Will this buoyancy engine-based generator work?

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Offline imatfaal

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Will this buoyancy engine-based generator work?
« Reply #50 on: 24/10/2011 18:23:29 »
Peter - OK I worked it out - its just a replacement of the flow by the cross-sectional area multiplied by a rearrangement of the old suvat equation v^2=u^2+2as.

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Offline imatfaal

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Will this buoyancy engine-based generator work?
« Reply #51 on: 24/10/2011 18:28:24 »
Just recap on the economics -
1. your tank that sinks must be able to withstand 5 atmospheres pressure and hold 67000m3 of water - being very generous this tank itself will have to be constructed of about 10k mt of steel and will total about 80k m3
2. to drag this to the bottom with a ratio of 25 to 1 your pontoon which is moving by 2m will have to displace around 2M m3
3. you will need miles of steel wire - the breaking strength of a 300m 42mm steel wire rope is about 900k N but the safe working load is around 200k N

1.  your tank will cost 5 million bucks in steel alone
2.  easiest way to get 2M m3 of floating pontoon is to buy 7 vlccs (large tankers not supertankers) - scrap price of about 20 million bucks each
3.  i seem to remember that each SWR costs us about 5,000 bucks and weighs over a tonne- you will be needing lots.  and these are designed for use above sea not underwater. 

Set up costs are well over 150 million bucks lets say £100M - there is just a lot of steel involved

Wholesale electricity prices last month in the uk were £47 per MWh

Your set up generates 16 MWh per day (on your calcs 2MW for 4 hours twice daily) thats an income of £750 per day

To break even at today's prices and not including interest, labour, maintenance, insurance, and downtime you would need to generate 365 days a year for 365 years
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Offline Bored chemist

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Will this buoyancy engine-based generator work?
« Reply #52 on: 24/10/2011 19:26:05 »
This is going nowhere.
Mootle,
Please tell us the numbers you are working from, in particular,
The volume of the floating pontoon,
Its rise and fall distance.
The volume of the moving tank
The number of pulleys or the vertical range of the moving tank.
The number of tides each day.

That is (more than) enough information to work out how much energy is stored each day.
For the sake of this  bit of work we can assume that water is incompressible and has a density of 1 tonne per m^3. We can also assume, to make the maths easy, that the efficiency of the turbine and generator are 100%.

Then we can have a sensible look at
(1) are you actually ignoring the rules of physics and
(2) are you ignoring the rules of economics.

Incidentally, I think for the record, that your equation is correct, provided that you are calculating the right quantity. My best guess is that somewhere or other we are at crossed purposes.
If you can give us the information above then we can all get a better look at the problem.
Imatfaal,
Your dissection of his equation is right when you say.
"your equation dissects flow into two components cross sectional area and sqrt(2.Δh.g)"

the root 2gh factor is the speed at which water would fall if it dropped down a pipe with no viscous losses.
Multiply that by an area and you have cubic metres per second.
Multiply by density and you get mass per second. Multiply by acceleration and you get force per second (an odd unit, but it's legitimate)
Multiply by distance and you get force times distance divided by time; which is work done/ time which is power.

The formula is OK. I think the values put in as the volume etc need clarification.
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Offline Mootle

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Will this buoyancy engine-based generator work?
« Reply #53 on: 24/10/2011 19:28:30 »
Just recap on the economics -
1. your tank that sinks must be able to withstand 5 atmospheres pressure and hold 67000m3 of water - being very generous this tank itself will have to be constructed of about 10k mt of steel and will total about 80k m3

2. to drag this to the bottom with a ratio of 25 to 1 your pontoon which is moving by 2m will have to displace around 2M m3
3. you will need miles of steel wire - the breaking strength of a 300m 42mm steel wire rope is about 900k N but the safe working load is around 200k N

1.  your tank will cost 5 million bucks in steel alone
2.  easiest way to get 2M m3 of floating pontoon is to buy 7 vlccs (large tankers not supertankers) - scrap price of about 20 million bucks each
3.  i seem to remember that each SWR costs us about 5,000 bucks and weighs over a tonne- you will be needing lots.  and these are designed for use above sea not underwater. 

