Why is there sometimes a lot of dark smoke coming from the power station chimneys?
As the power station is not needed to supply 100% of the island’s demand, we have frequent ‘start-up’ and ‘shut-down’ periods as generators are turned on and off, which can sometimes produce more smoke than normal.
This is similar to starting up a car first thing in the morning when it’s been parked for a number of hours, particularly after a cold night. The smoke from the power station usually clears within 5-10 minutes once the generators have reached their optimum operating temperatures for electricity generation.
As with most internal combustion engines (ICE), start-up and shutdown are not optimal conditions for the most efficient combustion of fuel. Our power station is a giant system with many large components, and when it’s turned on these parts need a few minutes to reach the right performance conditions to help power over 30,000 customers. This includes making sure the combustion process – burning fossil-fuels to create energy – is stable, and that the generator is synchronised with our electricity network to make sure the power generated in the station is in harmony with the island’s overall electricity system.
Dark smoke may sometimes be a sign of an engine issue which means our operation and maintenance teams need to intervene, however generally this isn't the reason for the smoke.
The maximum energy we can import through the subsea cable is 60MW, which has been marked up on the graph below. On 10th January 2024, we needed to start using the power station at around 6:00am until around 11:00pm, after which time the island could rely on our imported low-carbon electricity.
This means a 'start-up' would be required to meet the 6:00am demand as the generators haven't been used for 7 hours on a cold winter's night.
What type of fuel is used at the power station?
Our medium and slow speed diesel engines run on either Very Low Sulphur Fuel Oil or Ultra Low Sulphur Diesel, and we’re also able run diesel-fired gas turbines. Each generator delivers power outputs ranging from 12MW to 16.5MW and can be used to top up our 60MW importation cable.
Why are there no scrubbers on the power station chimneys?
The power station is used only as a top-up/back-up to the 60MW importation cable and scrubbers do not work well with this type of start-stop operation as they're best suited to ‘baseload generation’ - i.e. used for many hours/days (such as in a cruise ship). At the time Guernsey’s electricity plant was commissioned, scrubbers were not a requirement.
To have them retrospectively fitted would cost approximately £3-5 million for our most recent engine projects. A project of this scale would involve not only purchasing scrubber equipment but modifications to the existing infrastructure such as duct work, chimneys, and other components, together with engineering, and construction. As the scrubbing process consumes energy, there would also be potential losses in the net power the power station could provide Guernsey.
Wastewater management may also be a challenge as the scrubbing process produces a wastewater by-product containing the absorbed sulphur compounds. This would add an additional layer of complexity and cost as proper management and treatment of this wastewater would be needed to prevent environmental contamination.
Scrubbers are a diverse range of devices that remove particles and gases from industrial exhaust streams to reduce air emissions. They’re generally a wet systems variety for exhaust gases and wash out pollutants.
In line with the Electricity Strategy, Guernsey Electricity is focusing on long-term aims recently approved by the States of Guernsey:
- to increase the capacity of Guernsey’s cable links to the European grid and importing low-carbon electricity, which last year supplied over 90% of our electricity in Guernsey.
- supporting on-island supplementary renewable energy generation
- retiring the slow speed diesel plant in favour of more appropriate back-up generation capacity.
