Tidal Turbines (vaguely boaty)

[ParaHandy]

Why would you run the machine at only 50% of full load.

Out of every 24hrs, for 7hrs there's insufficient flow to turn the blades; for the remaining 17hrs the tidal flow varies up to the maximum and if the power generated is proportional to tidal flow then the average power generated is somewhere between nil and 240MWh and I'm assuming an average of 50% or 120MWh for 17hrs which gives approx a 24hr average of 85MWh or 35% ...

So we continue with the present system creaking along with equipment failures so that at times it is close to forcing voltage drops and soon, I would guess, power cuts.

The gov's bacon has been saved this winter due to the recession eg Corus knocking off 2 furnaces (puzzled by that as there is a risk of the walls cracking and that's the end) and what's left of our manufacturing industry either on an early christmas break or short time.

[Olivepage]

If we were looking at the proposed turbines for sitting on the bottom of the sea then yes I would follow your reasoning. But I understood the idea of a barrage was that it effectively gave full flow for a much longer period.

If we start with the dam full, the tide starts to ebb and the down tide level drops. If the outflow through the turbnes is less than that which would takeplace without the barrage then the down tide level will very quickly be below the uptide level. If the flow through the turbines is less than would occur without the barrage then this head of water will be sustained through almost the full 6 hours of the ebb. Near the end of the ebb the levels can be allowed to equalise and the reverse will occur on the flood.

Effectively using the water stored behind the barrage as a reserve on the ebb and the water up tide of the barrage as a reserve on the flood. I would expect this to significantly extend the full power part of the cycle.

BTB the proposal for a Severn barrage is to only generate on the ebb tide, which will effectively half the figures. If you start to factor in the capital cost of that proposal and the running costs I would guess that its difficult to make a financial case that - err - well - holds water. Which is the main reason that I would favour the sea bottom machines, even accepting the duty cycle limitations.

Further on the subject of sea bottom turbines. I would have thought that the machines would be designed so that the full power was available over a range of tidal flows. I understand the wind machines give their rated power over a range of windspeeds.

I have no idea how these things are rated and the material Nick put on here clearly will not go into that level of detail, but even considering the changes in flow between springs and neaps there will be a substantial drop in O/P if full power is only available on the biggest spring tides.

I think we need more detailed information before making a firm decision on this.


PS Winter isn't over yet!!

[ParaHandy]

So we continue with the present system creaking along with equipment failures so that at times it is close to forcing voltage drops and soon, I would guess, power cuts.

This week is the critical week for UK power generation. The maximum demand was forecast in September based on two scenarios: one, a normal winter and the other, a 1 in 20 yr winter. The second scenario was what triggered the huge increase in forward energy contracts because the forecast demand of 58GW + reserve of 5GW just exceeded the available UK capacity, excluding the French help of 2GW. In fact, demand is running this week at 56GW which is almost exactly the former forecast and which had been reduced to reflect anticipated UK economic activity.

Even though the actual demand is a "normal" forecast, the grid still pulled in 2GW from France which I wouldn't have thought would be wise at current euro rates unless the UK capacity just doesn't exist. I presume all this power comes through the tunnel? The other thought is that as peak demand occurs over a very narrow period - perhaps 60 minutes - it is fortuitous that France is always 1 hr ahead of us.

[Olivepage]

With some of the stories doing the rounds about equipment failures I'm surprised that we were able to meet 58G.

I think the cables from France are underwater. I seem to remember the link up pre-dated the tunnel. Originally we used to export it to France. Of course there could be some more bits of wire in the tunnel as well.

With the CEGB, they had the responsibility to maintain reliable supply- I am unclear where that responsibility now lies. It seems that absolutely nothing has been done for many years to actually achieve this, and I've an awful feeling that in the next few months we may suffer for that negligence.

Eventually someone will have to realise that pragmatism outranks political correctness.

[DaveS]

With the CEGB, they had the responsibility to maintain reliable supply- I am unclear where that responsibility now lies. It seems that absolutely nothing has been done for many years to actually achieve this, and I've an awful feeling that in the next few months we may suffer for that negligence.

Eventually someone will have to realise that pragmatism outranks political correctness.

Under EU law the responsibility for continuity of electricity supply lies squarely with the UK government. Of course the current electricity market arrangements mean that the government has no effective tools at its disposal to enable it to meet that obligation. For years its advisors have assured government that there was no need to worry because with an efficient free market the hidden hand of capitalism would always work to ensure that supply met demand. Those of us who pointed out the flaws in this approach (market theory is essentially short term: a power station can't be built overnight regardless of how high the electricity price becomes) were routinely dismissed as luddites.

