To have a better discussion I will now number Peter Lynn’s claims:
[Skipping the onboard energy gen for now]
[Also skipping over “has not shown to be working yet” without evidence of someone trying]
- developing autonomous flying (kite auto-pilots) that will operate reliably in marginal and turbulent conditions is probably unachievable
- When there’s too much wind, above 40knots, kites cannot usually be flown safely.
- When there’s too little wind (less than 6 or 7 knots), kites fall into the water.
- Until there is 15knots or so they don’t develop useful pull.
- the ‘steady mid range winds’ that I have not often experienced in my kite flying life, not yet anyway, though I live in hope.
- It’s not believable that ‘just-in-time’, customers will accept 5 weeks plus or minus 3 weeks instead of the 10 days to-the-hour trans Atlantic delivery schedule that internal combustion power allows. And, such delayed and irregular schedules would be the reality if kites (or sails) were used now instead of diesel motors.
- As well as unacceptable reliability because of wind variability, there is a technical reason why kite power cannot be useful for commercial shipping- unless container ships change to submarine form so as to reduce their above-water-line drag profile. Aerodynamic drag is the killer. A largish container ship, with containers stacked up 15m and more above deck level can have side area above the water line of about 5000sq.m. Even if it’s kite is also 5000sq.m’s (5 x larger than any kite that’s yet been built, but probably possible), the ship’s superstructure drag will reduce the efficiency of the kite/line/ship system (measured by lift to drag ratio, L/D) to less than one, and options for upwind courses will fade away. When other other inefficiencies, such as hydrodynamic drag, are also allowed for, even if the apparent wind strikes the ship’s superstructure at 45degrees rather than the worst case of beam-on, upwind sailing will still not be achievable to any bankable extent.
- Fuel use per tonne km is perhaps 70 times better for a container ship than for a truck or train- they’re VERY fuel efficient.
- wind speed is never easy, and especially not over any sustained period. So, the wind speed will have to be 25knots or more if kites are to propel ships at the speeds the market demands.
[OK, so say kites are only used when the wind is appropriate by direction and strength?]
- Hmm, for downwind sailing, is the wind in a useful direction 35% of the time, and in a useable strength range for 10% of the time? Let’s be generous and say it’s going to work for one day in every 25.
- Are ships owners going to install the equipment, add extra crew, and supply specialist training for some kite assistance barely one day a month? And then there’s the associated reduced load capacity- and the downtime from running over the lines etc, and the risks to the boat itself and its crew and to other craft from out of control and escaping kites (which will happen sometimes, no matter what fail safe systems are installed) -more costs.
- Oil is so effective and efficient for ship’s propulsion that commercial shipping will be the last transport mode to switch to alternatives should oil prices ever climb to unaffordable levels again.