Idea

The basic idea behind Prediktor is to try to model as much as possible using physical models. The reason being that by doing this we can understand and explain as much of what we see as possible.

The basic steps are as follows (cf the figure): the overall weather patterns are predicted by a NWP model. Such a model can only predict the overall winds and to get predictions valid at a specific location, it is necessary to tailor-make these predictions. This tailor-making is done by the Risų WAsP model, which models the local influences on the flow. These local influences are the effects of orography (hills and ridges), roughness, and obstacles together with the influence that the wind turbines have on each other (the park effects).

It is well known that no model can simulate nature perfectly, so to correct for any short-comings two MOS (model output statistics) filters are used. The observed wind farm productions are used to adjust the parameters of these filters.

The final output of the model is the expected production of the wind farm every 3 hours over the next 48 hours.

The idea behind Prediktor (Landberg, 1999). Click on a box for further information.

To see how this model is implemented in a on-line prediction system please see the implementation page. For further information please see below and the references page.

Brief explanation of terms

HIRLAM wind: The predicted overall wind predicted by the NWP model (here DMIs HIRLAM)

Geo drag law & log profile: the two equations to transform the geostrophic wind (ie the wind in the free atmosphere) to the surface

z₀, f: the meso-scale roughness (or average roughness) and the Coriolis parameter (connected to the rotation of the earth)

surface wind: the transformed geostrophic wind at the surface

WAsP: a program to calculate the influence of local effects (orography, roughness and obstacles), see the WAsP web-site for further details

orography, roughness, obstacles: a digital description of the local effects

local wind: the real wind at the site at hub height

MOS 1, MOS 2: model output statistics modules for correcting any effects not modeled by the physical model

PARK: the Park module of WAsP, which takes the shadowing effects of the turbines into account.

park lay-out: digital description of the lay-out of the wind turbines in the wind farm

power curve: the digital power curve, ie the relation between the wind speed and the power outout of the turnbine

Power prod.: the calculated predicted output of the wind farm. Typically given out to 48 hours ahead in 1- or 3-hourly steps

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Gregor Giebel, Risų National Laboratory
2006-04-13