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Abstract In this paper, two robust decentralised proportional integral (PI) control designs are proposed for load frequency control (LFC) with communication delays. In both methodologies, the PI based LFC problem is reduced to a static output feedback (SOF) control synthesis for a multiple delay system. The first one is based on the optimal H ∞ control design using a linear matrix inequalities (LMI) technique. The second control design gives a suboptimal solution using a developed iterative linear matrix inequalities (ILMI) algorithm via the mixed H 2 / H ∞ control technique. The control strategies are suitable for LFC applications that usually employ PI control. The proposed control strategies are applied to a three control area power system with time delays and load disturbance to demonstrate their robustness.

Abstract In this paper, two robust decentralised proportional integral (PI) control designs are proposed for load frequency control (LFC) with communication delays. In both methodologies, the PI based LFC problem is reduced to a static output feedback (SOF) control synthesis for a multiple delay system. The first one is based on the optimal H ∞ control design using a linear matrix inequalities (LMI) technique. The second control design gives a suboptimal solution using a developed iterative linear matrix inequalities (ILMI) algorithm via the mixed H 2 / H ∞ control technique. The control strategies are suitable for LFC applications that usually employ PI control. The proposed control strategies are applied to a three control area power system with time delays and load disturbance to demonstrate their robustness.

Abstract A validated MATLAB code is developed to design a dry cooling unit for a 25 MW solar power plant operated with supercritical CO2 (sCO2) Brayton cycle. Both direct and indirect cooling systems are designed for the power plant and their performance are compared. For direct cooling system, air cooled heat exchanger unit is designed whereas for indirect cooling system, optimum size of shell and tube heat exchanger is selected addressing the retainment of shell side heat transfer correction factor within a reasonable limit. The nonlinear property variation of sCO2 near the critical condition is reasonably well captured by the present code in both shell and tube and air cooled heat exchanger units. The comparative study of direct and indirect cooling system is performed for inlet sCO2 temperature of 71 °C, operating pressure of 7.5 MPa and ambient air temperature from 15 °C to 40 °C. For the same heat rejection, indirect cooling system requires a much higher cooling tower. During high ambient temperature period, direct dry cooling system shows superior cooling performance in terms of lower sCO2 outlet temperature compared to indirect cooling system.

Abstract A validated MATLAB code is developed to design a dry cooling unit for a 25 MW solar power plant operated with supercritical CO2 (sCO2) Brayton cycle. Both direct and indirect cooling systems are designed for the power plant and their performance are compared. For direct cooling system, air cooled heat exchanger unit is designed whereas for indirect cooling system, optimum size of shell and tube heat exchanger is selected addressing the retainment of shell side heat transfer correction factor within a reasonable limit. The nonlinear property variation of sCO2 near the critical condition is reasonably well captured by the present code in both shell and tube and air cooled heat exchanger units. The comparative study of direct and indirect cooling system is performed for inlet sCO2 temperature of 71 °C, operating pressure of 7.5 MPa and ambient air temperature from 15 °C to 40 °C. For the same heat rejection, indirect cooling system requires a much higher cooling tower. During high ambient temperature period, direct dry cooling system shows superior cooling performance in terms of lower sCO2 outlet temperature compared to indirect cooling system.

The phytoplankton of the upper ocean remove carbon dioxide from the atmosphere by photosynthesis. Their detritus or that of their grazers falls into the deeper ocean taking carbon with it. The ocean uptake of carbon dioxide is limited by the availability of nitrogen in the upper waters over much of the global ocean. This paper examines the cost of providing nitrogen to the upper ocean from a pilot plant with a capacity to sequester 2,000,000 tonnes of carbon dioxide per year. The plant would provide reactive nitrogen at the edge of the continental shelf and monitor the enhanced phytoplankton growth by satellite. The costs compare very favourably with other strategies of carbon dioxide capture and direct placement in carbon sinks. This comes about because the capture mechanism exploits solar energy and the large surface area of the ocean. The sequestration is shown to be permanent and not dependent on the overturning time of the ocean.

