[Mootle (OP)]

Your system wasn't fully defined so I've run a rough order calculation for a continuous 3kW demand.

I encourage you to scrutinize my numbers very carefully. Either I mucked them up, or you are stiffing yourself by making the pontoons twice as large as they need to be.

As I mentioned a couple of times already, and as any engineer worth their salt will point out, it's generally a really good idea to figure out how much energy is actually going into a system so that we can compare and contrast it with the amount of energy that is coming out of the system. When we figure it all out, net energy should be pretty close to zero.

As I indicated your system wasn't fully defined.

I find it better to start with a generator rating, this is used to establish the Storage Volume, once the generation time is determined. Then comes the Pontoon sizing based on the selected gearing ratio.

I've done a rough and ready estimate based on a system which will produce 3kW continuously. Our system efficiency may vary but otherwise I would expect the figures to work out. This increases the Storage Vessel volume which will in turn increase the Pontoon volume.

Since you didn't define the operating time I thought this was preferable to second guessing what you've allowed for although in broad terms, for a 3,000m3 Pontoon a matched Storage Vessel of 120m3 @ 25:1 gearing would be estimated as little over 4 1/2hrs of generation for your stated load.

[Geezer]

I find it better to start with a generator rating, this is used to establish the Storage Volume, once the generation time is determined. Then comes the Pontoon sizing based on the selected gearing ratio.

Yes, but it looks as if you are basing the storage volume based on the way you believe your invention ought to work. If you don't determine the energy supplied by the tide directly, you have no means of cross checking your answer. It's not as if it's difficult to determine the energy input either.

I simply determined the power input by the maximum tidal rate (which, admittedly, I did sort of noodle) and derated it according to a efficiency factor. My calculation pays absolutely no attention to gear ratios etc. because they are completely irrelevant.

More specifically;

Power input x efficiency = power output.

[Mootle (OP)]

I find it better to start with a generator rating, this is used to establish the Storage Volume, once the generation time is determined. Then comes the Pontoon sizing based on the selected gearing ratio.

Yes, but it looks as if you are basing the storage volume based on the way you believe your invention ought to work. If you don't determine the energy supplied by the tide directly, you have no means of cross checking your answer. It's not as if it's difficult to determine the energy input either.

I simply determined the power input by the maximum tidal rate (which, admittedly, I did sort of noodle) and derated it according to a efficiency factor. My calculation pays absolutely no attention to gear ratios etc. because they are completely irrelevant.

More specifically;

Power input x efficiency = power output.

It has been demonstrated that all things being equal and accounting for efficiency it really doesn't matter which way you work out the energy balance.

Generator work done = Pontoon work done = Storage Vessel work done.

I'd rather hoped that we had moved on from the energy balance. From a economy of scale perspective this scheme doesn't make sense for the buoyancy engine but I would agree that it is useful to look at the small scale as it can sometimes help to quantify matters. 

[Bored chemist]

The payback time of this project will certainly be longer than the lifetime of a government.
The only way it could work is with government backing (because it produces electricity that's a lot more expensive than the current wholesale rate).
So, when you say "Suffice to say I will use meaningful data for the business case rather than ill informed guess work. " all you can mean is that you will use your guess of what government subsidy will be available, rather than my guess.

Fair enough, but don't pretend it's anything but a guess.

[Mootle (OP)]

The payback time of this project will certainly be longer than the lifetime of a government.
The only way it could work is with government backing (because it produces electricity that's a lot more expensive than the current wholesale rate).
So, when you say "Suffice to say I will use meaningful data for the business case rather than ill informed guess work. " all you can mean is that you will use your guess of what government subsidy will be available, rather than my guess.

Fair enough, but don't pretend it's anything but a guess.

I'm not pretending anything. When writing a business case the revenue is calculated based on the extant government incentives.

It is true that the FIT scheme is under review and as such that uncertainty would have to be declared. However, would you not agree that if the Buoyancy Engine was set to work today, the given revenue figures would be achievable according to the rough order energy balance that has been agreed?

