An electrifying muddle

Yesterday evening, I went to the Caberfeidh Hotel in Stornoway, where SSEN (which maintains the electricity network in this part of the world) were hosting a public meeting. In this meeting, they were presenting their plans for a HVDC Converter Station and GIS Substation, which are pencilled in for the industrial site at Arnish Point. HVDC is a high voltage direct current converter station, GIS is a gas-insulated sub station. What would happen there is that the alternating current electricity, generated by on-shore (sic) renewable energy sources gets converted to direct current and transmitted to the Scottish mainland through a 600 MW subsea cable, also known as an interconnector. This 50-mile line comes ashore at Dundonnell, from where the power will be reconverted to A/C and transmitted to an existing switching station at Beauly, west of Inverness.

This is a long-standing project with which I am well acquainted. Some years ago, SSEN had to abandon the idea of an interconnector, because there was insufficient input from on-shore renewable sources. At the meeting, I was reminded this was only 180 MW, whereas a cable is only economical from 600 MW upwards. SSEN told me that sufficient projects were going to be consented, upon which I asked what the likelihood was that these projects were going to receive consent. One major development would be the proposed windfarm, nestled between the Lochs Road (the A859 Stornoway to Tarbert road) and the Pentland Road, the old A858 to Achmore. 

My next question was regarding the Gas-Insulated Substation. It would appear that the chemical compound Sulfur Hexafluoride is widely used for insulation purposes, to prevent arcing from high-voltage cables. SF6 is a potent greenhouse gas, 23,500 times more powerful than CO2 in fact, and it is being phased out. SSEN was not entirely sure what compound was going to be used instead of SF6, which itself is a gas. 

As this project relates to on-shore renewables, the question about the input from the offshore renewables was not factored into this project. The N4 Northwind project could generate 2GW (2,000 MW), which obviously needs to be transmitted to the mainland as well. Part of this would be used to produce hydrogen, which would be coupled with nitrogen into ammonia at an on-shore facility at Floday, off the west coast of Lewis near Carishader and Geshader.

It strikes me that the Arnish project is still bedevilled by many uncertainties. The required throughput is not certain, and SSEN will probably need to revisit it again in view of the Northwind project off the West Side of Lewis. The completion date of 2027 looks more hopeful than realistic.