**5. Conclusion**

The population's growth and economic development in many countries require an increase in demand for electrical energy. On the other hand, meeting the need for electric energy society in the future should consider the limitations of non-renewable resources while providing energy sustainability and significantly reducing the negative impact on the environment. In this case, the role of renewable energy resources should thus be a priority.

The geothermal energy is one of the sustainable and environmentally friendly sources. Also, it is of a high usage factor and reliability. While geothermal dry steam and flash power plants utilize medium to high enthalpy underground source to generate electricity, geothermal binary power systems are suitable for electricity production from low underground heat source; generally, an inlet temperature range between 80 and 170°C. The secondary working fluid in the binary geothermal system operates in a conventional Ranking cycle. The main feature of the working fluid is having a low boiling point. The configurations of the cycle and the type of working fluid should be optimized for the sake of obtaining the best possible thermodynamic performance and efficiency of the geothermal binary facility. The binary Rankine cycle that used an organic working fluid has demonstrated its efficiency and practicality. Among the reported configurations of ORC for binary geothermal power plants include simple ORC, regenerative ORC and ORC-IHE.

Besides the standard binary geothermal power system, advanced configurations of geothermal energy conversion systems have been also well investigated. They include hybrid single-flash and double-flash systems, hybrid flash-binary configuration and hybrid fossil geothermal technology. In addition, the development of hybrid power systems integrating geothermal plants with biomass, fuel cells, wind, solar systems, and WTE technologies has been gaining a lot of interest. It is reported that the binary ORC plant, when compared to single-flash and double-flash cycles, attains the highest thermal efficiency and output power. On the other hand, the single-flash/ORC integrated cycle offers the highest energy and exergy efficiencies as compared to double-flash counterpart.

The accumulated global installed capacity of geothermal power amounted to 13.28 GW by the end of 2018 and is forecast to reach 16.5 GW worldwide by 2022. United Stated of America has been standing at the top world rank in terms of geothermal power capacity. On the other hand, Turkey, Kenya, Indonesia and the Philippines would be responsible for most of the technology growth and continue to lead capacity additions beyond 2022. Although most existing geothermal facilities worldwide use flash or dry-steam technologies, binary-cycle technology has been the fastest progressing technology in recent time. Direct Use of geothermal energy technology is one of the common forms of utilizing the underground heat. The distribution of geothermal Direct Use applications, relative to their widespread use, are: heat pumps, bathing and swimming, space heating, greenhouse heating, industrial applications, raceway heating and aquaculture pond, agricultural drying and snow melting and cooling, etc.

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. In addition, the global crisis COVID-19 has caused deferrals of strategic decisions such as financing and disruptions to the global supply chain for materials and machinery. The economic feasibility of the geothermal power plants depends greatly upon the type of working fluid and cycle configuration. Geothermal power plants have relatively much lower land requirement than other technologies. Methods to alleviate the environmental concerns of geothermal power systems include reinjection for surface water pollution, the use of silencers for noise pollution and air-cooled condensers for water usage. NCGs accompanying the geothermal power generation can be alleviated by reinjecting geothermal fluids into the reservoir.

As a future work, an optimized hybridization of geothermal energy with other renewables needs further exploration and demonstration, either for small scale CHP or cascaded applications. As the availability of better data about geothermal resources facilitates the attraction of new investors and developing new projects, more deeper studies and financial support is critical to assess sites of appropriate

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

geothermal potential. This is of significance to make the cost of geothermal electricity more competitive to conventional and other cheaper renewable electricity. Advanced technologies to eliminate the environmental effect of geothermal power plants are also required including complete reinjection of NCGs that needs further research, fund, and practical demonstration.
