Maximum combined cycle efficiency

Refs. [72, 73] are based on the use of Ni- and Fe-based OCs. In Ref. [72], different GT compressor ratios are investigated in order to optimize the performance of the plant. The maximum temperature of the GT is dictated from the maximum temperature acceptable from the solid material in the air reactor. In the study by Wolf [73], a sensitivity analysis is carried out by using an air reactor temperature of 1000 °C and 1200 °C. By increasing the maximum solid temperature, the efficiency increases from around 49% up to 52.4% with a CO2 capture rate of 100%. In the study by Consonni [72], the maximum solid temperature has been varied from 850 to 1050°C with an electrical efficiency of 43-48% and CO2 capture rate of 100% (Figure 5.26). A supplementary natural gas post-firing has been adopted to improve the combined cycle efficiency up to 52.5% (with reduced CO2 capture rate to 54%) by increasing the maximum turbine inlet temperature (TIT). 

After allowing for the performance penalties arising from the CO2 removal, Lozza and Chiesa estimated an efficiency of 46.1%, for a maximum gas turbine temperature of 1641 K and a pressure ratio of 15 (compared with the basic CCGT plant efficiency of 56.1%). They concluded that the plant cannot compete, in terms of electricity price, with a semi-closed combined cycle with CO2 removal (Cycle A2). 

The combined cycle is designed to gain maximum efficiency from the primary heat source. In most cases, both cycles are used for the same purpose—usually to generate electricity. The major combined-cycle options currently under development include open-cycle gas turbines, closed-cycle turbines, fuel cells, and magnetohydrodynamics with vapor cycles. Other combined cycles include the Diesel/Rankine cycle (Boretz, J.E.,... 

The GT-off design performance has also been investigated by Naqvi et al [76], The use of C02-rich stream gas turbine is also included in the analysis, which accounts for 14% of the electric gross power produced. The net electric efficiency is around 52% in the case of maximum solid temperature of 1200°C (Figure 5.26), and the electric efficiency decay due to the part-load operation is lower than that in the conventional combined cycle (higher than 94% of the nominal electrical efficiency in the case of 54% of full load) if an advanced control strategy is adopted. 

In plant layouts without supplementary firing. 111 is limited by the resistance of the OC at high temperature, which limit the maximum temperature of the combined cycle and thus the maximum efficiency. Therefore, CLC processes will not take advantage of future advancements in the gas turbine material technology. 

Chen, J. (1994). The Maximum Power Output and Maximum Efficiency of an Irreversible Carnot Heat Engine, /, Phys. D Appl. Phys., Vol. 27, pp. 1144-1149 Chen, J. (1996). The Efficiency of an Irreversible Combined Cycle at Maximum Specific Power Output, /, Phys. D Appl. Phys. Vol. 29, pp. 2818-2822 Chen, L. . Zhang, W. Sun, F. (2007). Power, efficiency, entropy generation rate and ecological optimization for a class of generalized universal heat engine cycles. Applied Energy, Vol. 84, pp. 512-525... 

This cycle produces an increase of 30% in work output, but the overall efficiency is slightly decreased as seen in Figure 2-15. An intercooling regenerative cycle can increase the power output and the thermal efficiency. This combination provides an increase in efficiency of about 12% and an increase in power output of about 30%, as indicated in Figure 2-16. Maximum efficiency, however, occurs at lower pressure ratios, as compared with the simple or reheat cycles. 

Maintenance practices are being combined more and more with operational practices to ensure that plants have the highest reliability with maximum efficiency. This has led to the importance of performance condition monitoring as a major tool in the operation and maintenance of a plant. Life cycle costs, rightly so, now drive the entire purchasing cycle and thus the... 

Mechanical cryocoolers are used either to liquefy a gas for use away from the machine or to provide a cold platform for a refrigerator. A cryocooler must be as efficient as possible, whilst taking account of any constraints there may be for particular applications. For this to occur, the maximum possible use must be made of any cold substance that is produced. It is important in a helium liquefier that the fraction of gas which was cooled but did not liquefy is used to precool further incoming gas. This leads us directly to consider the heat exchangers. The combination of a cyclical process with the need for efficient heat exchange led to the idea of a regenerator in which heat may be stored for a short time, so that heat output from one phase of the cooling cycle may be reinserted at some phase. 

In the present paper, the performance of a non-endoreversible heat engine modeled as a Curzon-Ahlborn cycle is analyzed. The procedure in [5] is combined with the procedure in [16], arriving to linear approaches of the efficiency as a function of a parameter that contains the compression ratio in both regimens maximum power output and maximum ecological function. From the limit values of the non-endoreversibility parameter and the compression... 

Figure 19. Transformations of Fe(II, III) at an oxic anoxic boundary in the water or sediment column (modified from Davidson, 1985). Peaks in the concentration of solid Fe(III) (hydr)oxides and of dissolved Fe II) are observed at locations of maximum Fe(III) and Fe(II) production, respectively. The combination of ligands and Fe(ll) produced in underlying anoxic regions are most efficient in dissolving Fe(III) (hydr)oxides. Redox reactions of iron—oxidation accompanied by precipitation, reduction accompanied by dissolution—constitute an important cycle at the oxic-anoxic boundary which is often coupled with transformations (adsorption and desorption) or reactive elements such as heavy metals, metalloids, and phosphates.

---