Archimedes screw turbines
Western Renewable Energy, with other hydro-electric specialists GP Electronics and Castleford Engineering, has commissioned a new type of system at the River Dart Country Park, Ashburton. This system is located at the site of an old turbine, within the Dartmoor National Park, on the River Dart, a Salmonic river.
WRE Ltd installed another screw turbine this year, for Water Power Enterprises in Derbyshire. This type of turbine is becoming increasingly popular for lower head sites. It is especially suited to sites with large flows - typically at least 200 litres/second are required - and up to 6,000 l/s are easily accommodated in one machine - but heads can be as low as 1 metre. Installation costs can be significantly lower then comparable Kaplan or crossflow turbines. This therefore makes these machines worth considering for fitting into existing weirs on main rivers.
Archimedean screws are a new type of turbine in this country, and they have a number of advantages over conventional turbines.
- They require very little fish and debris screening
- Their installation costs can be lower than comparable Kaplan turbines
- They are mechanically simple - less to go wrong
- They have good visibility - people can see the water generating the power
Fish screening can be a stumbling block with many systems, and can contribute to both the capital costs and the ongoing costs. The usual need is to exclude all fish as far as reasonably possible - sometimes meaning screen mesh sizing of as little as 3mm is requested. This can make a conventional turbine unworkable, but with the slow turning Screw turbine it is possible to simply let the fish through. There are no trapping points for the fish and no pressure discontinuities which can upset them also.
Installation can be relatively simple, and costs can tend to be lower on low head sites, for instance on the many river weirs which exist.
There are few moving parts, so less parts to get damaged and go wrong.
And unlike nearly all turbines, you can see the water doing the work.
For more information on these machines visit www.mannpower-hydro.co.uk Ritz-Atro manufacture a range of Archimedean screw systems, their UK agent MannPower Consulting offer a wide range of hydro-power services on sites suitable for such systems.
The following collection of photos shows the installation of the UK's first Archimedean screw for power generation, carried out by Western Renewable Energy, working with Castleford Engineering and GP Electronics. The site is in the Dartmoor National Park, and construction took approximately four months. Commissioning happened in January 2007, using innovative variable speed drive equipment from GP Electronics.
Click on the pictures below to see the installation process.
