scholarly journals How much atmospheric dynamics do we need to capture yield reductions from proposed large wind parks in the German Bight?

2021 ◽  
Author(s):  
Jonathan Minz ◽  
Marc Imberger ◽  
Jake Badger ◽  
Axel Kleidon
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Energy Budget ◽  
German Bight ◽  
Large Scale ◽  
Atmospheric Dynamics ◽  
Offshore Wind ◽  
Wind Speeds ◽  
Wind Park ◽  
Large Wind

<p>German energy scenarios expect 50 - 70 GW of wind turbine capacity to be installed in the German Bight by 2050. Such deployments were expected to yield ∼4000 full load hours (FLH) per year, owing to higher wind speeds compared to land. However, a recent reevaluation of these estimates using the Weather Research and Forecasting model with Explicit Wake Parameterization (WRF-EWP) and the Kinetic Energy Budget of the Atmosphere model (KEBA) found that if the proposed deployments are installed, yield per turbine could be as low as 3000 - 3500 FLH per year, although the total yield still increases. Whereas WRF represents a comprehensive physical representation of atmospheric dynamics, KEBA is an simple approximation of complex atmospheric processes. It states that it is the fixed kinetic energy budget of the boundary layer volume encompassing the wind park which determines large wind park (order of10<sup>4</sup>km<sup>2</sup>) yields rather than just wind speeds. This budget is a function of park geometry and boundary layer heights. Increasing the number of turbines within the wind park removes more kinetic energy from the budget. This leads to slower wind speeds and lower overall yields. The estimates from both approaches were within 20% of each other. Here, we examine these results in greater detail to uncover key atmospheric constraints on the performance of large offshore wind parks. We investigate the role of atmospheric variables like wind direction, atmospheric stability, boundary layer height and surface friction on large scale generation by comparing the estimates of the two modelling approaches. We consider the WRF simulations of large-scale wind power generation and atmospheric circulation as the most realistic available representation, since farms of the scale considered in this study are not yet in operation. We also test the underlying assumptions of KEBA and hence the limits of its applicability. Through a detailed comparison of the two approaches we will provide insights into the effectiveness of KEBA. We posit that estimates of regional wind energy potential need to account for large wind park - atmosphere interactions which may constrain large wind park yields. Our analysis will provide policy makers with a simple yet physically representative tool for making robust predictions of future offshore wind park performance, thereby enabling the design of better energy policies.</p>

A kinetic energy budget perspective to understand efficiency reductions of offshore wind generation in the German Bight in the North Sea

2021 ◽  
Author(s):  
Jonathan Minz ◽  
Marc Imberger ◽  
Axel Kleidon ◽  
Jake Badger
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
North Sea ◽  
Energy Budget ◽  
German Bight ◽  
Offshore Wind ◽  
Energy Potential ◽  
The North ◽  
The North Sea ◽  
Atmospheric Variables

<p>The European Commission’s net zero decarbonization scenarios estimate that up to 450GW of offshore wind capacity could be installed in Europe by 2050. German energy scenarios estimate that 50 to 70 GW of this could be installed in the German Bight in the North Sea and yield about 4000 full load hours (FLH) per year of power. However, these assume that wind speeds and yields are not reduced by the increased extraction of kinetic energy from the regional atmospheric flow by large wind farms. Our initial assessment of these assumptions, using two different approaches - the simple Kinetic Energy Budget of the Atmosphere model (KEBA) and the Weather Research and Forecasting model with Explicit Wake Parameterization (WRF-EWP), showed that emplacing such a large turbine capacity within the German Bight may lower expected yield down to 3300-3000 FLH. Here, we identify the major factors leading to this reduction. We use the two models to evaluate the role of atmospheric variables like wind directions, atmospheric stability, boundary layer height and surface friction in constraining large scale offshore wind energy generation. We test the KEBA model concept of limited kinetic energy fluxes through the boundary layer determining generation potential, and investigate deviations between the models to identify limitations of the simpler approach.The WRF model sets our ”best guess” of energy yield from regional wind turbine deployments (at scales of 10<sup>4</sup>km<sup>2</sup>) since the scale of deployments that we assess are not in operation yet. Our analysis will provide insights about key atmospheric variables that shape regional offshorewind energy potential of the German Bight. We propose that estimating regional wind energy potential should account for atmospheric response.</p>

scholarly journals The Kinetic Energy Budget of the Atmosphere (KEBA) model 1.0: a simple yet physical approach for estimating regional wind energy resource potentials that includes the kinetic energy removal effect by wind turbines

2020 ◽  
Vol 13 (10) ◽  
pp. 4993-5005
Author(s):  
Axel Kleidon ◽  
Lee M. Miller
Keyword(s):  
Kinetic Energy ◽  
Wind Energy ◽  
Energy Budget ◽  
Wind Turbines ◽  
Large Scale ◽  
Energy Resource ◽  
Wind Farms ◽  
Energy Yield ◽  
Wind Speeds ◽  
Kinetic Energy Budget

