Mapping Initiative:

Background

Government planners, energy service companies, private developers, businesses and homeowners have little quantitative information from which to make informed wind energy siting and planning decisions unless they first invest in additional time-consuming and expensive wind measurement programs.

Objective

The objective of this mapping initiative is to define and map the wind resource characteristics of Utah, to support the planning and evaluation of future wind energy development opportunities.

A GIS-based effort will also be employed to identify the most promising potential wind development areas. Overlays will include roads, transmission lines, boundaries of sensitive wilderness areas, National Parks and Indian reservations, and urban areas.

Recently, NREL completed a series of maps for the State of Utah School and Institutional Trust Lands Administration:

Utah State Lands January 2005 Map Project (ppt)

Utah State Lands June 2005 Map Project (pdf's)
Top 20 Class >= 3 MW Potential
Top 20 Class >= 4 MW Potential
Top 21 Class >= 5 MW Potential

Benefits

High resolution wind resource maps and the associated information products benefit a broad cross-section of users - government planners, energy service companies, private developers, businesses and homeowners.

These products enable users to make informed decisions by giving them direct access to the latest and most comprehensive information available on the wind resource. At the local level, these products help users decide, for example, whether wind energy development is feasible and if an investment in a site-specific study is warranted. On a larger scale, the products help answer such questions as: how much development potential is there, where are the best areas, what are the economic development opportunities, what are the most obvious barriers and sensitivities, at what cost can electricity be generated, and so on.

States and energy companies can adapt these maps to their specific energy programs. In short, this wind mapping initiative is designed to facilitate future wind energy planning and siting decisions - as well as technology transfer activities - by utilizing state-of-the-art modeling techniques to improve access to the most important planning parameters.

Approach

TrueWind Solutions used its advanced MesoMap™ mesoscale modeling system to produce the wind resource maps of Utah. MesoMap was developed to simulate complex meteorlogical phenomena not adequately represented in standard wind flow models. It is therefore capable of modeling sea breezes, offshore winds, mountain/valley winds, low-level nighttime jets, temperature inversions, surface roughness effects, flow separations in steep terrain, and channeling through mountain passes, which are of importance in the Northwest.

This model utilizes historical upper air and surface meteorlogical data, thereby providing a consistent long-term, 3-dimensional wind resource record. This record could later be used as a substitute for long-term surface wind measurements in the correlate-measure-predict (CMP) method, which adjusts short-term site measurements to the long-term climatological norm.

The results of this model provide a highly-resolved spatial definition of the wind resource that can be used to determine the relative performance of wind turbines at potential development sites. This will in turn provide much greater certainty about site specific wind conditions, wind plant performance, and project economics without the need for a widespread wind measurement program. Indeed, the modeling results would help identify where limited wind measurement resources should be applied.

The MesoMap system simulates the wind speed and direction over the state on a 400 meter grid at multiple heights (e.g. Wind speed maps at 30, 50, 70 and 100 m agl, and 50 m wind power maps.) above ground level.

Meteorological input data were randomly sampled from a historical database (known as reanalysis data, which were compiled by the National Centers for Environmental Prediction and National Center for Atmospheric Research) to establish the boundary conditions at the top and sides of the model domain, while all significant processes that determine winds near the surface were calculated internally by the model.

The results of the simulations were then collected and processed into wind roses, speed frequency distributions, and color-coded maps of mean wind speed.

To validate the wind resource maps, TrueWind generated long-term mean wind speed estimates for locations where there are reliable and representative measurements on high-elevation terrain. The predicted speeds were compared with measured speeds (adjusted to the long-term norm) extrapolated to a standard hub height (such as 70 m). Error statistics were generated and, where necessary, were analyzed and corrected for sources of error. Based on prior model validations, the expected range of discrepancy between measured and predicted winds in complex terrain is 3 to 7%.