Hasil untuk "Fuel"

Xiao Jiang, X. Nie, Xinwen Guo et al.

The utilization of fossil fuels has enabled an unprecedented era of prosperity and advancement of well-being for human society. However, the associated increase in anthropogenic carbon dioxide (CO2) emissions can negatively affect global temperatures and ocean acidity. Moreover, fossil fuels are a limited resource and their depletion will ultimately force one to seek alternative carbon sources to maintain a sustainable economy. Converting CO2 into value-added chemicals and fuels, using renewable energy, is one of the promising approaches in this regard. Major advances in energy-efficient CO2 conversion can potentially alleviate CO2 emissions, reduce the dependence on nonrenewable resources, and minimize the environmental impacts from the portions of fossil fuels displaced. Methanol (CH3OH) is an important chemical feedstock and can be used as a fuel for internal combustion engines and fuel cells, as well as a platform molecule for the production of chemicals and fuels. As one of the promising approaches, thermocatalytic CO2 hydrogenation to CH3OH via heterogeneous catalysis has attracted great attention in the past decades. Major progress has been made in the development of various catalysts including metals, metal oxides, and intermetallic compounds. In addition, efforts are also put forth to define catalyst structures in nanoscale by taking advantage of nanostructured materials, which enables the tuning of the catalyst composition and modulation of surface structures and potentially endows more promising catalytic performance in comparison to the bulk materials prepared by traditional methods. Despite these achievements, significant challenges still exist in developing robust catalysts with good catalytic performance and long-term stability. In this review, we will provide a comprehensive overview of the recent advances in this area, especially focusing on structure-activity relationship, as well as the importance of combining catalytic measurements, in situ characterization, and theoretical studies in understanding reaction mechanisms and identifying key descriptors for designing improved catalysts.

H. Chung, D. Cullen, Drew C. Higgins et al.

J. Serp, M. Allibert, O. Bene et al.

D. Strmčnik, M. Uchimura, Chao Wang et al.

S. Zinkle, K. Terrani, J. Gehin et al.

Alain Goeppert, M. Czaun, John-Paul Jones et al.

Pamela Peralta-Yahya, Fuzhong Zhang, S. D. Cardayré et al.

M. Mehl, W. Pitz, C. Westbrook et al.

D. J. Durbin, C. Malardier-Jugroot

W. Chueh, C. Falter, M. Abbott et al.

Yu‐Guo Guo, Jinsong Hu, L. Wan

L. Guzzella, A. Sciarretta

P. McKendry

V. Stamenković, B. Mun, K. Mayrhofer et al.

A. Bard, M. Fox

Walid Matar

Saudi Arabia is currently implementing fuel price reforms. The reforms are being executed in phases, where the ultimate goal is to have fuel prices approach their market equivalent values. Using the KAPSARC Energy Model, this analysis shows that such reforms would be more costly for Saudi Arabia without the availability and cost reductions of renewable electricity technologies. Solar photovoltaic technologies, in particular, have made enacting fuel price reforms more tenable. As the use of oil products for power generation and industrial processes cease due to price reforms, renewable technologies mitigate the scarcity of natural gas. For instance, lower natural gas use by the electricity sector would result in a market-clearing (meaning, demand equals supply) natural gas price of 3–4 $/mmBtu in 2040 with the deployment of renewable technologies. The projected rise in Saudi natural gas supply and these prices are sufficient to accommodate nearly 50 GW of renewable electricity capacity. Comparatively, this natural gas price would be above 7 $/mmBtu without renewable electricity. The advent of inexpensive renewable electricity lowers fuel costs for all natural gas users in industry and utilities. Moreover, the marginal electricity generation cost with renewable electricity drops by 30 %, on average. While renewable electricity reduces energy system costs, the magnitude of these benefits is highly dependent on the exogenously-defined domestic gas availability and the global LNG price. These findings suggest aligning fuel price regulations with renewable electricity deployment to minimize cost shocks and reduce oil use in industrial and utility sectors.

Wei Gao, Qifeng Li, Kai Sun et al.