The phytoplankton of the upper ocean remove carbon dioxide from the atmosphere by photosynthesis. Their detritus or that of their grazers falls into the deeper ocean taking carbon with it. The ocean uptake of carbon dioxide is limited by the availability of nitrogen in the upper waters over much of the global ocean. This paper examines the cost of providing nitrogen to the upper ocean from a pilot plant with a capacity to sequester 2,000,000 tonnes of carbon dioxide per year. The plant would provide reactive nitrogen at the edge of the continental shelf and monitor the enhanced phytoplankton growth by satellite. The costs compare very favourably with other strategies of carbon dioxide capture and direct placement in carbon sinks. This comes about because the capture mechanism exploits solar energy and the large surface area of the ocean. The sequestration is shown to be permanent and not dependent on the overturning time of the ocean.

Abstract This study focuses on the effects of process and operating parameters – feed gas temperature, evacuation pressure and feed concentration – on the performance of carbon dioxide vacuum swing adsorption (CO 2 VSA) processes for CO 2 capture from gas, especially as it affects power consumption. To obtain reliable data on the VSA process, experimental work was conducted on a purposely built three bed CO 2 VSA pilot plant using commercial 13X zeolite. Both 6 step and 9 step cycles were used to determine the influences of temperature, evacuation pressure and feed concentration on process performance (recovery, purity, power and corresponding capture cost). A simple economic model for CO 2 capture was developed and employed herein. Through experiments and analysis, it is found that the feed gas temperature, evacuation pressure and feed concentration have significant effects on power consumption and CO 2 capture cost. Our data demonstrate that the CO 2 VSA process has good recovery (>70%), purity (>90%) and low power cost (4–10 kW/TPDc) when operating with 40 °C feed gas provided relatively deep vacuum is used. Enhanced performance is obtained when higher feed gas concentration is fed to the plant, as expected. Our data indicates large potential for application of CO 2 VSA to CO 2 capture from flue gas.

Abstract This study focuses on the effects of process and operating parameters – feed gas temperature, evacuation pressure and feed concentration – on the performance of carbon dioxide vacuum swing adsorption (CO 2 VSA) processes for CO 2 capture from gas, especially as it affects power consumption. To obtain reliable data on the VSA process, experimental work was conducted on a purposely built three bed CO 2 VSA pilot plant using commercial 13X zeolite. Both 6 step and 9 step cycles were used to determine the influences of temperature, evacuation pressure and feed concentration on process performance (recovery, purity, power and corresponding capture cost). A simple economic model for CO 2 capture was developed and employed herein. Through experiments and analysis, it is found that the feed gas temperature, evacuation pressure and feed concentration have significant effects on power consumption and CO 2 capture cost. Our data demonstrate that the CO 2 VSA process has good recovery (>70%), purity (>90%) and low power cost (4–10 kW/TPDc) when operating with 40 °C feed gas provided relatively deep vacuum is used. Enhanced performance is obtained when higher feed gas concentration is fed to the plant, as expected. Our data indicates large potential for application of CO 2 VSA to CO 2 capture from flue gas.

Abstract In this article, the synthesis, characterization and catalytic performance of the Pd and Pt promoted Ni-Cu/MgO·Al2O3 catalysts were investigated in the thermocatalytic dehydrogenation of methane to highly pure hydrogen. The physicochemical properties of the prepared catalysts were investigated using different characterization methods such as XRD, BET, SEM, TEM, XPS, H2-TPR and TPO techniques. The Ni–Cu/MgO·Al2O3 catalyst possessing mesoporous structure and large BET surface area (126.28 m2 g−1) was successfully synthesized by facile simultaneous sol-gel method (SSGM) in the absence of surfactants. The results showed that the addition of Pd significantly improved the catalytic activity and stability. The effect of different nominal loadings of palladium (2, 4 and 6 wt%) on the catalytic performance was also studied. Among the prepared samples, the promoted sample with 4 wt% of palladium showed optimal catalytic performance and stability at higher temperatures towards methane thermocatalytic decomposition.