I sense that they are now waking up and realising that there is a serious problem. The Credit Crunch has badly shaken confidence in "The Market", and the possibility of an Energy Crunch is now being openly discussed - unthinkable as little as 6 months ago. A government - of whatever political colour - which lets the lights go out will almost certainly fall. As Para pointed out, the irony is that the financial downturn will probably let them off the hook this winter - provided the weather doesn't turn cold or there isn't a major plant failure.

But what then? The pessimists speak of a 2 year recession, but building power stations takes much longer.

[ParaHandy]

I sense that they are now waking up and realising that there is a serious problem.

I was listening to an interview with Mike O'Brien, the Energy Minister on R4 Today on Wednesday. He was asked to respond to the views reported earlier of experts warning that this country will face an unacceptable risk of major blackouts in less than 10 years unless policy is radically improved. He responded that the National Grid have published data that there would be a 37% capacity increase by 2015 and that contrary to the lights going out, his government would "make them burn brighter".

The National Grid document he is referring to is the 7 year plan from 2008 to 2015 which shows a capacity currently of 80GW increasing to 110GW by 2015. An increase of 30GW.

However, of that increase, 12GW is wind power and, unless all that power is available between 6 and 8pm every day, it can not be included as capacity available to meet maximum demand. 13GW comes from new Combined Cycle Gas plants; 1GW from Holland and the remaining 4GW is from various other sources including 1.6GW from an IGCC (carbon capture) plant at Blyth.

The capacity from nuclear and coal fired stations, 10 and 30GW respectively, is shown as constant at 40GW throughout this period and yet 2 years ago the DTI forecast that nuclear capacity would halve by 2015 and that between 15 and 25GW of coal plant capacity would have to be retired by 2016 to meet the EU Large Combustion Plant Directive (1999) which mandates the reduction of acid gas emissions, primarily SO2 and NOx, from large combustion units.

4GW of the 110GW comes not from this country but from France and Holland.

Even if you ignored these circumstances, the expectation that 40GW is going to be output from stations with a median age of 30-40yrs is risible if not treating us as idiots. Nuclear power has never achieved better than 60% utilisation and if one applied current efficiencies, the total capacity available, excluding Holland & France, in 2015 to meet maximum demand is 78GW and our current 2008 maximum demand in a normal winter will be 58GW.

The gap between capacity and demand is tiny and depends on us keeping in commission clapped out plants and, as regards our coal-fired stations, polluting everyone else in the EU.

It's reasonable to expect a Minister of the Crown to be honest. The deceit shown by O'Brien, particularly when it is his own country's future that he's traducing, is appalling.

[little boy blue]

...... Enough to power the onboard wine cooler perhaps (60 bottles of ordinary or 40 of Moet).....

hi pete

[Olivepage]

Whatever happened to the fluidised bed idea for coal burning.

I remember visiting Grimethorpe colliery in the early 1980s where they had a FB boiler installed and working. A joint venture between NCB and a German company.

The intention was to move to a phase 2 where they installed a gas turbine on the exhaust of the FB burner to up te efficiency.

Never heard any more about it.

[Nick]

What is the RTT?
The RTT is a bi-directional horizontal axis turbine housed in a symmetrical venturi duct. The venturi draws the existing ocean currents into the RTT in order to capture and convert energy into electricity. Use of a gravity foundation will allow the RTT to be deployed quickly and with little or no seabed preparation at depths in excess of 40 metres. This gives the RTT a distinct advantage over most of its competitors and opens up a potential energy source that is 5 times the size of that available to companies using pile foundations.

[quote] “Overall, it is noted that deep sites (>40m) represent some 63% of the UK resource.â€Â

[Olivepage]

Yes

Makes sense to me too.

But its necessary to understand it's limitations.

A 1MW machine in itself will never solve anything. It needs lots of these things with overlapping duty cycles to make a significant contribution. And by lots I mean in thousands.

As Para points out a 1MW machine only gives 1MW for a proportion of the tidal cycle so a 1MW machine may only produce 10-15 MWHrs per day- not 24MWHrs as some may assume.

You then have to have the grid control and management system engineered to maximise the benefits of this technology.

But most of all you need some new BIG stations. By big I mean gigawatt big. And that means either coal or nuclear.

More significantly we need them sometime yesterday.

Para gives the numbers that make the scale of the problem clear.

The so called "green" technologies are never going to generate power on this scale.

Using Drax as an example the original 3 x 660MW sets were first operational in 1974. So these machines have been working for more than 30 years. There is a limit to how long these can continue. A further problem is ash - the station produces 11 million tons of the stuff a year and managing its disposal is an interesting and increasing problem. Going back to the CEGB days the plan for Drax was to close between 2000 and 2004

The other two big stations in the Aire Valley are even older, as are the big Trent Valley stations and Fiddlers on Merseyside. These big coal stations form a major part of the system and they are all very long in the tooth.

