Predictive jellyfish bloom dispersal maps for UK coastal electricity generating facilities

The sudden 'en masse' appearance of jellyfish has serious consequences for coastal power stations through biofouling of cooling water systems. The reduction in water flow caused by jellyfish has forced power plants to run at reduced efficiency or temporarily shut down as a precautionary measure to prevent overheating, which impacts the provision of electricity to customers at a significant financial cost to the electricity supplier. A persistent difficulty lies in identifying the origin of blooms and when they will appear at a coastal facility and water intake. The main project partner for this proposal is EDF (nuclear), however the methodology is intentionally generic to allow adaptation to other sensitive coastal sites and therefore our project has the support of both SSE (gas energy) and SSPO (Scottish Salmon Producers Organisation).

The aim of this proposal is to provide a robust tool for rapid evaluation of the likelihood and scale of jellyfish ingress at EDF's Torness Nuclear Power Station based on simulated patterns of historic bloom dispersal within the North Sea from the last 20 years. To achieve this we will translate our previously NERC-funded research with the state-of-the-art marine Connectivity Modelling System to simulate dispersal of individuals within blooms incorporating specific biological behaviours of jellyfish (e.g. vertical migration, rough surface conditions avoidance and buoyancy-related effects of aging). We have two objectives which will be completed within 18 months at a cost of £161,618 (80% fEC):

(1) to provide gridded maps, specific to the time of the year or oceanographic conditions, giving the probability of jellyfish arriving at Torness, as well as minimum and peak arrival times, for blooms arising at any given source location within the North Sea.

(2) to test the suitability of the tool for providing an early warning of potential ingress threat from jellyfish blooms, including validation with historic and satellite-based observational data.

This tool will allow rapid risk evaluation and inform operational response by EDF when a jellyfish bloom is located in the future or during specific weather events. The tool will also identify critical locations in the North Sea where ongoing monitoring is essential for an early warning system for Torness Nuclear Facility.

Knowledge of ingress threat probability, timing and the geographical scale of jellyfish bloom dispersal will benefit coastal power stations by allowing affected stations to plan ahead, enabling a range of actions that are presently not possible. Currently, the first thing that a power station knows about a severe jellyfish bloom is the sudden loss of differential pressure across the cooling water screens (as they become blocked with jellyfish). When this happens, the station has no choice but to immediately shut down the nuclear reactor(s), turbine generator(s) and cooling water pumps. This equipment is not designed to be regularly turned on and off, and such procedures are expected to contribute to premature failure. The high water pressure generated by the water column behind the blocked screens usually leads to damage of the drum screens and the drive units, requiring costly repair and further lost generation during the repairs. The clean-up operation can also be very time-consuming and expensive. In 2011, Torness Power Station was shut down for a week after a severe bloom of the moon jellyfish, Aurelia aurita. This represented a huge loss of electricity generation (with a value in the order of £10m) to EDF, but also impacted the provision of electricity to customers.

Knowledge of ingress threat probability, timing and the geographical scale of jellyfish bloom dispersal will enable a range of other actions which are not currently possible. The main option would be to reduce load prior to a predicted ingress event. This could be done in a gradual, and much more controlled, manner such that equipment is not stressed. Reducing load corresponds to a reduced requirement for cooling water and, in the event of the predicted bloom arriving at the intakes, a slower ingress of jellyfish - to a rate which the screening system can cope with. In this way, it may not be necessary to shut down entirely, and the station could increase load as soon as the bloom has passed by, keeping generation losses to an absolute minimum. With a reliable early warning system, other options could also be considered in order to further reduce generation losses; such as installing temporary nets or screens to shield the cooling water intakes; or sending fishing vessels to fish-out the jellyfish swarms. Jellyfish are becoming an increasingly recognised and valuable resource (for food, using extracts (e.g. collagen) in other products, and research), and this option could even lead to commercial exploitation of the blooms.

Overall outcome: a decrease in the financial cost and customer disruption caused by temporary shut-downs and rapid unnecessary reductions in load by coastal power stations on the North Sea.