[Geezer]

I was thinking you might consider something like this -

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Also available as a PDF - see link at end of message.

It's basically a concrete tank that's open to the sea near the bottom. Compressed gas displaces the water in the tank. The rising tide increases the pressure. It probably needs to be an inert gas that won't dissolve in water. Nitrogen perhaps - BC?

At the other end of the pipe, and it could be a long distance away, is a similar arrangement only with different dimensions, that elevates fresh water into a storage reservoir. What you end up with is a pumped storage hydroelectric generator that uses tidal energy to pump the water up to the storage reservoir.

Doing work with compressed gas is usually horribly inefficient, but that may not be the case here because the rate of compression is very slow. So slow in fact, that the pressure in the pipe would be constant if the work taken out at the pump end was the same as the work put in by the tide. There is no change in the energy stored in the gas if the pipe is sized properly.

It's a very sketchy idea, and there are probably a whole bunch of nasty issues, but it might be reasonably compatible with a harsh marine environment. I've no idea how the economics would work out, but I do know you would need an awful lot of tanks to generate a significant amount of power. On the other hand, it might be a lot more acceptable than a bunch of whopping great wind turbines growing out of the sea.

(The pipe does not need to stick up above sea level as shown - it could be routed along the seabed. The entire caboodle would obviously have to be anchored to the seabed with number 9 screws to stop it floating away!)

[Mootle (OP)]

I would need to see the whole system to be able to offer a more meaningful comment.

With a static system the output would be greatly diminished. There is the potential to employ the storage element to generate a useful and reliable power output when the demand is there, which is a common failing of other renewables. The real challenge is to get an investor a return on investment.

My preference is to use a dynamic system working with water rather than a static system working with compressed air as denser working fluid and greater pressure differential gives a better energy density and output capability.

btw please confirm if you now concede the point on capacity?

[peppercorn]

Mootle,

I looked your idea and wondered if you have thought of using another method that might use compressed air instead of the cables and pontoons.

We done dis idea before dint we []

Here:
How much work in the form of pressure is there at the bottom of the deep ocean?

... oh, and here:
Does deep ocean have potential energy due to pressure?
 []

[Mootle (OP)]

Whilst some of the concepts are similar to some earlier threads here I would venture that there are several key differences to the animimation which is linked to in the original post. My idea is patent pending so I guess I'll know if the idea has been done before if the IPO decide to grant the patent or not. However, according to searches to date it is a new arrangement.

[Geezer]

btw please confirm if you now concede the point on capacity?

What point? Are you saying your system will be able to produce more than 4.36 MWh per day?

If you believe that is the case, please take a look at this informative video

[Geezer]

We done dis idea before dint we []

Here:
How much work in the form of pressure is there at the bottom of the deep ocean?

... oh, and here:
Does deep ocean have potential energy due to pressure?
 []

I think those were more to do with energy storage. The subsea pressure tank thing is just a way of tapping tidal energy. While the air in the tank is being forced out of the tank by the rising tide, it would drive a pump to elevate fresh water into a high level reservoir for subsequent use by a water turbine.

The tank would have to be enormous to pump a lot of water, or there would have to be a lot of them, and the static head between the high and low fresh water reservoirs would determine how much water could be elevated. However, the turbine would still extract the same amount of work. A greater head just means a smaller turbine can do the same amount of work (assuming they are equally efficient).

The amount of water displaced by the tide in the air tank determines the amount of work that the system can do. In that respect it is no different from a pontoon doing work by rising on the tide and pulling on a cable.

The advantage of the compressed air approach is that there are no moving parts immersed in salt water, and there is nothing to get kicked around by currents and storms. It's a concrete box, so it should last quite a long time with zero maintenance. The pipe to bring the air ashore would be a weaker point. Mind you, if the system was designed so that the pump was driven very slowly as the tide came in (constant air pressure driving a whopping great piston) the pipe bore would be really small compared to the size of the tank.

BTW, if somebody didn't already patent this idea, it's too late now [] 

[Bored chemist]

The patent office are quite happy to take your money without checking (or caring) if the idea works.
I still think this idea is pointless. It needs a really big construction project to make relatively little power.
Fundamentally it  can not extract more energy from the tide than my suggestion of a big box on a rope. The only aspect of it that might be novel enough to get a patent is the use of the rope and pulleys to convert a small movement with a large force into a larger movement with a smaller force. Obviously, that's been done before but probably not in this context because it doesn't offer any great advantage.

