The cost of running a shipping
line is not only about variable costs like fuel
Time will always be a factor because you have to pay crews, pay insurance
, pay for depreciation, pay for maintenance
and pay for the cost to build the vessel. The faster a ship can move cargo to its next destination
the more money
it makes because it can then turn around and move more cargo to the next destination
. The more total cargo a ship can make in a given time period, the more money
it stands to make over its useful lifetime.
There are both fixed and variable costs associated with operating a ship. The fixed costs are accruing whether the ship is sitting at the dock
or making way. A ship tied to the dock
is not making any money. Its losing money. Therefore a ship moving 5 knots under sail versus a ship moving 20 knots under power is better able to pay its fixed costs and make more money for its owners/shareholders.
A sail powered cargo ship is a great idea in theory but there are a lot of practical considerations. One such consideration is that a ship generates a great deal of apparent wind
which shifts the wind
direction forward which makes a kite all but worthless, unless you have a very strong true wind from abaft of the beam. This brings up the question of how often would a kite be usable? Would the savings in fuel
offset the increase in fixed costs?
I'm speaking from a business perspective and not an environmental perspective obviously. The shipping business though is so competitive that they have to think money and costs just to stay alive. If a kite is going to increase their costs overall then I would think that idea would go right out the window.