Thermal Stability and Performance Testing of Oil based CuO Nanofluids for Solar Thermal Applications

For solar thermal systems, nanofluids have been proposed as working fluids due to their enhanced optical and thermal properties. However, nanoparticles may agglomerate over time, heating and thermal cycles. Even though pristine nanofluids have be proven to enhance performance in low temperature application, it is still unclear if nanofluids can meet the reliability requirements of solar thermal applications. To investigate this, the present study conducted experiments with several formulations of oil‐based CuO nanofluids in terms of their maximum operational temperature and their stability upon cyclic heating. In the samples tested, the maximum temperature ranged from 80oC to 150 22 oC and the number of heating cycles of ranged from 5 to 45, with heating times of between 5 to 60 minutes. The results showed that heating temperature, heating cycles, and heating time all exacerbated agglomeration of the samples. Following these experiments, orthogonal experiments were designed to improve the preparation process and the resultant thermal‐impulse stability. Thermal properties of these samples were characterized and thermal performance in an ‘on‐sun’ linear Fresnel solar collector was measured. All tests revealed that thermal performance of solar collecting system could be enhanced with nanofluids, but that thermal stability still needs to be further improved for industrial applications

Simulation and economic analysis of an innovative indoor solar cooking system with energy storage

Solar energy technology and energy storage technology are promising to make a contribution to current energy and global climate issue. The energy demand of daily cooking is enormous, and conventional cooking methods use gas or electricity with large carbon emissions. This paper proposes an innovative solar cooking system (SCS) integrated with rock-bed thermocline storage. Thermal oils transfer heat from the collectors to the rocks in the charging process and release heat in cooktop unit for cooking. The energy consumption of a household is first assessed by a reasonable hypothesis. Mathematical models and simulation models are then established to analyze the heat transfer performance of the cooktop unit and the annual running performance of the SCS. The rock-bed thermocline storage, single-tank thermocline storage and two-tank storage are compared. The simulation results indicate that the rock-bed thermocline storage unit employed to SCS will enhance the annual running performance and acquire the minimum initial investment cost. The economic analysis shows that the lowest levelized cost of cooking energy (LCOC) of the SCS is 0.3884 $/kWh, while the corresponding levelized cost of cooking a meal (LCCM) is 0.953$/Meal and the solar fraction (SF) is 71%. Compared to the electrical and natural gas cooker, the SCS saves 1.75 tons and 0.52 tons of carbon emissions annually, respectively

Confined FeNi alloy nanoparticles in carbon nanotubes for photothermal oxidative dehydrogenation of ethane by carbon dioxide

Oxidative dehydrogenation of ethane with CO2 (ODEC) is an attractive reaction for reduction of carbon footprints and ethene production. In this work, we present photothermal catalysis on confined bimetal catalysts for ODEC. Carbon nanotubes confined non-noble bimetal alloy (i.e., CoNi@CNTs and FeNi@CNTs) catalysts were prepared and FeNi@CNTs showed effective performance in photothermal catalytic ODEC to ethene. Experiments and simulations reveal that UV and visible lights (420 – 490 nm) are responsible for ODEC and non-oxidative dehydrogenation of ethane, respectively, to ethene. Additionally, ODEC to ethene is preferred to C-C cracking to methane on FeNi@CNTs in light ( \u3e 490 nm)-induced thermocatalysis. The photothermal effect turns more significant when introduced into thermocatalytic ODEC (500 °C), with ethene generation at one order of magnitude. This work advances new mechanism of photo-mediated catalysis and sheds light on utilization of full-spectrum solar energy and non-noble metallic catalysts for ethene production and CO2 recycling at moderate conditions