[Geezer]

The patent office are quite happy to take your money without checking (or caring) if the idea works.

Yup, that about sums it up. Their initial response is usually to reject everything you claim so they can stick your application back at the bottom of the heap []

[Mootle (OP)]

Ah, but if the storage vessel is 67,000m3, the pontoon will have to displace six times that volume, or about 400,000 cubic meters, otherwise it will sink. A cubic meter of water weighs about 1t, so your pontoon displacement is about 400,000t which is about 80% of the supertanker I mentioned, and that is only capable of generating 0.5MW, so you are only going to get 0.4MW, and that's without allowing for the inevitable losses in the system

It doesn't matter how you cut it, but ultimately, the thing that is doing the work is the tide lifting the mass of water displaced by the pontoon against gravity. If your calculation says that you are doing more work than that, you are trying to get something for nothing, which has never worked thus far.

Geezer - does it help if I remind you of the point to which I was referring (see above). The total energy available is not the generation rating. However, the total energy available was given as part of the build up to the revenue calculation.

To repeat, do you now concede that the rating claim was in fact ok.   

[Mootle (OP)]

The patent office are quite happy to take your money without checking (or caring) if the idea works.
I still think this idea is pointless. It needs a really big construction project to make relatively little power.
Fundamentally it  can not extract more energy from the tide than my suggestion of a big box on a rope. The only aspect of it that might be novel enough to get a patent is the use of the rope and pulleys to convert a small movement with a large force into a larger movement with a smaller force. Obviously, that's been done before but probably not in this context because it doesn't offer any great advantage.

I'm not sure I agree with your comments regarding the IPO, at least this hasn't been my experience.

Renewables (including tidal) is a very active research area. The reason for this is that various government incentives are in place to make investment into new developments more viable. I would have to agree that without the incentives, investment would not be possible but now they are new possibilities come to light - 'necessity is the mother of all invention'. I tend to think in terms of jobs for the people of the UK and would regard large engineering projects such as this, a good thing for social mobility provide there is a good rate of return. Like it or not we face an extreme energy shortage which is set to get worse. I doubt a quick fix will come along, so we need to get our thinking caps on now and plan for the future. Otherwise, what will happen when the gas, coal and uranium becomes uneconomical to extract? It's easy to forget that gas, coal and nuclear were massive infrastructure projects.

A big advantage of this system is that the rating of the system can be geared / scaled to suit the demand and unlike wind and solar would be completely reliable. The UK's energy demand profile isn't smooth, it has peaks and troughs and the system will fall over if the peaks can't be met. If the UK is to meet its commitments on renewables we will need a well thought out mix of technologies, get that mix wrong and there is a very real risk that the lights will go out in the not so distant future.

At the moment we get by with help from our French compatriots but as population increases and power infrastructure capacity declines, when push comes to shove we must be self reliant or face severe penalties when we have to tell industry to turn off their manufacturing plants.

[Mootle (OP)]

btw please confirm if you now concede the point on capacity?

What point? Are you saying your system will be able to produce more than 4.36 MWh per day?

If you believe that is the case, please take a look at this informative video

fyi, each of the buoyancy engines would provide ca. 12MWh/day, giving a total of around 120MWh/day for the set of (10) described in the revenue calculation given previously. This is a nett figure including purge pumping and ancillary losses but I suspect the discrepancy is in the gearing ratio which has been applied.

As for the video - I did like that  []

[Geezer]

fyi, each of the buoyancy engines would provide ca. 12MWh/day,

Then you are trying to violate the second law of thermodynamics. It's not up for "debate". It's really quite simple. You cannot extract more work from a system than the work that was put into the system. The tide is the thing that is putting in the work, but you seem determined to ignore that inconvenient fact.

My calculation clearly shows each generator can't possibly produce more than 4.36MWh per day (and it will actually be a lot less due to parasitic losses.) If there is a flaw in my calculation, you should be able point it out, quite easily. Either you don't understand basic science, or you didn't make any attempt to understand what I posted.

I'm not going to waste any more time trying to help you understand where you are going wrong, and please don't blame me if you are chased out of town by an angry mob of investors who want their money back. (You won't be able to blame the patent office either.)

[Mootle (OP)]

Then you are trying to violate the second law of thermodynamics. It's not up for "debate". It's really quite simple. You cannot extract more work from a system than the work that was put into the system. The tide is the thing that is putting in the work, but you seem determined to ignore that inconvenient fact.