[Geezer]

Generator work done = Pontoon work done = Storage Vessel work done.

IMHO, that's a dangerous way to look at it, and it can easiliy lead to confusion, QED.

It should be;

Tide work done = all lost energy + captured energy.

The tide is the source of the energy, not the pontoon.

[Mootle (OP)]

Generator work done = Pontoon work done = Storage Vessel work done.

IMHO, that's a dangerous way to look at it, and it can easiliy lead to confusion, QED.

It should be;

Tide work done = all lost energy + captured energy.

The tide is the source of the energy, not the pontoon.

You're leaning against an open door here - my point is that it works out all ways around, the only question mark relates to the system efficiency. Turbines and generators can work very efficiently if correctly matched to the application and this should be the main input for a well designed system. It is more difficult to establish the overall system efficiency. This will be a function of the the pulley system, the additional buoyancy needed to drive the ascent phase, allowances for coral growth etc, trimming losses (governing swell,) cable stretch, Pontoon sinkage, down time for maintenance / unsuitable operating conditions.... 

[Bored chemist]

"would you not agree that if the Buoyancy Engine was set to work today, the given revenue figures would be achievable according to the rough order energy balance that has been agreed?"
My deliberately absurdly high estimate of the combined tariffs and subsidies was the equivalent of 4 times the actual value of the electricity produced.
I think your figures came out at something like half that figure.
It doesn't matter because, as I pointed out, many times,

Unless you can show how you are suddenly going to make this scheme a lot cheaper, it will never "break even" because the guessed revenues will never exceed the cost of paying the interest on the capital investment.

Worse, even if you could make it break even, it would still be a couple of orders of magnitude more expensive that just buying an absurdly expensive system.

I have asked the same question plenty of times and you don't seem to understand the importance of it.
How are you going to make your system ten times cheaper than the scrap value of the pontoon?


Oh, BTW, I write, and review business cases for the government.

We do take account of the fact that the plug might get pulled and, if that looks likely, we simply don't support the work. We don't do work that is likely to depend on long term support because that's not a good use of the investor's capital. So that's "When writing a business case the revenue is calculated based on the extant government incentives." scuppered.

[Geezer]

Generator work done = Pontoon work done = Storage Vessel work done.

IMHO, that's a dangerous way to look at it, and it can easiliy lead to confusion, QED.

It should be;

Tide work done = all lost energy + captured energy.

The tide is the source of the energy, not the pontoon.

You're leaning against an open door here - my point is that it works out all ways around, the only question mark relates to the system efficiency. Turbines and generators can work very efficiently if correctly matched to the application and this should be the main input for a well designed system. It is more difficult to establish the overall system efficiency. This will be a function of the the pulley system, the additional buoyancy needed to drive the ascent phase, allowances for coral growth etc, trimming losses (governing swell,) cable stretch, Pontoon sinkage, down time for maintenance / unsuitable operating conditions.... 

Your pontoons are capable of producing 588.6MJ in 24 hours which means your efficiency is 44.1%

How does that strike you?

[Mootle (OP)]

Generator work done = Pontoon work done = Storage Vessel work done.

IMHO, that's a dangerous way to look at it, and it can easiliy lead to confusion, QED.

It should be;

Tide work done = all lost energy + captured energy.

The tide is the source of the energy, not the pontoon.

You're leaning against an open door here - my point is that it works out all ways around, the only question mark relates to the system efficiency. Turbines and generators can work very efficiently if correctly matched to the application and this should be the main input for a well designed system. It is more difficult to establish the overall system efficiency. This will be a function of the the pulley system, the additional buoyancy needed to drive the ascent phase, allowances for coral growth etc, trimming losses (governing swell,) cable stretch, Pontoon sinkage, down time for maintenance / unsuitable operating conditions.... 

Your pontoons are capable of producing 588.6MJ in 24 hours which means your efficiency is 44.1%

How does that strike you?

Without trying to second guess your calculations did you take into account my comment:

'Therefore, there is scope to engineer an arrangement such that both Storage Vessels operate from one Pontoon, which carries a number of operational and financial advantages.'

