Owner`s manual

put the turbine on your property line so that it is closer to a neighbor’s house than to your own and not

give those neighbors any advance notice of your intentions.

In general, we do not recommend that a BWC EXCEL 1 be installed on property of less than one acre in

size. We say this because the impact of a wind turbine on the neighbors in such a “tight” area is signifi-

cant and the potential for disputes is too great.

If you have questions about procedures, requirements, or tactics, please contact us. Since so few wind

systems have been installed and communities are generally unfamiliar with them, you may face some

obstacles in gaining permission to install a unit. We appreciate the pioneering spirit and resolve demon-

strated by our customers and we stand ready to help out in any way that we can.

B. Towers

The smooth flow of the wind over the land is interrupted by obstructions and topographical variations.

These interruptions bring about two important phenomena: wind shear and turbulence. Wind shear

describes the fact that close to the ground the wind is slowed down by friction and the influence of obsta-

cles. Thus, wind speed is low close to the ground and increases with increasing height above the ground.

Wind shear is more pronounced over rough terrain and less pronounced over smooth terrain. Turbulence

is essentially rough air caused by the wind passing over obstructions such as trees, buildings, or terrain

features. Turbulent air reduces energy output and puts greater strain on the wind turbine.

The effects of both wind shear and turbulence diminish with height and can be largely overcome simply

by putting the machine sufficiently high above the ground. Taller towers usually will provide better eco-

nomics because the power in the wind increases as the cube of the wind velocity (P = V

; e.g., a 26%

increase in wind speed doubles the energy output). A small increase in average wind speed will result in

a large increase in long-term energy output.

Table 2 shows the influence that tower height can have on annual energy output for the BWC EXCEL 1

wind turbine under typical DOE Class 2 inland site conditions with a shear exponent of 0.20. Wind speed

may increase more radically with tower height in hilly or wooded areas. In flat open areas, power produc-

tion will increase less significantly with tower height.

The BWC EXCEL 1 wind turbine must be placed on a tower that is tall enough to give the rotor proper

exposure to the wind. Putting a wind turbine on a tower that is too short is like installing a solar system in

the shade. As a “rule-of-thumb” the BWC EXCEL 1 should be 9 m (30 ft) above obstacles within 100 m

(320 ft), particularly in the prevailing wind direction. So, the minimum recommended tower height is 18m

(60 ft.).

Table 1: Variation in wind speed and expected relative energy output with tower height

Tower Height

Ft - (meters)

Average Wind

Speed (m/s)

Relative Energy

Production

30 (9) 4.8 100%

40 (13) 5.2 121%

60 (18) 5.6 147%

80 (24) 5.9 165%

100 (30) 6.2 186%