Technical Analysis

Technical Constraints

To get an idea of Scotland's realistic tidal resource it was essential to take into account technical factors that limit the resource. A technical constraint can be anything that limits the deployment of tidal turbines at a specific site. It is important to note that some technical constraints are device specific and not all technical constraints will affect those looking to invest in certain areas. This was one of the main advantages of displaying this data in GIS Software as the site selection tool allows the users to turn off technical layers depending on their individual circumstances.

The table below shows examples of technical constraints that can be taken into account when assessing the viability of a site for deploment of marine current turbines.

Depth
Proximity to Grid
Flow Characteristics
Geology/Sediments
Dredging and Disposal Areas
Site Access
Typography of Seabed
Geographical Obstructions
Oil and Gas Pipelines
Electricity Cables

 

Depth

The first major constraint that was considered in this study was the water depth. The depth of water is a major technical constraint for marine current turbines as the majority of devices have to be piled into the seabed during installation. The pile is drilled by jack-up barges and they are limited to the depth of water that they can work in due to the length of their legs. Through consultation with marine drilling engineers at Fugro Seacore it was found that current technology was being used to install wind turbines up to a water depth of 50m. We used our GIS mapping software populated with data from the Proudman Oceanographic Laboratory (POL) to produce our first depth constraint map of Scotland.

It was found that this constraint alone significantly depleted Scotland's tidal resource but as this project is focused on the future of tidal power in Scotland further investigation was undertaken to find out how jack-up barge technology was developing. It was found that the fledgling offshore wind power industry round the world was forcing drilling companies to develop barges that can work at greater water depths. One company that is leading the way in offshore wind installation is MPI Offshore who are developing jack up barge technology in China. Through consultation with a marine installation expert it was assumed that the maximum theoretical depth that a piled tidal turbine could be installed at was around 100m; this is due to the maximum depth that divers can safely work at. The GIS map below shows any sites with a maximum water depth of over 100m marked as constrained.

 

Grid Proximity and Capacity

For the purposes of this study the proximity and capacity of the electricity grid was ignored. This was decided after our initial assessments showed that most of the major tidal sites in Scotland were discounted due to the limited capacity of the electricity grid in remote areas. It was assumed for the purposes of this study that the future electricity grid in Scotland will be upgraded and extended in order to incorporate large marine generation from remote areas.

Seabed Geology

The geology of the seabed at a specific site can be considered as a technical constraint as it can hugely affect the cost of deploying tidal turbines. In our analysis we used data on the seabed geology around Scotland from the Scottish Government Marine Renewables Strategic Environmental Assessment . Following consultation with marine drilling engineers we came to the conclusion that areas of mud and solid rock should be displayed as technical constraints as the cost of piling devices into solid rock and mud is significantly more expensive than sand. The GIS image below shows the areas of mud and solid rock in a tidal area off the coast of Dumfries and Galloway .

 

Undersea Cabling and Pipelines

The seabed around Scotland is littered with a variety of offshore oil and gas pipelines and communication cables. These cables and pipelines can span hundreds of miles and any attempt to develop a tidal power farm in their vicinity will be met with objections during planning . In our analysis we used data on undersea cabling and pipelines around Scotland from the Scottish Government Marine Renewables Strategic Environmental Assessment . The GIS image below shows the impact of undersea cabling and pipelines on a tidal area off the coast of Dumfries and Galloway .

Cables and Pipelines

 

Disposal Sites and Dredging Areas

Various dredging and disposal sites for the dumping and excavation of material are situated around the coast of Scotland. These are areas delegated by the government and it is highly unlikely that planning permission would be granted to tidal power projects proposed in these areas. In our analysis we used data on the location of dredging and disposal areas around Scotland from the Scottish Government Marine Renewables Strategic Environmental Assessment . Although these sites didn't have a major impact on any of our chosen tidal locations they can still be viewed on the GIS Shapelayer files available for download