[Geezer]

Wait a minute! I realized something just after my last post.

Mootle could be short-changing himself. His system is supposed to be tidal, but is it really? There is no doubt that the tide is a major element here, but what about waves?

If the pontoons(s) are not too enormous, they will also be lifted by any ocean swell, and each time the swell lifts the pontoon, the turbmarine (sorry []) will get cranked a bit lower. It might actually descend much faster than we think. It's a question of sizing the pontoon relative to the wavelength of the swell.

I bet Mootle already knew that and he was just waiting to see if we could figure it out. (Oops! I hope I didn't put my foot in it again.)

[Mootle (OP)]

I should have added that Mootle really only needs to specify the pontoon's displacement and the tide height.

EDIT: I forgot to factor in the efficiency of the generator! That might knock off another 10% perhaps? 80% efficiency to get to kWh might be more realistic.

Most mathematicians (worth their salt at least,) would run check calculations - this is a healthy thing for engineers to do as well, so I'm grateful for the grilling. As it is we have now completed three checks and it has been demonstrated that the original claims are sound. Once again, I apologise for my part in the misunderstanding by not making it clearer in my presentation. It would be good to move forward, if we can so that our time here is used productively.

[imatfaal]

I should have added that Mootle really only needs to specify the pontoon's displacement and the tide height.

EDIT: I forgot to factor in the efficiency of the generator! That might knock off another 10% perhaps? 80% efficiency to get to kWh might be more realistic.

Most mathematicians (worth their salt at least,) would run check calculations - this is a healthy thing for engineers to do as well, so I'm grateful for the grilling. As it is we have now completed three checks and it has been demonstrated that the original claims are sound. Once again, I apologise for my part in the misunderstanding by not making it clearer in my presentation. It would be good to move forward, if we can so that our time here is used productively.

Peter - I speak as a company executive who proposes, evaluates, and decides upon projects of this sort of size - your proposal is not sound. 

Even using the most generous evaluations of set-up costs, zero running costs, and "free" tidal energy this idea will not make money and would be a burden upon any authority that tried to promote it.

1.  Tidal power obtained through a floating pontoon could be better harnessed through land based power generation (per BC suggestion or others)
2.  Most places with significant tides also have significant currents - this will add to the cost - but more importantly to the danger.  You will have SWR under working loads - add currents to this and you have the risk of breaking cables.  You will need mariners and engineers on site to deal with problems and these men's safety has to be paramount - most masters would not dream of tying up alongside another vessel in open seas, let alone a complicated system of tying both to the ocean floor and to other sections of the floating pontoon
3.  the environmental impact would be vast - you are talking about a fifth of a million tonnes of steel in the ocean.  all of which need anti-fouling, anti-corrosion, and regular structural integrity checks.

All in all it is a huge undertaking, expensive and technically difficult. 

[Mootle (OP)]

Right, now we have an agreed set of data.
The weight of the pontoon is g * rho * V
9.81 m/s/s * 1025 kg/m^3 *  1,675,000m3
So the weight is 1.68 E 10 Newton
It travels up 2 metres on each tide so that's
3.36 E 10 Joules

Lets all agree on something here.
That, if I have got the arithmetic correct, is all the energy that the tide provides to the system, so that's all the energy that could ever hope to get into the turbines and thus to the generator and eventually as electricity. In fact it will be less than that but, since it's not my field, I can't come up with a realistic guess for the efficiency so I will pretend it's 100%. We can always allow for that later.
It does that every 12 hours
i.e. every 43200 seconds

So the mean power is 0.78 MW.

The air conditioning system where I work takes more power than that.
Now you can get that power from this system, but it needs, at the very least a big metal box as the float.
That box has to displace nigh 1.7 million tonnes of water. So it's at least comparable with building some large tankers or buying them as scrap (probably not a great move- they will have been scrapped for a reason). You will need about six of them.
That's roughly $120M

It's never going to pay.

0.78MW
6833 MW Hr per year.
At £47/ MW Hr
£300,000
Lets assume that a bizzare government subsidy pays 5 times the going rate (that's rather more than all your figures added together)
If you  invest $120M or £75M  you could- with no other building costs and no allowance for the other infrastructure like the pulleys , not maintaining it nor building labour.... and with absurdly generous subsidy and assuming 100% efficiency get a return of £1.5M

2%

LOL

I'm glad that we now have a comparable view of the systems energy and rating.

