Pentland Firth – Nick Balmer

This was written as a comment to:


A few years ago I was working for BAM Nuttall pricing renewable energy projects including offshore windfarms.

We became part of a consortium looking at the possibility of installing wave or tidal current turbines in the Pentland Firth.

It was one of the most interesting projects that I have ever worked on because of the sheer difficultly of installing anything in the Firth.

The underlying seabed is Pre Cambrian rock and is extremely hard. We know the rock is there, but there is remarkably little real information on just where, what the strata depths and what strengths it has. Each turbine is in effect a separate “building” and the foundations have to be individually designed if one is to drive down the cost to a figure that is viable against other forms of generation.

Colleagues at BAM Ritchies who are specialists at hard rock drilling came up with an extremely clever way of deploying an underwater drilling rig which was tested in the waters off Orkney.

The trouble is that the costs of every thing has to be so much lower than things like oil rig drilling to get viability.

We then looked at how to deploy the kit and turbines.  The extremely short weather windows and the height of the waves encountered means that the number of days suitable to install is very low.  A typical existing jackup can only move in waves less than 1.5m wave height.  This only rarely occur, and the predictability of suitable weather windows is very poor, with forecasting just not accurate enough.

Ports into which vessels could run to take shelter are some distance away, and unlike something like an aircraft that could wait on the tarmac and deploy in an hour or so to the site, a vessel or vessels would take up to a day to deploy, by which time it is quite likely the weather would have gone off.

We did some weather modelling trying to predict forward in real time and then compared it to what happened.

When you factored in the costs of the vessel down time it was frightening in its implications looking at this from the point of view of a contractor who would probably be asked to take on board the weather risk.

We would need to build an entirely new jackup or specialist vessel that would have the ability to move in wave heights two to three times bigger, and to be able to ride out some of the worst weather conditions encountered off our shores.  Again this would be too costly to do unless you had several years of orders ahead.

You were almost certainly not get into that position until after you had several successful reference plants.

It is chicken & egg situation.

No jackup, no reference plants. No reference plants, no jackup.

We did however come up with an alternative method using robotics and another form of vessel.

I hope one day to be able to do this so I am not going to go into detail.

However the same chicken & egg situation, but with a lower CAPEX obtained.

These issues are all technically feasible given a sufficiently large pocket and project.  Say 300 or more turbines.

Just like the first round of offshore windfarms 30 turbines isn’t enough.

That is why innovation and investment is coming forward so much faster now we are looking at 300 turbine sites, and several of those.

You can then start to make a business case stack up.

The real killer of any proposal like this in the Pentland Firth is  however not the development and installation of the turbines, but the sheer distance from any real customer base for the energy you are going to generate who would be prepared to pay enough for the electricity you made.

You have a couple of hundred miles of cabling to get to the nearest cities or significant energy users.

Do you go with your cables through the Highlands?

Do you put in overhead lines on pylons?

Both of those ideas will go down like a lead balloon with the conservationists, the NIMBY’s and a lot of others as well.

Do you route the energy by underwater cables?

Probably the best solution, but still many times more expensive than the cost of building and installing the current turbines themselves.

The trouble is that this cabling burden makes an out-turn cost per MWe enormous with the result that makes generating electricity by almost any other method cheaper.

The cost of the cabling kills this  project dead.

The only way it could be viable would be if the Government or some such body paid the cost of the cabling.

Sadly, I think there are a lot of other things that the money should be spent on before this one.

There are lots of ways of making energy much nearer the end users, for much lower costs per MW and all of them are renewable.

Incidentally nuclear also suffers from the same  effects from cost of cabling .

When Prescott was announcing a few years ago that dowries would be given to communities in places like Cumbria if they took the new nuclear, a colleague working with me looking at the cabling, said in good contracting language, that it was never going to be reality because the sheer cost of installing (or renewing) the cables from sites like Dunreay or Sellafield to the energy customers mainly in the SE of England would make it unviable vis a vis other forms of generation.

This is proving to be correct as the only sites getting any real interest from nuclear developers are all in the South of England.

Sadly this also means that for the foreseeable future the only viable tidal sites are likely to be in the Bristol Channel or off North Cornwall.

Those sites require much less cabling and are technically less challenging for early installations.  The technologies developed in those relatively “easier” waters would bring the installed cost per MW down, and establish a risk profile and level of predictability that could then be marketed to the investment community.

The risks are so great that if at the moment you spent £100 million with me as a contractor, you would have to pay £350 to £400 million (plus my £100million) to the investor to get access to the money to pay over the 25 year plus life of the project.

This has to be down at the £200 million (plus £100m for me) level before tidal even has a slight chance of going ahead.

The banker would make far more out of the deal than I would and for far less of the risk.

We need reference plants to get this risk profile understood.

These do exist off Korea, and I expect in about 20 years time that we will be buying back technology originally conceived 20 years ago in Britain when our first significant tidal site gets built.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.