Siemens is among those who believes it is a good idea. Since 2000, all Siemens turbines with rated capacities of 2 MW and more include vibration-based condition monitoring. "We have excellent operating experience with the system and it is nowadays completely integrated with the service planning," says Henrik Stiesdal, chief technology officer at the Danish wind division. Units rated at less than 2 MW do not include CMS.
Germany's Nordex, which announced its re-entry into the American market last year with its 2.5 MW unit, provides CMS as an option for its basic or extended service package. It comes standard when a customer orders a full service package. Here too the system is vibration based CMS and Nordex's procedure is reflective of a common approach. The system records the structure-borne vibration from the bearings and the gear teeth. This is done using acceleration sensors located at measurement points in the individual drive train components. During the three-month start-up phase, a unique vibration profile for each wind turbine and its components is created. The measurements taken are stored in a database as parameters. During operations, real time measurements are automatically compared with the earlier baseline readings stored in the system.
"In the event of any deviations or irregularities in these parameters, the system sends an alert or warning to our remote centre. On the basis of many years of experience, Nordex is able to reliably determine the extent of the change and initiate any steps which may be necessary," says the company's Felix Losada.
Gamesa, too, includes CMS as standard with all its turbines and the technology is linked with its operations and maintenance contracts. The system, "practically eliminates major repair jobs and increases availability, as well as turbine life," says the company.
The approach by Vestas, which declines to discuss its CMS strategy, is mixed, according to its customers. Condition monitoring is an option on some models but not all units. The big V90 3 MW turbine includes CMS as standard but CMS is not offered on all smaller units. Clipper wind includes CMS as a standard facility on its single wind turbine model, a 2.5 MW unit.
GE Energy, the largest provider of turbines to the American market, bucks the CMS trend. It does not offer CMS on its workhorse 1.5 MW turbine, a machine with a long technical pedigree stretching back to way before GE's ownership of the technology. Only this machine is available from GE for the American market. The company's 2.5 MW turbine, being sold to the European market, includes CMS.
"Regarding GE's 1.5 MW platform, we see potential value in a CMS solution and are working with customers to develop an appropriate product," says the company's Kristin Schwartz. GE supplied 43% of the US wind turbine market last year, with roughly 2340 MW installed.
Like GE, Mitsubishi does not include CMS on its wind turbines, citing the extra cost and questionable effectiveness of CMS, according to Tsuneo Nakano, senior vice president, Mitsubishi Power Systems Americas. Suzlon is not currently selling CMS with its units but is still in a testing phase of the technology, says the company.
But whether CMS is offered or not, a turbine customer's decision to pay extra for the system is a big overlooked factor, says Eric Smith with SKF Group, which provides full condition monitoring systems for a variety of industries. CMS is often the first option to be removed in the negotiation between a turbine supplier and a buyer, he says, and this is exacerbated by the frenzied business climate right now, with high turbine demand, high prices, and buyers looking to cut options to bring the prices down any way possible.