'Milestone' for wave energy plans

16-03-2010 02:04PM #1

http://news.bbc.co.uk/1/hi/scotland/highlands_and_islands/8564662.stm

Ten sites on the seabed off the north coast of Scotland have been leased out to power companies in an effort to generate wave and tidal energy. In the first project of its kind in the world, areas in the Pentland Firth and around Orkney have been leased to seven companies by the Crown Estate.
The companies are to push forward plans to generate enough electricity to supply 750,000 homes by 2020.

Looks like something that could work off the west coast of Ireland as well.

Cunsiderthis · 16-03-2010 03:13PM

Deleted User wrote: »

http://news.bbc.co.uk/1/hi/scotland/highlands_and_islands/8564662.stm

Looks like something that could work off the west coast of Ireland as well.

Like so many projects which seem at a glance to be wonderful, harnessing waves for electricity is not as easy or simple as it might appear. The problem is that it's not easy to harness this energy and convert it into electricity in large amounts.

Wavegen operate a commercial wave power station called "Limpet" on the Scottish island of Islay. Greenpeace offer this as an explanation as to how it works http://www.greenpeace.org.uk/files/swfs/migrated/MultimediaFiles/Live/Video/5352.swf

There are other technologies which are largely variations of the waves being harnessed to move pistons to drive turbines, and this technology is more likely to be beneficial on a larger scale than Limpet technology, but the technology is in the early stages and its problematic.

they also largely depend on the waves and , like wind power, sometimes the waves are non existent and other times they are readily available. At other times the sea, in a storm, can smash up the equipment, so its not as easy as it looks.

16-03-2010 03:26PM

Cunsiderthis wrote: »

Like so many projects which seem at a glance to be wonderful, harnessing waves for electricity is not as easy or simple as it might appear. The problem is that it's not easy to harness this energy and convert it into electricity in large amounts..

That issue can be said of all kinds of uncontrolled energy sources. Until a method of cheap and reliable electrical storage is developed, it will always be an issue.

Ultracapacitors could provide the answer, but they would need to be at the ends of the grid (in the consumers property) and the consumer would then be able to soak up excessive supply and return power to the grid as needed.

Cheeble · 16-03-2010 07:54PM

Since half the capacity is to come from tidal projects, the resource is more predictable than wind... or oil or gas or coal for that matter.

Cheeble-eers

Cunsiderthis · 17-03-2010 08:36AM

Cheeble wrote: »

Since half the capacity is to come from tidal projects, the resource is more predictable than wind... or oil or gas or coal for that matter.

Cheeble-eers

Tidal power is intermittent and, like a wind turbine or wave generators, does not give a constant flow of electricity.

The load factor for tidal power is between 25-30%, which means that it is more expensive to produce electricity from tidal power machines than from other sources of power, and the intermittent supply created is less useful than a source of power which is constant.

Tidal power systems also restrict fish migration, kill fish, and cause silt build up which affects tidal basin ecosystems.

Because of intermittency and variable flow problems of tidal energy, it is a very limited resource. The U.S. Department of Energy Tidal Energy Report states that there are only about 40 really good sites on Earth with high enough flows to be considered economically practical.

Finally, what's the "cheeble-eers" thing about?

Cheeble · 17-03-2010 11:06AM

Cunsiderthis wrote: »

Tidal power is intermittent

Yes, it is cyclic. The word I used was predictable.

The load factor for tidal power is between 25-30%, which means that it is more expensive to produce electricity from tidal power machines than from other sources of power

If by load factor, you mean the proportion of time when energy can be generated, it's about the same as for wind or solar. When you say, "other sources of power", do you mean fossil fuels? Surely it's relevant to compare tidal with other forms of renewables. Else, what do you mean by Load Factor?

Finally, what's the "cheeble-eers" thing about?

You've already sent me several private messages on this, I have already told you (and you have already sneered at the explanation), that it started as a sign-off in the pub when I was a teenager. I'm not ashamed of it, I don't understand why you find it necessary to keep bringing it up.

Cheeble-eers

Cunsiderthis · 18-03-2010 11:29AM

Cheeble wrote: »

Yes, it is cyclic. The word I used was predictable.

If by load factor, you mean the proportion of time when energy can be generated, it's about the same as for wind or solar. When you say, "other sources of power", do you mean fossil fuels? Surely it's relevant to compare tidal with other forms of renewables. Else, what do you mean by Load Factor?

You've already sent me several private messages on this, I have already told you (and you have already sneered at the explanation), that it started as a sign-off in the pub when I was a teenager. I'm not ashamed of it, I don't understand why you find it necessary to keep bringing it up.

Cheeble-eers

I'm not sure which aspect of it you consider predictable? While it is certainly predictable that the tides, and wave, magnitute is unpredictable, I'm not sure how this helps it as a source of power generation. While it's also predictable that tides rise and fall, the source of power is intermittent and the magnitude and force of the rise and fall is unpredictable beyond a couple of days in advance.

Load factor, in electricty terms, is a measure of the output of a power plant compared to the maximum output it could produce.

