WHILE THE highest costs for a wind project are typically associated with initial capital costs for development, construction and installation, and operations and maintenance (O&M) costs “constitute a sizeable share of the total annual costs of a wind turbine,” according to Wind Energy: The Facts.

“For a new [onshore] turbine, O&M costs may easily make up 20%–25% of the total levelised cost per kWh produced over the lifetime of the turbine,” the project's website says. “If the turbine is fairly new, the share may only be 10%–15%, but this may increase to at least 20%–35% by the end of the turbine's lifetime.”

Moreover, as turbines come out of warranty, any inherent financial risk rests with the owner, making good O&M planning even more critical, the American Wind Energy Association (AWEA) stresses. Indeed, last year nearly US$40 billion worth of wind installations in the U.S. came out of warranty, “thrusting the financial risk on the owner to provide cost-effective operation and maintenance.”

An original equipment manufacturer (OEM) typically operates a wind project through the warranty period, with optional continued services. While in some instances, the OEM may be contracted further to conduct O&M for another term, the owner usually takes responsibility, either conducting it in-house or contracting out to a third party.

It is important, however, that the operational data is transferred to the owner on completion of the OEM service period. While a range of automated systems, on-site and remote operators determine the operational parameters of a turbine, routine servicing of a typical onshore wind farm should take place once or twice a year.

“Oil and filters need to be changed, operating components need to be inspected, and bolts need to be torqued,” the AWEA says. “Worn parts need to be routinely repaired or replaced every 5–15 years, depending on the component.” And as the AWEA makes clear: “Operating and maintaining wind turbines requires workers to have extensive technical knowledge and safety training; sophisticated capabilities to diagnose component performance; knowledge and skills to schedule replacement components; and ability to accommodate changing weather conditions.” So using the right personnel and equipment is vital.

Escalating costs

Meantime, for offshore wind, O&M costs account for significantly more than onshore, and are “subject to considerable uncertainty,” according to the European Wind Energy Association's (EWEA) report The Economics of Wind Power. In fact with O&M for offshore projects being far more complicated and intensive, due to the difficult conditions at sea, they can equal that of any initial capital investment.

Offshore O&M is 2–6 times higher than for onshore turbines, says a 2011 Wind Energy Update (WEU) Operations and Maintenance report, with operators facing O&M costs as high as €100,000–300,000 per year, per turbine, as opposed to around €45,000 per turbine onshore. Moreover, it warns that in the short-term costs could be 20% higher than that. Indeed, the report found that spattered debris accumulation on the blade's leading edge could result in a staggering 10% loss in revenue.

Unknown component failure rates, unknown logistic equipment costs, weather windows dependent on deployment site, and a general lack of understanding of O&M cost correlation to shore distance, amongst others, are busting offshore operations and maintenance budgets beyond all expectation. And WEU warns that offshore O&M costs are likely to increase around 253% over a 20-year turbine lifespan.

Keeping these costs down is therefore a natural aim of any wind farm owner, whether looking at future or existing plants. O&M costs, for both on- and offshore projects, are now attracting greater attention in the wind community.

Manufacturers are doing their bit by trying to lower these costs by developing new turbine designs that require fewer regular service visits and less turbine downtime. An effective maintenance strategy will also increase operating efficiency and plant availability, which in turn helps maximise project returns. Adopting a ‘bare-minimum’ reactive/corrective approach – at its worst, dealing with faults only when they occur or cause a major problem – may be seen as tempting in these tough economic times.

It is, however, a false economy and can be the costliest option in the long-term. Indeed, the WEU report notes that 66% of offshore O&M costs are caused by unscheduled corrective maintenance, much of which could be avoided if a proactive, preventative maintenance approach is adopted instead.

A good O&M plan

The key elements of a good O&M strategy, according to O&M company Wind Prospect, should include:

• Good liaison: An operations manager should preferably be appointed who then acts as a “conduit for communication” between the wind farm owner, turbine manufacturer, maintenance contractors, inspectors, land owners, neighbours, authorities and emergency services;
• Regular site inspections: While modern data systems have eliminated the need for a full-time permanent presence at sites, “regular and thorough inspections of the balance of wind farm infrastructure are a must”. This includes inspection of gates, fences, access tracks, signage, met masts and electrical infrastructure;
• The right technology: This includes conditioning monitoring systems [see box Condition monitoring, p. 46], remote monitoring, and supervisory control and data acquisition (SCADA);
• Health and safety: This can come under the remit of an operations manager. A good health and safety management plan is vital, incorporating risk assessments, method statements and procedures, while safety auditing of contractors should be carried out and regular inspection of on site safety equipment should be conducted regularly;
• Rapid response to alarms: O&M providers need to guarantee response times to alarms, “24 hours per day, seven days a week”. In some instances, a local or remote reset of equipment may be necessary, while sometimes a technician may have to attend the site to diagnose the problem;
• On site turbine inspections: These should be conducted on a regular basis, usually at three-month intervals. “The inspection is not just visual in nature,” Wind Prospect says. “An abnormal sound or unfamiliar smell can provide tell-tale signs that something is amiss with the mechanical plant. The nacelle should be checked carefully for oil leakage or any other indicators that may suggest an imminent problem”;
• Scheduled maintenance: This is a must for any truly effective proactive O&M plan to work, and involves the contractor or in-house service team to perform all servicing and repairs of turbines;
• Ability to deal with non-scheduled repairs: This should be carried out swiftly and preferably in times of low wind to minimise loss of production. In any service contracts, maximum response times for diagnosis and repair must be stipulated. “Most trip events or breakdowns of turbines occur in strong winds, meaning that every 1% of loss in availability could mean a significantly higher loss in production,” it says. “Prompt assessment, organisation and supervision of the work is therefore of utmost importance”;
• Spare part planning: To reduce the potential for extended downtime due to lead time in obtaining spares, an inventory of spare parts on site should be maintained. This is especially important for wind farms in remote locations; and
• Reporting: Thanks to modern SCADA systems and other equipment, an enormous amount of data is collected from today's wind farms, and the operations manager must extract what is most relevant to the wind farm owner and present the information in a concise, readable form. Information can be gleaned from conditioning monitoring systems, which can include vibration analysis, oil analysis, infrared thermography and ultrasonics. Monthly and annual reports are the norm. This includes production (in MWh and monetary terms) versus budget, scheduled and non-scheduled servicing, availability, capacity factors, alarms, downtime, expenditure and any other information of interest to the wind farm owner.

About the author:
Gail Rajgor is Managing Editor of Renewable Energy Focus.