Exergy and Thermoeconomic Analyses for Thermal Systems
A general exergy balance equation [EX-1] and the corresponding cost-balance equation [Ex-2] that are applicable to any component of thermal systems have been formulated. The exergy of material stream involved in the component of any thermal system was decomposed into thermal, mechanical and chemical exergy flows and an entropy-production flow. A unit exergy cost is assigned to each disaggregated exergy in the stream at any state. This methodology permits us to obtain a set of equations for the unit costs of various exergies by applying the cost-balance equation to each component of the system and to each junction. The monetary evaluations of various exergy costs as well as the production cost of thermal system are obtained by solving the set of equations. The lost costs of each component of the system can also be obtained by this method. Application to a 1000 kW gas turbine cogeneration system show that the unit exergy costs increase as the production process continues and that the production cost of electricity increase nearly proportional with the fuel cost [EX-3].
The application of the proposed exergy and thermoeconomic analyses to 500-MW combined cycle plant [EX-4] has revealed that the model provides the productive structure of the system considered, consequently could visualize the cost formation process and the productive interaction between components clearly. In the analyses, it has been found that the exergy and cost balance equations for the plant boundary play a crucial role for the determination of the production costs. A comparative study of thermoeconomicmethodologies between the SPECO(Specific Cost) methodology proposed by Professor G. Tsatsaronis and our MOPSA(Modified Productive Structure Analysis) for the predefined CGAM cogeneration system has been done [EX-3]. It has also been found that the unit cost of products is dependent on the chosen level of aggregation of the system only when one consider the entropy production rate as one of parameters to determine the unit cost of products, which suggest that the cost structure of energy system is interrelated by the irreversibilities occurred at each component [EX-5, EX-6]. Exergetic and thermoeconomic analysis were also performed for a 200-kW phosphoric acid fuel cell plant by using MOPSA and was found that the system might be viable economically when the initial investment cost per power is reduced to the level of the gas turbine co-generation plant of 1500 $/kW [EX-7]. Optimal configuration and optimal operation condition of the cogeneration plant [EX-8] and the economic evaluation of the plant [EX-9] were determined by considering annual energy demand pattern of commercial building such as hotels and hospitals and apartments[EX-10]. Thermoeconomic analysis was performed for the high-temperature gas-cooled reactors coupled with a steam methane reforming plant in order to estimate the hydorgen production cost [EX-11].
Recently, optimal operation of PEMFC-based CHP system [EX-12], a support strategy for the promotion of photovoltaic uses in Korea [EX-13] and thermoeconomic analysis of ground-source heat pump system [EX-14] were published with collaboration of researchers in Blue Economy Strategy Institute Co. Ltd. in Seoul Korea. Recently, a cost-effective method for integration of existing grids with new and renewable energy sources in public buildings in Korea was suggested [EX-15]. A key factor of the method is based on the fact that the unit costs of the products from the energy systems depends on the capacity factor or the utilization factor which is crucially dependent on the interaction between the energy demand pattern for the building and the production time of the specific energy from the new and renewable energy sources. Recently, a thermoeconomoc analysis of a 20-kW ocean thermal energy conversion (OTEC) plant which was built and operated at the Korea Research Institute of Ships and Ocean Engineering was performed [EX-16]. The OTEC plant was found to be economocally viable renewable energy source in the region where the temperature of warm sea water remains to be 25 centigrade or the condenser effulent from power plant is avaiable.
[EX-1] Si-Doek Oh, Hyo-Sun Pang, Si-Moon Kim and Ho-Young Kwak, “Exergy analysis for a gas turbine cogeneration systems,” Journal of Engineering Gas Turbines and Power, Vol. 118, pp. 782-791, 1996.
[EX-2] Si-Moon Kim, Si-Doek Oh, Yong-Ho Kwon and Ho-Young Kwak, “Exeroeconomicanalysis for thermal systems,” Energy, Vol. 23, pp. 393-406, 1998.