I'm not trying to ignore anything but rather get you to acknowledge that a simple misunderstanding has caused the discrepancy.

My calculation clearly shows each generator can't possibly produce more than 4.36MWh per day (and it will actually be a lot less due to parasitic losses.) If there is a flaw in my calculation, you should be able point it out, quite easily. Either you don't understand basic science, or you didn't make any attempt to understand what I posted.

If anyone is not following the thread it's you. I have shown my rating calculation and identified why there is a discrepancy: 1, You assumed a longer generation time than me (I've allowed for the Storage Vessel ascent time,) 2, You assumed the 6:1 gearing ratio of the schematic animation would carry forward when it was stated that the gearing ratio of the Scaled application is 25:1 which in turn increases the Pontoon volume.

I'm not going to waste any more time trying to help you understand where you are going wrong, and please don't blame me if you are chased out of town by an angry mob of investors who want their money back. (You won't be able to blame the patent office either.)

There are a few issues here, 1, you've made various errors throughout this thread and it's difficult to see how you've reached the conclusion that I don't understand the principles involved. 2, In fairness you've acknowledged some of your errors but you seem to have a major issue conceding the point of the rating which comes about from your mishandling of total energy vs energy flow. 3, I'm not looking to blame anyone for anything - I have no idea where you get that from. 4. As for the total energy available, if you substitute the correct Pontoon volume and density based on the 25:1 gearing ratio which I gave then you will understand why it is your input to the calculation that is flawed.

[Bored chemist]

The patent office are quite happy to take your money without checking (or caring) if the idea works.
I still think this idea is pointless. It needs a really big construction project to make relatively little power.
Fundamentally it  can not extract more energy from the tide than my suggestion of a big box on a rope. The only aspect of it that might be novel enough to get a patent is the use of the rope and pulleys to convert a small movement with a large force into a larger movement with a smaller force. Obviously, that's been done before but probably not in this context because it doesn't offer any great advantage.

I'm not sure I agree with your comments regarding the IPO, at least this hasn't been my experience.

I only made one comment about the patent office. That comment is that they do not check if things work.
Do you think they have the time or facilities to test all the inventions they are asked about?


Also, in your debate with Geezer you seem not to have understood where the discrepancy is.
The fundamental difference is between what you are claiming and what the laws of physics will allow.
If your ideas do not tally with reality then it is not reality that has got it wrong.

Incidentally, there is one aspect of inventions that the PO looks at before awarding a patent. They don't patent perpetual motion machines.
If you were to connect the output of your system to a pump to make an "artificial tide" then you would have made a perpetual motion machine. They certainly wouldn't patent that.

Your system might provide a possible benefit in places where the tidal range is too small to use conventionally, but even there it would be pointless because there simply would not be enough energy available to make it worth while.

[Mootle (OP)]

I only made one comment about the patent office. That comment is that they do not check if things work.
Do you think they have the time or facilities to test all the inventions they are asked about?

I agree, it is not the job of the patent office to check if things work or not. But that wasn't the point I objected to it was the comment about them not caring.

Also, in your debate with Geezer you seem not to have understood where the discrepancy is.
The fundamental difference is between what you are claiming and what the laws of physics will allow.
If your ideas do not tally with reality then it is not reality that has got it wrong.

The 'reality' is that Geezer put the wrong figures into the calculation - a point that I've made several times. If anything, I find it amusing that people who obviously have an understanding of the principles cannot concede a point when the error has been clearly identified. The point would have been easy to concede since it is easy to see where the misunderstanding arose. However, to maintain the position after the corrections given is dissapointing. I asserted a nett energy of 12MWh/day. If we compare this with the calculation you kindly indicated earlier and account for the cycle occurring twice per day we have a gross energy available of 500,000 * 67,000 * 2 = 67GJ or 18.6MWh/day. The difference being my allowance for purge pumping and ancillary motor drives, i.e., the equation balances.

Incidentally, there is one aspect of inventions that the PO looks at before awarding a patent. They don't patent perpetual motion machines.
If you were to connect the output of your system to a pump to make an "artificial tide" then you would have made a perpetual motion machine. They certainly wouldn't patent that.

You will be aware that there are several types of perpetual motion. This idea is powered by the gravitation forces of the planets, the sun and the moon. Perpetual motion is not one of the claims of my patent application. This is what causes the tide and so this would not be a perpetual motion machine of the 1st kind - to which you refer. It is true that as the tides persist the machine could continue to function, providing it is properly managed. In this respect, it is no different to a solar PV system / battery powering a motor continuously. If your 'system' boundary did not extend to the sun, you might draw the conclusion that this is also a violation of the laws of thermodynamics but I think you will find such systems have been granted patents. The total energy to lift the 'correct' sized Pontoon does not exceed the power generated - if Geezer reran his calculations he would see that.

