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Guest Post: Shore Power - Ships and Plugs

In our first Guest Post, we welcome Dr Derek McGlashan, a leading voice on

Environment and Sustainability in the UK Ports Industry.

Derek has Chaired a number of national industry groups looking at environment and sustainability, and held a senior position with a UK Major Port. He is an Honorary Research Fellow at The University of Dundee.



In this article, first published on Linkedin in February 2022, Derek presents the view from a port perspective, discussing some of the challenges and concerns associated with this technology.

As many ports launch their own decarbonisation strategies and explore Shore Power as an option, Derek's article raises some interesting points for consideration that aren't always highlighted by proponents of the solution.

This is an interesting debate, and one that will no doubt carry on for some time. Of course, this post has a UK focus, but other regions may have a different perspective. What's your experience of Shore Power in your area? We'd love to hear your thoughts in the comments below.

If you'd like to engage on this with Derek, you can connect with him to start a conversation in The Smart Ports Alliance app (available from the App Store and Google Play store)


On the face of it, plugging ships that call at ports into the electricity network looks like a clear winner for decarbonisation and emissions reductions. This has been the start place for many a discussion over the years. There has been shore power in some UK ports for many years at a small scale for workboats, tugs and pilot vessels. Not so much for larger vessels. Why is that?

Electricity Infrastructure

Electricity is expensive in the UK (and currently becoming more-so), electrical infrastructure is expensive to purchase, install and maintain. But those costs pail into insignificance if there is not the capacity available in the port’s connection agreement, greater capacity has to be purchased and this carries a cost.

Under the UK Government’s recent changes (the TCR for example) those costs for transmission charges are now based on your maximum capacity, a change from the current ‘triad’ approach, where the charge is based on usage in three peak 30 minute periods.

If the physical infrastructure is not capable of supplying the maximum demand of electricity needed, then that infrastructure needs to be upgraded as well – this bill could be many, many millions of pounds, depending on how much of an upgrade is needed. I have heard of cases where the upgrade would need to extend beyond the Distributor into the National Transmission Network – then the costs really rise… It could also take many years to secure.

When I was at a COP26 event in Glasgow last year there was a presentation from a major Spanish port. Their plan to allow up to one third of calling ships to plug in meant having to build a completely new electricity network dedicated to shore power with a capacity of 50MVA (there are few ports in the UK with a connection that size).


Inevitably, this electrical draw will only be when there are ships on the berth that are connected to the supply. This fluctuation stresses the electricity network, such a demand may only be for short periods and not necessarily on any regular cycle – though for the investment to make sense it probably needs to apply to ships on a regular call.

The investment case is more challenging if the item you are raising funds for is not in use and generating an income frequently. To stack up, all of these capital costs and operating costs have to calculated, a margin added and then applied over the anticipated lifespan of the relevant assets to come up with what the charging should be. That lifespan will depend on individual components.

However, if the shipping industry migrates to a zero carbon fuel (green hydrogen or ammonia or something else) then why would they connect to the electricity network when in port? So are ports going to be left with stranded assets after all that expense? Can ports and shipping lines agree 30+ year contractual terms to take shore power? In most cases that would seem unlikely.

What if ships end up being electrically powered? That also seems unlikely given the size of batteries needed for all but small vessels, also the electrical demand would increase again, which means more infrastructure reinforcement, costs etc.…


What problem does shore power solve? It decarbonises a small fraction of the emissions from a ship and reduce emissions to air in that location (whilst alongside – which is not where the biggest gains are to be made).

Will it make any difference? Yes, it will reduce ship emissions, marginally.

At what cost and to whom: ports (consumer), ships (consumer), the state (taxpayer)?

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