Increasing lengths of wind turbine blades make it possible to increase annual energy production (AEP), reduce the overall cost of wind power, and open up lower wind-speed sites for development.
But as turbine component sizes increase, logistical constraints can either reduce the number of developable sites or elevate costs, which can make some projects economically uncompetitive, researchers at DNV GL explained.
Therefore, solutions to logistical challenges are needed as increasingly large blades are manufactured.
The largest blades installed in the US are currently 67 metres, DNV GL noted. But in Europe, blades of up to 88.4 metres have been deployed, and lengths exceeding 100 metres are expected.
In a study for the US department of energy's (DOE's) Lawrence Berkeley National Laboratory, researchers highlight three pathways to help identify high-value research and development opportunities: innovative transportation, segmented blades and on-site manufacturing.
The most promising transportation solutions include using lighter-than-air (LTA) airships or controlled blade bending — the bending of blades to navigate curves — ahead of transportation by rail, DNV GL stated.
If certified and commercialised, LTA airships could be used to transport blades across the US in a cost-competitive way, the researchers found.
Although there are active commercial efforts to bring this technology to market, there is uncertainty about the timing and cost of this option, DNV GL added.
There would also be concerns that the landing area or terrain flatness required for airships might be insufficient at some sites.
In theory, controlled blade bending could also be used ahead of transportation by rail, the researchers suggested. Developing slenderer blades would better facilitate this method of transport, they added.
However, this loading method has not been established in blade design and transport infrastructure has not been developed to enable it, they added.
Segmented or modular blades have the ability to enable supersized blade deployment across the entire US, DNV GL concluded.
However, segmented blades can increase system LCOE (levelised cost of energy), the researchers added, and so cost savings would need to be made elsewhere. This approach to blade manufacturing would enable more cost-effective transport, the researchers suggested.
A balance would therefore need to be made between increased costs of manufacturing and cost saving opportunities created elsewhere.
Temporary factories could be set up in close proximity to wind farms so that long-haul transportation and the associated costs are avoided, DNV GL suggested.
However, this approach faces economic challenges as time spent relocating and commissioning a mobile manufacturing plant would ramp up costs.
It may also increase local labour costs due to hiring and training of workers, the researchers noted.
Additive manufacturing techniques could also be used to create blade moulds or pre-manufactured blade skin panels to be used at such on-site facilities, DNV GL suggested.
Ryan Wiser, a senior scientist at the US DOE’s Lawrence Berkeley National Laboratory, said that these findings would be fed into a project assessing and prioritising technology needed for a cost-competitive 5MW onshore turbine with 100-metre-long blades.
Through research for its Big Adaptive Rotor report, the DOE seeks to identify rotor technologies and turbine design configurations to enable the next generation of high capacity factor wind farms.
DNV GL added that further research could be carried out into further areas to help increase cost-competitiveness as increasingly longer blades are produced.
Such areas include:
- Further advances in high-stiffness, low-cost materials like industrial carbon fibre and thermoplastics;
- Advanced controls and sensor technologies that could be applied to monitor or enable blade bending in transport or monitor or control segmented blade loads so that blades’ weights could be reduced;
- Reducing blade chord dimension to enable operation at higher tip speeds and improve blade transport potential.