P: 402 426-2104

F: 402 426-2105

Modular Wind Tower Manufacturers

Joints between tower sections Towers are normally fabricated in several sections for transport reasons, so joints are required. Welding on site is an expensive operation, so bolted joints are almost always used, although sleeved joints, in which each tapered tower section is threaded over the one beneath and forced into place by jacking, have been used successfully. The structurally most effective joint is made with friction grip bolted splice plates oriented vertically and sandwiching the walls of the abutting tower sections between them. Provided the grip force is adequate, the joint will not slip even under extreme load, with the result that the bolts are not subject to fatigue loads. Unfortunately, apart from the effect of splice plates on the external appearance, there are practical difficulties of joint assembly, because bolting requires the provision of some form of personnel access on the outside of the tower. Nevertheless splice plates are used on some towers. Above excerpt taken from pages 460-61 of the Wind Energy Handbook.

WEIGHT AND BOTTOM DIAMETER RESTRICTIONS CONTINUE TO TROUBLE THE WIND ENERGY INDUSTRY.

Conventional tubular wind tower designs have limitations in their connections and by having restrictions on the allowable base diameter; transportation is an ever increasing cost for the end user. Handling the increasing loads from larger turbines calls for a new solution...

NORTHSTAR’s engineering team meets the challenge:

• Developing a wind tower system that can efficiently handle the ever increasing loads induced by expanding rotor sizes and multi Mega Watt turbines.
• Maintaining the overall look and general properties of the current wind tower designs.
• INCREASING SAFETY MARGINS by incorporating an added level of redundancy into the wind tower connection design.
• Lowering installed wind tower cost by 10-15%.

SOLUTION: MODULAR TOWER

Wind towers with a continuous taper or an increasing taper are by design the most efficient way to handle wind turbine loads. It is, however, not possible to continue the taper for current welded wind towers where the bottom diameter exceeds transportation restrictions. In order to design a light wind tower with a large diameter, a modular approach must be used.

Modular or segmented wind towers must be reassembled before erection. Rather than trying to design a new fastening system or connection method for these segments our engineers went searching for connection styles used in other cyclically loaded structures. We also studied various methods used in previous generation wind turbine towers.