Originally Posted by waterman46
As road vehicles have vastly different propulsion requirements, there is no point in comparing them to boats. And there is no point in comparing small boats to any very large vehicle, such as a railroad engine
or ship either.
For small boats with displacement
hulls, which need to travel long distances for several days at low speed without access to any outside sources of fuel or electricity, and with limited area for solar panels
, the only reasonable and most overall efficient solution other than wind
power is the direct drive diesel engine, with modern design of pollution reduction and high efficiency.
The topic has been discussed ad-infinitum in previous Forum posts.
I'm sorry but I don't agree with this assessment. The full electric
sailboat with regen using hydro generation and solar
is absolutely possible today and more efficient in use than the alternatives. My back of an envelope calculation earlier showed this. With 20kW of engines and an induction stove
you would need on average to generate maybe 30kWh a week. Hydro generation will get you 5-10 of those, so you need enough solar to supply 20-25kWh a week. Make it 21kWh to make the math easy, then you need enough solar to generate 3kWh a day. In the Caribbean
average daily insolation is 5kWh/m^2. The efficiency of todays solar panels
batteries is about 20%, so you will need about 3m^2 of panels
. That is easily doable on a catamaran
and not impossible on a monohull
The fossil free cruising sailboat
is possible with today's tech and in use it will be massively greener than the fossil fuelled alternative. Its just that the embodied emissions of such a boat
and its enormous initial cost (and how that money
could accomplish way more carbon abatement elsewhere) entail that while it is possible it is not advisable if your goal is saving the planet.
The full electric
displacement motorboat is a totally different kettle of fish
. Let's imagine a 45ft cat with very skinny easily driven hulls powered by two 10kw motors. You will want that boat
to be able to motor
continuously 24/7 and to be able to do that even in inclement weather
when full power is needed. Here we can ignore ships systems as the drives totally dominate the calculation. 2x10x24 is as near as makes no difference 500kWh a day including drive inefficiencies. Even with the multilayered solar panels of the future (45% efficient) capable of netting you on average 2kWh/m2 a day you are going to need 250m2 of panels. At most the footprint of a 45ft cat is 14x8=112m2. Basically you would need twice that real estate to have a hope of making this work
, but then you would have greater windage and more mass and so you would need bigger drives and thus would need even bigger panel area. It just does not work. The full electric long-range motor cruiser is just not possible with today's tech or even with tech available in the near future, period. Also for reasons outlined earlier series hybrids aren't clever either (max75% efficiency of straight diesel).
Basically, until we have commercially available hydrogen and a means of storing onboard at really high pressures SAFELY (at least 10000psi, see footnote) then the motor cruiser is stuck with diesel.
Footnote, 33kWh of hydrogen at STP is 11000 litres give or take and has the same energy content at the drivetrain as roughly 6 litres of diesel. To compress H2 to the same energy density requires storage
at 1750 atm, which is 26000psi. Let's allow 250% greater volume for storage
of the H2 than we do today for diesel. Then we need to store the H2 at 10000psi. 10000psi storage of gases is feasible with today's tech, but such containers are heavy, expensive, and not something you want to be standing next to incase of an accident