Set up costs are well over 150 million bucks lets say £100M - there is just a lot of steel involved

Wholesale electricity prices last month in the uk were £47 per MWh

Your set up generates 16 MWh per day (on your calcs 2MW for 4 hours twice daily) thats an income of £750 per day

To break even at today's prices and not including interest, labour, maintenance, insurance, and downtime you would need to generate 365 days a year for 365 years

Imatfaal - thanks for this, I really need to get some accurate costings.

First of all I would agree that the idea has little scope for value for money if wholesale prices alone are used. Fortunately, government incentives are available for technologies such as this so we can substitute your revenue figure with the ones I gave, i.e., ca. £1m/yr or £2,8k/d including the FIT / RO and Export Values to which I can give references if required. Even so, based on your figure, the platform would need to serve additional functions such as forming a platform for wind turbines, in order to provide a return on investment within a reasonable period of time.

Secondly, whilst I like the idea of using the nearest comparison, I have no reference for the scrap value of a tanker or the Storage Vessel, so will need to research this for myself to gauge the accuracy of the information, but any references your have will be gratefully received. However, there is a lot of scope to value engineer the Pontoon, which in comparison to a tanker would be a far simpler design.

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Offline Mootle

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Will this buoyancy engine-based generator work?
« Reply #54 on: 24/10/2011 19:38:52 »
This is going nowhere.
Mootle,
Please tell us the numbers you are working from, in particular,
The volume of the floating pontoon,
Its rise and fall distance.
The volume of the moving tank
The number of pulleys or the vertical range of the moving tank.
The number of tides each day.

I have already given all of this information but once more:
The volume of the floating pontoon = 1,675,000m3
Its rise and fall distance = 2m
The volume of the moving tank = 67,000m3
The number of pulleys or the vertical range of the moving tank = 50m
The number of tides each day = 2.

That is (more than) enough information to work out how much energy is stored each day.
For the sake of this  bit of work we can assume that water is incompressible and has a density of 1 tonne per m^3. We can also assume, to make the maths easy, that the efficiency of the turbine and generator are 100%.

Sea water density is 1,025kg/m3
Generator efficiency is taken as 85%
Refer to calculation given earlier.

Then we can have a sensible look at
(1) are you actually ignoring the rules of physics and
(2) are you ignoring the rules of economics.

Incidentally, I think for the record, that your equation is correct, provided that you are calculating the right quantity. My best guess is that somewhere or other we are at crossed purposes.
If you can give us the information above then we can all get a better look at the problem.


That would be very useful - thank you.

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Offline Geezer

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Will this buoyancy engine-based generator work?
« Reply #55 on: 24/10/2011 20:37:18 »
This is going nowhere.
Mootle,
Please tell us the numbers you are working from, in particular,
The volume of the floating pontoon,
Its rise and fall distance.
The volume of the moving tank
The number of pulleys or the vertical range of the moving tank.
The number of tides each day.

That is (more than) enough information to work out how much energy is stored each day.
For the sake of this  bit of work we can assume that water is incompressible and has a density of 1 tonne per m^3. We can also assume, to make the maths easy, that the efficiency of the turbine and generator are 100%.

Then we can have a sensible look at
(1) are you actually ignoring the rules of physics and
(2) are you ignoring the rules of economics.

Incidentally, I think for the record, that your equation is correct, provided that you are calculating the right quantity. My best guess is that somewhere or other we are at crossed purposes.
If you can give us the information above then we can all get a better look at the problem.
Imatfaal,
Your dissection of his equation is right when you say.
"your equation dissects flow into two components cross sectional area and sqrt(2.Δh.g)"

the root 2gh factor is the speed at which water would fall if it dropped down a pipe with no viscous losses.
Multiply that by an area and you have cubic metres per second.
Multiply by density and you get mass per second. Multiply by acceleration and you get force per second (an odd unit, but it's legitimate)
Multiply by distance and you get force times distance divided by time; which is work done/ time which is power.

The formula is OK. I think the values put in as the volume etc need clarification.


It should always come back to work done by the tide against the pontoon. The displacement of the pontoon and the elevation of the tide defines the maximum energy that can be produced.

All the other stuff about pressures and flows is in regard to the extraction of the energy, and there are a bunch of ways of doing that, some of which may be more efficient than others. Whether we use Mootle's "Turbine in a giant submarine" approach, pump water up a hill and let it drive a turbine on the way back down, or use BC's pontoon pulling a string idea, might have some effect on the efficiency, but it won't alter the available energy one bit.

