Electric yachts recharded by tidal flow?

[Adios]

You can't get more energy out of the system than there is in there. It doesn't matter how much gearing you do.

Yes I realise that's a basic rule. I just mean despite the slow rate of fall, the weight allows with gearing, having a very fast spinning rotor in a generator, much faster than the rotating prop on the back of a yacht which is somehow able to produce useful amounts of electricity. Thats whats surprising to me

The calculation could be off though due to your very conservative 5 ton weight of pontoon and boats. A large marina will have hundreds of tons of boats and pontoons rising and falling each tide. If it is 100 tons is that still not useful potential energy?

 

[TLouth7]

Don't forget that you can't really extract the full displacement of your yacht multiplied by the height, only the difference in displacement from equilibrium.

So if you tied a cable to the bottom of your boat that pulled down with 3T equivalent force and caused your decks to be awash you would get 3T x gravity x 5m / 6 hours = 6.8W

On the ebb you would need a cable that lifts your yacht by the same amount, leaving only the keel in the water!

 

[Sandy]

About the new electric motor equipped yachts that recharge while sailing. Will they trickle charge their batteries while a boat is on a tidal mooring? Other than a bit of slack many boats have tide flowing past the boat the whole time, some places quite fast tide. Not seeing that mentioned as a feature. Bit of a waste if its not possible for some reason. If typical tidal flow is not enough power to turn the prop perhaps a larger prop could be lowered while on the mooring?

It would be interesting to see if anybody uses a Watt and Sea like this and if they get any usable energy, I doubt it.

 

[Blueboatman]

Hmmm
Thank you Angus Mc D.. about as clear and helpful as can be ..
time to learn up ?
There was a time when I was half decent/ok at crunching energy calcs and torque and stuff .
It might even come back ( thank goodness I learnt in SI units )
Athomson, pretty good question eh!
TBC possibly

 

[JumbleDuck]

In my minds eye now I really really want to attach a solar panel driven 12v motor to 2 gears and a chain drive to deliver an actual 5w to a lift to elevate this 5t pontoon through 5m over 6 hours and see how we get on.. that’s a lot of joules needed surely , converted back into potential energy . Imagine doing it with blocks and tackle or levers or hydraulic jacks ..
Without wishing to try the patience of those who do these calculations all day every day and get paid to do it ... Something doesn’t seem right ... or is it ?

As you all say , things ain’t necessarily what they seem .

Intuition is a very deceptive , wobbly thing. ?

What it really shows is that "storing potential energy" is a a relatively small use for the power needed to lift cars and pontoons up. Friction and other losses generally account for much more.

 

[mjcoon]

Bridge? They are talking of a floating tunnel.
Floating tunnel to be assessed for Northern Ireland 'fixed link' - Marine Industry News

Boris listening? He probably is as it was reported in the Daily Mail.

Sounds like the bridges of Madison Avenue! Do the vehicles have to break step as they drive along to avoid a Millennium Bridge, or water bed, resonance effect?

 

[mjcoon]

... There's not much resistance to a generator rotor is there?

Not if the generator is open circuit!

 

[TernVI]

You can get useful work out of waves, using a yacht on a mooring, remember those bilge pumps powered by the mooring strop?

Sometimes, although the amount of power may be very small, it can be worthwhile.
A few years ago, 'energy harvesting' was a big thing in one of my client companies.
Numbers like single figures of watts may sound a bit pathetic, but you can process a lot of data with very little electricity these days. It can be worth lot of money to avoid having to send a bloke 40 miles to change a couple of AA batteries, and many ways of harvesting that power have been looked at.
Solar panels have made remote energy cheap, but they are not the answer to everything.

 

[Pete7]

Solar panels have made remote energy cheap, but they are not the answer to everything.

Agreed, today we have learnt that if you feed a forumite a chocolate eclair he can lift a ford transit 10 times. Just think what he could generate with a AC75 winch grinder and a dynamo.

 

[JumbleDuck]

Agreed, today we have learnt that if you feed a forumite a chocolate eclair he can lift a ford transit 10 times. Just think what he could generate with a AC75 winch grinder and a dynamo.

A trained athlete is good for about 500W continuous and 1kW peak.

 

[AntarcticPilot]

A trained athlete is good for about 500W continuous and 1kW peak.

Over what period? Your athlete will need to eat and sleep! So I suspect that even the 500w figure is only good for a few hours. When I was rowing I could only keep up a figure at the low end of the range for about quarter of an hour.