Based on your financial analysis no renewable energy system would get off the ground. In fact I doubt any traditional system would either. The challenge is to get a Return on Investment, RoI within a reasonable time period. I've indicated the revenue for (10) systems (enough power for your AC and then some,) for a 20yr period as this is the period that the incentives are available for. Retail energy costs are assumed to be fixed but based on the past 12 months this is likely to be a very conservative estimate. For the idea to have a reasonable RoI the total cost would need to be less than say £100m for the (10) systems or the revenue of £208m would need to be increased to account for any cost beyond that. I haven't began to cost the system yet but experience tells me that even with best value engineering the revenue will need to be increased. Whilst wind and solar are not as reliable as this tidal system they may offer improved RoI's if the pontoon is engineered to serve multiple functions. I've noticed a number of floating offshore wind proposals around so this isn't as far fetched as it might seem. The benefit is that such a mix would improve reliability.

You might think the incentives are 'bizarre' but the reality is that we need to replace our current systems and developing new ideas costs money!

The system processes have good synergy with low cost hydrogen or fresh water production. In the future it likely that both resources will become valuable commodities.

[Mootle (OP)]

Wait a minute! I realized something just after my last post.

Mootle could be short-changing himself. His system is supposed to be tidal, but is it really? There is no doubt that the tide is a major element here, but what about waves?

If the pontoons(s) are not too enormous, they will also be lifted by any ocean swell, and each time the swell lifts the pontoon, the turbmarine (sorry []) will get cranked a bit lower. It might actually descend much faster than we think. It's a question of sizing the pontoon relative to the wavelength of the swell.

I bet Mootle already knew that and he was just waiting to see if we could figure it out. (Oops! I hope I didn't put my foot in it again.)
[/quote]

Mootle could be short-changing himself. His system is supposed to be tidal, but is it really? There is no doubt that the tide is a major element here, but what about waves?

If the pontoons(s) are not too enormous, they will also be lifted by any ocean swell, and each time the swell lifts the pontoon, the turbmarine (sorry []) will get cranked a bit lower. It might actually descend much faster than we think. It's a question of sizing the pontoon relative to the wavelength of the swell.

I bet Mootle already knew that and he was just waiting to see if we could figure it out. (Oops! I hope I didn't put my foot in it again.)

I'm sorry to dash your spirits but the idea started with wave theorem. This is an active topic of research in itself, I was especially interested in one company which is developing wave prediction technology, that could be used in conjunction with renewable wave power technology amongst other applications.

However, I soon realised that for a meaningful power output, wave power could not play a big part for the Buoyancy Engine, mainly because the Pontoon will be so big. This is made worse since it is beneficial for the Pontoon to be a shallow profile, i.e., cover a wide area in order to minimise sinkage losses.

[Mootle (OP)]

I should have added that Mootle really only needs to specify the pontoon's displacement and the tide height.

EDIT: I forgot to factor in the efficiency of the generator! That might knock off another 10% perhaps? 80% efficiency to get to kWh might be more realistic.

Most mathematicians (worth their salt at least,) would run check calculations - this is a healthy thing for engineers to do as well, so I'm grateful for the grilling. As it is we have now completed three checks and it has been demonstrated that the original claims are sound. Once again, I apologise for my part in the misunderstanding by not making it clearer in my presentation. It would be good to move forward, if we can so that our time here is used productively.

Peter - I speak as a company executive who proposes, evaluates, and decides upon projects of this sort of size - your proposal is not sound. 

Even using the most generous evaluations of set-up costs, zero running costs, and "free" tidal energy this idea will not make money and would be a burden upon any authority that tried to promote it.

1.  Tidal power obtained through a floating pontoon could be better harnessed through land based power generation (per BC suggestion or others)

You may prove to be right based on the current presentation. However, whilst I value your input before I give the idea up I need to work this thing through to a conclusion one way or the other. This includes value engineering and costing a scaled model and looking at ways to improve the revenue.

2.  Most places with significant tides also have significant currents - this will add to the cost - but more importantly to the danger.  You will have SWR under working loads - add currents to this and you have the risk of breaking cables.  You will need mariners and engineers on site to deal with problems and these men's safety has to be paramount - most masters would not dream of tying up alongside another vessel in open seas, let alone a complicated system of tying both to the ocean floor and to other sections of the floating pontoon

There are a number of associated acronyms for SWR, please advise which one you mean to allow me to directly address that concern.

