Rezachek & Associates'
Energy & Environmental Resources

WIND

WIND POWER - What Is It?

Wind is the natural movement of air across the land or sea. Wind is caused by uneven heating and cooling of the earth's surface and by the earth's rotation. Land and water areas absorb and release different amount of heat received from the sun. As warm air rises, cooler air rushes in to take its place, causing local winds. The rotation of the earth changes the direction of the flow of air. This produces prevailing winds, including Hawaii's trade winds. Surface features such as mountains and valleys can change the direction and speed of prevailing winds. Wind power is harnessing the wind with turbines to produce mechanical power or electricity.

Advantages

Wind is a renewable energy resource. Wind patterns in Hawaii provide strong, steady trade winds in specific areas throughout most of the year.
Used as a "fuel," wind is free and non-polluting, producing no emissions or chemical wastes.
Use of wind power as a source of electricity will help reduce Hawaii's almost complete dependence on imported fossil fuels.
Wind power can be used with battery storage or pumped hydro-energy storage systems to provide a steady flow of energy.
Wind farms can be combined with agricultural activities such as cattle grazing.
Wind power is a proven technology and has been used to generate electricity for many years.
Equipment for wind machines is commercially available.
The State of Hawaii offers a 20 percent tax credit for the cost of buying and installing a wind energy device.

Disadvantages

Wind machines must be located where strong, dependable winds are available most of the time.
Because winds do not blow strongly enough to produce power all the time, energy from wind machines is considered "intermittent," that is, it comes and goes. Therefore, electricity from wind machines must have a back-up supply from another source.
As wind power is "intermittent," utility companies can use it for only part of their total energy needs.
Wind towers and turbine blades are subject to damage from high winds and lighting. Rotating parts which are located high off the ground can be difficult and expensive to repair.
Electricity produced by wind power sometimes fluctuates in voltage and power factor, which can cause difficulties in linking its power to a utility system.
The noise made by rotating wind machine blades can be annoying to nearby neighbors.
People have complained about aesthetics of and avian mortality from wind machines.

The Basic Process

The wind turns the blades of a windmill-like machine. The rotating blades turn the shaft to which they are attached. The turning shaft typically can either power a pump or turn a generator which produces electricity. For producing large amounts of electricity, many machines can be grouped together to form a "wind farm."

Most wind machines have vertical blades attached to a horizontal shaft. This shaft transmits power through a series of gears which provide power to a water pump or electric generator. However, the Darrieus wind machine has two or three long curved blades on a vertical shaft. It resembles a giant eggbeater in shape. The Darrieus machine provides ease of maintenance as the operating gears and controls are located close to the ground, but it needs power assistance to start turning.

The amount of energy produced by a wind machine depends upon the wind speed and the size of the blades in the machine. In general, when the wind speed doubles, the power produced increases eight times. Larger blades capture more wind. As the diameter of the circle formed by the blades doubles, the power increases four times.

Use of Wind Power for Electricity in Hawaii

Hawaii currently has the third largest capacity in wind-generated electricity in the nation. In 1993, those wind machines produced about 23,000,000 kilowatt hours (kWh) of electricity. Most of the wind machines produce and sell electricity to local utilities.

The huge 3.2-megawatt (MW) MOD-5B wind turbine at the Makani Moa'e wind farm in Kahuku, Oahu, is an experimental machine furnished by the U.S. Department of Energy and operated by Makani Uwila Power Corporation. This machine has two blades which together measure 98 m from tip to tip. It is the largest machine of its kind in the world. Electricity produced by the MOD-5B machine, and a number of Westinghouse 600-kW wind machines, is sold to the Hawaiian Electric Company for use on Oahu.

Kahua Ranch in the Kohala district of the Island of Hawaii furnishes electricity to the ranch and to Hawaii Electric Light Company. Lalamilo Wind Farm is located in Waikoloa on the Island of Hawaii. It supplies electricity to the Hawaii County Department of Water Supply, which uses it primarily for pumping water.

The Kamaoa Wind Farm at South Point on the Island of Hawaii has a total capacity of 9.3 MW and furnished approximately 14,500,000 kWh of electricity in 1993 to Hawaii Electric Light Company, enough to power about 7,000 homes.

Research on wind flow patterns through rows of wind machines was carried on at the Kamaoa Wind Farm. Other research on the use of wind-diesel hybrid systems and pumped-storage, wind-hydro systems has been conducted on the Islands of Molokai, Maui and Hawaii.

At least 50 other wind machines are located throughout the state. They are operated primarily for farm and residential use.

Most of information contained in this summary was excerpted from a Fact Sheet prepared by the staff of the Energy Division of the State of Hawaii-Department of Business, Economic Development, and Tourism (DBEDT) and published with funding from the U.S. Department of Energy, Grant No. DE-FG49-94R900023. This information does not necessarily reflect the views of the State of Hawaii, the United States Government, or any agency thereof.