From the Guardian:
The world’s best site for tidal power, the Pentland firth, could provide half of Scotland‘s electricity, according to the first robust estimate of its potential. The tidal streams, which surge through the firth at five metres per second, could bring large amounts of renewable energy in reach within a decade if enough government support is available, said the Oxford University engineer behind the new study.
From Anglesey to the Severn estuary to Portland Bill, the UK has the greatest potential for generating predictable, clean energy from tidal channels. Turbines are already operating at Strangford Loch in Northern Ireland and prototypes are being tested in the Menai Straits off Anglesey.
But the Pentland firth is the greatest resource. “It is almost certainly the best site for tidal stream power in the world,” said Thomas Adcock, at Oxford University, who led the new work published in the journal Proceedings of the Royal Society A. The water flow is rapid there because the tide shifting from the Atlantic into the North Sea is forced through a narrow eight-mile channel.
The engineers developed new models to find the technical and economic “sweet spot” between the extremes of bringing water in the firth to a standstill and having a free flow. They calculated that underwater turbines strung across the entire width of the firth could generate a maximum 1.9GW of energy, averaged across the fortnightly tidal cycle. That is equivalent to 16.5 terawatt hours of electricity a year, almost halfScotland’s entire annual electricity consumption in 2011. As Scotland already produces 14.6Twh a year of renewable energy, a fully exploited Pentland would bring Scotland close to meeting its aim of 100% renewable electricity by 2020.
Tallbloke's Talkshop 
Tidal stream power makes far more sense than wind power because it is 100% predictable. It is then really easy to plan demand balancing with conventional power. On the contrary, wind is randomly intermittent and very expensive to balance. Balancing wind with gas is like accelerating and breaking your car continuously – fuel costs rise dramatically! These hidden extra costs (£60/MWh) should be added onto wind subsidies (£50/MWh – onshore, £100/MWh – offshore). Of course they never are !
“with government support”. I expect they meant to say “taxpayer support” but just slipped up. It certainly looks exciting, possibly requiring it’s own TV show. Extreme subsidy farming! Underwater!!
While tidal power is more reliable than wind power, it is still intermittent. Maybe it could be backed up by huge hydrocarbon power plants wasting energy in spinning idle reserve? Perhaps there is an energy storage system capable of storing half of Scotlands power?
Exactly what effect would this have on fish and marine mammals? Chop chop?
And how would extracting so much energy from the tidal flow affect the marine environment on either side of the Firth. Slowing down the tide would presumably turn a scouring flow into a much slower depositing stream.
The SeaGen website is remarkably silent. It seems to have stopped posting after installation. Can anyone provide a link to the promised monitoring?
“a fully exploited Pentland would bring Scotland close to meeting its aim of 100% renewable electricity by 2020.”
So the working day in an independent Scotland will need to be governed by the moon !
It might be predictable, but it’s still tidal! What/who provides the power at slack tide, four times a day? No doubt the ‘could provide half of Scotland’s power’ is in the same category as windmills providing enough power for ‘1000 homes’, i.e. in the best possible circumstances. In the case of tides, that’s roughly one week in four, for maybe 8 hours a day…
Richard North at EU Referendum has a good article about STOR – short term operational reserve –
which essentially describes STOR being supplied by privately owned diesel generators at considerable extra cost to the consumer.
We have such clever and thoughtful politicians.
At least tidal electricity is reliably intermittent but again at what cost.
The degree to which energy intensive domestic operations such as heating bathwater, washing clothes and cooking food could be timed to fit in with the peak generation times is an interesting one. With modern electronic controls I would have thought it would be possible to make good use of the energy generated, and minimise demand at slack water times.
Since the tides gradually shift round the clock there would be periods when peak generation coincides with ‘normal’ peak demand, and other times when Scots could dig the slow cooker they got as a wedding present out of the back of the cupboard. Timers on washing machine for clothes and crockery are simple enough, and fridges can handle being turned off for a few hours at a time.
I think it’s worth Scots looking at this stuff seriously, since we’d like to keep some shale gas as strategic reserve in the longer term.
‘Half Scotland’ is 2.65 million people.
It’s not going to keep Britain’s lights on.
Frack baby frack!
“As Scotland already produces 14.6Twh a year of renewable energy..”
Anyone got the details and source of that claim?
“domestic operations such as heating bathwater, washing clothes and cooking food could be timed to fit in with the peak generation times”
We may be an unusual family, but we do tend to cook and eat at roughly the same times of day. I’m not sure I’m willing to put off my dinner by 50 minutes every day because of celestial mechanics!
http://www.scotland.gov.uk/Publications/2008/11/05115324/6
Has a 2006 breakdown of Scottish energy sources
Confirmation, if ever any was necessary, that Scotland is run by a bunch of self harming lunatics.
“The engineers … calculated that underwater turbines strung across the entire width of the firth could generate a maximum 1.9GW of energy, averaged across the fortnightly tidal cycle.”
Here’s the fortnightly tidal cycle:
Figure 3.11 Absolute value of tidal-current velocity in the Fall of Warness (Orkney).
Location: 59.135°N, 2.805°W, hourly values for 2003 computed with TotalTide.
