performance improvement innovation

Generally, the design conditions of old wind turbines are very conservative compared to the reality of the sites where they are located, so they have a huge potential to be unlocked, in terms of life extension, performance improvement and maintenance optimization. In this sense, the retipping solution proposed by nabla wind hub aims to increase the rotor diameter of wind turbines in order to significantly impact in the energy Production.

By upgrading the rotor of wind turbines with modular configurable tip extension designs, nabla manages to deliver Annual Energy Production (AEP) increases of up to 10% and a significant reduction in the Levelized Cost of Energy (LCOE). The objective of this solution is to achieve a redevelopment of the asset, reformulating the business plan for each wind farm, unlocking the hidden potential that the site-specific conditions are allowing.

The retipping solution consists of using tip extensions of 1, 2 or 3 meters depending on the site conditions to ensure an optimal tip extension for each wind turbine. The proposed length for the tip extension depends on the wind conditions of each site and it is designed using aerodynamic nested optimization algorithms that balance the chord and twist distributions to find the optimal power coefficient and energy extraction.

The tip extensions are designed using the independent aeroelastic models for each turbine, created via reverse engineering and owned by nabla, making this process independent from the manufacturer. The intensive use of the aeroelastic model allows to guarantee the structural safety of the wind turbine in all components, verifying with a specific site suitability report the extreme loads, blade deflections towards the tower and the accumulation of fatigue in the different components.

Why retipping:

  • Most cost effective re-rotoring solution
  • Flexible solution: optimal AEP upgrade adapted to each site
  • Minimal impact on the turbine
  • Minimizing permitting risks
  • Fast track certification via EC directive 2006/42
  • Plug&play no need to change the controller
  • Up-tower installation without cranes
  • Installed and ready to use in 8h
  • Can be reversed to original configuration
  • Best value for money
  • PBP 3 years (reference from first fleet)
  • IRR 10% (reference from first fleet)

Site specific

Although benign, average and restrictive site conditions have been defined for tips design and certification purposes. For every wind farm, a specific site suitability report will be issued, analyzing in detail wind conditions, extreme loads, blade deflections towards the tower, and fatigue.

Designed for safety

Acoustic noise

All relevant sources of aeroacoustic noise have been evaluated; boundary layer trailing edge noise, separated flow noise, laminar boundary layer vortex shedding noise, trailing edge bluntness vortex shedding noise, turbulent inflow noise, and airfoil tip vortex formation noise, using nrel nafnoise aeroacoustic code for wind turbines.

Noise increase is considered negligible and inside the uncertainties of the OEMs that are in +/-2dB

Internal structure

Tip extension internal structures are based on lean engineering and design-to-manufacture concepts, minimizing the number of substructures and subassemblies to minimize failure modes.

Maximum reliability


Due to structural connection of the tip extension with the base blade is based on crestomer high performance adhesive due to:

  • Low polymerization time (e.g. 25min)
  • No need to curing cycle nor temperature application
  • Multi-molecular adhesive: capable of bonding polyester and epoxy substrates
  • Viscous and capable if standing vertical without dropping
  • Intensive test plan for risk minimization launched

Tip extension bonded to base blade with x5 reserve factor scarf joint

Lightning Protection System

Aluminum winglet body acts as tip receptor for the system, with external housing for the LPS wiring, including a double draining system to prevent moisture accumulation at the tip extension. Ensuring enough mass, area and section to absorb thermal expansion due to lightning, following latest state of the art.

Lightning tests acc IEC61400/24 can be performed at client request

Erosion Protection System

Due to higher tip speeds, erosion on the leading edge must be prevented.

Widely tested product with very robust results up to tip speeds of 80m/s


With a track record of over 2,000 blades produced starting 2012 for international customers and markets, nabla wind hub, through its Design, Manufacturing, Moulding & Tooling, Blade Service and Testing & Certification departments, supports customers to extract the maximum value from their wind farms, partnering with them from new wind development opportunities up to large scale Reblading programmes.

Different competences, coming from our top management entrepreneurial experiences in wind, marine and aerospace, and multi-skilled teams, lead together with our partners, are joined to craft new blade profiles, adopting advanced materials and innovative technologies driving the efforts towards the next wind farm generation needs: enhancing the value of assets (vs lower or no incentives) while improving wind farm efficiency (vs market saturation) at a lower environmental impact (vs. deteriorated social acceptance).

Our manufacturing abilities come from advanced marine aerospace state-of-the-art techniques, with particular regard to the infusion process and the mix of advanced materials we are able to use when designing and actually producing a new blade or tip.

eTa Blades has established the production facility in Fano, on the eastern cost of Italy next to the Adriatic sea, within the most important Italian naval district. This further enables our competitiveness in terms of cost, access to key suppliers, to all logistics and highly skilled resources.

With its covered 5,500 sqm and 3,000 external warehouse, nabla wind hub can manage high volumes of blade manufacturing.

The facility is equipped with attractive features among which:

  • 5 axes machine centre for quality epoxy monolithic modular 20mm post-cured 80C° mouldings for blades up to 45m
  • Paint cabin for all relevant finishing procedures specific finishing cycles while respecting all HSE requirements
  • Kuka fot T-Bolts, root machining up to 3m diameter