Wind turbines are getting bigger every year. When I joined the wind energy sector, the maximum turbine in India was 350 KW, and now it has grown up to 3.4 MW.
The trend towards gigantism was started by Vestas globally. From its 55 KW model in 1981 to 500 KW in 1995 and then to 2MW in 1999 to 5.6 MW in 2019.
Globally, the trend is to make higher capacity turbines for better ROI. Manufacturers like Vestas and GE are introducing 10 and 12 MW turbines soon.
The blade size and the tower height is also increasing simultaneously.
These growths are throwing a challenge to the maintenance team. How to carry out the repair and replacement jobs in a cost-effective way?
Since the turbine is getting bigger and heavier, tower height is also increasing, so a taller and bigger crane will be required to de-erect or exchange a damaged component.
Birth of Crane-less idea
The availability of these cranes are very limited (particularly in India). Hence there could be a long waiting time while the crane is being arranged and then moving to the site location.
Transporting giant cranes needs many vehicles and wide roads. Roads are not available everywhere, particularly on hilly terrains. Space required for assembling cranes at the location is another issue. Overall it is the most expensive and difficult task in all cases.
Therefore, the idea of doing wind turbine services in a crane-less way took birth.
My first attempt
I recall my first successful attempt to carry out major maintenance work of wind turbines way back in the year 1999. It was a project of gearbox oil replacement in sixty-five 350KW turbines sitting at the top of 62 meters high towers.
My task was to do it in a crane-less way. Pump for delivering oil to such height wasn’t also available with us at that time.
So, we (me and my team of 5-6 engineers) thought of a very simple/crude method using a rope pulley, a couple of plastic jerrycans and a small truck.
The pully hung at the tower top. Oil-filled jerrycans knotted at one end of the rope at the ground, and the other end got tied to the back of the small truck after passing through the pulley.
As the truck moved forward, the jerrycans went up and reached the tower top. The team at the top received them and released the rope for the next trip of oil supply.
This method was very successful, and we could do crane-less oil replacement of 5-6 gearboxes daily.
The era of wind turbines without an inbuilt hoist
In that era (from 1996 to 2000), the inbuilt lifting hoist was not a part of the turbines in India.
Activities like exchange of yaw gearbox, fluid coupling or rotor brakes were done using the same crane-less way.
In 2002, a small maintenance service provider proposed to replace a damaged blade tip of a stall-controlled turbine without using any crane.
He proposed to make a steel cage to arrest the blade tip, then remove and lower it on the ground with a rope-pulley arrangement. The activity was successful.
Eventually, I met a young man who wanted to enter the wind turbine maintenance business with our company. His idea was to use the crane-less method for the replacement of components (like generators, gearbox, blades). These were otherwise done using the giant cranes at that time.
The man stepped in, and in the following years had developed many arrangements for crane-less work.
Crane-Less Method World Wide
Across the world, meanwhile, many companies had also started developing equipment and method to carry out maintenance/exchange of major turbine components in a crane-less way.
- Liftra, a company from Denmark developed (2013) and introduced a crane less method called ‘Self-Hoisting Crane’ for the replacement of generator and gearbox without de-erecting the nacelle.
- Liftra also introduced a crane less method to replace single blade and pitch bearing and now they are working to erect a complete wind turbine without using the giant crane. They have named this new solution as LT1500.
- Dutch company Lagerwey developed a ‘climbing crane’ for installing their own turbines. It can install complete tower section by section, nacelle and rotor. Thus, can avoid the use of conventional giant cranes.
- Spanis company Esteyco developed a “self-elevating” concrete tower system in 2014.
- Nabrawind developed ‘Nabralift’ technology for “self-erecting” lattice towers.
- LiftWerx developed many crane-less methods for the replacement of rotor shaft/main shaft, blade and pitch bearing.
- Enercon also had developed ‘climbing crane’.
- Chinese company ‘Ansoncranes’ had also developed a complete crane-less method for heavy component replacement.
Crane-Less Method in India
Here on the home ground, That young man is doing a fantastic job. Now, after almost two decades, his company has become a renowned name in the Indian wind energy sector.
They are hired by all leading wind energy players for an effective, safe and low-cost solution.
They have innovated their own crane-less methodology and also obtained a couple of patents.
They have successfully replaced many generators, gearboxes, pitch bearings, yaw motors and blades with their home-grown technology.
Across this article, all photographs (except one) are from their archives.
In 2019 they have also joined hands with Barnhart (USA) to provide service to US customers for their blade and bearing replacement requirements.
Understanding the potential of crane-less in the wind turbine maintenance field in India, some more companies are also stepping in. I found one of them is also present on the web.
Why Crane-Less Method is a preferred option
Benefits are multifold like:
- There is no need for a large vacant space around the tower to install and manoeuvre a giant crane.
- There is no need to create parking space for the vehicles carrying the crane structures.
- Savings in crane and crane transferring vehicle hiring cost.
- There is no need to make roads to travel the crane vehicles.
- Savings in Labour cost.
- Savings in time involved in crane and infrastructure arrangement.
- Minimum turbine downtime.
- Minimum generation loss.
- In addition, reduction of emissions due to a considerable number of vehicle movement for mobilizing the crane.
Cost Comparison Crane Vs Crane-less Method
It is considered that the cost of “major component replacement by conventional crane method the major portion of expenditure is at crane end including Mobilization/De-mobilization, Fuel consumption, Access of pathway, ROW etc.”
For example, in a blade repairing activity, the actual repairing cost is 20% of the total cost, rest 80% is for crane-related activities. In the case of pitch bearing replacement, this cost ratio is 15% and 85%.
There is enormous scope for the crane-less method to expand in both areas, onshore as well as offshore. Though there is a lot of development scope is still awaiting in the onshore field, the next frontier for parallel expansion could be offshore.
Existing turbines are getting older every day, and every year a large number of wind turbines are also getting installed. Over time all these will need component replacement.
On the other hand, crane hiring costs will continue to rise along with various related peripheral costs. The crane-less method has emerged as a boon to overcome this difficulty.