Sensitivity of transcritical cycle and turbine design to dopant fraction in CO2-based working fluids

Experimental Characterisation of Co2 + C6f6 Mixture: Thermal Stability and Vapour Liquid Equilibrium Test for its Application in Transcritical Power Cycle

“…On the other hand, the minimum cycle temperature of 51 °C is chosen in order to ensure that the mixture is in saturated liquid condition at the outlet of an air-cooled condenser in hot and arid regions (∆T mixOUT,airIN =10°C with a maximum ambient temperature equal to 41°C in Seville, Spain, a typical site used as European reference for CSP plants [7]). The other design parameters of the simple recuperative transcritical cycle, such as fluid machines efficiency, heat exchangers pressure drops and the minimum internal temperature approach in the recuperator, are taken in agreement with previous studies [7,23,26,27]. The pressure at the turbine inlet is varied between 200 and 350 bar.…”

“…Another important characteristic for the selection of the dopants is the working fluid thermal stability with expected values, for the highest efficiency applications, up to 700 °C. Excluding the inorganic compounds class, perfluorocarbons compounds are suggested by preliminary activities of the SCARABEUS project and other research studies [24][25][26][27]: they are characterised by good solubility into CO 2 , good molecular complexity, low-toxicity and low-flammability [28] and they are potentially thermally stable and chemically inert at temperatures higher than 400°C [25,[29][30][31][32]. On the other hand, they are very expensive fluids and with a high global warming potential (i.e.…”

On the Design of Recuperator for Transcritical Cycle Adopting CO2‐Based Mixture as Working Fluid: A Focus on Transport Properties Prediction

“…The main assumptions of the power cycles are summarized in Table 5: most of the values are taken from previous studies. [8,[57][58][59] The maximum temperature depends on the mixture thermal stability and, as a consequence, on the related CSP technology: for the CO 2 þ C 6 F 6 mixture, the power cycle can be coupled with a CSP-tower plant configuration with molten salts as HTF, while, for the CO 2 þ C 10 H 22 mixture, a linear Fresnel reflector with commercial HTFs is considered. However, longterm thermal stability of the latter should be investigated: the selected temperature level (350 °C) is in line with the upper limit range for thermal stability of hydrocarbons and n-Decane experimental data availability range (up to 402 °C).…”

Overview and outlook of research and innovation in energy systems with carbon dioxide as the working fluid

“…Ongoing research is currently tackling this challenge in two very different ways: a) the use of blends between CO 2 and other compounds, e.g. TiCL 4 , C 6 F 6 [53,54], to shift the critical point above ambient conditions and therefore ensure that the working fluid is still in the liquid phase at moderate heat sink temperatures and, b) the design and control of turbo-compressors to operate slightly above the critical point, where CO 2 experiences low compressibility and, in turn, requires low power to be compressed [55][56][57][58]. The CO 2 heat to power research is relevant and spans the whole power generation spectrum: fossil-fuelled, nuclear, waste heat, geothermal and concentrated solar power (CSP) [21].…”