Our debt to Archimedes

The collective noun for wind turbines has to be wind farm, which has always seemed a semantic fudge dreamed up by the advertising industry to confuse a credulous public

Wind turbines, with the hypnotic mesmerism of their gently spinning blades going nowhere, are a familiar feature of our north-east landscape. The coastal plain, which makes up much of the area, is better suited than inland to this form of electricity generation. Wind speeds are generally higher and more constant nearer the coast as there are few mountains and other natural barriers to affect the strength of the wind.

The collective noun for wind turbines has to be wind farm, which has always seemed a semantic fudge dreamed up by the advertising industry to confuse a credulous public. No one ploughs the fields and scatters wind seeds, nobody grows wind and farmers don’t combine a wind harvest. Wind farms are electricity generating stations – so why not call them so?

Solar panels on house roofs and other buildings provide another source of renewable energy. Probably less well known are commercial solar parks, sited in fields and comprising rows of thousands of solar panels installed at ground level. Spin-off benefits are that sheep can graze the grass between the rows, meaning the farmer can get two bites at the solar cherry, and the

parks can help support biodiversity in comparatively undisturbed wildlife habitats that over the years become increasingly pesticide free.

With an abundance of high mountains and freshwater lochs, Scotland has led the way in the UK with hydroelectric generation. Readers of a certain age will remember the old North of Scotland Hydro-Electric Board and its claim to be bringing “power from the glens” into homes.

Turn of the screw

Now, a new generation of small hydro schemes is gaining popularity which employs a soft way of capturing clean energy from the environment. The Greek engineer, inventor and astronomer Archimedes (287212BC), invented the Archimedes screw, a revolving spiral blade which traditionally was used to raise water to a higher level, such as for irrigation. By reversing the direction of the screw so that it acts like a waterwheel, engineers can harness the power of the natural flow of rivers to generate electricity.

I accompanied Tony Andrews, former director of the Atlantic Salmon Trust, to see the recently completed Archimedes screw turbine built on the Kinnaird weir on the River South Esk at Kinnaird Park, outside Brechin.

Water from the weir is diverted into an intake, turning the Archimedes screw which is connected by a gearbox to a generator and electricity comes out at the other end.

The South Esk was one of Scotland’s premier salmon rivers but, in recent years, stocks of the King of Fish have declined.

In spring, two and three-year-old salmon known as smolts leave the headwaters of their mother river where they hatch and migrate downstream to the sea. They journey to the North Atlantic Ocean and Norwegian Sea where they feed heavily for a year, growing in weight, before making the return journey to their river of origin as grilse, to start their timeless breeding cycle all over again.

It seemed the smolts would be vulnerable to being sucked into the screw, but I was assured its slow rotation is perfectly fish friendly and any that are caught are pitched out into the river again, unscathed, to continue their journey to the sea. As an added safeguard a fish pass was constructed in the weir, down which most smolts pass and which assists returning grilse navigate the weir on their journey upriver.

Salmon tales

A fascinating piece of information Tony passed on is that returning salmon on their journey upstream contribute to the spread and regeneration of freshwater mussels. Larvae are released by the adult mussels and most are swept away on the current, but a few manage to attach themselves to the salmon’s gills until they are big enough to drop off and bury themselves into sand and grow a prized Scottish freshwater mussel pearl. Nature’s ingenuity never ceases to astonish me.

And I learned that 2019 is the Year of the Salmon, not in the Chinese zodiac sense, but highlighting the need to improve public and political awareness of salmon’s cultural, social and economic importance, and the challenges salmon face from major environmental changes and human impact.

It was a most informative morning along a part of the river I last walked up with my father about 60 years ago.

And Inka enjoyed a good run on new ground.

The Archimedes screw generator house and fish pass at Kinnaird Park.