As for safety of the operators I would entirely agree that their safety is paramount. I would not allow any design carrying my name to reach the market without an indepth design, construction and operation risk assessment. This would include compliance with associated regulations and collaboration with marine experts and Ship Masters alike. I would expect this to include: tension monitoring of the cables and anchorages, position monitoring of Cables / Storage Vessel / Pontoon in order to alarm in the event of any operation outside of design tolerance. Cables would be designed for the dynamic loading including plenty of redundancy. I would tend to follow existing protocols for oil rig maintenance, i.e., all systems would be within helicopter range although ship to Pontoon transfer would be facilitated via rib. I would foresee living accommodation pods for longer stay. All power technologies carry risk (Exxon Valdez oil spill,Fukushima Daiichi nuclear disaster...) and this is no exception. Fail-safe mode would need to be carefully considered and incorporated into the costings. For instance, the reason I'm looking toward submarine design is that the separate ballast / main storage tank, SV i.e., if there was an issue with the SV ascending too quickly the ballast tanks could be used as a secondary means to regulate the rate of ascent - if that doesn't work there would also be a skuttle option (recovery options would be engineered). The Pontoon would be tethered to cater for a loss of tension....

I haven't got around to evaluating the risks in depth but to date haven't seen anything that was beyond mitigation.

3.  the environmental impact would be vast - you are talking about a fifth of a million tonnes of steel in the ocean.  all of which need anti-fouling, anti-corrosion, and regular structural integrity checks.

All in all it is a huge undertaking, expensive and technically difficult. 

I agree, this is not a small undertaking but as an engineer I love a good challenge. Whilst steel will obviously form a part of the structure, the value engineering will establish the best use of materials. I've already covered a number of the issues but please quote against any reply which didn't go into sufficient detail. In environment terms I would be keen to evaluate the carbon return rate, i.e., care would be taken to manage the embedded carbon of the system as well as the financial cost. Part of the Environmental Impact Assessment would be to use materials that are conducive to establishing and encouraging marinelife. I've followed various studies including skuttling of ships and coral reef promotion which have enhanced the environment rather than detract. I would look to collaborate with the teams who were involve such that the Pontoon design would effectively become a sanctuary for wildlife.

Thank you for your input, it really helps me to understand the issues that prospective investors will be interested in.

[imatfaal]

SWR = Steel Wire Rope

Peter - I think we all appreciate your enthusiasm for this, but you are missing all the power-economic realities involved. 

As one mad example - I have suggested using old ships as your pontoon (I really think you would struggle to find anything even close in price that could withstand years at sea).  Even if you could pick up 7 large tankers FOR FREE - if we assume that you have to move the ships an average of 2000nm to install them (which is fairly generous, eg sale could be in England but more likely in India) then you have to put into consideration the fuel cost.  You would have to burn about 4000 barrels of fuel oil to get the ships that distance - that's about 6750 MWh worth of fuel.  In either an economic or a carbon review it soon shows that even getting the ships in position costs more in energy than your system produces in a year! 

we need either cheap systems that generate small "household size" amounts of power - or expensive systems that generate large "town size" amounts of power; but expensive set-ups that provide only tiny power returns are just a waste of time, money, and probably energy.

[Mootle (OP)]

SWR = Steel Wire Rope

Peter - I think we all appreciate your enthusiasm for this, but you are missing all the power-economic realities involved. 

As one mad example - I have suggested using old ships as your pontoon (I really think you would struggle to find anything even close in price that could withstand years at sea).  Even if you could pick up 7 large tankers FOR FREE - if we assume that you have to move the ships an average of 2000nm to install them (which is fairly generous, eg sale could be in England but more likely in India) then you have to put into consideration the fuel cost.  You would have to burn about 4000 barrels of fuel oil to get the ships that distance - that's about 6750 MWh worth of fuel.  In either an economic or a carbon review it soon shows that even getting the ships in position costs more in energy than your system produces in a year! 

we need either cheap systems that generate small "household size" amounts of power - or expensive systems that generate large "town size" amounts of power; but expensive set-ups that provide only tiny power returns are just a waste of time, money, and probably energy.

Your idea to use old stock was useful in that it gives a useful budget but I don't think this would be useful for a working solution. The design would have to be bespoke to cater for the forces involved and the function, although lessons learned would be taken from a number of vessels that approximate to the desired function. All things considered a new build approach would be best.

