biology

SeaGen

SeaGen is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand SeaGen rather than just read about it. In short: SeaGen was the world's first large scale commercial tidal stream generator. It was four times more powerful than any other tidal stream generator in the world at the time of installation in 2008.

Key takeaways

SeaGen belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect SeaGen to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of SeaGen from memory before moving on to harder problems.

Reference excerpt

SeaGen was the world's first large scale commercial tidal stream generator. It was four times more powerful than any other tidal stream generator in the world at the time of installation in 2008. It was decommissioned by SIMEC Atlantis Energy Limited in summer 2019, having exported 11.6 GWh to the grid since 2008. The SeaGen device was installed in Strangford Narrows between Strangford and Portaferry in Northern Ireland. Strangford Lough was also the site of the first known tide mill in the world, the Nendrum Monastery mill where remains dating from 787 CE have been excavated.

History

Marine Current Turbines, the developer of SeaGen, demonstrated its first prototype of a tidal stream generator in 1994 with a 15 kilowatt system in Loch Linnhe, off the west coast of Scotland. In May 2003, the prototype for SeaGen, 'SeaFlow', was installed off the coast of Lynmouth, North Devon, England. Seaflow was a single rotor turbine which generated 300 kW but was not connected to the grid. SeaFlow was the world's first offshore tidal generator, and no larger turbines were installed until SeaGen. The first (and only) SeaGen generator was installed in Strangford Narrows between Strangford and Portaferry in Northern Ireland, in April 2008 and was connected to the grid in July 2008. It generated 1.2 MW for between 18 and 20 hours a day while the tides are forced in and out of Strangford Lough through the Narrows. During the commissioning of the system, a software error caused the blades of one of the turbines to be damaged. This left the turbine operating at half power until autumn 2008. Full power operation was finally achieved on 18 December 2008. Marine Current Turbines was sold to Siemens in 2012. Siemens sold the company and technology to rival Atlantis Resources (SIMEC Atlantis Energy) in 2015. The power generation system was shut down, decommissioned, and removed in stages between 2016 and 2019.

Technology SeaGen generator weighed 300 t (300 long tons). It consisted of twin axial-flow rotors, each driving a generator through a gearbox like a hydro-electric or wind turbine. The gearboxes were three-stage, with two planetary and one spur, giving a 69.8:1 speed increase. The turbines rotated at around 12 rpm, each with a 16 m diameter (200 m² swept area). Adding two rotors doubled the power, for less than twice the cost. MCT were thus considering further multi-rotor systems in future, e.g. six 24 m diameter rotors were claimed to generate over 8 MW. The SeaGen turbines had a patented feature by which the rotor blades can be pitched through 180 degrees allowing them to operate in both flow directions – on ebb and flood tides. The company claimed a capacity factor of 0.59 (average of the last 2000 hours). The power units of each system were mounted on arm-like extensions either side of a tubular steel monopile some 3 metres (9.8 ft) in diameter and the arms with the power units could be raised above the surface for safe and easy maintenance access. The SeaGen was built at Belfast's Harland and Wolff's shipyards.

Environmental impact

SeaGen had been licensed to operate over a period of 5 years, during which it was accompanied by an environmental monitoring programme to determine the precise impact on the marine environment. No major impacts on marine mammals were detected in three-years of operational monitoring. Seals appeared to avoid the device, or transit passed at slack water when the turbine was not generating (i.e. not turning). While there was some small-scale displacement of marine birds, overall numbers in the Strangford Narrows did not change.

References

External links

Marine Current Turbines Ltd.

Illustrations

SeaGen: 1,800,000 m3 (400 million imp gal) of water flow in and out of Strangford Lough twice a day. — 1,800,000 m3 (400 million imp gal) of water flow in and out of Strangford Lough twice a day.

Worked examples

Example 1 — a first encounter with SeaGen

Start with the simplest possible case. Write down what SeaGen claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to SeaGen before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about SeaGen ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of SeaGen

In research: SeaGen appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses SeaGen in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: SeaGen is common in secondary-school and first-year university syllabi. It links to neighbouring topics Scottish inventions, Tidal power stations in Northern Ireland, Tidal stream generators, so understanding it makes those chapters shorter.
In everyday life: Look for SeaGen outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study SeaGen in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what SeaGen means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain SeaGen out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is SeaGen in simple terms?

SeaGen was the world's first large scale commercial tidal stream generator. It was four times more powerful than any other tidal stream generator in the world at the time of installation in 2008.

Why does SeaGen matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study SeaGen?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on SeaGen.