Where will the electricity come from?

[John55]

By changing the system. That's cheating only to a scientist, not to an engineer.

Analogy follows:
Electric source is 0.1 Ohm Resistive and 0.1 Ohm Inductive.
Existing load is resistive only.
Greater power transfer can occur if you also add 0.1 Ohm capacitive to the load even if resistance is increased. As an EE power engineer of the (very) old school, this is basic stuff.

Or, back to the Irish Sea, since it has two entrances the power entering can be changed by building structures that have and effect of adjusting the timings between tides at the two entrances. I.E. by building some loads. Tides and associated ebbs and flows are analogous to electric charge and current.

As I say, astoundingly, government policy is based on trivially wrong assumptions, presumably because it lines someone's pockets.

A tidal lagoon works by essentially tapping the energy used to raise a body of water as it enters and leaves an artificial enclosure built on the seabed close to the low water mark. As the tide come in the water enters the enclosure via turbines and when the tide goes out the water leaves via the same turbines. So for 18-22 hours per day the system can generate useful power.

The amount of energy available is limited by the mass of water in the lagoon and the height through which it is raised/falls. So to increase energy available you either increase the size of the lagoon or the height difference between high and low tide.

So are you suggesting that the tidal range of the Irish Sea is increased by modifying the coastline to use the energy of the North Atlantic to drive resonant oscillations of the water in the Irish Sea to raise high tide and lower low tide? Or is there some other mechanism you are considering?

By how much are you expecting the level of tides to be changed? While there may be some advantages in that the tide may come in more than twice per year at Southport will the flooding of much of North West England and North and West Wales twice per day be the consequence of this idea?

 

[eastdyke]

A tidal lagoon works by essentially tapping the energy used to raise a body of water as it enters and leaves an artificial enclosure built on the seabed close to the low water mark. As the tide come in the water enters the enclosure via turbines and when the tide goes out the water leaves via the same turbines. So for 18-22 hours per day the system can generate useful power.

The amount of energy available is limited by the mass of water in the lagoon and the height through which it is raised/falls. So to increase energy available you either increase the size of the lagoon or the height difference between high and low tide.

So are you suggesting that the tidal range of the Irish Sea is increased by modifying the coastline to use the energy of the North Atlantic to drive resonant oscillations of the water in the Irish Sea to raise high tide and lower low tide? Or is there some other mechanism you are considering?

By how much are you expecting the level of tides to be changed? While there may be some advantages in that the tide may come in more than twice per year at Southport will the flooding of much of North West England and North and West Wales twice per day be the consequence of this idea?

You can take energy at point A, which will increase energy available at point B, but at the same time also reduce energy available energy at point C.

This could go International!

Unless of course there is never any resistance .....

 

[Holly]

... So are you suggesting that the tidal range of the Irish Sea is increased by modifying the coastline to use the energy of the North Atlantic to drive resonant oscillations of the water in the Irish Sea to raise high tide and lower low tide?

By how much are you expecting the level of tides to be changed? While there may be some advantages in that the tide may come in more than twice per year at Southport will the flooding of much of North West England and North and West Wales twice per day be the consequence of this idea?

As to the first paragraph, substantially yes. Or more modestly, tidal range can be largely sustained despite extracting lots of energy from the tide. Popular models which give no account to resonance do not allow that. Oh, and it's not exactly modifying the coastline to build huge offshore lagoons connected to land only by bridges, but it's comparable in effect (without being so ugly in appearance).

As to the second paragraph, yes a badly designed system could cause flooding damage. But that is a matter of not screwing up the design. The basic point stands that by inducing North-South resonance large amounts of power generation are possible but government policy holds contrariwise. According to one respected authority,
http://www.inference.phy.cam.ac.uk/withouthotair/cG/page_312.shtml
the tidal power presently entering the Irish Sea averages 45Gw. Which is roughly the same as UK average (not peak) demand.

Without resonance it would be hard to capture even 30%. With resonance over 100% is possible.

Such a project is huge, on a par with Dutch polder land reclamation. But Britain has it all - huge seas that are relatively shallow, natural channels (English channel and Irish Sea), high tidal ranges by worldwide averages, proximity to demand, land suitable for giant quarries, electricity to move materials, Engineering expertise, industry (that can be reinstated e.g. steel). Expensive, yes, but it is all home grown industry and resources. We just need to pay people to do this work instead of paying them to be idle/unemployed/learning/retired/military/discouraged.

 

[The Ham]

As waves at Dawlish cause problems to the trains, why not kill two birds with one stone and have wave power generation off the coast there, which will flatten the waves which will reduce the number of days that there are problems for the trains from the waves.

 

[MattRobinson]

Without resonance it would be hard to capture even 30%. With resonance over 100% is possible.

Correct me if I'm wrong, but I thought a fundamental principal of physics was that energy could be neither created nor destroyed? Therefore, nothing can be >100% efficient.

We just need to pay people to do this work instead of paying them to be idle/unemployed/learning/retired/military/discouraged.

I agree about the unemployed/idle and some of the military, but if we don't pay for people to learn, we won't have the people to design these types of system in the first place! (Although I do agree that some degrees are pointless, we do need education/academia as a whole).


Sent from my HTC Sensation Z710e using Tapatalk 2

 

[Holly]

Correct me if I'm wrong, but I thought a fundamental principal of physics was that energy could be neither created nor destroyed? Therefore, nothing can be >100% efficient. ...

A system can be changed so as to capture more than 100% of the net energy that used to enter the system's physical boundaries before the system was physically rebuilt. It applies particularly to a canal that is stimulated from both ends with a phase displacement. Standing waves and resonance are important concepts.

I think scientists (I'm not one) would call this the difference between an open system and a closed system.

 

[brianthegiant]

Note that you can never capture 100% of the energy in water or wind.

In wind turbines its called the Betz limit & is about 33% I think. Basically a single turbine can never extract more than ~33%. If you tried to extract 100% you would effectively have to stop the wind, at which point there is no motion to push the blades.

I think pretty much the same would apply to varying degrees to any wave or tidal energy device.

However it's not all doom & gloom, we have one of the worlds best Marine enerrgy resources, we just need to develop some robust/cost effective collection devices & mature the technology a bit more.

 

[starrymarkb]

As waves at Dawlish cause problems to the trains, why not kill two birds with one stone and have wave power generation off the coast there, which will flatten the waves which will reduce the number of days that there are problems for the trains from the waves.

Waves only cause problems with a strong easterly, as the prevailing wind is from the west it means the wave generators will be idle much of the time. (Dawlish is actually quite sheltered)