Renewable Energy Sources

High Resolution Wind Resource Maps

Key to maximizing power output from wind farms is locating wind sites with good wind regimes. Existing wind resource maps for Hawaii were developed over 20 years ago. New methods, based on dynamic numerical simulation models, and increased computational capabilities have since been made available. This provides an opportunity to develop more accurate and detailed assessments of Hawaii's wind resources. Higher resolution wind maps may reveal new locations with rich wind regimes and accelerate the initial stages of wind project development. Detailed meteorological monitoring at a proposed wind site still needs to be collected for wind project financing.

Hawaiian Electric, the Hawaii Department of Business, Economic Development & Tourism and the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) have funded a project to develop high-resolution wind resource maps for the islands of Oahu, Hawaii (Big Island), Maui, Molokai, Lanai, and Kauai. These maps have a grid resolution of 200 meters and provide wind speeds at 30, 50, 70, and 100 meters as well as wind power densities at 50 meters. The maps include basic overlays of significant features such as cities, parks, roads, and power lines.

High-Resolution Wind Resource Maps

Wind Development Potential on Oahu

As follow-up to work on the high resolution wind resource maps, AWS Truewind produced an estimate of the wind development potential of the Island of Oahu, Hawaii using a remote, desktop screening methodology.

In conducting this study, AWS Truewind systematically employed a desktop Geographical Information System (GIS) approach designed to remotely assess the wind energy development potential of Oahu. The key drivers of this study include the 100 meter resolution wind resource map created by AWS Truewind using its proprietary MesoMap system, as well as various ESRI datasets that identify land uses that could prohibit wind energy development. The specific datasets used in defining this restricted area as well as the assigned offset for each are based upon AWS Truewind's extensive experience working on over 15,000 MW of planned, proposed and installed capacity in North America. The datasets and the specified offset used are outlined in Table 1.

Table 1. Offsets Utilized in Study.

Offset  Distance 
Airports removed
Kaena Point 1 mi
Buildings 350 m
Major highways 180 m
Cemetery 120 m
Microwave 40 m
Detailed parks 120 m
Parks 120 m
Detailed rivers 100 ft
Protected areas 100 ft
Detailed water 100 ft
Shore outline 300 ft
Federal land 120 m
Slope >15%
Highways 180 m
Streets 120 m
Interstates 180 m
Transmission lines 132 m
Wind speed >6.5 m/s
Wetlands 100 ft

Upon establishing the restricted area, or the area that is likely incompatible with wind energy development, AWS Truewind further screened the island and removed any land areas that had a wind resource that is predicted to be less than 6.5 m/s at 80 meters. It is AWS Truewind's experience that the vast majority of wind development throughout the nation will occur at sites that have a mean annual average wind speed of 6.5 m/s or greater. Given the high power prices on Oahu, it is likely that a project with a mean speed of this magnitude could be considered for development assuming other costs such as construction and turbine procurement are reasonable.

The remaining land area was determined to have attributes that are suitable for wind development. As such, the next step in the analysis was to determine the approximate installed capacity that the remaining land area could support. Due to the fact that actual wind development of any given site is highly sensitive to the site's topography, existing land uses and exposure to the wind resource, a density of 8 MW/km2 was used as a preliminary estimate of installed capacity. The density of a given wind plant can range from as little as 5 MW/km2 for flat sites with a multi-directional wind rose to more than 12 MW/km2 for ridgeline sites that are oriented perpendicular to the prevailing wind resource[1]. As a last step in this process, AWS divided the island into four quadrants to better facilitate subsequent analysis.

Lastly, it is worth noting that given this is a desktop based approach, it is possible that some of the data used in this analysis do not represent what one would find at any given location today. For example, some datasets may only be updated every few years and may not accurately capture the most recent changes in local development.

The results of this study show that, using the constraints identified above, the Island of Oahu has the potential for approximately 92 MW of installed capacity. Of course, it is possible that this number could vary slightly upward or downward based upon the given site's exposure to the wind resource, topography and land use. The largest area of potential clearly lies in the northeastern quadrant of the island near the Kahuku range and the Island's north shore. This area is known to have very complex terrain while still having a good exposure to an outstanding wind resource. The second largest area of potential is located in the southwestern corner of the island near Barbers Point military reserve.

Table 2. Development Potential by Quadrant

Quadrants Area km2  MW 
Northwest 0.3 2
Northeast 7.5 60
Southwest 3.7 30
Southeast 0 0
Total 11.5 92

[1] The majority of Hawaii has a prevailing wind direction out of the Northeast. Of course, actual wind direction is highly site specific.