As for "sneering", I merely notice you seem to end most of your posts with "Cheeble-eers" which sound a little Bruce forsytehesque trying to create a catch phrase like "Nice to see you, to see you nice" on the generation game, and I don't understand why anyone wants to do that on a boards site. I didn't sneer, I asked why, as I am genuinely puzzled as to why anyone wants to do that.

Macha · 18-03-2010 12:00PM

Cunsiderthis wrote: »

I'm not sure which aspect of it you consider predictable? While it is certainly predictable that the tides, and wave, magnitute is unpredictable, I'm not sure how this helps it as a source of power generation. While it's also predictable that tides rise and fall, the source of power is intermittent and the magnitude and force of the rise and fall is unpredictable beyond a couple of days in advance.

Intermittent is the wrong word to use as intermittent implies dropping off unexpectedly. The correct word is "variable". Tidal is very predictable and improvements are being made in the prediction of wind power. I don't know that much about wave power tbh.

Cunsiderthis wrote: »

As for "sneering", I merely notice you seem to end most of your posts with "Cheeble-eers" which sound a little Bruce forsytehesque trying to create a catch phrase like "Nice to see you, to see you nice" on the generation game, and I don't understand why anyone wants to do that on a boards site. I didn't sneer, I asked why, as I am genuinely puzzled as to why anyone wants to do that.

Cut out the nonsense and personal questions.

Cheeble · 18-03-2010 12:02PM

Cunsiderthis wrote: »

I'm not sure which aspect of it you consider predictable? While it is certainly predictable that the tides, and wave, magnitute is unpredictable, I'm not sure how this helps it as a source of power generation. While it's also predictable that tides rise and fall, the source of power is intermittent and the magnitude and force of the rise and fall is unpredictable beyond a couple of days in advance.

Quite the contrary. The magnitude, timing and available energy for tides are predictable, with considerable precision, for at least fifty years into the future. Predictions are accurate to within minutes and centimetres.

[edit] See, for example, http://easytide.ukho.gov.uk/EASYTIDE/EasyTide/Support/faq.aspx

Cheeble-eers

18-03-2010 12:11PM

Cheeble wrote: »

Quite the contrary. The magnitude, timing and available energy for tides are predictable, with considerable precision, for at least fifty years into the future. Predictions are accurate to within minutes and centimetres.

[edit] See, for example, http://easytide.ukho.gov.uk/EASYTIDE/EasyTide/Support/faq.aspx

Cheeble-eers

It's the predictability of tidal energy that makes it so attractive, if correctly positioned it should be possible to generate power 24/7.

Of course it can't be matched up to demand without building some form of storage facility, but at least the energy can me managed.

Cunsiderthis · 18-03-2010 12:11PM

Cheeble wrote: »

Quite the contrary. The magnitude, timing and available energy for tides are predictable, with considerable precision, for at least fifty years into the future. Predictions are accurate to within minutes and centimetres.

[edit] See, for example, http://easytide.ukho.gov.uk/EASYTIDE/EasyTide/Support/faq.aspx

Cheeble-eers

Even if it were true that we know the magnitude and speed of tides into the future (I think the people of sri lanka, for example, might disagree with you), it still doesn't mask the fact that the power available from tidal power schemes or wave power schemes is intermittent, and that the load factor is roughly the same as it is for wind power generation.

That's not to say that we shouldn't explore and use either, but to think either is a magic bullet or reliable might be foolish.

Deleted User wrote: »

It's the predictability of tidal energy that makes it so attractive, if correctly positioned it should be possible to generate power 24/7.

Of course it can't be matched up to demand without building some form of storage facility, but at least the energy can me managed.

The answer is that it's not possible to generate constant power from tidal or wave power generators with our current technology, hence it is classified as intermittent.

The problem for most forms of intermittent power, such as wind and tidal or wave power, is storage. If, and when, we can develop efficient storage for electricity, then the usefulness of many forms of power generation suddenly becomes much more attractive and viable.

Cheeble · 18-03-2010 12:27PM

Cunsiderthis wrote: »

...I think the people of sri lanka, for example, might disagree with you...

That was nothing to do with tide. It was a wave, caused by a geological event.

Tide and waves are not the same thing.

Cheeble-eers

18-03-2010 12:45PM

Cunsiderthis wrote: »

The answer is that it's not possible to generate constant power from tidal or wave power generators with our current technology, hence it is classified as intermittent.

That is true of individual tidal generators, what I am suggesting is a diverse system of tidal generators.

The tides occur at different times along the coast, so by having a string of generators along the coast, at any point in time some will have either a rising or falling tide and others will be "becalmed" at either end of the tide cycle.

Would it be cost effective? depends on the cost of the alternative!

Cunsiderthis · 18-03-2010 12:50PM

Deleted User wrote: »

That is true of individual tidal generators, what I am suggesting is a diverse system of tidal generators.

The tides occur at different times along the coast, so by having a string of generators along the coast, at any point in time some will have either a rising or falling tide and others will be "becalmed" at either end of the tide cycle.

Would it be cost effective? depends on the cost of the alternative!

