It is well known that when wind turbines are deployed in large arrays, their efficiency decreases due to complex interactions among themselves and with the atmospheric boundary layer (ABL). For farms whose length exceeds height of ABL by over an order magnitude, a “fully developed” flow regime can be established. In this asymptotic regime, changes streamwise direction neglected relevant exchanges occur vertical direction. Such fully developed wind-turbine array (WTABL) has not been studied...

Solar energy has the potential to offset a significant fraction of non-renewable electricity demands globally, yet it may occupy extensive areas when deployed at this level. There is growing concern that large renewable installations will displace other land uses. Where should future solar power be placed achieve highest production and best use limited resource? The premise work panel efficiency function location's microclimate within which immersed. Current studies largely ignore many...

Monin-Obukhov similarity theory (MOST) forms the basis for parametrizations of turbulent exchange in virtually all numerical models atmospheric flows. Yet, its limitations to flat and horizontally homogeneous terrain have plagued since inception. Here we present a first generalized extension MOST based on inclusion turbulence anisotropy as an additional nondimensional term. This novel developed unprecedented ensemble complex datasets covering mountainous terrain, is shown be valid conditions...

Wind harvesting is fast becoming an important alternative source of energy. As wind farms become larger, they begin to attain scales at which two-way interactions with the atmospheric boundary layer (ABL) must be taken into account. Several studies have shown that there a quantifiable effect on local meteorology, mainly through changes in land-atmosphere fluxes heat and moisture. In particular, observed trends suggest increase surface this could due increased turbulence wakes. Conversely,...

Abstract To improve the performance of solar photovoltaic devices one should mitigate three types losses: optical, electrical and thermal. However, further reducing optical losses in modern is becoming increasingly costly. Therefore, there a rising interest minimizing thermal losses. These correspond to reduction power output resultant working at temperatures above 25 °C associated accelerated aging. Here, we quantify impact all possible strategies case mainstream crystalline silicon...

Turbulence data from the CASES-99 field experiment, over comparatively horizontally homogeneous and flat terrain, are separated based on anisotropy of Reynolds stress tensor (into isotropic, two-component axisymmetric one-component turbulence) flux-variance similarity scaling relations tested. Results illustrate that different states correspond to relations, especially under unstable stratification. Experimental with close isotropic turbulence match relationships well. On other hand, very...

The development of a unified similarity scaling has so far failed over complex surfaces, as studies show large deviations from the empirical formulations developed flat and horizontally homogeneous terrain well between different data sets. However, recent study turbulence anisotropy for shown that separating according to limiting states (isotropic, two-component axisymmetric one-component turbulence) improves near-surface scaling. In this paper we explore whether finding can be extended...

Abstract Performance of solar PV diminishes with the increase in temperature modules. Therefore, to further facilitate reduction cost photovoltaic energy, new approaches limit module natural ambient conditions should be explored. Thus far only based at individual panel level have been investigated, while more complex, systems approach remains unexplored. Here, we perform first wind tunnel scaled farm experiments investigate potential for through system-level flow enhancement. The percentage...

An isolated wind turbine and a very large farm are introduced into large-eddy simulations of an atmospheric boundary layer. The flow is forced with constant geostrophic time-varying surface temperature extracted from selected period the CASES-99 field experiment. A control volume approach used to directly compare transfer mean kinetic energy around characteristic throughout diurnal cycle considering both scenarios. For case, results illustrate that recovery dominated by vertical flux,...

Abstract A reduced‐order model for a wind turbine wake is sought from large eddy simulation data. Fluctuating velocity fields are combined in the correlation tensor to form kernel of proper orthogonal decomposition (POD). Proper modes resulting represent spatially coherent turbulence structures wake; eigenvalues delineate relative amount turbulent kinetic energy associated with each mode. Back‐projecting POD onto snapshots produces dynamic coefficients that express amplitude mode time....

A data-driven approach is an alternative to extract general models for wind energy applications. spatial sensitivity analysis achieved using a probabilistic model quantitatively identify the variability in performance due individual parameters and visualize distributions. Proper orthogonal decomposition results are combined with linear discriminant under clustering framework present low-dimensional classifiers. Using enables system be far away from ill-conditioned states. The optimal sensor...

Recent works on wall-bounded flows have corroborated the coexistence of wall-attached eddies, whose statistical features are predicted through Townsend's attached-eddy hypothesis (AEH), and very-large-scale motions (VLSMs). Furthermore, it has been shown that presence eddies within logarithmic layer is linked to appearance an inverse-power-law region in streamwise velocity energy spectra, upon significant separation between outer viscous scales. In this work, a near-neutral atmospheric...

Abstract In high‐altitude alpine catchments, diurnal streamflow cycles are typically dominated by snowmelt or ice melt. Evapotranspiration‐induced less observed in these catchments but might happen simultaneously. During a field campaign the summer 2012 an catchment Swiss Alps (Val Ferret catchment, 20.4 km 2 , glaciarized area: 2%), we transition early season from to evapotranspiration‐induced cycle one of two monitored subbasins. The different were comparable amplitudes and happened within...

A large eddy simulation framework is used to explore the structure of turbulent flow in a thermally stratified wind turbine array boundary layer. The field driven by constant geostrophic with time-varying surface conditions obtained from selected period CASES-99 experiment. Proper orthogonal decomposition extract coherent structures under considered thermal stratification regimes. discussed context three-dimensional representations key modes, which demonstrate features ranging size wakes...

This paper focuses on modeling and control of in-ground-effect (IGE) multirotor unmanned aerial vehicles (UAVs). As the vehicle flies hovers over, around, or underneath obstacles, such as ground, ceiling, other features, IGE induces a change in thrust that drastically affects flight behavior. effect each rotor can be vastly different vehicle's attitude varies, this phenomenon limits ability for precision control, navigation, landing tight confined spaces. An exponential model describing is...

It was discovered several decades ago that eddy covariance measurements systematically underestimate sensible and latent heat fluxes, creating an imbalance in the surface energy budget. Since then, many studies have addressed this problem proposed a variety of solutions to problem, including improvements instruments correction methods applied during data postprocessing. However, none these measures led complete closure balance gap. The leading hypothesis is not only surface-attached...

Turbulent secondary flows are defined as Prandtl's flow of the first or second kind, former produced by stretching and/or tilting vorticity, latter via spatial heterogeneity Reynolds stresses. Both mechanisms instantaneously active within inertia-dominated wall turbulence; stress is required for Reynolds-averaged flows. Spanwise-variable surface roughness can induce turbulent in spanwise–wall-normal plane and provide sustenance streamwise-aligned mean Herein, we demonstrate that also be...

Here we present unique evidence of a k−1 scaling behaviour in the atmospheric boundary layer and its connection to large scale coherent structures within layer. Wind lidar measurements were conducted above lake under cold conditions. The could be visually observed over Lake Geneva Switzerland when air met relatively warm water. Proper orthogonal decomposition experimental data acquired with wind clearly reveals oscillations both fluctuating velocity field water aerosol surface lake. Precise...

When solar photovoltaic (PV) module temperatures rise during operation, commonly-installed modules experience an efficiency loss between 0.1 and 0.5% per degree above 25∘C. Thus, extensive research has aimed to reduce the operating temperature of modules. However, many cooling solutions require additional cost or equipment that precludes their implementation in utility-scale PV plants. Based on previous studies land-atmosphere interactions surface thermal heterogeneity, we hypothesize...