Exergo-economic and exergo-environmental analysis of a binary geothermal power plant with solar boosting

Abstract

The exploitation of renewable energies is a solution to the energy, economic and environmental issues related to the massive use of fossil resources. Thus, investing in renewable technologies is essential to achieve the carbon-neutral scenario within 2050. In this framework, geothermal energy may have a key role. In particular, power plants with a closed binary cycle are suitable for harnessing geothermal resources with low and medium enthalpy levels. They are prone to be integrated with other renewable devices to increase the global power output. Geothermal fluid can be drawn constantly from underground throughout the day and seasons. Conversely, the availability and intensity of solar energy depend on weather conditions and the time of year. In Italy, geothermal energy is currently harvested for continuous electricity generation, while solar energy is mainly used for photovoltaic generation. For small-to-medium size plants, rated between 5 and 20 MWe, the geothermal and thermodynamic solar hybridization may lead to relevant benefits for the economic competitiveness regarding separate photovoltaic or thermodynamic solar systems. This article aims to investigate the economic and environmental aspects of geothermal power plants with a closed binary cycle coupled with a topper cycle fed by linear parabolic solar collectors. The system operation in both design and off-design conditions was analysed, and exergo-economic and exergo-environmental simulations were conducted. The application site was selected near Torre Alfina (Italy). It has a water-dominant reservoir with a pressure of 44 bar, a temperature of 140 °C, and content of non-condensable gases (NCGs) approximately equal to 2% by weight. At the design point, the net power is 8.4 MW and the first and second principle efficiencies are 9.31% and 18.45%, respectively. The exergo-economic and exergo-environmental analyses indicate that the components with the highest economic and environmental impact are the condenser, the field of solar collectors, the evaporator, and the low-pressure turbine. The levelized cost of electricity (LCOE) is equal to 14.19 c€/kWh.

Bibliometric Analysis and Review of Low and Medium Enthalpy Geothermal Energy: Environmental, Economic, and Strategic Insights

“…Finally, cluster 5 (purple) contemplates the area called "groundwater in the use of geothermal energy", in which hydrogeological and thermal characterisation studies of shallow aquifers for use in heating and cooling systems stand out, as well as the evaluation of the environmental impact in the different stages of construction of this type of system [72][73][74][75][76][77][78][79][80][81][82][83][84][85][86].…”

“…Although implementing geothermal systems represents a sustainable alternative, inadequate resource management can contribute to physical properties and soil temperature alterations [58,80]. Among the environmental effects registered by geothermal energy, most consider the construction phase [81] owing to the diesel consumption by the drilling platform, the steel used for the casing of the wells, and the construction of the power plant [82,83]. One option to mitigate these environmental effects is to use biodiesel or noncontact drilling technologies [84].…”

“…Although the evaluation of the economic and environmental aspects of geothermal resources is rarely addressed in scientific literature, specific studies have presented the advantages and disadvantages of these aspects (e.g., [58,62,65,83]). Implementing a geothermal system requires a novel concept of drilling that does not involve overpricing through an innovative design and intelligent measurement of business associations to reduce the initial investment costs significantly [77].…”