There ought to be plans in place to replace them, but as far as I can see there are none. The situation really is becoming serious and it appears that until we start to see actual power cuts no-one in government seems to care.

[Nick]

300 of these units units are to be deployed in a 300MW commercial field in S Korea, to be operational by 2015

The company recognises the need for bigger installations.

In order to benefit from the economies of scale that can be derived from this new technology and enable it to compete with other electricity generators whilst offering an attractive return to investors it is essential that fields (sea farms) of RTT units be created. It is envisaged that the first commercially viable fields could vary in size from 100 to 500 linked 1MW RTT units.

The 1MW unit is due to be scaled up to 2MW in due course, so 1GW installations are not beyond the scope of the company's imagination.

It is estimated (Stephen Salter, Edinburgh Uni) that the Pentland Firth alone could produce as much as 10-20 gigawatts (GW) of electricity - Hunterston B produces 1GW

The problem to my mind is the lack of willingness of government to grasp the nettle and make serious investments in tidal technology. When small start-up companies have to go it alone the r&d costs restrict development and commercial deployment to a snails pace.

Both coal and nuclear are to an extent failed technologies - nuclear has failed to grasp the decommissoning nettle and has made a mockery of its original promise of 'electricity to cheap to meter' while coal is essentially a dirty Victorian technology that has already killed millions and which becomes uneconomic once you try to clean it up sufficiently to meet emissions targets.

Too many snouts are in the wind trough . . . leaving no money for alternative technologies. Tidal has always made more sense than wind IMO.

Surely it is time to drag ourselves out of the comfort zone and make some bold moves. If a design were adopted and production put on a 'war footing' (which is appropriate to the seriousness of the crisis) then I am confident we could revive our engineering industry, gain a world lead, drag ourselves out of recession, keep the lights on and get the job done within the time frame required.

(I hasten to add that I hold no particular brief for Lunar Energy - there are other promising technologies - but as a former offshore energy worker I recognise the sort of rugged, simple technology that is likely to be effective and reliable in the undersea environment).

[JackJ]

production put on a 'war footing' (which is appropriate to the seriousness of the crisis) .

Must say that much of this debate is way beyond my simple mind but its good to see some experts spending a considerable amount of their valuable time trying to explain it to this little corner of the virtual world. Thanks.
Oh, by the way, is this electricity crisis the next Y2K, BSE, Bird Flu, global warming and can we safely say it will go the same way? If so what will the scaremongers think up next or will they finally open their front doors and experience the real world?

[Olivepage]

Is it a crisis?

Well Y2K was a non-event because people took it seriously and spent real money preparing for it.

BSE was real enough - the farmer adjacent to my home almost went bust, he reared cattle for beef, has not touched beef since, now has sheep.

Birdflu - don't know, it hasn't happened yet but serious people are taking it seriously, I did a presentation to a large police force a few months ago and they have considerable worries about the possible effects - lets hope we never see for real.

Global warming - I will refrain from comment.

I suggest you look at the US/Canada experience of the effects of widespread power failure, there have been several over there.

As with most disasterous events you generally have two or more factors that coincide, typically a failure of some technical nature combined with a failure to manage that event.

Managing elctrical supply is a complex and highly skilled task which the national grid controllers have done for many years with remarkably few failures.

The management matches supply to demand on a minute to minute basis, simplifying considerably, they predict the demand and ensure supply is available minute by minute to meet this. Not a simple thing when demand is increasing (or has been) and supply varies with availability of equipment, which can take a considerable time to bring on stream.

A situation that stresses the resources of the equipment and the people charged with the complex task of managing it has all the seeds of of a disaster.

Will it happen? Perhaps we will see.

[ParaHandy]

Tidal has always made more sense than wind.

Is that so? These technologies all require a subsidy to be viable. They are the ultimate in make-believe economics.

The subsidy we will be paying, at current ROC values and if all the envisaged renewable capacity of 14GW is realised by 2015, will be £1.6bn per year and every year thereafter. A typical 400MW CCGT plant costs £240m so you could build 6 of these plants for the cost of the subsidy every year and the annual output of all 6 would exceed that obtained from 14GW of renewables.

[Alcyone]

Nick, have any studies been carried out on the effect on currents direction or force, tide times or the effects on filter feeding organisms?

Nothing is for nothing, and if you take energy out of a sysyem, you affect that system, so presumably there is some effect, however small, on tidal flow? A guess would say it would be miniscule, but a bit of wild thinking could see, in a large installation with many turbines, a chage in tidal flow, with subsequent environmental impacts?