Your system might provide a possible benefit in places where the tidal range is too small to use conventionally, but even there it would be pointless because there simply would not be enough energy available to make it worth while.

The system has the potential to exceed the power output of conventional tidal systems. In the scaled model (10) 2MW buoyancy engines would be able to reliably power 14,500 smaller homes or 9,000 average sized homes. The viability, rests with the return on investment. I won't know if this stacks up until I've completed the scaled model and assessed the costings.

This thread has become scrambled by misunderstanding part of which I'm to blame. The schematic animation was only intended to show the basic operation, so I think I'll bow out at this point and work on presenting the idea in a more coherent way. Once, I've completed the scaled animation I would like to pick up, if that's OK?

Thanks to 'everyone' for their input, it was informative especially the possible gearing adaptation and costing information - much appreciated!

[Geezer]

I asserted a nett energy of 12MWh/day.

You can assert as often or as loudly as you care to, but according to the data you provided, it remains impossible to exceed 4.36mWh per day []

If it's so obvious to you that I mucked up the calculation I used to determine that figure, you might want to point out where I went wrong.

[Mootle (OP)]

I asserted a nett energy of 12MWh/day.

You can assert as often or as loudly as you care to, but according to the data you provided, it remains impossible to exceed 4.36mWh per day []

If it's so obvious to you that I mucked up the calculation I used to determine that figure, you might want to point out where I went wrong.

I have, more than once, but to my frustration you've not conceded the point on rating nor have you followed the instruction and input the correct Pontoon volume into your energy calculation based on the 25:1 (rather than the 6:1, used for demonstration purpose of the ratchet pulley system in the schematic animation) gearing ratio.

Further, I've modified Bored chemist's calculation as a check to take into account the twice daily operation and this verifies that my asserted energy balance is ok.

From your comments, I can see where you've got the wrong end of the stick so in this regard I'm afraid that I've failed to properly convey the full operation of the system but this is something I plan to put right with the scaled animation.

Once again, thank you for your input.

[Bored chemist]

I asserted a nett energy of 12MWh/day.

You can assert as often or as loudly as you care to, but according to the data you provided, it remains impossible to exceed 4.36mWh per day []

If it's so obvious to you that I mucked up the calculation I used to determine that figure, you might want to point out where I went wrong.

I have, more than once, but to my frustration you've not conceded the point on rating nor have you followed the instruction and input the correct Pontoon volume into your energy calculation based on the 25:1 (rather than the 6:1, used for demonstration purpose of the ratchet pulley system in the schematic animation) gearing ratio.

Further, I've modified Bored chemist's calculation as a check to take into account the twice daily operation and this verifies that my asserted energy balance is ok.

From your comments, I can see where you've got the wrong end of the stick so in this regard I'm afraid that I've failed to properly convey the full operation of the system but this is something I plan to put right with the scaled animation.

Once again, thank you for your input.

No wonder you keep getting the wrong answer.
I already allowed for the fact that the tide rises twice a day. that's why my post includes this "That energy is available twice a day so that's once every 12 hour"
So, if you don't change my maths to make it wrong, it pretty much tallies with Geezer's.

Rather than repeatedly saying that you have pointed out his error (which, as far as I can see, you have not) could you please point it out now?

If it doesn't work with a 6 to one ratio, it also won't work with 25 to one. You don't get more energy out than the tide puts in, no matter how much rope you use.

I ask you to calculate how much energy you would need to use (with an idealised, perfect crane) to raise the pontoon, rather than using the tide.
If it turns out to be less than 12MW Hr a day then you don't need the tide at all.
You have then made a perpetual motion machine that doesn't rely on the moon.
Your proposal breaches that principle of conservation of energy.
It's that sort of perpetual motion machine, and the PO won't patent it. (And if they cared they would check- they don't have time or kit to do either)

When it comes down to it, for the cost of a supertanker sized building project (and then some for the other structures) you can get a bit less than 0.4MW
You say that electricity is £100 per MW Hr, fair enough.
0.4MW for 24Hr gives £960 per day in revenue. Call it £1000 to make the maths easy
The money markets are screwed at the moment so let's assume you can borrow money at 2% (which is ridiculously cheap)
1000 a day is £365000 per year which will cover a debt (interest only without paying capital) of £18M
But the steel alone will cost you £15M
That leaves no room for any of the generator, the concrete to hold it in pace, paying off the capital, designing, building and so on.