[Mootle (OP)]

"would you not agree that if the Buoyancy Engine was set to work today, the given revenue figures would be achievable according to the rough order energy balance that has been agreed?"
My deliberately absurdly high estimate of the combined tariffs and subsidies was the equivalent of 4 times the actual value of the electricity produced.
I think your figures came out at something like half that figure.
It doesn't matter because, as I pointed out, many times,

Unless you can show how you are suddenly going to make this scheme a lot cheaper, it will never "break even" because the guessed revenues will never exceed the cost of paying the interest on the capital investment.

Worse, even if you could make it break even, it would still be a couple of orders of magnitude more expensive that just buying an absurdly expensive system.

I have asked the same question plenty of times and you don't seem to understand the importance of it.
How are you going to make your system ten times cheaper than the scrap value of the pontoon?


Oh, BTW, I write, and review business cases for the government.

We do take account of the fact that the plug might get pulled and, if that looks likely, we simply don't support the work. We don't do work that is likely to depend on long term support because that's not a good use of the investor's capital. So that's "When writing a business case the revenue is calculated based on the extant government incentives." scuppered.

You are presupposing which way the future FIT scheme will go. I've already indicated that the current uncertainty would need to be declared:
 
'It is true that the FIT scheme is under review and as such that uncertainty would have to be declared.'

Your difficulty comes from not being able to distinguish points of view from fact. The fact is no costing claims have been made. I've set out why I don't think the assumptions made are reliable. For now I will press on with the scaled model animation, after which reasonably accurate costs can be established.

We seem to be going around in circles so unless anyone has some new questions I declare myself out of the thread for the time being.

Once again, thanks to all that took the time to comment.

[Bored chemist]

This isn't a POV, it's a fact.
I can get the same nominal electricity generating potential as your machine for something like £2.4M

It's also renewable power, so it would presumably get the same FIT. (Granted that is a POV, but I think it's a reasonable one.)
So, unless you can build your scheme for less than that sum your system isn't financially viable.

It's also a fact that your rig needs a big pontoon.
It's a reasonable POV to say that it's in many ways similar to a ship. The stresses on it are different, but comparable (actually they are probably more difficult to manage).

It's not an unreasonable POV that shipbuilders know what they are doing.
They use steel so it's fair to say that steel is a good material to use in terms of cost versus practicality.
SO it's not unreasonable to conclude tat your system, which is quite like a ship, will have a cost comparable with a ship of the same displacement.

I have asked several times what you could do to make it significantly cheaper than a ship of that size. You don't seem to have offered any answer to that.
So, it seems that you must agree that the cost estimate is not absurdly wrong.

However that means that, if someone built your system they could sell it for the scrap value.
That value is rather more than £2.4M. Probably one or two orders of magnitude more.
So they could sell it for scrap, buy the wind turbines, sell the same power back to the grid for the same  money and pocket a huge sum of money.

Let me know which of my assumptions you feel is actually unreasonable, rather than just pointing out that they are assumptions. I know they are not cast in stone, but the point is that they only need to be very roughly correct to show that your system will fail to cover its cost.

[Geezer]

Generator work done = Pontoon work done = Storage Vessel work done.

IMHO, that's a dangerous way to look at it, and it can easiliy lead to confusion, QED.

It should be;

Tide work done = all lost energy + captured energy.

The tide is the source of the energy, not the pontoon.

You're leaning against an open door here - my point is that it works out all ways around, the only question mark relates to the system efficiency. Turbines and generators can work very efficiently if correctly matched to the application and this should be the main input for a well designed system. It is more difficult to establish the overall system efficiency. This will be a function of the the pulley system, the additional buoyancy needed to drive the ascent phase, allowances for coral growth etc, trimming losses (governing swell,) cable stretch, Pontoon sinkage, down time for maintenance / unsuitable operating conditions.... 

Your pontoons are capable of producing 588.6MJ in 24 hours which means your efficiency is 44.1%

How does that strike you?

