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Two-dimensional numerical simulations based on an immersed boundary method are performed for the two-foil system with varying spacings, and a staggered arrangement with a spacing normalized by chord length (X d / D , Y d / D) = (2.0 , 2.5) is found to be the most favorable for energy harnessing with the efficiency enhancement of nearly 40% for the downstream foil. By scrutinizing the mean flow characteristics and the instantaneous wake dynamics, it is revealed that convective flow acceleration and vortex impingement in synchronized timing with foil motion are the two primary mechanisms that contribute to significant efficiency improvement. Based on the staggered arrangement for the two-foil system, a V-shape formation is further proposed for the multiple-foil system and verified with the highest efficiency of energy harnessing up to nearly twice that of a single foil. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators are shown a recent development in the energy field in various applications powering sensors to biomedical applications. The research development of tribogenerators is trending in the renewable energy area as it can harness waste mechanical energy due to the friction. Studies have shown various mathematical modeling done on the triboelectric principle based on Gauss electric field principle. Triboelectricity generation due to contact electrification depends on various factors that include the surface charge density, materials, the geometrical features of the tribo pairs, the mode of operation in terms of velocity etc. The significance of nanomaterials in the generation of triboelectricity is a research area where polymers have shown good results. In this study, a detailed computational and numerical simulation is done on selected pairs of triboelectric material combination chosen from the triboelectric series. Computational simulation is performed using Comsol Multiphysics to evaluate the output performance in terms of Voc and Qsc. Numerical simulation is performed using MatLab to evaluate the output performance current, power, voltage with respect to time for selected input parameters. The numerical performance of the device is validated by the experiments. The numerical method adopted will be a useful tool for determining the output characteristics of any triboelectric pairs. [ABSTRACT FROM AUTHOR]

Transient processes generally constitute part of energy-system cycles. If skillfully manipulated, they actually are capable of assisting systems to behave beneficially to suit designers' needs. In the present study, behaviors related to both thermal conductivities ( κ ) and heat capacities ( c v ) are investigated. Three major findings validated by COMSOL simulations and micro-Hamiltonian-Oscillator analyses are reported: (1) effective κ and effective c v can be controlled to vary from their intrinsic material-property values to a few orders of magnitude larger; (2) a parameter, tentatively named as “nonlinear thermal bias”, is identified and can be used as a criterion in estimating energies transferred into the system during heating processes; (3) For bodies of fluids confined by a cold bottom and a hot top, it may be feasible to install a propeller that can be turned by a weak buoyancy force induced by the top-to-bottom heat conduction via the propeller, provided that densities of the propeller and the fluid are similar. Such a turning motion serves double purposes of performing the hydraulic work and increasing the effective κ of the propeller. Hence, hot-top-and-cold-bottom fluid-filled enclosures (e.g., oceans) that induce nearly no buoyancy flows may now, in principle, become energy-harnessing sources. [ABSTRACT FROM AUTHOR]

Wind energy harnessing is a new energy production alternative in Iceland. Current installed wind power in Iceland sums to 1.8 MW, which in contrast is 0.1% of the country's total electricity production. This article is dedicated to the exploration of the potential cost of wind energy production at Búrfell in the south of Iceland. A levelized cost of energy (LCOE) approach was applied to the estimation of the potential cost. Weibull simulation is used to simulate wind data for calculations. A confirmation of the power law is done by comparing real data to calculated values. A modified Weibull simulation is verified by comparing results with actual on-site test wind turbines. A wind farm of 99MWis suggested for the site. Key results were the capacity factor (CF) at Búrfell being 38.15% on average and that the LCOE for wind energy was estimated as 0.087-0.088 USD/kWh (assuming 10% weighted average cost of capital (WACC)), which classifies Búrfell among the lowest LCOE sites for wind energy in Europe. [ABSTRACT FROM AUTHOR]