Abstract. With the current expansion of wind power as a renewable energy source, wind turbines increasingly extract kinetic energy from the atmosphere, thus impacting its energy resource. Here, we present a simple, physics-based model (the Kinetic Energy Budget of the Atmosphere; KEBA) to estimate wind energy resource potentials that explicitly account for this removal effect. The model is based on the regional kinetic energy budget of the atmospheric boundary layer that encloses the wind farms of a region. This budget is shaped by horizontal and vertical influx of kinetic energy from upwind regions and the free atmosphere above, as well as the energy removal by the turbines, dissipative losses due to surface friction and wakes, and downwind outflux. These terms can be formulated in a simple yet physical way, yielding analytic expressions for how wind speeds and energy yields are reduced with increasing deployment of wind turbines within a region. We show that KEBA estimates compare very well to the modelling results of a previously published study in which wind farms of different sizes and in different regions were simulated interactively with the Weather Research and Forecasting (WRF) atmospheric model. Compared to a reference case without the effect of reduced wind speeds, yields can drop by more than 50 % at scales greater than 100 km, depending on turbine spacing and the wind conditions of the region. KEBA is able to reproduce these reductions in energy yield compared to the simulated climatological means in WRF (n=36 simulations; r2=0.82). The kinetic energy flux diagnostics of KEBA show that this reduction occurs because the total yield of the simulated wind farms approaches a similar magnitude as the influx of kinetic energy. Additionally, KEBA estimates the slowing of the region's wind speeds, the associated reduction in electricity yields, and how both are due to the depletion of the horizontal influx of kinetic energy by the wind farms. This limits typical large-scale wind energy potentials to less than 1 W m−2 of surface area for wind farms with downwind lengths of more than 100 km, although this limit may be higher in windy regions. This reduction with downwind length makes these yields consistent with climate-model-based idealized simulations of large-scale wind energy resource potentials. We conclude that KEBA is a transparent and informative modelling approach to advance the scientific understanding of wind energy limits and can be used to estimate regional wind energy resource potentials that account for the depletion of wind speeds.

Estimating offshore wind power potentials that account for the kinetic energy removal by wind turbines: the Kinetic Energy Budget of the Atmosphere (KEBA) approach

2020 ◽  
Author(s):  
Axel Kleidon ◽  
Lee Miller
Keyword(s):  
Kinetic Energy ◽  
Wind Energy ◽  
Wind Power ◽  
Energy Budget ◽  
Wind Turbines ◽  
Wind Farms ◽  
Offshore Wind ◽  
Offshore Wind Energy ◽  
Offshore Wind Power ◽  
Wind Speeds

<p>Offshore wind power is seen as a large renewable energy resource due to the high and continuous wind speeds over the ocean.However, as wind farms expand in scale, wind turbines increasingly remove kinetic energy from the atmospheric flow, reducing wind speeds and expected electricity yields.Here we show that this removal effect of large wind farms and the drop in yields can be estimated in a relatively simple way by considering the kinetic energy budget of the lower atmosphere, which we refer to as the KEBA approach.We first show that KEBA can reproduce the estimated, climatological yields of wind farms of different sizes and locations using previously published numerical model simulations with an explicit wind farm representation.<span>  </span>We then show the relevance of these reductions by evaluating the contribution of offshore wind energy in specific scenarios of Germany’s energy transition in the year 2050.Our estimates suggest that due to reduced wind speeds, mean capacity factors of wind farms are reduced to 33 - 39%, which is notably less than capacity factors above 50% that are commonly assumed in energy scenarios.This reduction is explained by KEBA by the depletion of the horizontal flow of kinetic energy by the wind farms and the low vertical renewal rate, which limits large-scale wind energy potentials to less than 1 W m<sup>-2</sup> of surface area.We conclude that wind speed reductions are likely to play a substantial role in the further expansion of offshore wind energy and need to be considered in the planning process.These reduced yields can be estimated by a comparatively simple approach based on budgeting the kinetic energy of the atmosphere surrounding the wind farms.</p>

scholarly journals The Kinetic Energy Budget of the Atmosphere (KEBA) model 1.0: A simple yet physical approach for estimating regional wind energy resource potentials that includes the kinetic energy removal effect by wind turbines

2020 ◽  
Author(s):  
Axel Kleidon ◽  
Lee M. Miller
Keyword(s):  
Kinetic Energy ◽  
Wind Energy ◽  
Energy Budget ◽  
Wind Turbines ◽  
Large Scale ◽  
Energy Resource ◽  
Wind Farms ◽  
Energy Yield ◽  
Wind Speeds ◽  
Kinetic Energy Budget

