Techno-economic analysis of a solar thermal retrofit for an air-cooled geothermal Organic Rankine Cycle power plant. (December 2017)

• Record Type: Journal Article
• Authors: Heberle, Florian; Hofer, Markus; Ürlings, Nicolas; Schröder, Hartwig; Anderlohr, Thomas; Brüggemann, Dieter
• Is Part Of: Renewable energy. Volume 113(2017)
• Page Start: 494
• Page End: 502
• Publication Date: 2017-12
• Subjects: Organic Rankine Cycle -- Retrofit -- Geothermal energy -- Solar energy -- Parabolic trough collectors; Renewable energy sources -- Periodicals; Power resources -- Periodicals; Énergies renouvelables -- Périodiques; Ressources énergétiques -- Périodiques; 333.794
• DOI: 10.1016/j.renene.2017.06.031
• Languages: English
• ISSNs: 0960-1481

Abstract

Abstract: High ambient temperatures are often coupled with high levels of solar irradiation and lead to a significant reduction of the power output of air-cooled geothermal Organic Rankine Cycle (ORC) power plants. Consequently, hybridisation based on solar thermal power is promising. In this work, a solar thermal retrofit based on superheating of the ORC working fluid is analysed under technical and economic criteria considering typical conditions in Turkey. The conducted off-design simulations prove that the isentropic efficiency of the turbine has a major impact on the performance of the entire system. The solar field size and the corresponding degree of superheating is limited in the respect to the built-in components. Therefore, the thermal stability of the examined ORC working fluid is sufficient and a low-temperature parabolic trough field with water as heat transfer fluid can be realized. For the retrofit, detailed simulations over the period of one year show up to 7.8% more electricity, a solar-to-electric efficiency of 10% and a significant power gain during summer. Besides, an increased reinjection temperature could lead to an improved management of the geothermal reservoir. Economically, the medium sized solar field is related to the lowest levelised costs of electricity ( LCOE) with 145 $/MWh. Highlights: The solar retrofit significantly improves the performance of the geothermal system. The built-in components limit the degree of solar superheating. Low operational temperatures guarantee the thermal stability of the ORC fluid. Economic feasibility is obtained for a yearly sum of direct irradiance by 2086 kWh/m 2.