**How many wind turbines per sustainable airliner?**

‘Sustainable aviation’ assumes emission-free flying on hydrogen generated with green electricity, for example by wind turbines. How many modern offshore wind turbines are needed to fuel one passenger plane?

Aviation expert Joris Melkert (Faculty of Aerospace Engineering) answers that question: "On the site planestats.com you can find all kinds of data. If I take as an example a Boeing 787-10, the largest version of the Dreamliner, a type that KLM also flies, you can estimate quite a bit. That site says that this type uses 1753 gallons of kerosene per hour. On average, long-haul aircraft fly 12.8 hours a day. That's per year in energy then: 1753 gallons per hour * 12.8 hours per day * 365 days per year * 3.78 litres per gallon * 0.81 kg per litre kerosene * 43 megaJoules per kg kerosene = 1.078*10^15 J/year. The efficiency of kerosene is about 35% when used in a jet engine.

Remarkably, this is also exactly the same as electrolysis combined with a fuel cell. An electrolyser has an efficiency of say 70%, a fuel cell 50%. Their combination is 70% * 50% = 35%. So the energy from kerosene and electricity is directly comparable.

Suppose the power comes from a modern offshore wind turbine with a capacity of 15 MW and a capacity factor of 50% (according to IEA). On an annual basis, that produces: 15 MW * 50% * 3600 s/hour * 24 hours/day * 365 days/year = 2.365*10^14 J/year.

That means it takes 1.078*10^15 / 2.365*10^14 = 4.55 wind turbines for one sustainable Dreamliner."

So the correct answer is: **5 wind turbines per aircraft. **