Evaluation for Scalability of a Combined Cycle Using Gas and Bottoming SCO2 Turbines

Abstract

Bottoming cycles are drawing a real interest in a world where resources are becoming scarcer and the environmental footprint of power plants is becoming more controlled. Reduction of flue gas temperature, power generation boost without burning more fuel and even production of heat for cogeneration applications are very attractive and it becomes necessary to quantify how much can really be extracted from a simple cycle to be converted to a combined configuration. As supercritical CO2 is becoming an emerging working fluid [2, 3, 5, 7 and 8] due not only to the fact that turbomachines are being designed significantly more compact, but also because of the fluid’s high thermal efficiency in cycles, it raises an increased interest in its various applications. Evaluating the option of combined gas and supercritical CO2 cycles for different gas turbine sizes, gas turbine exhaust gas temperatures and configurations of bottoming cycle type becomes an essential step toward creating guidelines for the question, “how much more can I get with what I have?”. Using conceptual design tools for the cycle system generates fast and reliable results to draw this type of conclusion. This paper presents both the qualitative and quantitative advantages of combined cycles for scalability using machines ranging from small to several hundred MW gas turbines to determine which configurations of S-CO2 bottoming cycles are best for pure electricity production.

Performance of a Supercritical CO2 Bottoming Cycle for Aero Applications

“…The S-CO 2 turbomachinery component efficiencies assumed herein are ambitious, but should not be untenable considering the 35-year prelude to the estimated entry into service of the engines. Studies into S-CO 2 cycles for the close-to mid-term future [19,41] assume isentropic efficiencies of 85% and 90% for the compressor and turbine respectively, though for larger mass flows. Figure 2b in Section 2.1 illustrated the sensitivity of the cycle to the turbomachinery efficiencies.…”

Axial Turbo-Expander Design for Organic Rankine Cycle Waste-Heat Recovery With Comparative Heavy-Duty Diesel Engine Drive-Cycle Performance Assessment

“…The temperature of the wasted heat is a measure of availability and quality. The higher the temperature, the greater the amount of energy that can be extracted and recuperated (Moroz et al, 2015).…”

“…However, due to the small specific enthalpy drop and large volumetric flow rate, it is possible to design turbines with relatively simple geometry and good efficiency (Pesiridis, 2014). According to Moroz et al (2015), the application of turboexpanders ranges from power ratings of 10 kW to over 1 MW, with radial turbines preferred for applications under 500 kW and axial turbines for more than 500 kW.…”

“…FIGURE 2 | (A) Slope of the saturation curve of an organic fluid(Moroz et al, 2015), (B) Criteria for ORC working fluid selection and (C) suitable organic fluids classified by the heat source temperature(Milkov et al, 2015).…”

Constructing a novel supercritical carbon dioxide power cycle with the capacity of process switching for the waste heat recovery

“…Based on simple cycle, the recuperated S-CO 2 cycle can be obtained by adding a recuperator, 8 which can effectively reheat the working fluid and reduce the heat load of the cooler. 9 In addition, considering that thermophysical properties of CO 2 vary greatly near the critical point, which makes the heat exchanger prone to pinch point problems, 10 the recompression cycle was proposed. In this cycle, there are two recuperators, namely high and lowtemperature recuperator (HTR and LTR).…”