A 5 MW wind turbine nearing launch in China from developer Xemc, had a concept birth in Europe and deserves a closer look. For example, the company says the unit is:

• Fully sealed – Tower and nacelle are sealed to keep out the salty and moist  sea air. This protects critical components, increases operational availability, and saves a great deal of maintenance.
  

  The XEMC-Darwind is based on a single main-bearing concept. The large diameter bearing lets it handle the enormous load and forces from the rotor. Notice that there is no central shaft.

• Single main bearing and generator are one unit – The XEMC-Darwind turbine is based on the single main-bearing concept. The large diameter bearing lets it handle the enormous load and forces from the rotor. And there is no central shaft. The main bearing is integrated into the generator and that is possible because the turbine uses a direct-drive design. This allows a compact and lightweight permanent magnet, direct-drive generator and results in significant savings in logistics, foundation, and support-structure costs.
• Air-cooled generator – The exterior shell of the generator is covered with small surface extensions to transfer the heat to cooler air. This avoids using a power consuming and potentially unreliable cooling system.
• Light weight – The design and new materials have resulted in a large yet easy-to-install lightweight turbine with a 5 MW capacity.
• Direct–drive principle – All this company’s turbines are based on direct drives, thereby dispensing with the need for gearboxes. These have posed a significant problem for offshore wind turbines because the torque of multi-megawatt wind turbines is enormous. In contrast, gearless turbines require less maintenance, are more reliable, and therefore boast higher operating availability.

A direct drive design calls for permanent magnets in the generator. Because no additional electricity is required to magnetise the rotor coils, there is no need for generator brushes to transfer this electricity. This increases efficiency and reliability because the rotating part of the generator contains no electrical systems.

• Monitoring system – A monitoring system for wind farms allows for maximum control and an efficient O&M system at a minimum of cost, according to the company.
• Offshore logistics – These are the dominant cost drivers in the offshore world. Hence, the company has partner with experienced marine contractors to offer a best lifetime cost package.

Xemc-Darwind
www.xemc-darwind.com