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Summary: For the global future energy systems, concentrated solar power (CSP) and direct CO2 capture systems are of the most important key technologies, however, each of these systems has shortcomings. This study addresses the solar intermittency and power control complexity of the CSP systems and the substantial energy penalty of the direct oxy‐combustion (DOC) supercritical carbon dioxide (sCO2) power systems by integrating both systems. Herein, innovative power cycle configurations that integrate the CSP tower system with DOC sCO2 power cycle are introduced. The configurations include two basic cycles for comparison and validation purposes and three integrated cycles. The basic configurations are: an intercooled sCO2 power cycle driven by DOC system (S1), and a stand‐alone basic CSP tower system (S2). The integrated configurations are: CSP/DOC system where the CSP works as a preheater (S3); CSP/DOC system where the CSP works as a reheater (S4); and CSP/DOC system where each system heats part of the working fluid to drive its high‐pressure turbine (S5). The hybrid configurations reduce the fuel and the parasitic power consumptions of the basic DOC systems (S1) and reduce the capital cost associated with the conventional CSP systems (S2) by eliminating the need for thermal storage. Over practical ranges of operational parameters, comprehensive thermoeconomic, exergoeconomic, and optimization analyses for the proposed configurations are performed. Compared to the conventional CSP system, the LCOE of the hybrid system is lower by 50%. Among the hybrid configurations, the energetic and exergetic performances of S4 are the best with the lowest LCOE. According to the optimization analysis, S4 has a thermal efficiency of 55.29% at LCOEs of 7.705¢/kWh. S3, S5, S2, and S1 have thermal efficiencies of 52.90%, 48.72%, 45.56%, and 40.54% at LCOE of 7.970, 8.138, 7.864, and 6.351¢/kWh, respectively. [ABSTRACT FROM AUTHOR]

Summary: Small‐scale‐liquefied natural gas (LNG) cold‐utilized power generation systems are the sustainable solutions in the rural and inland areas where the large‐scale power generation is infeasible. This study investigates three different small‐scale LNG cold‐utilized power generation systems, which are called as the single, combined, and carbon dioxide (CO2)–reduced combined systems according to their design details. The assessments are done according to the life‐cycle‐based enviroeconomic and life‐cycle‐integrated thermoeconomic assessment (LCiTA) models that are recently developed and new approaches, in order to better monitor their feasibilities in real operations. The life‐cycle‐based enviroeconomic assessment shows that the combined system has the lowest environmental payback period with 7.35 years that is nearly 6 months and 1 year lower than the single and CO2‐reduced combined systems, respectively. The LCiTA study deduces that the combined system has the minimum levelized product cost while the single system has the highest values. The integration of CO2 capture components increases the levelized product cost nearly by 16.0% in the combined design, but the levelized product cost value is still found lower than the single system. Moreover, the sustainability performance of the systems is evaluated according to the improved sustainability index calculated by the life‐cycle‐integrated fuel and destruction costs. The index value of the combined system is twice that of the single system. The multiobjective optimization study is performed in cases of closed operation rooms. The best trade‐off points are found in the close ambient air temperature range between 300.50 and 302.00 K. To observe the dynamic outdoor performance, the finite sum approach is applied for the LCiTA model. The highest fluctuations are seen for the CO2‐reduced combined system while the smallest fluctuations belong to the combined system. [ABSTRACT FROM AUTHOR]

Summary: Recent research has been focused on the utilization of low‐grade waste heat, and the industrial high‐temperature heat pump can be an alternative technology because of its simplicity and outstanding performance. However, the use of carbon dioxide in vapor compression heat pumps with high‐temperature heat source is still to be optimized because of low critical temperature. In the present study, a system for waste heat recovery from the steam condenser using CO2 vapor compression cycle is modeled from the energetic, exergetic, and economic perspectives, and optimized system performances are obtained by dual‐objective Jaya algorithm. Potential optimized operating strategies for transcritical cycle are discussed by the parametric study and T‐s diagrams. The transcritical and supercritical cycles are further compared with each other considering different steam temperatures. The optimization strategies of transcritical cycle are based on the main purpose to improve the evaporation potential and achieve transcritical cycles with the critical point inside the closed region surrounded by the process curves, so lower superheating degree and minimum temperature difference of gas cooler, higher evaporating temperature, and more return water cooling should be employed in order to promote the cycle performances. In comparison with transcritical cycles performances, the supercritical operation shows superior performances, which are less sensitive to the variations of return water temperature. The use of carbon dioxide in vapor compression heat pumps for waste heat recovery from the steam condenser is optimized from the energetic, exergetic, and economic perspectives by dual‐objective Jaya algorithm. Potential optimized operating strategies for transcritical cycle are discussed by the parametric study and T‐s diagrams. The transcritical and supercritical cycles are further compared with each other considering different steam temperatures, and the supercritical operation shows superior performances, which are less sensitive to the variations of return water temperature. [ABSTRACT FROM AUTHOR]

SUMMARY A thermoeconomic analysis of a ground-source heat pump (GSHP) system with a vertical or horizontal ground heat exchanger, a type of heat delivery system, was performed using the modified productive structure analysis method. In this analysis, the unit cost of geothermal heat delivered to a room using GSHP system was estimated. The unit cost of heat delivered was calculated to be $0.063/kWh for input of electricity with a unit cost of $0.140/kWh for a GSHP with a coefficient of performance (COP) of 3.27. Exergy destruction and monetary losses due to the irreversibility that occurs at each component of the system were also estimated. The unit cost of heat was found to be inversely proportional to the COP of the heat pump and proportional to the electricity input. The greatest monetary loss occurs in the geothermal heat exchanger in which considerable mass of brine flows in long pipes and in the fan-coil unit which features a complex configuration of pipes in the air passages, respectively. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY The optimal design for heat recovery steam generator (HRSG) should be chosen based on technical and economic considerations. Therefore, parameters that are related to thermodynamic and economic aspects should be considered in optimization approaches. It is worth mentioning that one of the significant issues in the HRSG design is the diversity of arrangements between various components (economizer, evaporator, and superheater), which absolutely affect the HRSG performance. According to these facts, in the present article, different arrangements of a dual pressure HRSG are analyzed, and the economizer at the high-pressure level is divided into two parts; these arrangements are optimized by applying different optimization approaches to achieve the optimal configuration. These approaches include the reduction of gas pressure drop, the reduction of generated steam cost and the consideration of both approaches as the third approach. These three approaches are also considered to perform economic and thermodynamic optimization. With regard to the limitations of optimization such as the pinch and approach point, seven different configurations are considered. First, a comprehensive model is developed for calculating thermodynamic, heat transfer, and pressure loss. To perform a thorough optimization, both thermodynamic and geometric variables as well as diversity of various arrangements is considered using genetic algorithm. The results of the optimization study show that the best arrangement is not unique, and each arrangement has different characteristics. Hence, the best arrangement for the HRSG is chosen according to the importance of the objective functions. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The large industrial production systems face several conflicting challenges of energy efficiency improvements, lower consumption of raw materials per unit of production, extending the product durability, minimizing the environmental impacts, and cautious use of natural resources. In this context it is well obvious that the optimization problem is multiobjective in nature. The paper emphasizes critical review of optimization methods of large-scale industrial production systems and presentation of a novel systematic multiobjective and multiscale optimization methodology based mainly on a combined local optimality search with global optima determination, and advanced system decomposition and constraint handling. © Her Majesty the Queen in Right of Canada, as represented by the Minister of Natural Resources, 2007. [ABSTRACT FROM AUTHOR]