Breaking the logistic barriers in XXL blades industy
MODULAR BLADES MARKET
The growth of the wind market, together with the low availability of sites with optimal wind conditions, is creating a rapid increase in the size of turbines and therefore the diameter of some rotors that work at specific low power levels. This leads to the need for longer blades whose transport is, more and more frequently, a major logistical challenge that manufacturers must face. The modularization of these blades is presented as a solution to reduce costs, or even make feasible, wind farms with more complicated logistics. The main OEMs are all working on modularization developments that aim to lead to a reliable solution with an acceptable impact on the rest of the machine.
Modular blades in the wind industry
The trend towards increasing the size of blades is evident. The major wind turbine manufacturers are announcing rotors of more than 150m diameter for new land-based wind turbines.
The idea that blades shall be modular at these sizes is widely accepted within the sector. Most of the main wind turbine manufacturers are investing in the development of a solution for large blades segmentation. The key factor in this challenge is finding a reliable mechanical solution with minimal increase in weight and cost.
Modular blades transport
Growing blade length continues to be the most important trend influencing wind turbine technology. Any increase in blade length implies facing new challenges in advanced materials, innovative construction techniques, blades root solutions, loads management and aerodynamics. Consequently, new designs and products that will appear in the near future will require new ways to transport and install these long blades.
Segmented blades have been seen for a long time as a solution to the logistic issue but are still not mainstream. The barriers totheir adoption are; the added weight and cost, load concentration, maintenance and field assembly process.
Modular blades alternatives
The development of a reliable joint in a component that must withstand high loads and in which the geometry and the weight impact are serious constraints, is a challenge that the blade manufacturers have faced from different approaches that can be divided in two main groups.
BOLTED JOINTS, including examples of the T-bolts and Tension Fitting solutions.
T-bolt is a very well-known connection in standard blades as it is the commonly used blade root connection that serves to transfer the loads from the entire blade to the rotor hub. A T-bolt consists of a stud, a barrel nut and a standard nut.
Tension Fitting type of blade joint where blade segments are connected by a bolted joint between each set of two channel fittings. Each channel fitting consists of inserts and bolt connections, where the inserts are metallic parts bonded into the blade laminate.
BONDED JOINT concept corresponds to blades where the two segments are glued together. Bonded joints are usually lighter than bolted joints. However, they require moving a complex infrastructure to the wind farm in order to achieve a bonding process in controlled conditions. This means that the duration of the assembly process is increased; the response capacity is limited and consequently the blade structural integrity and aerodynamics are compromised.
Nabrawind modular blade solution: Nabrajoint
Nabrawind Technologies was founded in 2015 by veterans of the renewable industry with decades of experience in development of innovative technologies. The team currently consists of 20 engineers, who have spent the last 20 years working with the major global manufacturers of wind turbines. In response to theabove-mentioned market trend, they have developed a solution to break these logistic and installation barriers: the modular blade system Nabrajoint.
The joint uses a patented design, with metallic inserts bonded to the blade laminate, with a strength 30% higher than the solutions developed to date in the industry, and with the use of a singlestud to join the opposite inserts on both sections of the blade.
Nabrajoint main components
The pre-tensioning of the aforementioned studs is carried out with a simple and compact system, also patented. The assembly process is entirely automated and robust, ensuring 100% control of the joints. This process is purely mechanical, avoiding the use of adhesives which are highly sensitive to environmental conditions and therefore with critical reliability for on-site assemblies. Nabrajointâ is also maintenance free and does not require any type of intervention during its service life.
Automatic tightening tool
Nabrajointâ has been designed to be integrated into any of the market available blades, with minimal design adjustments in the joint area and especially, minimal investment in tooling and equipment. Due to this, existing blade moulds can be utilised to manufacture modular blade versions, coordinating this smoothly with the conventional production processes.
The validation and certification of the joint (currently ongoing with certification authority DNV-GL) is based on an exhaustive testing campaign, covering from the testing of materials and design elements to the validation of a 1:1 scale joint.
Nabrajointâsegment full scale specimen
Nabrajoint was compared with the alternative solutions for modular blades by MAKE Consulting in their report “Global Wind Turbine Trends 2016”, where Nabrajoint was identified as the best alternative in their respective fields, describing it as “a technology capable of revolutionising the wind energy industry”.
Logistic market solutions
Blades segmentation is not the only way that the wind industry is developing solutions for logistic barriers, there are also existing transport alternatives that provide specific solutions.
Companies such as Mammoet, Scheuerle, Noteboom, or Vamdrup are working on the development of modular semi-trailers, self-propelled modular transporters, or blade lifter adaptors as solutions for the transport of >60m blades.
These types of devices are currently being used in some wind farm locations with difficult access (mountainous regions, bad road conditions, etc). Its use is restricted to the very last kilometers of the journey due to its high cost.
Identifying the modular blades market
Nabrawind has developed a Logistic Cost Model whose aim is to determine the suitable conditions of windfarm sites where modular bladesare especially competitive.
The Logistic Cost Model is based on the whole transport route between the blade manufacturing and the windfarm site and includes the main decision parameters such as blade length, distances, road complexity, region or windfarm size. To do so, the model has been developed and validated on the basis of a huge blade transport database.
Logistic model phases
Therefore, the total Logistic Cost of each considered case can be compared for both types of blades: Standard and Modular. Based on this, the cost difference between each simulation can be set against the blade modularization cost, resulting in a potential recommendation on the suitability of modularization for certain conditions.
Consequently, this tool can simulate a high number of routes in a short period of time, identifying the windfarms where a modular blade’s extra cost is compensated by the logistic savings.
Conclusions
There is a clear market trend to develop increasingly larger machines with blades that are already well over 60m in length. The logistical challenge has become a point to consider in the economic study or even the feasibility of a windfarm. Although there are alternatives in the transport industry that can be useful in specific cases, the modular blades are presented as an increasingly demanded solution as it is the only one that simplifies logistics in all steps of the route. Due to this, the development of modular blades is gaining importance in the catalogs of the main manufacturers. They know that it not only brings logistical savings but can also make some wind farms feasible that would normally be discarded due to logistical impact, or that can serve to optimize concepts such as repowering.Within the matrix of existing alternatives, Nabrajoint is presented as a reliable and robust solution. It minimizes the impact on cost and weight of the modularization. In addition, the industrial impact is minimal, allowing the development of two variants (integral and modular) of the same blade model on the same manufacturing line, depending on the conditions of the destination wind farm.
