Abstract
Analytical formulas make it possible to observe thermodynamic processes without using advanced numerical procedures, as the relationships between the physical parameters become clearly visible. While less accurate, these formulas enable students at the academic research level to quickly and easily model the phenomena using simple calculation programs.For a single-flash system, the linear approximation makes it possible to obtain the expression for the optimum flash temperature and maximal specific power in the assumed temperature interval of geothermal fluid (100–250°C).These formulas were presented in the author’s previous works. Now, this procedure was used in example analyses for double-flash, combination single & second, and combination single & ORC systems. It was shown that, in the assumed temperature interval of geothermal fluid, the percentage of the additional power of composite-flash geothermal systems is almost a linear function of geothermal fluid temperature as related to a single-flash plant and that the single-flash & ORC cycle gives the highest additional specific power.
Highlights
In 1996, electricity was being produced from geothermal sources in 21 countries, and geothermal energy had the largest installed electrical capacity (61%) and electricity production (81%) among the “new renewables” [1]
The most common energy conversion systems that can be used for the generation of electricity from geothermal energy are single flash and double flash
A method for expressing the efficiency and specific power of a flash geothermal plant as a function of flash temperature was examined by Ryley [5]
Summary
In 1996, electricity was being produced from geothermal sources in 21 countries (with a total production of 38 TWh/a), and geothermal energy had the largest installed electrical capacity (61%) and electricity production (81%) among the “new renewables” (geothermal, solar, wind, and tidal energy) [1]. The most common energy conversion systems that can be used for the generation of electricity from geothermal energy are single flash and double flash. The total installed capacity in the world for these types of power plants are single-flash plants (42.2%) and double-flash plants (23%) [4]. In Europe, single- and double-flash installations operate in Iceland, Italy, and Turkey, where the exergy of geothermal resources is sufficiently high [9]. The problem of maximizing the power output of a single-flash plant is a well-known issue and involves identifying the value of the optimal flash temperature at which the maximum of the product of the steam mass flow rate and the expansion enthalpy is obtained (for a given wellhead temperature t0 and condensation temperature t2) [10]. Owing to the theoretical nature of the issues presented, these factors have not been accounted for in this paper
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