A tidal dam works the same way, except the head is the tidal variation. It has the advantage that it can have an enormous "displacement" with a very simple mechanism. Ignoring ecological implications, the downside is that the head is small which means the turbines are rather chunky.

Not having a good handle on the energy input is a bit like trying to design a coal fired power station without having any idea about how much coal it's going to burn. With any tidal system, the displacement (or water elevated) dominates the design and cost. After that, it's "simply" a question of extracting the energy as efficiently as possible.

A water turbine that's designed for the available flow and head should operate with an efficiency of at least 90%, so, to get a reasonable estimate of the energy output we can avoid a huge amount of futzing around by simply multiplying the work done by the tide on the displacement by 0.9

Any calculation that produces a significantly different result is suspect, not to mention mucked up  [:D]
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.

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Offline Geezer

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Will this buoyancy engine-based generator work?
« Reply #56 on: 24/10/2011 20:47:32 »
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.
« Last Edit: 24/10/2011 20:56:58 by Geezer »
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Offline Bored chemist

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Will this buoyancy engine-based generator work?
« Reply #57 on: 24/10/2011 22:08:06 »
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
« Last Edit: 24/10/2011 22:09:45 by Bored chemist »
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Offline Geezer

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« Reply #58 on: 25/10/2011 01:15:54 »
Yes, as I said about a week ago,

Quote
A half million tonne pontoon can only generate 250kW (average)

So a 1.7Mt pontoon will only generate 0.85 MW (average) on that basis. I think I was a bit generous with my rounding. 
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.

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Offline Geezer

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Will this buoyancy engine-based generator work?
« Reply #59 on: 25/10/2011 06:33:26 »
Mootle,
What's the reason for not building a scale model?

I have worked up the sketch designs, component selections and costs for a small system (3kW,) which came out at ca. £50k in materials and special pool rental plus my time to build and transport. Having already invested in software and time I think my wife would think me quite selfish to spend this kind of money on my idea rather than the kids college fund. Since the fundamentals of the system are well established I was hoping to get investment for the pilot.

But maybe I should research a design for a micro-scaled model to say power an LED lamp (3W) just to demonstrate the principles. The problem is I would probably have to develop my own turbine and generator set as I couldn't find anything that small on the market.

I actually agree with Mootle! (Watch for the carefully concealed insults.) There isn't much point in producing a scale model of the turbine end because it's already well known what a water turbine will do at various heads and flow rates, so why bother? Also, turbines don't scale well either, so the results could be very misleading. The pulley system should work too. Why wouldn't it?

The questions are to do with the sheer size of all the working parts, their ability to survive and function in a hostile marine environment, and their cost relative to the power generated. Some of those can only be answered by building a model that is large enough to operate in the hostile marine environment.

I don't think there is any question that the "turbine in a submarine" (subturbine? turbmarine? soupterrine?) could not be made to work, so there isn't much point in modelling that part of the system. What could be done is to model the system with a dummy turbmarine that doesn't produce any power. That would help to keep the cost down, a lot.



 
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Offline Geezer

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« Reply #60 on: 25/10/2011 07:14:03 »
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 [;D]) 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.)
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Offline Mootle

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« Reply #61 on: 25/10/2011 15:38:58 »
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.

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Offline imatfaal

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« Reply #62 on: 25/10/2011 16:09:38 »
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. 
There’s no sense in being precise when you don’t even know what you’re talking about.  John Von Neumann

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Offline Mootle

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« Reply #63 on: 25/10/2011 16:13:51 »
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.
« Last Edit: 25/10/2011 16:16:42 by Mootle »

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Offline Mootle

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« Reply #64 on: 25/10/2011 16:30:28 »

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 [;D]) 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 [;D]) 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.
« Last Edit: 25/10/2011 16:32:31 by Mootle »

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Offline Mootle

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« Reply #65 on: 25/10/2011 17:31:18 »
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.
« Last Edit: 25/10/2011 17:41:50 by Mootle »

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« Reply #66 on: 25/10/2011 18:25:50 »
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.
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« Reply #67 on: 25/10/2011 19:02:51 »
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!
« Last Edit: 25/10/2011 19:07:48 by Mootle »