• new moon; ? full moon.
How do you average it out?
The problem with blades is that they chop. Can a blade be rethought, though, and turned into an internal Archemides screw, with a narrowing end, so that all things going through spin their way through rather than get chopped?
I can’t imagine a thin “fluid” like air would let the thing work, but salt water might.
Certainly mechanical efficiency would be reduced, but impact reduction and possibly increased turbine life (less wear/year) could be brought into the equation.
In public services, ROR, pay-out time, don’t need as much consideration as operating cost and lifespan (think of bridges and roads and sewers: pay more now for longer time between repairs seems to be really important).
Dunno.
Isn’t this a Three Gorges like project, just five times more megalomanical, while producing 10+ times less electricity and with much less stable operation?
Looks like the Angsoc comrades are ready to outstrip even the Eastasia comrades and that this “lunar energy” will outdo even the solar one – at least in degree of absurdity. Poor British taxpayer…
Thanks TB.
I’m having problems with “Scotland already produces 14.6Twh a year of renewable energy” and “16.5 terawatt hours of electricity a year, almost half Scotland’s entire annual electricity” when nuclear is said elsewhere to generate ~50%, and then gas and coal weigh in with hefty contributions.
In the 2006 document, it appears that they include the large pumped hydro storage in the category of “Amount of Electricity Generated, By Energy Source”, which seems a bit bizarre. Are they pumping all that water uphill with nuclear electricity, I wonder? Maybe it becomes slightly greener in appearance when it runs back down hill.
As with wind it extracts energy from the environment so changes it. In the long run this must have effects, which aren’t accounted for. No free lunch anywhere.
”Confirmation, if ever any was necessary, that Scotland is run by a bunch of self harming lunatics”
So True, we can but hope that enough of the Scots have a passing knowledge of their own history, and that it may influence the upcoming vote 🙂
Having the potential energy and harnessing it are two different beasts entirely. Just as with offshore wind turbines, getting the generators in place and keeping them there as well as maintenance and repairs/replacements are a massive engineering undertaking that may make it interesting but entirely uneconomic.
where does the energy that drives tidal power come from? You can’t have something for nothing. So what is the consequence of tapping into tidal energy? As I understand it the tides are caused by the gravitational interaction between earth and moon. So are we harnessing gravity power? And thereby reducing the gravitational pull?
In my back yard so to speak. Read the news updates.
http://www.tidalenergyltd.com/
I note with interest that “the DeltaStream device sits on the seabed under its own gravity and consists of three independent 400kW turbines mounted on a triangular frame”. Seemingly it is not anchored or pinned down in any way. This seems a little bit hairy to me.
“what is the consequence of tapping into tidal energy?”
It removes potential energy from the earth and will alter the earth orbit.
A somewhat small proportion.
Roger, I have spent the last 20 mins scanning your link from this am. They state targets for 2011.
Do you know if they have achieved their targets?
Charge 5p/kWh for power while the tide is running. >:)
@mitigatedsceptic
That triangular tube frame is filled with water. It won’t move.
” it is not anchored or pinned down in any way.”
While sitting in a tidal race that can reach 12 knots! What could possibly go wrong..?
nTropywins says:
July 10, 2013 at 6:57 pm
So are we harnessing gravity power? And thereby reducing the gravitational pull?
No. Gravity is a force, not an energy. It is’t ‘used up’ by things being acted on by it.
G Watkins: sorry, dunno.
M Hart: Reliable figures for alternative energy actual output – hard to find.
Actually it will slow down the rotation of the Earth causing the day to get longer ! Shock horror – another anthropogenic effect !
It will also decrease the time until the moon leaves the Earth. “Space 1999” anyone?
Looks like The Register is onto it..
http://www.theregister.co.uk/2013/07/11/alex_salmonds_fantasy_of_a_tidalpowered_scotland_washed_away/
Dear Grauniad,
“a maximum 1.9GW of energy, averaged across the fortnightly tidal cycle”
1) Watts aren’t energy, but never mind.
2) Is it a maximum or an average? Do they know the difference?
3) The tidal cycle is monthly, not fortnightly.
Apart from that.. 🙂
Power is not used on average, It is used on demand. Tides flow two cycles per day, at least in most locales.
I do wonder if proper environmental accounting has been avoided for this green-pushed scheme as it is with wind mill power, and I wonder if the actual power yield will be better than stated vs. real with wind as well.
Wind produces a small fraction of stated capacity in the real world. Will tide power do better?
Although it might be fine in theory, what will make it viable is the cost. The reason that the Pentland Firth is such a good source of potential power generation is because the tides are extremely strong. It has always been extremely dangerous to shipping as a result. In the nineteenth century a great-great grandfather of mine made a living piloting ships through the dangerous waters. Travel the ferry between John O’Groats and Orkney and you will see the swirling waters, and observe the wide berth the ferry gives them. Both construction and maintenance would have to be outside of the tidal surges, the numerous storms, and in daylight hours (about 5 in December and 20 in mid-June).
Even with less inhospitable conditions, construction costs would be huge. But in the Pentland Firth you have far greater challenges. It would be much easier and cheaper to build equivalent full-size nuclear reactor at Dounreay.