Effects of relative volume-ratios on dynamic performance of a direct-heated supercritical carbon-dioxide closed Brayton cycle in a solar-thermal power plant

Abstract

The effect of the relative hot-to-cold side volume-ratios on dynamic characteristics of a closed Brayton cycle (CBC) with supercritical carbon-dioxide (sCO 2) as the working-fluid is investigated in this study. The analysis of the CBC is conducted in the context of power generation in a direct-heated (no thermal-oil loop) and dry-cooled parabolic-trough solar thermal power plant, using a control-oriented model. Dynamic performance of the sCO 2 CBC with different relative volume-ratios between the hot and cold sides of the sCO 2 CBC is compared using simulations for conditions on a representative summer day. The CBC hot-to-cold side volume-ratio influences CO 2 mass movement and hence power output. Increasing the hot-to-cold side volume-ratio in the CBC results in slower, more gradual dynamic response when there are fluctuations in solar heat input and ambient air temperatures. The dynamic response characteristics of a CBC with a hot-to-cold side volume-ratio lower than one is shown to differ significantly from one with a volume-ratio greater than or equal to one.

Thermoeconomic analysis & optimization of the combined supercritical CO 2 (carbon dioxide) recompression Brayton/organic Rankine cycle

“…They concluded that the CO 2 mass-flow should be controlled in summer time. In another paper, Rajinesh Singh et al [19] studied the effect of the relative hot-to-cold side volume-ratios on dynamic characteristics of a closed Brayton cycle with supercritical carbon-dioxide as a working-fluid and showed that an increase in the hot-to-cold side volume-ratio results in a slower and gradual dynamic response. B. D. Iverson et al [20] assessed the behavior of a supercritical recompression Brayton cycle under a fluctuating thermal energy input and concluded that despite these fluctuations, the thermal mass in the system effectively enables the Brayton cycle to continue to run for short periods until the thermal input can recover.…”

A review on solar‐assisted gas turbines

“…Changes in absorbed heat by the solar irradiation results in variations in mass flow rate, pressure, temperature, and the output power. In addition, to output power, mass flow (as a result of ambient condition) affects dynamic response of the cycle . Cycle specifications (configuration, applied working fluid, working condition etc.)…”

Extremum-seeking control of a supercritical carbon-dioxide closed Brayton cycle in a direct-heated solar thermal power plant

“…This ratio was chosen as it was shown in Ref. [27] to provide the benefit of relatively fast cycle dynamic response while also reducing the sensitivity of the cycle to fluctuations in solar heat input and ambient air temperatures.…”