Your idea doesn't make sense.
With a more realistic interest rate, like 5%, it still makes no sense, even if we ignore the laws of physics and let you get out twice as much energy as the ocean puts in.

[Mootle (OP)]

No wonder you keep getting the wrong answer.
I already allowed for the fact that the tide rises twice a day. that's why my post includes this "That energy is available twice a day so that's once every 12 hour"
So, if you don't change my maths to make it wrong, it pretty much tallies with Geezer's.

The error is that neither of you seem understand how the Buoyancy Engine works.

The reason for the modification to your maths is that the Storage Vessel descends twice per day but each time ascends to the surface due to its own buoyancy (since it remains buoyant even when full of water).

Therefore, the energy is 500,000 * 67,000 * 2 = 67GJ (check) rather than the 33.5GJ that you have indicated.

Rather than repeatedly saying that you have pointed out his error (which, as far as I can see, you have not) could you please point it out now?

If it doesn't work with a 6 to one ratio, it also won't work with 25 to one. You don't get more energy out than the tide puts in, no matter how much rope you use.

Your calculation is based on the working head and the Storage Vessel volume this checks out with the generator calculation I provided that is also based on the working head and the Storage Vessel volume.

For the Pontoon we can do the check sum by finding the mass (displaced) for 67,000 * 25 = 1,675,000m3
(the gearing ratio makes all the difference since this drives the required storage vessel).

Using sea water @ a density of 1,025kg/m3 this gives a mass of 1,716,875,000kg

1,716,875,000 * 4 * 9.81 = 67GJ (check)

I ask you to calculate how much energy you would need to use (with an idealised, perfect crane) to raise the pontoon, rather than using the tide.
If it turns out to be less than 12MW Hr a day then you don't need the tide at all.
You have then made a perpetual motion machine that doesn't rely on the moon.
Your proposal breaches that principle of conservation of energy.
It's that sort of perpetual motion machine, and the PO won't patent it. (And if they cared they would check- they don't have time or kit to do either)

I think we're getting into a bit of a circuitous argument here. If you wish to do more maths even though the calculation checks out all ways then please be my guest.

When it comes down to it, for the cost of a supertanker sized building project (and then some for the other structures) you can get a bit less than 0.4MW

The power rating could be any number of values depending on the desired fill time of the Storage Vessel, I've chosen one that fits with the optimum cycle time to get the most out of the Feed in Tariff. Much greater power outputs could be achieved but the fill time would be faster. Alternatively, if a location can be found where the ocean depth affords a greater working head whilst maintaining the tidal range, there is also scope for scaling up.

You say that electricity is £100 per MW Hr, fair enough.

No this is the revenue due the Renewable Obligation certificates. Electricity Export and Feed in Tariff is given separately.

0.4MW for 24Hr gives £960 per day in revenue. Call it £1000 to make the maths easy
The money markets are screwed at the moment so let's assume you can borrow money at 2% (which is ridiculously cheap)
1000 a day is £365000 per year which will cover a debt (interest only without paying capital) of £18M
But the steel alone will cost you £15M
That leaves no room for any of the generator, the concrete to hold it in pace, paying off the capital, designing, building and so on.

We obviously disagree about the fundamental output of the system and you have disregarded the revenue information given previously which somewhat alters the financial viability. However, I do intend to obtain meaningful costings in the fullness of time. However, wrt the interest rates this is accounted for since the government incentives are index linked over 20yrs.

Your idea doesn't make sense.
With a more realistic interest rate, like 5%, it still makes no sense, even if we ignore the laws of physics and let you get out twice as much energy as the ocean puts in.

I think your conclusions are premature and flawed but nevertheless I thank you for your input.

[Geezer]

I understand perfectly well how it works, and I also understand that you have magically made the pontoon more than four time larger to let you reverse into your original, incorrect, power calculation.

The pontoon is now 3.5 times larger than the World's biggest supertanker (er, or whatever Matt wants us to call it.)

This isn't the Tommmy Cooper Show ewe know  []

"The 'reality' is that Mootle put the wrong figures into the calculation - a point that I've made several times. If anything, I find it amusing that people who obviously have an understanding of the principles cannot concede a point when the error has been clearly identified."