I have no specific knowledge of any such proposed schems, but if you are suggesting a tidal generator, or generators, which might be 100 miles or more, long, that I think common sense indicates that the cost of both installation and maintenance, coupled with the increased transmission losses, might be so enormous as to make any such scheme economically unattractive.

Have you heard of such a scheme?

18-03-2010 01:26PM

Cunsiderthis wrote: »

I have no specific knowledge of any such proposed schems, but if you are suggesting a tidal generator, or generators, which might be 100 miles or more, long, that I think common sense indicates that the cost of both installation and maintenance, coupled with the increased transmission losses, might be so enormous as to make any such scheme economically unattractive.

Have you heard of such a scheme?

It would be a series of individual generators, strategically located and connected to the grid.

Cunsiderthis · 18-03-2010 01:37PM

Deleted User wrote: »

It would be a series of individual generators, strategically located and connected to the grid.

I'd be interested to see the costs involved, both installation and running costs. Do you know of a scheme or proposal similar to the one you are thinking of?

18-03-2010 02:48PM

Cunsiderthis wrote: »

I'd be interested to see the costs involved, both installation and running costs. Do you know of a scheme or proposal similar to the one you are thinking of?

I have seen the idea floated in the past, but I don't have any costings at all. Essentially each unit would be separately built and run, it's the aggregated power generated that make such a system 24/7.

It's a way to make intermittant power generation sources viable, they will still need to be combined with electrical storage systems.

Cunsiderthis · 18-03-2010 02:57PM

Deleted User wrote: »

I have seen the idea floated in the past, but I don't have any costings at all. Essentially each unit would be separately built and run, it's the aggregated power generated that make such a system 24/7.

It's a way to make intermittant power generation sources viable, they will still need to be combined with electrical storage systems.

Efficient electrical storage is obviously the key, and lets hope we make great strides towards this goal.

Deleted User wrote: »

I have seen the idea floated in the past...

:D

Cheeble · 18-03-2010 03:42PM

Deleted User wrote: »

That is true of individual tidal generators, what I am suggesting is a diverse system of tidal generators.

The tides occur at different times along the coast, so by having a string of generators along the coast, at any point in time some will have either a rising or falling tide and others will be "becalmed" at either end of the tide cycle.

Would it be cost effective? depends on the cost of the alternative!

It's similar to the diversity case often presented for wind farms which argues that the wind is always blowing "somewhere", so if we build enough wind farms in diverse locations and connect them with a grid, we can have 24/7 power generation. The arguement works better for tidal than for wind.

One of the things that tidal power schemes seem to suffer from is the over-hype that accompanied the early days of wind farms where developers make exaggerated claims to secure investment and planning consent. e.g. http://www.berr.gov.uk/files/file30617.pdf

There are a lot of people working on the technology though, and the technical solutions are improving rapidly, in part because we've learned the lessons from wind. Resources such as EMEC http://www.emec.org.uk/ are providing a lead in terms of testing and certification.

Opinion coming up: I think tidal will form a small part of the energy mix in future due to exploitation of the few "ideal" sites combining ease of development, low environmental impact and a good tide resource however, I don't see it as ever becoming a large scale (or do I mean mainstream

)contributor to our energy needs.

Cheeble-eers

Marcelproust · 18-03-2010 04:06PM

Cheeble wrote: »

It's similar to the diversity case often presented for wind farms which argues that the wind is always blowing "somewhere", so if we build enough wind farms in diverse locations and connect them with a grid, we can have 24/7 power generation. The arguement works better for tidal than for wind.

One of the things that tidal power schemes seem to suffer from is the over-hype that accompanied the early days of wind farms where developers make exaggerated claims to secure investment and planning consent. e.g. http://www.berr.gov.uk/files/file30617.pdf

There are a lot of people working on the technology though, and the technical solutions are improving rapidly, in part because we've learned the lessons from wind. Resources such as EMEC http://www.emec.org.uk/ are providing a lead in terms of testing and certification.

Opinion coming up: I think tidal will form a small part of the energy mix in future due to exploitation of the few "ideal" sites combining ease of development, low environmental impact and a good tide resource however, I don't see it as ever becoming a large scale (or do I mean mainstream )contributor to our energy needs.

Cheeble-eers

I tend to agree with you that tidal power schemes are based on an natural element ( the tide) which is more predictable than the wind or the sun needed for power generation.

Over hype or not, while tidal power schemes are still relatively inexpensive at between €0.02 - €0.05 per kw-h, when the load factor is taken into account the cost then appears to be less attractive compared to other forms of power generation.

Other estimated costs per kW-h are:

Wind €0.04 - €0.06

Geothermal €0.045 - €0.30

Hydro €0.05 - €0.113

Gas €0.039 - €0.044

Solar €0.15 - €0.30

thermal Electric €0.03 - €0.15

The USA is about to build two Ocean Energy Thermal Conversion plants which should provide 14.5 megawatts between them, and it's rumoured that the EU, among others, is taking a keen interest in the results as these plants are capable of providing a non intermittent supply of power which is regular and dependable.

'Milestone' for wave energy plans

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