Discussions over the Operation and Maintenance (O&M) of projects is gaining prominence as the scale of wind power grows; POWER TODAY takes a look at what O&M entails and the costs associated with these processes.
Inadequate O&M can lead to minor faults or defects not being recognised. This not only impacts yield but can also result in major component failure, potentially leading to costly repairs and lengthy downtime. Thus, O&M is a growing issue for the onshore wind industry. Due to the increased probability of component failure and that defects will fall outside of the manufacturer´s warranty period, the importance and cost of O&M increases with the length of time from commissioning.
The variables involved in the O&M for wind power projects are the wind turbine technology, size and location of wind farm and the O&M philosophy adopted. ¨O&M for off-shore wind projects have additional variables such as distance of wind farm from shore, wave condition, logistics at the harbor and transfer system for O&M staff from shore to the wind farm to contend with,¨ shares Sudhir Nunes, CEO, Orange Renewable Power.
O&M costs constitute a sizeable share of the total annual costs of a wind turbine. For a new turbine, O&M costs may easily make up 20-25 per cent of the total levelised cost per kWh produced over the lifetime of the turbine. If the turbine is fairly new, the share may only be 10-15 per cent, but this may increase to at least 20-35 per cent by the end of the turbine´s lifetime.
As a result, O&M costs are attracting greater attention, as manufacturers attempt to lower these costs significantly by developing new turbine designs that require fewer regular service visits and less turbine downtime.
The cost of electricity from wind has two primary components: capital cost repayments (with interest) and O&M costs. O&M costs covers a range of costs including land, insurance, servicing and spare parts (predictive, preventive and corrective maintenance), electricity purchases (import power) from grid, statutory electrical inspections, taxes, management and administration costs, and forecasting and scheduling costs. The O&M costs can account for up to 25 per cent of the project´s total life time cost for maintenance, repair and overhaul work.
Some of these cost components can be estimated relatively easily. For insurance and regular maintenance, it is possible to obtain standard contracts covering a considerable share of the wind turbine´s total lifetime. Conversely, costs for repair and related spare parts are much more difficult to predict. And although all cost components tend to increase as the turbine gets older, costs for repair and spare parts are particularly influenced by turbine age; starting low and increasing over time. Due to the relative infancy of the wind energy industry, estimates of O&M costs are still highly unpredictable, especially around the end of a turbine´s lifetime; nevertheless a certain amount of experience can be drawn from existing, older turbines.
Based on experiences in Germany, Spain, the UK and Denmark, O&M costs are generally estimated to be around 1.2 to 1.5 eurocents (c¤) per kWh of wind power produced, over the total lifetime of a turbine. Figure 1.6, shows how total O&M costs for the
period between 1997 and 2001 were split into six different categories, based on German data from DEWI. Expenses pertaining to buying power from the grid and land rental (as in Spain) are included in the O&M costs calculated for Germany. For the first two years of its lifetime, a turbine is usually covered by the manufacturer´s warranty, so in the German study O&M costs made up a small percentage (2-3 per cent) of total investment costs for these two years, corresponding to approximately 0.3-0.4 c¤/kWh. After six years, the total O&M costs increased, constituting slightly less than 5 per cent of total investment costs, which is equivalent to around 0.6-0.7 c¤/kWh. These figures are fairly similar to the O&M costs calculated for newer Danish turbines (see below).
Figure 1.7 shows the total O&M costs resulting from a Danish study, and how these are distributed between the different O&M categories, depending on the type, size and age of the turbine. The study revealed that expenses for insurance, regular servicing and administration were fairly stable over time, while the costs for repairs and spare parts fluctuated considerably. In most cases, other costs were of minor importance. Figure 1.7 also shows the trend towards lower O&M costs for new and larger machines and that O&M costs increase with turbine age.
Adds Nunes, ¨Operation and maintenance costs vary significantly between projects depending largely on the service contract price and the duration of the contract. The experience of the IPP´s show that the expenses have not changed significantly over the years.¨ The trend towards larger wind farm capacities coupled with higher component reliabilities (for major components such as blades, gear box and generator) and availability of skilled manpower has helped to stabilise the expenses. In general, the O&M expense for off-shore projects is expected to be double when compared with on-shore projects.
Services in O&M
On their part service providers Shell Lubricants are very buoyant about O&M growth in the wind sector. ¨If you look at some areas like in Gujarat or the southern states, there are a lot of wind energy projects coming up. Also, looking at the way wind original equipment manufacturers (OEMs) like Suzlon and other major Indian player are growing, there are a lot of opportunities,¨ states Akhil Jha, Vice President Technical, Shell Lubricants India.