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« Reply #68 on: 25/10/2011 19:28:09 »
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.
« Last Edit: 25/10/2011 20:08:33 by Bored chemist »
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« Reply #69 on: 25/10/2011 20:10:20 »
Perhaps we should lock this thread before it becomes contentious?  [:D]

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.
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« Reply #70 on: 25/10/2011 20:50:51 »
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)
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« Reply #71 on: 25/10/2011 22:05:26 »
..." 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

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« Reply #72 on: 25/10/2011 22:10:17 »
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.
« Last Edit: 25/10/2011 22:36:34 by Mootle »

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« Reply #73 on: 25/10/2011 22:23:13 »
Perhaps we should lock this thread before it becomes contentious?  [:D]

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.

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Offline Geezer

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« Reply #74 on: 26/10/2011 00:40:26 »
Perhaps we should lock this thread before it becomes contentious?  [:D]

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?"
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Offline imatfaal

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« Reply #75 on: 26/10/2011 10:48:33 »

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.   

Quote
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

Quote
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


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« Reply #76 on: 26/10/2011 11:05:08 »

...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.

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« Reply #77 on: 26/10/2011 12:06:33 »
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.
Quote

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.
« Last Edit: 26/10/2011 12:12:08 by Mootle »

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« Reply #78 on: 26/10/2011 19:28:28 »
"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?
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Offline Geezer

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« Reply #79 on: 26/10/2011 20:30:32 »
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.
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Offline Bored chemist

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« Reply #80 on: 26/10/2011 22:04:21 »
To be fair (and to stop myself looking silly for saying the pontoon is a lot like a ship) ships are actually quite strong. They need to be because, from time to time, they find themselves with the ends held up by waves and with nothing holding up their middles.
It might need to be a bit stronger than a ship but not much. Also, there would be several damn great eye bolts along the hull so the load would be distributed a bit.
It's still not going to work unless there's some magic change in the economics so I'd still like to see Mootle's answer to my question.
What can you change to make this idea work?
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« Reply #81 on: 26/10/2011 23:28:25 »
To be fair (and to stop myself looking silly for saying the pontoon is a lot like a ship) ships are actually quite strong.

True, but they are not submarines. On the other hand, pontoons are sort of shallow depth submarines. They have to displace water with something a lot less dense (probably air) in order to exert a force on the cable. I'm not an expert by any means, but I seem to remember that large tankers rely on their contents to limit the stress on their hulls when they are submerged, and that won't work with a pontoon cos it would sink when the cable pulled on it [:D]

(Obviously, I was being silly with the single eyebolt to make the point.)
« Last Edit: 26/10/2011 23:30:06 by Geezer »
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Offline imatfaal

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« Reply #82 on: 27/10/2011 10:37:09 »
to be fair both BC and Geezer are correct.  When a ship is correctly loaded within design parameters they are very tough and will ride out unbelievable seas in the North Atlantic and the Southern Oceans.  But - misloading or loading a cargo outside design parameters will rapidly cause the vessel to crack.

large ships draw a fair amount of water - but not enough I believe to make the structure overly weak when at full draft without cargo (ie forced further into the water without being filled with cargo). A vlcc will be around 15m deeper in the water when fully laden compared to a safe ballast and 18m deeper than being completely empty.  Whilst these ships do rely on the support of water to an extent - they are quite capable of being taken from the water and propped up on blocks for a few weeks every couple of years. 
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« Reply #83 on: 27/10/2011 12:12:59 »
"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've tried to describe it to you but evidently without much success - it will all become clear once I've completed the scaled model if the house rules permit me to post it but as it stands it would be unfair for me to take your bet.

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?


As I've said before there are many developmental steps required.

I agree, steel prices are only likely to go up with time (as energy costs soar). This is one reason for aiming to minimise the use of steel in the system design.

One of the biggest challenges will be the anchorage. I don't think the use of large quantities of concrete will be sustainable or cost effective. I'm working on a construction animation to show the sequences involved and would post this in due course - house rules permitting.

The system design will benefit from a flat pontoon structure. Since the hydraulic forces will be modest (compared with the Storage Vessel,) I'm researching the possibility of reinforced plastics for the main base. The challenge is to effectively spread the forces - time and a bit of FEA will tell.

