engleski

Possibilities of electricity generation in the Republic of Croatia by means of low temperature geothermal sources

In the Republic of Croatia there are several medium temperature geothermal sources with relatively low temperature of geothermal water in the range 90–125 C, by means of which it is possible to produce electricity. For the generation of electricity from medium temperature geothermal sources, binary plants come to the fore, either with the Organic Rankine Cycle (ORC) or with the Kalina cycle. In literature, the Kalina cycle is cited as thermodynamically more favorable than ORC, i.e. reaching higher thermal efficiency and giving more power. On the other hand, experiences of the authors of this paper published in previous papers, obtained on the basis of calculations for a medium temperature geothermal source in the Republic of Croatia with higher temperature of geothermal water in the range 140–175 C (Velika Ciglena - 175 C and Lunjkovec–Kutnjak – 140 C) are opposite - the ORC cycle is thermodynamically better than the Kalina cycle! Now, in this paper the comparison of the ORC and Kalina cycles is performed on the basis of energy analysis results for a medium geothermal field with relatively low temperature of geothermal fluid: Babina Greda (125 C). Also in this case, ORC has better the thermal efficiency (the First Law efficiency): 11.53% vs. 10.65%. Again, this is explained by relatively high average annual temperature of cooling air in condenser (15 C) that has more unfavorable influence in the Kalina cycle than in the ORC. The ORC gives net power of 2509.9 kW with mass flow rate 47.77 kg/s, while the Kalina cycle gives net power of 2317.37 kW with mass flow rate 19.81 kg/s.

low temperature geothermal sources; electricity generation; Republic of Croatia

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