Helmut P. Frank

Wind power meteorology. Part I: climate and turbulence

Wind power meteorology has evolved as an applied science firmly founded on boundary layer meteorology but with strong links to climatology and geography. It concerns itself with three main areas: siting of wind turbines, regional wind resource assessment and short-term prediction of the wind resource. The history, status and perspectives of wind power meteorology are presented, with emphasis on physical considerations and on its practical application. Following a global view of the wind resource, the elements of boundary layer meteorology which are most important for wind energy are reviewed: wind profiles and shear, turbulence and gust, and extreme winds. Copyright

Wind power meteorology. Part II: siting and models

The data used in wind power meteorology stem mainly from three sources: on-site wind measurements, the synoptic networks and the reanalysis projects. Wind climate analysis, wind resource estimation and siting further require a detailed description of the topography of the terrain—with respect to the roughness of the surface, near-by obstacles and orographical features. Finally, the meteorological models used for estimation and prediction of the wind are described; their classification, inputs, limitations and requirements. A comprehensive modelling concept, meso/microscale modelling, is introduced and a procedure for short-term prediction of the wind resource is described. * c 1998 John Wiley & Sons, Ltd. Preface The kind invitation by John Wiley & Sons to write an overview article on wind power meteorology prompted us to lay down the fundamental principles as well as attempting to reveal the state of the art— but also to disclose what we think are the most important issues to stake further research eAorts on. Unfortunately, such an eAort calls for a lengthy historical, philosophical, physical, mathematical and statistical elucidation, resulting in an exorbitant requirement for writing space. By permission of the publisher we are able to present our eAort in full, but in two parts—Part I: Climate and Turbulence and Part II: Siting and Models. We kindly ask the reader to be indulgent towards inconsistencies, which are inevitable in the process of dividing the work of five authors. An ideal review paper is objective; however, this requires it to be written by someone not personally active in the field. This is contradictory to the provision of the most up-to-date knowledge. Therefore, because all five authors are employees of Riso National Laboratory, their view is to a large extent the ‘Riso view on things’. It is our hope that these views are shared by many, but we invite discussions on any subject in the review. Part I is an attempt to give an account of the advance of wind power meteorology, from the early days of modest wind turbines till today’s massive plans for large-scale power production by modern megawattsize turbines. The historical development of the concept of ‘wind atlas’ is portrayed, followed by an

Modelling the Wind Climate of Ireland

The wind climate of Ireland has been calculated using the KarlsruheAtmospheric Mesoscale Model KAMM. The climatology is represented by 65frequency classes of geostrophic wind that were selected as equiangulardirection sectors and speed intervals with equal frequency in a sector. Theresults are compared with data from the European Wind Atlas which have beenanalyzed using the Wind Atlas Analysis and Application Program, WASP. Theprediction of the areas of higher wind power is fair. Stations with lowpower are overpredicted.

Simulated wind power off-shore using different parametrizations for the sea surface roughness

The equation for the dependence of the Charnock constant on wave age proposed by Johnson et al. (Journal of Physical Oceanography 1998; 28: 1702 – 1716) is extended to include conditions of very young waves or short fetches. The effect on the simulated average wind speed and average wind power density off a straight east coast in Denmark is investigated by numerical simulations. Calculations are also performed employing the classical Charnock relation and a constant roughness of the sea. The formulations with variable sea surface roughness are combined with the equation for a smooth water surface for low winds. The wind climate is calculated with the Karlsruhe Atmospheric Mesoscale Model (KAMM) in 84 classes of the geostrophic wind. The difference between the fetch-dependent and the fetch-independent formulation is very small. Even a constant sea surface roughness yields good results near the coast. The influence of stratification, i.e. temperature differences between sea and land, is much more important than the fetch dependence of the sea surface roughness. Copyright

Calculations on the wind climate in northern Finland: the importance of inversions and roughness variations during the seasons

The wind power potential around Pyhatunturi Fell in northern Finland is calculated with WAsP and the Karlsruhe Atmospheric Mesoscale Model (KAMM) using a climatology of the geostrophic wind from the global reanalysis of NCEP/NCAR. The importance of roughness variations between summer and winter due to snow cover and of strong, low-level inversions during winter is investigated. At the position of a telemast on the fell the changing roughness led to an increase in the predicted wind power density of only 1% at 61 m. However, frequent inversions in winter have a major influence on the wind potential on the fell areas. Accounting for them increased the predicted wind power density by 10%–16%, giving better agreement with the observations. As expected, the wind in the plains is reduced during conditions with inversions. The simulations with KAMM were performed for a grid map with a resolution of 350 m. This is too rough to resolve the steep slopes of Pyhatunturi Fell. Therefore the predicted wind speed on the summit is underestimated by up to 15% depending on the wind direction. Copyright