Adds Felix Guerzoni, Shell Global Product Application Specialist, Shell Lubricants, ¨The way we operate is across the full spectrum (value chain) which involves products for operation and maintenance. Our role is to work closely with component manufacturers to understand and in some cases design a set specification of lubricants, greases and gear oils for those applications and allow them to operate more effectively.¨
Additionally, once the wind turbines are in operation, Shell maintains and operates those as cost effectively as possible, undertaking activities like oil analysis, with service technicians conducting tests on the gear boxes for example to understand the condition, operation procedures and effectiveness of the turbine.
¨We thus have a full offering across the value chain, and as part of it, we also work closely with OEMs manufacturers while supplying customised product range and also helping them to lower their cost of operation. Besides this, we also deal with the transitional affects on wind turbines parts as they move from construction phase to assembly, and finally focus on operational maintenance,¨ Guerzoni explains. Sharing his take on what has to be taken into consideration while determining O&M Jha points out, ¨when you look at turbine performance and efficiency in low and high temperature environments, the major concern is over how effective the greases and gear oils are going to be in such conditions. We are continuously working on low temperature fluidity and oil compatibility with the gears and surfaces and the other pipes and fixtures that are within the installation or on the surface.¨
His argument gains importance when you consider that most major wind farms are located a very remote areas and at a height, making maintenance and liability is a major concern. Reliability of the project on account of how far one has to travel to maintain it is another problem.
¨While OEMs generally rely on the in-built sensors alone, there is a need for more assurance, which we provide through our operation and maintenance services,¨ he adds.
In the recently held WINDPOWER 2015 Conference & Exhibiton in Orlando, Florida (USA), an education session on the theme ¨Future of O&M-The Technology Impact and Lessons Learned¨, was a centre point of discussion. While wind power costs have declined massively over the past several years, there´s still a need to wring even more economies out of the technology, and the growing use of big data in wind farm operations and maintenance (O&M) is going to be a major part of that effort. Session moderator Peter Wells of UpWind Solutions summarized the panel discussion by saying there are limits on the degree to which costs can be cut through taller towers and larger rotors and ¨the rest of the [cost reduction] journey .... is going to come through real material gains in technology, such as wearable intelligence, machine learning.¨
Vijay Narayanan, Director, Algorithms & Data Science, Microsoft provided a generic example of how data can be quickly collected and displayed with a graphic.
Brian Hayes, Executive VP, EDP Renewables NA LLC, offered some background on EDP Renewables´ history with O&M, noting that the company ¨has been doing the best it can to use new technology as it becomes available. In its first projects, by improving turbine availability and then switching focus to efficiency-how to get more power from turbines.¨
More recently, the introduction of Condition Monitoring Systems (CMS) has provided further opportunities for O&M improvement. With Non Destructive Testing (NDT) it is possible now to do an [infrared] scan of rotating blades-you can identify where repairs are needed without ever shutting the turbine down.
To this Nunes adds the India scenario, ¨Enormous amount of data is generated by today´s wind turbines and wind parks. SCADA systems (for smart grids) are commonplace, providing a treasure trove of data collected by sensors ?tted to the turbine. Operational data such as error logs, turbine status and operating conditions such as wind speed and direction reflect the real-time condition of a wind turbine.¨ ¨Continuous Monitoring Systems are used to analyse the vast amounts of SCADA data in real time to deduce the performance of the wind farm and health of turbine components. The use of software will continue to increase with the introduction of mandatory scheduling and forecasting for wind farms being planned by Load Dispatch Centers of many states,¨ he feels.
Current O&M strategies can be considered to fall broadly in three categories, viz. reactive, scheduled preventive and condition based/predictive maintenance. In the early days of wind power, the approach typically taken with regards to asset maintenance was ¨to run to failure¨. This approach was the result of a poorly consolidated and integrated supply chain industry.
However, this is not pursued by today´s standards, even towards the end of life of a turbine. Given the large capacity of the wind farms being installed presently in India, scheduled preventive maintenance strategy has been adopted by most wind farm owners. The reason for the popularity, despite the high cost in the early life of the asset, is the ability to permit work to be planned and aligned with periods of expected low wind season and result in minimal to no impact on yield. Some IPP´s are planning to move towards a predictive maintenance strategy that combines the bene?ts of both reactive maintenance and preventive maintenance. This strategy however involves a higher CAPEX for a lowered OPEX over the turbine lifetime.
- Jocelyn Fernandes