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Offline Geezer

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« Reply #84 on: 27/10/2011 17:16:04 »
but not enough I believe to make the structure overly weak when at full draft without cargo (ie forced further into the water without being filled with cargo).

But how would you know? Have you ever seen a ship at full draft without any cargo (or ballast) [;D]

That's really my point. Ships are not designed to be submarines.
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.

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Offline Geezer

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« Reply #85 on: 27/10/2011 17:44:58 »
One of the biggest challenges will be the anchorage.

Friction could be just as bad. A 25:1 "block and tackle" has so much friction that it may offer no mechanical advantage over one with a much lower ratio. When you turn a 25:1 around and try to use it as a 1:25, there could be so much friction that the storage vessel won't budge and something will break instead.

Using gears instead of pulleys doesn't help much either.
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.

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Offline Bored chemist

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« Reply #86 on: 27/10/2011 18:56:37 »
"I'm researching the possibility of reinforced plastics for the main base."
Do you think you will have some miraculous insight that has eluded the designers of things like bridge footings for millennia?

Seriously, if they still use concrete for building things like the Thames Barrier, why do you think plastic might be better?
Do you think they are idiots?
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« Reply #87 on: 27/10/2011 19:08:36 »
"I'm researching the possibility of reinforced plastics for the main base."
Do you think you will have some miraculous insight that has eluded the designers of things like bridge footings for millennia?

For the main base of the Pontoon.

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« Reply #88 on: 27/10/2011 19:45:45 »
"I'm researching the possibility of reinforced plastics for the main base."
Do you think you will have some miraculous insight that has eluded the designers of things like bridge footings for millennia?

For the main base of the Pontoon.

Yes, that's a big problem. Despite the statements of my learned colleagues Imatture and Bruised Chemist (who obviously couldn't engineer their way out of a paper bag) distributing the enormous force in the cable evenly over something with an enormous surface area like a pontoon (or a big honking boat) is a non trivial problem. And don't be fooled into thinking that distributing the pulleys will solve that problem either. The aforementioned friction will ensure that it won't.
There ain'ta no sanity clause, and there ain'ta no centrifugal force æther.

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« Reply #89 on: 27/10/2011 22:01:18 »
http://xkcd.com/969/
seems like an odd coincidence.
Anyway,
Whatever Mootle.
You can dream on. The laws of physics and economics are still going to be there when you wake up.
the pulleys are not just a source of friction, but pointless. If you have not worked out why then I don't think you are going to get much further with this.


Incidentally, Geezer, our views may differ, but the outcome is the same.
I think that he will need the pontoon to be built quite a lot like a boat because it's quite like a boat i.e. it is subject to huge stresses and it has to float.
You think it will be different from a boat because the forces will  be in essentially the opposite direction and point loads rather than distributed loads; which is fair enough.

When it comes down to it, what he will need will be a big strong floaty thing. He certainly won't get that any cheaper than a boat, so his price structure is dead in the water.
Perhaps he should fit it with some ropes and pulleys.
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« Reply #90 on: 27/10/2011 22:44:08 »
When it comes down to it, what he will need will be a big strong floaty thing.

Actually, it really does not need to be all that strong. It could just be a biggish block of expanded polystyrene (like the one under the floor of my boat). The tricky bit is connecting it to the cable  [:)]
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« Reply #91 on: 27/10/2011 23:12:56 »
Of course, you could eliminate the need for a big strong floaty thing entirely if you used the variation in head to pump water up a hill insted. That would also eliminate the need for a mechanical gearing system because hydraulic systems let you swap head for volume and vice-versa.

Unfortunately, you might end up with something that looked a lot like this

[attachment=15438]


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« Reply #92 on: 28/10/2011 06:58:27 »
A big strong non-floaty thing.
But the fish are smiling so it must be OK.
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« Reply #93 on: 28/10/2011 11:09:13 »
"I'm researching the possibility of reinforced plastics for the main base."
Do you think you will have some miraculous insight that has eluded the designers of things like bridge footings for millennia?

For the main base of the Pontoon.