I have researched various types of cable systems, there are a number of options including synthetic and cast iron. I will investigate the options further as part of the scaled application but as I indicated earlier the safe loading and testing of cables can all be managed through planned maintenance regimes.

All renewables technologies seem to have one thing in common, they only start to make sense when they are scaled up and even then nothing can be taken for granted and the particular circumstances have to be fully considered. Economies of scale is really important and the kind of reality check you guys are giving is much appreciated. However, having been involved in many renewable schemes, I tend to remain open minded until all avenues have been explored. 

I agree with much of the advice that has been given and that this would not be a venture without its challenges.

Then again nobody ever said it would be easy!

[Bored chemist]

The forum software does not support a large enough font size to be appropriate for the word "Bollocks!"  in response to " As it is we have now completed three checks and it has been demonstrated that the original claims are sound. ".
 Ditto "Based on your financial analysis no renewable energy system would get off the ground.".

" I haven't began to cost the system yet "
You don't need to. We already did and it's goosed before it starts.
"For the idea to have a reasonable RoI the total cost would need to be less than say £100m for the (10) systems"
But the cost is more than that for 1 system, never mind 10.
And the only way for the revenue to rise is for the price of electricity to rise. Now, just before you say "OK, All I have to do is wait", remember that much of the cost of the project is an indirect energy cost. For example it takes lots of energy to make steel or concrete so, if the price of energy rises, so does the cost of the project.
This will never work.

When you say "You might think the incentives are 'bizarre' but the reality is that we need to replace our current systems and developing new ideas costs money! " you are missing the point.
It's true that, for example, early solar cells were so expensive that only NASA used them (and it didn't use more than it could get away with). Decades of research means that solar cells are nearly competitive  with more conventional power. Perhaps they are better value than coal fired electricity if you consider the cost of transmission and  global warming (and I'm just not getting into that debate here: if you are unhappy about it, just remember I started the sentence with "perhaps").

They needed new ideas and, as you say, "developing new ideas costs money".
But your idea isn't new.
There's nothing about it that is not mature technology.
Ropes, pulleys, and barges have been around for a while. Even hydroelectric generators are not new.

What developments would you put on your "wish list" that would actually make your system anything other than a white elephant?

Furthermore, you seem not to have noticed that not all things benefit from economies of scale.
Making your design 10 times bigger makes it more than 10 times more expensive, but only produces 10 times more power. The reason it gets more expensive is the law of diminishing returns. If I want to buy a used tanker I will get the cheapest one I can find that still floats, it will cost me X million, but if I want to buy another tanker  t will cost more (because I already bought the cheapest one). The sixth tanker is going to cost me a lot more than the first. Your "plan" calls for something like 60.
I doubt there are 60 scrap oil tankers on the market at any time, so you will have to start buying newer ones to make your project bigger. The power output increases linearly with the number of ships but the cost increases faster than that.
The bang per buck falls as the system gets bigger.

On a good day with a following wind you might convince me that this system would be viable in the Antarctic, but only on a smallish scale. A research station might be able to get by on 250KW.
You could use an iceberg instead of old oil tanker.
In principle the idea is non polluting, and politically, that might make it an acceptable power source where people really really don't want a diesel spill.

It still wouldn't compete with mains electricity prices in the UK- but it might be cheaper than 12000 miles of extension leads.

There may be some other niche market for this but that's the opposite of an economy of scale.

[Geezer]

Perhaps we should lock this thread before it becomes contentious?  []

After all, it's really just a promotional plug for Mootle's patent. Mind you, the feedback he's getting isn't exactly what you'd call "promotional" so we probably don't need to worry about that.

[Bored chemist]

Since this discussion is public domain information, his chances of patenting it are less than the chances of it making any money.
It would seem impolite to lock it without giving him a last chance to defend it and I'd hate to start another of those "The establishment are against me! Look! they even locked my thread!" farces. (I know, they usually use more exclamation marks, but I can't bring myself to do that, even for effect)

[Mootle (OP)]

..." I haven't began to cost the system yet "
You don't need to. We already did and it's goosed before it starts.
"For the idea to have a reasonable RoI the total cost would need to be less than say £100m for the (10) systems"
But the cost is more than that for 1 system, never mind 10.
And the only way for the revenue to rise is for the price of electricity to rise. Now, just before you say "OK, All I have to do is wait", remember that much of the cost of the project is an indirect energy cost. For example it takes lots of energy to make steel or concrete so, if the price of energy rises, so does the cost of the project.
This will never work.

