Why three blades if two blades work as well? It is all the fault of 1970s Danish garage pioneers, who insisted there needed to be three blades. NASA did experiment at the same time with 2-blades (WTS-4), but that project was cancelled under Reagan, who decided that oil was American, not wind. And now we are stuck with three blades.
Or are we? The originally Dutch company Sea Wind Technology is betting on two-blades, especially for offshore, with higher wind speeds (higher loads) and more difficult installation.
Advantages two blades:
– simpler design
– less material (50% less weight, no heavy tower/monopiles necessary)
– easier offshore transportation and mounting (just pile them up)
– simpler installation vessels, flat barges suffice
– more rotor flexibility, 2 degrees of freedom: rotating and teetering, reducing load
– 2% less electricity gain, but offset by much lower installation and operational cost
– Levelized cost (LCOE) reduction: 50%
[seawindtechnology.com] – Company site
[linkedin.com] – Two-bladed offshore turbines could cut the cost of energy by 50%
[linkedin.com] – Why two blades are better than three for floating wind turbines
[crunchbase.com] – Seawind Ocean Technology
[windpowermonthly.com] – Are three blades really better than two? (2011)
[interestingengineering.com] – The Scientific Reason Why Wind Turbines Have 3 Blades
Offshore wind hub Eemshaven in the Netherlands. After [1:30] you see an (onshore) two-bladed windturbine in operation.
[gic.nl] – Nieuw type windmolen met slechts twee wieken getest in Eemshaven