Yes, that's a big problem. Despite the statements of my learned colleagues Imatture and Bruised Chemist (who obviously couldn't engineer their way out of a paper bag) distributing the enormous force in the cable evenly over something with an enormous surface area like a pontoon (or a big honking boat) is a non trivial problem. And don't be fooled into thinking that distributing the pulleys will solve that problem either. The aforementioned friction will ensure that it won't.

You are correct, to achieve an efficient 25:1 pulley for this application will be quite an engineering challenge. In this way, the pulley system would be another of those developmental areas.

Friction is a function of:

The quality of the pulley bearings.
Diameter of the pulley.
Slippage between the cable and the pulley.
Material selection for the cable.
Bend radius of the cable....

The strength of the cable would be a constraining factor, once the SWL is established for a suitable marine cable the number of pulleys would be determined from the total load (including dynamic loads,) and a sensible margin of safety (including redundancy).
 

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« Reply #94 on: 28/10/2011 11:41:46 »
....You can dream on. The laws of physics and economics are still going to be there when you wake up.
the pulleys are not just a source of friction, but pointless. If you have not worked out why then I don't think you are going to get much further with this...

I thought we had got to the bottom of the 'laws of physics' - are you still questioning my claims?

We don't have the necessary information to answer the question of economics but basing this on the value of existing vessels is flawed. These vessels are designed with a particular function in mind. The pontoon has a very different set of constraints and this opens up a wide array of possibilities to value engineer a far cheaper solution.

Once the design has been developed it will be possible to assign some realistic costs. To draw conclusions at this stage is conjecture or at best an educated guess. I'm not saying that guess work doesn't have its place but when refining the accuracy of the costs it is always a good idea to acknowledge the deficiencies of the estimate. If once a developed design has been costed it does not provide a healthy RoI then I would simply leave it at that, either way I will have learned a lot from the journey. My research has so far lead to several interesting fields of design and research that I wouldn't have reached in my usual walk of life, i.e., artificial coral reef, submarine / ship, bridge, tunnelling, anchorages, tidal systems, wave energy / prediction, ocean currents, hydropower, ocean floor topography.

Inventors need wide horizons, it is only from a unique perspective that original ideas are born.
« Last Edit: 28/10/2011 11:43:42 by Mootle »

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« Reply #95 on: 28/10/2011 16:29:59 »
....You can dream on. The laws of physics and economics are still going to be there when you wake up.
the pulleys are not just a source of friction, but pointless. If you have not worked out why then I don't think you are going to get much further with this...

I thought we had got to the bottom of the 'laws of physics' - are you still questioning my claims?
..../snipped
Inventors need wide horizons, it is only from a unique perspective that original ideas are born.

Unfortunately Peter your idea has run into 3 forum posters - one a research scientist, one an engineer. and one a businessman; and all have criticised your idea from multiple angles and I believe concluded from their own knowledge and the information posted that your idea is fatally flawed.  Scientifically; the energy is limited, regardless of how much gearing or pulleys the energy available is limited by the volume of the pontoon and the size of the tide (a point I am not sure you grasp).  In Engineering terms this project is huge - the largest displacement of any floating object ever, dragging an object the size of a block of flats to the sea bed every 12 hours, as much wiring as the millennium dome, and all for 16MWh/day.  And Economically, with the best will in the world, with zero maintenance and running costs, and with unheard of efficiencies - you might start breaking even sometime in the 23rd century.  A hard-nosed analysis from three independent views cannot see the worth in this project
There’s no sense in being precise when you don’t even know what you’re talking about.  John Von Neumann

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« Reply #96 on: 28/10/2011 17:06:21 »
A big strong non-floaty thing.
But the fish are smiling so it must be OK.

It doubles as an artificial reef, and, as you can see, fish like them.

Actually, it does not need to be very strong at all. It's pressurised so that it only needs to handle the variation in air pressure caused by the variation in head, which is not much at all (unfortunately). It could even be a flexible air bag of sorts. One big problem is securing the thing to the seabed.