[EX-3] Yong-Ho Kwon, Ho-Young Kwak, Si-Doek Oh, “Exergoeconomic analysis of gas turbine cogeneration systems,” Exergy; Int. J., Vol.1, pp.31-40, 2001.
[EX-4] Ho-young Kwak, Duck-Jin Kim and Jin-Seok Jeon, “Exergetic and thermoeconomicanalysis of power plant,” Energy, Vol. 28, pp. 343-360, 2003.
[EX-5] Ho-Young Kwak, Gi-Taek Byun, Yong-Ho Kwon and Hyup Yang, “Cost structure of CGAM cogeneration system,” International Journal of Energy Research, Vol. 28, pp. 1145-1158, 2004.
[EX-6] Ho-Young Kwak, Ki-Moon Kang, “Sensitivity analysis of component efficiencies on perfomance of a gas turbin cogeneration system,” International Journal of Exergy, Vol. 9, pp. 337-345, 2011.
[EX-7] Ho-Young Kwak, Hyun-Soo Lee, Jung-Yeul Jung, Jin-Seok Jeon and Dal-RyungPark, “Exergetic and thermoeconomic analysis of a 200-kW phosphoric acid fuel cell plant,” Fuel, Vol. 83, pp. 2087-2094, 2004.
[EX-8] Si-Doek Oh, Ho-Jun Lee, Jung-Yeul Jung and Ho-Young Kwak, “Optimal planning and economic evaluation of small scale cogeneration system,” Energy, Vol. 33, pp.760-771, 2006.
[EX-9] Si-Doek Oh, Hoo-Suk Oh and Ho-Young Kwak, “Economic evaluation for adoption of cogeneration system,” Applied Energy, Vol. 84, pp.266-278, 2007.
[EX-10] Hyon Uk Seo, Jinil Sung, Si-Doek Oh, Hoo-Suk Oh, and Ho-Young Kwak, “Economic optimization of a cogeneration system for apartment houses in Korea,” Energy and Buildings,Vol. 40, pp. 961-967, 2008.
[EX-11] Duk Jin Kim, Jong Hyun Kim, K.F.Barry and Ho-Young Kwak, “Thermoeconomic analysis of high-temperature gas-cooled reactors with steam methane reforming for hydrogen production,” Nuclear Technology, Vol. 176, pp. 337-351, 2011.
[EX-12] Si-Doek Oh, Ki-Young Kim, Shuk_Bum Oh and Ho-Young Kwak, “Optimal operation of a 1-kW PEMFC-based CHP system for residential applications,” Applied Energy, vol. 95, pp. 93-101, 2012.
[EX-13] Si-Doek Oh, Yeji Lee, Yungpil Yoo, Jinoh kim, Suyong kim, Seung Jin Song and Ho-Young Kwak, “A support strategy for the promotion of photovoltaic uses for residential houses in Korea,” Energy Policy, vol. 53, pp. 248-256, 2013.
[EX-14] Ho-Young Kwak, Yungpil Yoo, Si-Doek Oh and Ha-Na Jang, “Thermoeconomic analysis of ground-source heat pump systems,” International Journal of Energy Research, Published online in Wiley Online Library, 2013.
[EX-15] Si-Doek Oh, Yungpiul Yoo, Jeonghun Song, Seung Jin Song, Ha-Na Jang, Kwagwon Kim, Ho-Young Kwak, “A cost-effective method for integration of new and renewable energy systems in public buildings in Korea,” Energy & Buildings, Vol. 74, pp. 120-131, 2014.
[EX-16] Jung-Yul Jung, Ho Sang Lee, Hyeon-Ju Kim, Yungpil Yoo, Woo-Young Choi, Ho-Young Kwak, “Thermoeconomic analysis of an ocean thermal energy conversion plant,” Renewable Energy, vol. 86, pp. 1086-1094, 2016.