Without trying to second guess your calculations did you take into account my comment:

'Therefore, there is scope to engineer an arrangement such that both Storage Vessels operate from one Pontoon, which carries a number of operational and financial advantages.'

Yes, I did. As you didn't specify its displacement, I assumed it was twice the displacement of the two smaller ones. If you knew it was possible to generate the power output with half the total displacement, I would have thought you would have made that clear.

My calculation was simply the energy output over the maximum energy input based on the displacements and the tide.

[Mootle (OP)]

This isn't a POV, it's a fact.
I can get the same nominal electricity generating potential as your machine for something like £2.4M

It's also renewable power, so it would presumably get the same FIT. (Granted that is a POV, but I think it's a reasonable one.)
So, unless you can build your scheme for less than that sum your system isn't financially viable.

It's also a fact that your rig needs a big pontoon.
It's a reasonable POV to say that it's in many ways similar to a ship. The stresses on it are different, but comparable (actually they are probably more difficult to manage).

It's not an unreasonable POV that shipbuilders know what they are doing.
They use steel so it's fair to say that steel is a good material to use in terms of cost versus practicality.
SO it's not unreasonable to conclude tat your system, which is quite like a ship, will have a cost comparable with a ship of the same displacement.

I have asked several times what you could do to make it significantly cheaper than a ship of that size. You don't seem to have offered any answer to that.
So, it seems that you must agree that the cost estimate is not absurdly wrong.

However that means that, if someone built your system they could sell it for the scrap value.
That value is rather more than £2.4M. Probably one or two orders of magnitude more.
So they could sell it for scrap, buy the wind turbines, sell the same power back to the grid for the same  money and pocket a huge sum of money.

Let me know which of my assumptions you feel is actually unreasonable, rather than just pointing out that they are assumptions. I know they are not cast in stone, but the point is that they only need to be very roughly correct to show that your system will fail to cover its cost.

For the umpteenth time, I do not think it's a good idea to make an estimate until a design has been done. I have offered various answers to your questions that seem perfectly reasonable to me but you have chosen to disregard them.

I fail to see how you can offer up the comparison with any kind of seriousness. It is so flawed that it isn't worth consideration even if you did include things like installation and whether it could actually provide load when you need it.

Perhaps we should all purchase a domestic petrol powered generator rather than invest in our energy infrastructure since those power stations would probably represent poor value for money by comparison. 

[Mootle (OP)]

Yes, I did. As you didn't specify its displacement, I assumed it was twice the displacement of the two smaller ones. If you knew it was possible to generate the power output with half the total displacement, I would have thought you would have made that clear.

My calculation was simply the energy output over the maximum energy input based on the displacements and the tide.

I thought I did (3rd time lucky):
'Therefore, there is scope to engineer an arrangement such that both Storage Vessels operate from one Pontoon, which carries a number of operational and financial advantages.'

If you show your workings I can review further. The problem I have is that even when you are presented with irrefutable evidence you still don't concede points so I have no intention of trying to second guess what you have calculated.

[Geezer]

Yes, I did. As you didn't specify its displacement, I assumed it was twice the displacement of the two smaller ones. If you knew it was possible to generate the power output with half the total displacement, I would have thought you would have made that clear.

My calculation was simply the energy output over the maximum energy input based on the displacements and the tide.

I thought I did (3rd time lucky):
'Therefore, there is scope to engineer an arrangement such that both Storage Vessels operate from one Pontoon, which carries a number of operational and financial advantages.'

If you show your workings I can review further. The problem I have is that even when you are presented with irrefutable evidence you still don't concede points so I have no intention of trying to second guess what you have calculated.

OK - here you go.

Based on a 25:1 gearing ratio each Pontoon volume would be ca. 7,500m3
Tidal range is assumed as 2m.

Total displacement 2 x 7500 = 15,000m3, or 15,000,000kg (ignoring the salt in the water)
Therefore, max force is 147.2MN
Max work in 24 hours is 147.2 x 4 = 588.6MJ = 588,600kJ
Max work per second is 588,600/86,400 = 6.81kJ
Max power in = 6.81 kW
Power out = 3.0kw
Efficiency = 44.1%

(Or are you assuming one of the pontoons is going to spring a leak and sink?)