Mass transfer capability of reactants and hydrothermal management is important for the performance and durability of proton exchange membrane fuel cells. In the conventional rib flow field, the oxygen transport is affected by the accumulation of under-rib liquid water which causes excessive concentration loss and limits cell performance. To improve the cell performance, a composite foam-rib flow field structure is proposed by combining the metal foam flow field and the conventional rib flow field. The proposed design is simulated by using a three-dimensional homogeneous non-isothermal numerical model. The results show that the composite foam-rib flow field, by improving the oxygen transfer and water removal capabilities under the ribs, can improve the oxygen concentration and current density without increasing the pumping power, thus improving the cell performance under different conditions. The key parameters of the composite foam-rib flow field are optimized. With the optimal metal foam filling ratio of 0.75 and porosity of 0.85, the peak power density and the limiting current density for the composite foam-rib flow field are higher than the conventional rib flow field by 5.20% and 22.68%.

Zehua Dou, Laura Tropf, Tobias Lappan et al.

Low temperature water electrolyzers (LTWEs) and low temperature hydrogen fuel cells (LTFCs) present a promising technological strategy for the productions and usages of green hydrogen energy towards a net-zero world. However, the interactions of gas/liquid (fluid) transport and the intrinsic reaction kinetics in LTWEs/LTFCs present one of the key hurdles hindering high production rate and high energy conversion efficiency. Addressing these limitations requires analytical tools that are capable of resolving fluid transport across the heterogeneous, multiscale structures of operating LTWE and LTFC systems. This review provides a comprehensive overview of recent advancements in measurement technologies for investigating fluid transport. We first outline the technical requirements of such analytical systems, and assess the capabilities and limitations of established optical, X-rays and neutrons based imaging systems. We emphasis on emerging strategies that utilize integrated miniaturized sensors, ultrasound, and other alternative physical principles to achieve operando, high-resolution, and scalable measurements towards applications at device and system levels. Finally, we outline future directions in this highly interdisciplinary field, emphasizing the importance of next-generation sensing concepts to overcome the fluid transport hurdle, towards accelerating the deployment of green hydrogen technologies.

M. Moscheni, A. Herrmann, R. Kembleton et al.

An open-source database of 457 experimental and numerical entries representing 32 machines$-$including tokamaks, stellarators, and linear plasma devices$-$is assembled. From this dataset, we derive multi-machine scaling laws that predict the fuel and impurity puffing rates sufficient to edge plasma detachment$-$the leading reactor-relevant solution to the challenge of plasma-wall interaction. Validation against up to 40 L- and H-mode plasmas shows agreement within a factor of 1.5 in about 50\% of cases, and within a factor of 2 on average. Divertor volume alone is found to strongly correlate with the fuelling rate. Inclusion of plasma opaqueness leads to $Γ_{\text{D}} \propto [n_{\text{sep}}\, a\, (S_{\text{div}}/V_{\text{div}})^{-1.5}]^{1.05}$, valid across all toroidal devices. Its H-mode simplification, $Γ_{\text{D}}^{\text{HDL}} \propto 0.43\, a^{1.58}\, λ_q^{-0.89}$, avoids explicit dependence on $n_{\text{sep}}$ and carries intrinsic physical meaning through the H/L density limit and the power fall-off length. The impurity seeding rate is captured by a general non-linear law, from which the Greenwald-Eich-Scarabosio simplification, $Γ_{\text{Z}}^{\text{GES}} \propto a^{1.51}\, λ_q^{-0.27}$, is obtained. Similar relationships are defined for stellarators, consistent with tokamak trends but still awaiting validation$-$an opportunity for further study. These results have immediate relevance for reactor fuel-cycle design and edge plasma modelling. More broadly, they demonstrate that physics-based 0D laws can reliably link detachment access to engineering actuators, offering practical tools for reactor design. Our laws represent macroscopic patterns across machines rather than microscopic variations within an individual device$-$providing the basis for our forthcoming studies aimed at extending this framework to machine-specific behaviour.

Rémy Dassonneville, Cyril Elouard, Romain Cazali et al.

Recent progress in manipulating individual quantum systems enables the exploration of engines exploiting non-classical resources. One of the most appealing is the energy provided by the inherent backaction of quantum measurements. While a handful of experiments have investigated the inner dynamics of engines fueled by measurement backaction, powering a task by such an engine is missing. Here we demonstrate the amplification of microwave signals by an engine fueled by repeated quantum measurements of a superconducting transmon qubit. Using feedback, the engine acts as a quantum Maxwell demon operating without a hot thermal source. Measuring the gain of this amplification constitutes a direct probing of the work output of the engine, in contrast with inferring the work by measuring the qubit state along its evolution. Observing a good agreement between both work estimation methods, our experiment validates the accuracy of the indirect method. We characterize the long-term stability of the engine as well as its robustness to transmon decoherence, loss and drifts. Our experiment exemplifies the use of energy brought by quantum measurement backaction.