 

[JumbleDuck]

Over what period? Your athlete will need to eat and sleep! So I suspect that even the 500w figure is only good for a few hours. When I was rowing I could only keep up a figure at the low end of the range for about quarter of an hour.

Yes, good point. I would interpret indefinitely to mean "however long the event lasts".

 

[Daydream believer]

I do not know why you are all bothering. with all this complicated stuff.
The nuclear unit that was in the French submarine Redoubtable ( See the Museum at Cherbourg) had a fuel unit that was 1 metre * 1 metre * 1 mtere. It powered Redoubtable for circa 26 years. When they laid her up they just chopped it out & stuck it on the quayside for a while so it cannot have been that harmful. ( although some local French have been known to do some odd things with onions & little boats). So why not just have some made into 4 inch cubes & tow them in the dinghy ( 1 metre ones would be excessive for a 26 ft yacht)
Think of the advantages- ie no nav lights, you would glow all day & night. No one would come near you at anchor, Peace You would not need heating in the winter, free boiling water for the tea & most of all, no need to refuel for a thousand years ( unless you do a lot of motoring) Finally if we adopted a decent policy towards generation of electricity , you would not have to navigate around those horrid fans in the Thames estuary making all that excessive wind & I could find my way home at night by the lights on Bradwell power station again

 

[Deleted member 36384]

There was a turbine device fitted to navigation buoys that charged batteries. As the buoy rose up and down on the swell, air was sucked in, pushed out of a tube that passed through the buoy. The air movement spun a small turbine that charged a battery. I may be miss-remembering but I am sure that was how it worked. If the river pontoon was designed such that it was not stable, but moved a lot, I guess no longer being a pontoon, that movement could be used.

Real Life Food: Calorie, Weight Gain, Loss

A standard sized Mars Bar is one hour running at a moderate speed on a treadmill, about 369 Calories.

A Chinese Takeaway, Chicken monosodium glutamate plus chips, is 2 1/8lbs of weight increase, a 4 hour hill walk on one day and near fasting on the following day, to get rid of again.

 

[Adios]

There was a turbine device fitted to navigation buoys that charged batteries. As the buoy rose up and down on the swell, air was sucked in, pushed out of a tube that passed through the buoy. The air movement spun a small turbine that charged a battery. I may be miss-remembering but I am sure that was how it worked. If the river pontoon was designed such that it was not stable, but moved a lot, I guess no longer being a pontoon, that movement could be used.

Ah those f***ing mini finger pontoons that sink 3 foot when you step one leg onto them leaving the over leg hung up over the guard rail. Now they have a use!

 

[Daydream believer]

Ah those f***ing mini finger pontoons that sink 3 foot when you step one leg onto them leaving the over leg hung up over the guard rail. Now they have a use!

Well some people step over the guard rail & put both feet onto the gunwale first. ( assuming that they are not posh enough for a gate) Then step on to the wobbly pontoon--- before falling in.
Which is another reason not to line the whole side of the boat with horrid netting, so you cannot get your foot in .

 

[Adios]

Well some people step over the guard rail & put both feet onto the gunwale first. ( assuming that they are not posh enough for a gate) Then step on to the wobbly pontoon--- before falling in.
Which is another reason not to line the whole side of the boat with horrid netting, so you cannot get your foot in .

It depends what the person is used to, the first time I came in next to one of these buoyant only for its own weight finger pontoons I'd only ever encountered properly buoyant ones which look identical. Some bright sparks idea to save a few quid at the expense of many a sailors split trousers!

 

[dom]

A trained athlete is good for about 500W continuous and 1kW peak.

500W is a little high, pro athletes I think tend to to have a functional threshold power (FTP) of a little over 5W/kg , so that's circa 400W for a 75kg man. I.e. what they can whack out for an hour continuous.

Curiously though, peak power is through the roof for top sprinters: as you say 900W over a minute is about right, rising to a whacking 1900W over 5 seconds for that same 75kg bloke!

Not bad!

 

[Daydream believer]

It depends what the person is used to, the first time I came in next to one of these buoyant only for its own weight finger pontoons I'd only ever encountered properly buoyant ones which look identical. Some bright sparks idea to save a few quid at the expense of many a sailors split trousers!

Clearly not sailed to many French ports then.
Made more fun by the fact that they have hoops on the end so one has to get on one's hands & knees to get the line through the hoop then stand up again whilst the pontoon does its best to throw you in the oggin & the boat drifts away as if deliberately trying to avoid giving any side support.
If the pontoon decking is cheese grater metal mesh it adds to the pain in the aged knees & makes falling in a blessed relief
I am surprised that Dave Selby has not made an article about it in PBO magazine