I have to agree that it's probably not much use for a large power generation scheme, but it might be interesting for small scale generation on remote islands or similar where the cost of bringing in power is already prohibitive.
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« Reply #97 on: 28/10/2011 17:58:44 »
"I thought we had got to the bottom of the 'laws of physics' - are you still questioning my claims?"
There are two ways your idea could be made to work.
Make it vastly cheaper or get much more energy from it.
I was covering both bases.
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Offline Geezer

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« Reply #98 on: 28/10/2011 22:30:20 »
Mootle,

I agree with BC and Matt about the viability and practicality of your approach. From a practicality standpoint alone, even if you could overcome the many issues that have been raised, keeping all that "kit" functioning in a highly corrosive submerged environment would be horribly expensive.

On the other hand, it is an intersting problem to try to solve. Here's another suggestion. It may not address viability, but it might address some of the practicalities. I'm sure BC and Matt will be more than delighted to point out any flaws it might have.


[attachment=15469]

Basically, it consists of a pontoon attached to a (an?) hydraulic ram. The piston in the ram is attached to the seabed by a substantial cable. A high pressure hose connects the ram to a hydraulic motor (not shown) that could be used to do a lot of different things. The motor could sit on top of the pontoon, or on land, whichever is more convenient. The ram is filled with some sort of environmentally friendly liquid lubricant - vegetable oil perhaps?

As the tide rises, the force on the piston increases, and this drives the motor. (The fluid could also be prevented from escaping so that the energy can be tapped at a later point during the incoming tide.) When the tide falls again, the ram is refilled with liquid so that it's ready for the next cycle. The refilling does not consume much energy because it only has to lift the mass of the piston and cable against gravity.

To size the thing, we'd decide on the maximum hydraulic pressure in the hose between the ram and the motor first. If we decided that was 3000 psia, it tells us (I think!) that the volumetric ratio between the pontoon and the ram is around 3000/15, or 200:1 (that should be the equivalent of the pulley ratio in a mechanical version).

Although 3000 psia is highish, it's not all that high either. We might go up to around 12000 psia if it was worth it (the motor technology might get a bit exotic, but it would get us to an 800:1 ratio, which ain't too shabby).

That ratio would mean that every 1000 litres of pontoon displacement would require a whopping 1.25 litres of ram displacement.

However, even if this were to work in practice, it can't do anything to alter the fact that the available energy is determined by the displacement of the pontoon and tidal variation. Consequently, even if you can reduce the cost of the energy extraction system to zero, the cost of the pontoon is going to determine the viability of the system as a whole.

EDIT: Astute members of the forum will have already noted that the maximum possible travel of the piston in the ram should, ideally, be at least as great as the tidal variation.

EDIT2: I wonder how this stacks up against wind power? I do know that the economics of wind power are (to put it politely) a wee bit dodgy, and the aesthetic impact of wind power can be really horrible. The last time I was in Scotland, I was pretty disgusted by the desecration I observed. 
« Last Edit: 29/10/2011 01:09:41 by Geezer »
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« Reply #99 on: 29/10/2011 10:29:24 »
Unfortunately Peter your idea has run into 3 forum posters - one a research scientist, one an engineer. and one a businessman; and all have criticised your idea from multiple angles and I believe concluded from their own knowledge and the information posted that your idea is fatally flawed.

Interesting. The question posted was will this buoyancy engine work. In summary and disregarding areas of speculation the response was that the principle is sound and that the claimed energy balance and potential revenue stream is theoretically possible.


Scientifically; the energy is limited, regardless of how much gearing or pulleys the energy available is limited by the volume of the pontoon and the size of the tide (a point I am not sure you grasp).

Agreed, the tidal range and pontoon are the main constraints of the energy balance. I have no idea what gave you the impression that I do not understand this basic premise. 


In Engineering terms this project is huge - the largest displacement of any floating object ever, dragging an object the size of a block of flats to the sea bed every 12 hours, as much wiring as the millennium dome, and all for 16MWh/day.


Agreed, it is a big project, much bigger than you have indicated once it is scaled up. There are no easy rides with renewables, nothing comes for free.


And Economically, with the best will in the world, with zero maintenance and running costs, and with unheard of efficiencies - you might start breaking even sometime in the 23rd century.  A hard-nosed analysis from three independent views cannot see the worth in this project

It is too soon for me to draw any conclusions as to the economic viability. That can only come once there is more data to put into the business case. The schematic animation is only intended to get the principle across. Unfortunately, I'm not ready to answer the question on financial viability until the design has been sufficiently developed.

Once again, all input is appreciated - many thanks.