The system hasn't been costed and even the budget costs that were suggested are open to debate. For instance here http://www.marinelog.com/index.php?option=com_content&view=article&id=1280:increasedscrapping30august2011j01&catid=1:latest-news&Itemid=107 some indicative costs are given for VLCC's. A 2000 281,050DWT measuring 330m*60 is valued at $36m. The height is not given but I would guess somewhere between 50 - 100m, or 990,000m3 - 1,980,000m3, i.e., only one would be needed  - but as per previous posts I would not persue the idea to modify, the system would need to be a new build. There are many possibilities to value engineer and increase revenue but since you seem have disregarded the examples given I will not expand on the point. You will note from the description given in the link that this tanker is double skinned to provide protection from spillage. The Pontoon would not require an expensive propulsion or fuelling system, it only requires a single skin plus gantries, although it would be a sensible precaution to compartmentalise. Also, the DWT is what it can safely carry whereas the ideal Pontoon would be almost entirely immersed when loaded.

When you say "You might think the incentives are 'bizarre' but the reality is that we need to replace our current systems and developing new ideas costs money! " you are missing the point.
It's true that, for example, early solar cells were so expensive that only NASA used them (and it didn't use more than it could get away with). Decades of research means that solar cells are nearly competitive  with more conventional power. Perhaps they are better value than coal fired electricity if you consider the cost of transmission and  global warming (and I'm just not getting into that debate here: if you are unhappy about it, just remember I started the sentence with "perhaps").

They needed new ideas and, as you say, "developing new ideas costs money".
But your idea isn't new...

I agree, bringing global warming into this debate wouldn't be helpful. I'm developing the idea because resources are running out for conventional power generation.

As explained the idea is currently patent pending and the searches indicate that it is a new idea but we will await the outcome of the process to see if the patent is awarded. Solar PV is still a poor investment (in the UK) unless FIT's are taken into account.

There's nothing about it that is not mature technology.
Ropes, pulleys, and barges have been around for a while. Even hydroelectric generators are not new.

What developments would you put on your "wish list" that would actually make your system anything other than a white elephant?

I agree, the technology and know how already are well tested for many of the elements of the idea - this is good news, but there are various aspects of this application that we haven't touched on that would require development.

Furthermore, you seem not to have noticed that not all things benefit from economies of scale.
Making your design 10 times bigger makes it more than 10 times more expensive, but only produces 10 times more power. The reason it gets more expensive is the law of diminishing returns. If I want to buy a used tanker I will get the cheapest one I can find that still floats, it will cost me X million, but if I want to buy another tanker  t will cost more (because I already bought the cheapest one). The sixth tanker is going to cost me a lot more than the first. Your "plan" calls for something like 60.
I doubt there are 60 scrap oil tankers on the market at any time, so you will have to start buying newer ones to make your project bigger. The power output increases linearly with the number of ships but the cost increases faster than that.
The bang per buck falls as the system gets bigger.

This point has already been covered earlier - this is a new build project and most suppliers do tend to reduce their selling price when they have a larger order to deal with.

On a good day with a following wind you might convince me that this system would be viable in the Antarctic, but only on a smallish scale. A research station might be able to get by on 250KW.
You could use an iceberg instead of old oil tanker.
In principle the idea is non polluting, and politically, that might make it an acceptable power source where people really really don't want a diesel spill.

It still wouldn't compete with mains electricity prices in the UK- but it might be cheaper than 12000 miles of extension leads.

There may be some other niche market for this but that's the opposite of an economy of scale.

Interesting but sadly there are few opportunities for tidal in the Antarctic owing to the lack of tidal range (refer to link). My focus is on the UK where there are good opportunities owing to the continental shelf.

http://www.seafriends.org.nz/oceano/tides.htm

[Mootle (OP)]

Since this discussion is public domain information, his chances of patenting it are less than the chances of it making any money.
It would seem impolite to lock it without giving him a last chance to defend it and I'd hate to start another of those "The establishment are against me! Look! they even locked my thread!" farces. (I know, they usually use more exclamation marks, but I can't bring myself to do that, even for effect)

You & Geezer do make me smile  []

I really don't mind a harsh review (once the facts support,) or even profanities after all you only let yourself down.

