic renewable and clean production alternative [60].

Hybrid geothermal-fossil fuel power system, for low-enthalpy geothermal resources, is a practical alternative to reduce the extensive use of fossil fuels and associated emissions. The research study in [61] analyzed a 500 MW combined geothermal-coal power plant with a 210°C geothermal temperature and 400 kg/s brine flow rate. The study claimed that up to 0.3 million tonnes of coal can be saved per year in addition to annual reductions of up to 0.72 million tonnes of greenhouse gas emissions. Economically, a drop of 33–87% in energy cost is reachable in comparison to a sole geothermal power unit. A study conducted by [51] revealed that the hybridization of binary ORC with CSP system decreases the levelized energy cost by 2% and when the ORC geothermal configuration is optimized an 8% drop in the levelized energy cost is achieved.

In [55], an exergoenvironmental analysis is performed from the perspective of environmental impact. The study came to a conclusion that 98% of total environmental impact for the geothermal power system is caused by exergy destruction of the equipment involved; and as a treatment, exergetic efficiency for equipment should be improved rather than construction, operation/maintenance and disposal changes of facility equipment. The study advices obtaining a higher capacity plant by having a better condenser performance and enhancing the efficiency of the vaporizers and the pumps.