[Bored chemist]

OK, so I first asked "What developments would you put on your "wish list" that would actually make your system anything other than a white elephant?"
here
http://www.thenakedscientists.com/forum/index.php?topic=41578.msg370908#msg370908
Your reply was "there are various aspects of this application that we haven't touched on that would require development. "

So again I asked
"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?"
And I repeated essentially the same question
"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?"

And you said this
"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"

So you say you won't use steel because it's expensive. It is however in practical terms quite cheap. That's why shipbuilders use it.

And you say you won't use concrete for the footings.
Good luck finding anything strong enough, heavy enough and cheaper than concrete.
So, thus far you have yet to really answer the question. YOu have made a couple of questionable comments about what you won't do (i.e. use steel or concrete), but nothing about what you will do.

This suggestion "I'm researching the possibility of reinforced plastics for the main base." was kicked into touch by Geezer when he pointed out that it's going to need to be very strong. Anyway I don't think reinforced plastics are much cheaper than steel if you actually need much strength.


And you don't seem to have addressed the issue of tying the pulleys down.
"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?"

You don't seem to have replied to that. What you next said on the subject (unless I missed something was
"I've set out why the the reused value of 7 large tankers is not a useful representation of the cost of the pontoon. "
which is unfortunate since, so far as I can see, you didn't (though you did say you had deleted a post- perhaps it was there that you explained why your big strong floaty thing would be cheaper than someone else's design of big strong floaty thing.)

Again you say things like "I don't plan to use a traditional anchor. " without saying what you will use and ignoring the fact that traditional anchors wouldn't have got  to be traditional if they didn't work.

So, once again I asked " Fair enough, but can you (as I have asked before) come up with some explanation of why you feel that you will be able to make this cheaper than, for example, a scarp supertanker?"

And your reply was "Whilst it is interesting to get 'points of view' it does get a little tiresome going over the same points."
You don't seem to have understood that the way to avoid the tiresome repetition of a question is simply to answer it. Saying "this is a new idea so anchorage for such a development would need an innovative approach." doesn't actually tell us anything.

So, once again I asked
"How are you going to make your system ten times cheaper than the scrap value of the pontoon?"

And what do I get in reply?
I get this " I have offered various answers to your questions that seem perfectly reasonable to me but you have chosen to disregard them. "

Well, they may seem reasonable to you but from my point of view they seem to lack a fairly fundamental aspect.
You still haven't said what you are going to do to make this work for about 100 times less than the scrap value of the pontoon.

This is a science website.
People who put forward ideas are expected to answer questions asked about those ideas.

If I have missed an answer of the form "I will do (whatever) which is cheaper than using an old oil tanker" then please point it out to me
I'm not going to accept an answer that says "I haven't costed it yet" because that's the whole point; several of us have costed it and it's preposterously expensive.
I'm also not going to accept an answer that says "I will sprinkle magic pixie dust on the cost and make it go away" or, the roughly equivalent " I will need to do some research in reinforced plastics" or "I won't use a traditional anchor".

Now I challenge you to answer the question in a straightforward manner or leave.

How will you make this rig cheap enough that the revenue will, at least, service the loan for building it?

[johan_M]

Max power in = 6.81 kW
Power out = 3.0kw
Efficiency = 44.1%

I have'nt followed the whole thread, it's a bit convoluted. Please explain this efficiency part?

[Geezer]

Max power in = 6.81 kW
Power out = 3.0kw
Efficiency = 44.1%

I have'nt followed the whole thread, it's a bit convoluted. Please explain this efficiency part?

Which part of it do you not understand?

[damocles]

Max power in = 6.81 kW
Power out = 3.0kw
Efficiency = 44.1%

I have'nt followed the whole thread, it's a bit convoluted. Please explain this efficiency part?

Which part of it do you not understand?

Is it possible that the missing link is "efficiency = power out/power in" ?