Silicon Tetrachloride as innovative working fluid for high temperature Rankine cycles: Thermal Stability, material compatibility, and energy analysis

Silicon Tetrachloride (SiCl4) is proposed as a new potential working fluid for high-temperature Rankine Cycles. The capability to overcome the actual thermal stability limit of fluids commercially employed in the state-of-theart Organic Rankine Cycles (ORC) is demonstrated by static thermal stability and material compatibility tests. Experimental static test proves its thermo-chemical stability with a conventional stainless-steel alloy (AISI 316L) up to 650 degrees C. A preliminary material compatibility analysis performed with optical microscope on the AISI 316L cylinder, after exposure of 300 h to SiCl4 at temperature higher than 550 degrees C, confirms the potentiality of this fluid when coupled with high-grade heat sources. A thermodynamic analysis has been carried out accounting for the effect of operating conditions on the axial turbine efficiency. A comparison with fluids adopted in medium-high temperature ORCs is performed, evidencing that the proposed fluid could achieve more than + 10 % points as thermal efficiency gain compared to any commercial solutions when coupled with high-temperature sources such as solar, biomass, waste heat from industrial processes and prime movers. A 2 MW SiCl4 cycle operating fullelectric at 550 degrees C reaches a thermal efficiency of 38 %, exceeding values attainable by any other working fluid under similar conditions and power size

Design and commissioning of a thermal stability test-rig for mixtures as working fluids for ORC applications

Abstract A novel test-rig for studying the thermal stability of mixtures as working fluids for ORC applications was designed and commissioned at the Laboratory of Compressible-fluid dynamics for Renewable Energy Applications (CREA) of Politecnico di Milano, in collaboration with the University of Brescia. The set-up is a standard one, in which a vessel containing the fluid under scrutiny is placed in a vertical oven for ~ 100 hours at a constant temperature T = Tstress. During the test, the pressure P is monitored to detect thermal decomposition of the fluid. After the test, the vessel is placed in a controlled thermal bath, where the pressure is measured at different value of the temperature T, with

Experimental investigation of the CO2+SiCl4 mixture as innovative working fluid for power cycles: Bubble points and liquid density measurements

International audienceHighlights Carbon dioxide/Silicon Tetrachloride mixture is proposed as innovative working fluid. Bubble points and liquid densities of the mixture are experimentally obtained. The experimental data are used for the fine-tuning of the equation of state. The thermodynamic efficiency of the mixture is simulated in next-generation CSP plant. The mixture enables +2 % electric efficiency gain compared to pure sCO2

Design and commissioning of a thermal stability test-rig for mixtures as working fluids for ORC applications

A novel test-rig for studying the thermal stability of mixtures as working fluids for ORC applications was designed and commissioned at the Laboratory of Compressible-fluid dynamics for Renewable Energy Applications (CREA) of Politecnico di Milano, in collaboration with the University of Brescia. The set-up is a standard one, in which a vessel containing the fluid under scrutiny is placed in a vertical oven for ~ 100 hours at a constant temperature T = Tstress. During the test, the pressure P is monitored to detect thermal decomposition of the fluid. After the test, the vessel is placed in a controlled thermal bath, where the pressure is measured at different value of the temperature T, with T < Tstress and T < Tc (Tc critical temperature). The resulting isochoric pressure-temperature dependence is compared to that obtained before the fluid underwent thermal stress. If departure from the initial fluid behavior is observed, significant thermal decomposition occurred and a chemical analysis of the decomposition products is carried out using gas chromatography and mass spectroscopy. The novelty of the set-up is the possibility of taking samples of both liquid and vapor phases of the fluid, a capability that was introduced to study thermal decomposition of mixtures, whose composition depends on the pressure and temperature, as well as to capture the more volatile products of thermal decomposition of pure fluids and mixtures. Preliminary experimental results are reported for the pure siloxane fluid MDM (Octamethyltrisiloxane, C8H24O2Si3)

Electrification of compact off-highway vehicles—overview of the current state of the art and trends

Electrified vehicles have undergone great evolution during the last decade because of the increasing attention paid on environmental sustainability, greenhouse gas emissions and air pollution. Emission regulations are becoming increasingly tight, and governments have been allocating multiple funds to facilitate the spreading of the so-called green mobility. In this context, steering towards electrified solutions not only for passenger vehicles, but also for compact off-highway vehicles extensively employed, for instance, on construction sites located in urban areas, warehouses, and greenhouses, is essential even if seldom considered. Moreover, the electrification of compact offhighway machinery may allow manufacturers to increase their expertise in and lower the costs of these alternative solutions, while gathering useful data to be applied in bigger and more remunerative off-highway vehicles. In fact, while electric automobiles are as of now real alternatives for buyers, off-highway vehicles, regardless of the application, are mostly in the research and experimental phase, with few of them already on the market. This delay, in comparison with the passenger automotive industry, is caused by different factors, mostly related to the different tasks of off-highway vehicles in terms of duty cycles, productivity performance parameters and user acceptability. The aim of this paper is to give an overview of the many aspects of the electrification of compact off-highway vehicles, to highlight the key differences between on-highway and off-highway vehicles and to summarize in a single source of information the multiple solutions investigated by researchers and manufacturers