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Nowadays, gradual depletion of fossil fuels associated with emissions constraints due to greenhouse gases, leads to reuse wasted heat from power plant in order to increase the global efficiency. One of the implemented technologies for improvements is the application of combined cycles. In this scenario, the steam cycle is frequently combined with a Brayton cycle and the power plant performances and costs are competitive in the global market. Often, an energetic engineering company defines and studies the performance of the bottom steam cycle, thus it imposes operational conditions of steam turbine and heat recovery boiler and requires these components are built by two different manufacturers. For this reason, the plant cannot be globally optimized. From a steam turbines manufacturer point of view, the integration between proprietary simulation code and an energy balance code is an opportunity to simulate a complete bottom-cycle in order to define the best plant configuration. In the present paper, aone-pressure level heat recovery steam generator is studied in term of thermodynamic performance and cost analysis. The thermodynamic analysis is realized using a fixed steam turbine isentropic efficiency (as an energetic engineering company can do) and using anisentropic efficiency determined from steam turbine industrial tool, so a different best performance can be determined. Moreover, a comparison between two academic steam turbine cost correlations and steam turbine cost suggested by industrial cost is carried out. [ABSTRACT FROM AUTHOR]

Nowadays, gradual depletion of fossil fuels associated with emissions constraints due to greenhouse gases, leads to reuse wasted heat from power plant in order to increase the global efficiency. One of the implemented technologies for improvements is the application of combined cycles. In this scenario, the steam cycle is frequently combined with a Brayton cycle and the power plant performances and costs are competitive in the global market. Often, an energetic engineering company defines and studies the performance of the bottom steam cycle, thus it imposes operational conditions of steam turbine and heat recovery boiler and requires these components are built by two different manufacturers. For this reason, the plant cannot be globally optimized. From a steam turbines manufacturer point of view, the integration between proprietary simulation code and an energy balance code is an opportunity to simulate a complete bottom-cycle in order to define the best plant configuration. In the present paper, aone-pressure level heat recovery steam generator is studied in term of thermodynamic performance and cost analysis. The thermodynamic analysis is realized using a fixed steam turbine isentropic efficiency (as an energetic engineering company can do) and using anisentropic efficiency determined from steam turbine industrial tool, so a different best performance can be determined. Moreover, a comparison between two academic steam turbine cost correlations and steam turbine cost suggested by industrial cost is carried out. [ABSTRACT FROM AUTHOR]

A novel solar power plant concept is presented, based on the use of a coupled network of hybrid solar-dish micro gas-turbines, driving a centralized heat recovery steam generator and steam-cycle, thereby seeking to combine the high efficiency of the solar dish collector with a combined-cycle power block. A 150 MW e solar power plant was designed based on this concept and compared with both a conventional combined-cycle power plant and a hybrid solar-tower combined-cycle. The solar dish combined-cycle power plant could reach higher levels of solar integration than other concepts but was shown to be more expensive with current technology; solar electricity costs are double those of the hybrid solar-tower combined cycle. [ABSTRACT FROM AUTHOR]

Performance optimization of a single-effect lithium bromide water absorption refrigeration system is the subject of this paper. First, the thermodynamic model of the system wasderived based on the first and second law analysis of an absorption refrigeration cycle with LiBr-water as the working fluid pair. Then, the effects of different design parameters such as the generator inlet hot water temperature, evaporator inlet chilling water temperature and absorber and condenser inlet cooling water temperatures on the performance of the systemwere investigated. In order that, by defining the coefficient of performance (COP), exergy efficiency (Second-law efficiency) and total cost function of the system as the objective functions, the genetic algorithm optimization technique was implemented to evaluate these performance indexes. Finally, the optimal values of design parameters and objective functions were found and compared to the initial values. Results show significant improvement in system COP (about 75 %), exergy efficiency (47 %) and total cost (12 %). [ABSTRACT FROM AUTHOR]

District Heating (DH) is a rational way to supply heat to buildings in urban areas. This is expected to play an important role in future energy scenarios, mainly because of the possibility to recover waste heat and to integrate renewable energy sources. Even if DH is a well known technology, there are open problems to face. Some of these problems are related to tendencies to reduce design and operation temperatures, the improvement of control strategies, connection of new users to existing networks, implementation of energy savings initiatives and the access of multiple heat producers to the same network. This paper aims to show that exergy is an appropriate quantity for the analysis of DH systems and thermoeconomics can be profitably used to improve their design and operation. Three possible applications of thermoeconomic theories are presented: variation of supply temperature along the heating season, opportunities to connect new users, effects of energy savings initiatives in buildings connected with the network. [ABSTRACT FROM AUTHOR]

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