As I said a while back, I'm happy to step back from this thread for the time being whilst I develop the idea.

Once again, many thanks for your input.

BTW if your gearbox idea does turn out to be beneficial and the idea does confound your expectations and go onto make money I will be sure to recognise your contribution.

[Mootle (OP)]

Perhaps we should lock this thread before it becomes contentious?  []

After all, it's really just a promotional plug for Mootle's patent. Mind you, the feedback he's getting isn't exactly what you'd call "promotional" so we probably don't need to worry about that.

Interesting, promotion was the last thing I was considering - the presentation isn't ready for that and I would not consider a forum like this as a good place to promote once it is. However, you should realise that promotion works both ways and perhaps one lesson you could learn from this is not to be so quick to assume that people posting know less than you. Instead you could make room for genuine posters who simply want to conduct an honest review of an idea to help with development, because they believe many minds are better than one.

[Geezer]

Perhaps we should lock this thread before it becomes contentious?  []

After all, it's really just a promotional plug for Mootle's patent. Mind you, the feedback he's getting isn't exactly what you'd call "promotional" so we probably don't need to worry about that.

Interesting, promotion was the last thing I was considering - the presentation isn't ready for that and I would not consider a forum like this as a good place to promote once it is. However, you should realise that promotion works both ways and perhaps one lesson you could learn from this is not to be so quick to assume that people posting know less than you. Instead you could make room for genuine posters who simply want to conduct an honest review of an idea to help with development, because they believe many minds are better than one.

An honest review is only likely to be conducted on an honest and complete design specification. If a design is presented with an incomplete specification, the reviewers are obviously going to conclude that the design is also incomplete.

The lesson is that if you want a proper review, present proper data.

Mootle, I've already asked you to send me your observations by PM. Any more in-thread "editorials" and this thread will be locked.

Now, does anyone wish to add anything that helps to answer the question,

"Will this buoyancy engine-based generator work?"

[imatfaal]

The system hasn't been costed and even the budget costs that were suggested are open to debate. For instance here http://www.marinelog.com/index.php?option=com_content&view=article&id=1280:increasedscrapping30august2011j01&catid=1:latest-news&Itemid=107 some indicative costs are given for VLCC's. A 2000 281,050DWT measuring 330m*60 is valued at $36m. The height is not given but I would guess somewhere between 50 - 100m, or 990,000m3 - 1,980,000m3, i.e., only one would be needed  - but as per previous posts I would not persue the idea to modify, the system would need to be a new build. There are many possibilities to value engineer and increase revenue but since you seem have disregarded the examples given I will not expand on the point. You will note from the description given in the link that this tanker is double skinned to provide protection from spillage. The Pontoon would not require an expensive propulsion or fuelling system, it only requires a single skin plus gantries, although it would be a sensible precaution to compartmentalise. Also, the DWT is what it can safely carry whereas the ideal Pontoon would be almost entirely immersed when loaded.

What sort of engineer in this field thinks that a vessel that can carry 281 thousand tonnes has a displacement of 1.9 million tonnes!

  I told you that you needed about 7 vlccs and you do.  The deadweight - as I think I already mentioned - is the usable displacement (the total displacement less the steel weight, constants, and a safety margin).  The displacement of the tenzan will be about 360000 mt - but it will have about 25-30000 mt of steel, extras and you need a safety margin.  the double skin nature of takners does not massively increase the amount of steel needed - as the construction methods were changed to use the structural integrity of the double skin rather than needing extensive interior tank walls.   

For a new build you need to put your steel costs up by around 30-50 % and yard space will double the cost.   

This point has already been covered earlier - this is a new build project and most suppliers do tend to reduce their selling price when they have a larger order to deal with.

Not really no - in the consumer market perhaps - but in the commercial world most prices have been driven pretty far down already.  If one project requires 10000 metric tonnes of steel you might be able to negotiate a few tens of dollars off your price if order 10 - but you ain't gonna get much, both the steel mill and the building yard are already operating on very slim margins

I agree, bringing global warming into this debate wouldn't be helpful. I'm developing the idea because resources are running out for conventional power generation.

You do not seem to understand the minuscule amount of energy this produces - you would need 20,000 of them to balance just the UK's oil use (let alone our coal and our gas) - thats about one every 500 yards around the entire country!