Abstract. With the current expansion of wind power as a renewable energy source, wind turbines increasingly extract kinetic energy from the atmosphere, thus impacting its energy resource. Here we present a simple, physics-based model (KEBA) to estimate wind energy resource potentials that explicitly account for this removal effect. The model is based on the regional kinetic energy budget of the atmospheric boundary layer that encloses the wind farms of a region. This budget is shaped by horizontal and vertical influx of kinetic energy from upwind regions and the free atmosphere above as well as the energy removal by the turbines, dissipative losses due to surface friction and wakes, and downwind outflux. These terms can be formulated in a simple, yet physical way, yielding analytic expressions for how wind speeds and energy yields are reduced with increasing deployment of wind turbines within a region. We show that KEBA estimates compare very well to the modelling results of a previously published study in which wind farms of different sizes and in different regions were simulated interactively with the WRF atmospheric model. Compared to a reference case without the effect of reduced wind speeds, yields can drop by more than 50 % at scales greater than 100 km, depending on turbine spacing and the wind conditions of the region. KEBA is able to reproduce these reductions in energy yield compared to the simulated climatological means in WRF (n = 36 simulations; r2 = 0.822). The kinetic energy flux diagnostics of KEBA show that this reduction occurs because the total yield of the simulated wind farms approaches a similar magnitude as the influx of kinetic energy. Additionally, KEBA estimates the slowing of the region's wind speeds, the associated reduction in electricity yields, and how both are due to the depletion of the horizontal influx of kinetic energy by the wind farms. This limits typical large-scale wind energy potentials to less than 1 W m−2 of surface area for wind farms with downwind lengths of more than 100 km, although this limit may be higher in windy regions. This reduction with downwind length makes these yields consistent with GCM-based idealized simulations of large-scale wind energy resource potentials. We conclude that KEBA is a transparent and informative modelling approach to advance the scientific understanding of wind energy limits, and can be used to estimate regional wind energy resource potentials that account for the depletion of wind speeds.

Wind wake effects of large offshore wind farms, an underrated impact on the marine ecosystem?

2020 ◽  
Author(s):  
Corinna Schrum ◽  
Naveed Akhtar ◽  
Nils Christiansen ◽  
Jeff Carpenter ◽  
Ute Daewel ◽  
...  
Keyword(s):  
Boundary Layer ◽  
North Sea ◽  
Large Scale ◽  
Spatial Scales ◽  
Wind Farms ◽  
Offshore Wind ◽  
Offshore Wind Farms ◽  
The North ◽  
The North Sea ◽  
Ocean Hydrodynamics

<p>The North Sea is a world-wide hot-spot in offshore wind energy production and installed capacity is rapidly increasing. Current and potential future developments raise concerns about the implications for the environment and ecosystem. Offshore wind farms change the physical environment across scales in various ways, which have the potential to modify biogeochemical fluxes and ecosystem structure. The foundations of wind farms cause oceanic wakes and sediment fluxes into the water column. Oceanic wakes have spatial scales of about O(1km) and structure local ecosystems within and in the vicinity of wind farms. Spatially larger effects can be expected from wind deficits and atmospheric boundary layer turbulence arising from wind farms. Wind disturbances extend often over muliple tenths of kilometer and are detectable as large scale wind wakes. Moreover, boundary layer disturbances have the potential to change the local weather conditions and foster e.g. local cloud development. The atmospheric changes in turn changes ocean circulation and turbulence on the same large spatial scales and modulate ocean nutrient fluxes. The latter directly influences biological productivity and food web structure. These cascading effects from atmosphere to ocean hydrodynamics, biogeochemistry and foodwebs are likely underrated while assessing potential and risks of offshore wind.</p><p>We present latest evidence for local to regional environmental impacts, with a focus on wind wakes and discuss results from observations, remote sensing and modelling.  Using a suite of coupled atmosphere, ocean hydrodynamic and biogeochemistry models, we quantify the impact of large-scale offshore wind farms in the North Sea. The local and regional meteorological effects are studied using the regional climate model COSMO-CLM and the coupled ocean hydrodynamics-ecosystem model ECOSMO is used to study the consequent effects on ocean hydrodynamics and ocean productivity. Both models operate at a horizontal resolution of 2km.</p>

scholarly journals The contribution of X-ray polar blowout jets to the solar wind mass and energy

2013 ◽  
Vol 8 (S300) ◽  
pp. 239-242 ◽  
Author(s):  
Giannina Poletto ◽  
Alphonse C. Sterling ◽  
Stefano Pucci ◽  
Marco Romoli
Keyword(s):  
Solar Wind ◽  
Kinetic Energy ◽  
Energy Budget ◽  
Coronal Mass Ejections ◽  
Mass Flux ◽  
Large Scale ◽  
Coronal Holes ◽  
Magnetic Loop ◽  
Small Scale ◽  
X Ray

AbstractBlowout jets constitute about 50% of the total number of X-ray jets observed in polar coronal holes. In these events, the base magnetic loop is supposed to blow open in what is a scaled-down representation of two-ribbon flares that accompany major coronal mass ejections (CMEs): indeed, miniature CMEs resulting from blowout jets have been observed. This raises the question of the possible contribution of this class of events to the solar wind mass and energy flux. Here we make a first crude evaluation of the mass contributed to the wind and of the energy budget of the jets and related miniature CMEs, under the assumption that small-scale events behave as their large-scale analogs. This hypothesis allows us to adopt the same relationship between jets and miniature-CME parameters that have been shown to hold in the larger-scale events, thus inferring the values of the mass and kinetic energy of the miniature CMEs, currently not available from observations. We conclude our work estimating the mass flux and the energy budget of a blowout jet, and giving a crude evaluation of the role possibly played by these events in supplying the mass and energy that feeds the solar wind.

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