WE do need "blue sky thinking" - but we need to be hard-nosed over which projects to bin.  There are easier, more efficient, and safer ways to exploit tidal power

[Mootle (OP)]

...Mootle, I've already asked you to send me your observations by PM. Any more in-thread "editorials" and this thread will be locked....

It was a very kind offer but I didn't realise that we were breaking any house rules?

As far as I'm concerned this thread has been a simple series of Q&A's for which I'm most grateful.

Lock the thread or leave it to run its course - I really don't mind, either way I'm sure you will have your reasons.

[Mootle (OP)]

What sort of engineer in this field thinks that a vessel that can carry 281 thousand tonnes has a displacement of 1.9 million tonnes!

  I told you that you needed about 7 vlccs and you do.  The deadweight - as I think I already mentioned - is the usable displacement (the total displacement less the steel weight, constants, and a safety margin).  The displacement of the tenzan will be about 360000 mt - but it will have about 25-30000 mt of steel, extras and you need a safety margin.  the double skin nature of takners does not massively increase the amount of steel needed - as the construction methods were changed to use the structural integrity of the double skin rather than needing extensive interior tank walls. 

The Pontoon will not bare a significant resemblance to the vessel design upon which a budget comparison is being drawn and as such I would not consider such a vessel for reuse in this application. You are correct that based on DWT (7) vessels would be required (I'm sorry if I gave the wrong impression,) but since the Pontoon would not be constrained by the same sets of legislation / functionality I would anticipate various opportunities in the design / choice of materials etc., that will significantly reduce the gross volume of the Pontoon to achieve the required buoyancy.

For a new build you need to put your steel costs up by around 30-50 % and yard space will double the cost.

As previously indicated, steel would form part of the design but I would look to employ alternate materials to augment the Pontoon construction.

You do not seem to understand the minuscule amount of energy this produces - you would need 20,000 of them to balance just the UK's oil use (let alone our coal and our gas) - thats about one every 500 yards around the entire country!

WE do need "blue sky thinking" - but we need to be hard-nosed over which projects to bin.  There are easier, more efficient, and safer ways to exploit tidal power

I think this type of tidal energy storage has a place in the future energy mix. Hydropower does already exist but there are limited opportunities available for this in the UK. Once I have some meaningful costings and have reviewed the revenue potential I would look to compare with similarly rated dam projects.

I would agree that this technology alone would not be a suitable to replace oil and it goes without saying that the business case must stack up. I just think it is too early to draw conclusions at this time.

[Bored chemist]

"The Pontoon will not bare a significant resemblance to the vessel design upon which a budget comparison is being drawn"
I rather suspect it will. It might be more square in plan and it won't need a pointy front end, but essentially a ship is a big box that floats and so is your pontoon.
The shipwrights have spent the whole of history learning how to do that. If you think you can do better I'm willing to bet you are mistaken.

I asked earlier what you would like future development to improve on so this idea becomes viable.
I'm still waiting.
You can't change the tide and, as I have said, a rise in electricity cost won't help much.
All you can change are the construction materials and the method.
However those materials and methods have been with us for decades (at least) and millennia in some cases.
Do you really foresee an order of magnitude drop in the price of steel?
Do you think that the concrete that holds the pulleys down will become cheaper to make or pour?

Clearly, to make your idea work there has to be a major change somewhere and that change has to make your system a lot cheaper.

What do you think can make it work?

[Geezer]

For a bit of levity, I was about to make a phony post by Sheepy (who had to temporarily "borrow" Geezer's account) suggesting that "ewe might use a lot of balloons" when it struck me that there could be a problem here.

Hopefully Mootle already has it figured out, but, as I see it, you couldn't actually use a supertanker (or whatever the "official" nautical jargon is according to Admiral Matt). A supertanker (wash my mouth out with soap and water) is only capable of displacing its er, displacement, when it's full of a liquid.

If you were to attach a whopping great cable to a rather large eyebolt on the bottom of an empty supertanker's (wash etc) hull and drag it down towards the seabed, I'm PD sure the ensemble would fold like a cheap suit, bow up, stern up, midships submerged, assuming it didn't immediately split in two.

A loaded supertanker (yeah, yeah yeah) is a lot more like a constrained blob of oil than a solid object. On the other hand, the pontoon has to be submerged with pretty much nothing in it. That suggests to me that it's going to need a lot more steel to prevent it from collapsing, or maybe Sheepy had the right idea.