It’s True! The Archimedean Screw is Fish-friendly.

Archimedean Screws are the preferred hydro-turbine for the development of low head sites. They provides a fish-friendly alternative to conventional turbines and sites with fish protection issues.

As a renewable energy company that cares about environment we have done our research on all our products before taking them on board and are happy with the test results proving that the Archimedean Screw is in fact fish-friendly.

Fyke Net at oveflow

Fyke Net at oveflow

Fish Passage Testing:

Extensive fish passage tests have conclusively demonstrated that the large water chambers and slow rotation of the Archimedean Screw allow fish of all sizes, and debris safe passage through the turbine. As a result, the Environment Agency has agreed that no screening is required. Literally thousands of fish passages have been monitored and recorded using underwater cameras at the intake, inside the chamber of the Screw itself and at the outflow to assess the effect of the Screw on salmonids (including smolts and kelts), brown trout and eels.

Salmon smolt caught passing naturally downstream through the turbine

Salmon smolt caught passing naturally downstream through the turbine

Fish Passage Test Results Phase 1

Fish Passage Test Results Phase 2

Fish Passage Test results Phase 3

73cm Pike after passing through the turbine

73cm Pike after passing through the turbine

The trials looked at fish passage across a broad spectrum of sizes and turbine speeds, possibly the most impressive of which was the safe passage of a kelt measuring 98cm in length and weighing 7.6kg. In addition, behavioural and migrational patterns across the species have been shown to be entirely unaffected by the turbine. The implication of these findings is extremely positive for the economics of micro-hydro. Sites previously written off for hydro development owing to fish protection issues can be revisited, and the cost of installation for an Archimedean Screw turbine will be significantly reduced by the requirement for only minimal screening.

New recommendations in place for the UK:

Although over 100 screw turbine systems are currently operational on the continent, with no reported fisheries issues or problems, in the UK recommendations are in place to reduce the risk of Archimedean Screws even further.

Rubber bumper on leading edge of the Archimedean Screw

Rubber bumper on leading edge of turbine blade

Work by Fishtek Consulting  on risk of injury should a fish be struck by the leading edge of a turbine led to the recommendation that in order to minimise the risk of injury, the leading edges of small Archimedean Screws under 2.5m in diameter should be fitted with rubber bumpers and larger turbines with fish friendly compressible bumpers to mitigate the effects of higher inpact speeds on the largest screw turbines in use. These bumpers are now required as standard on larger Archimedean Screws.

For full report see: Archimedean Screw Risk Assessment: Strike and delay Probabilities

Rubber bumper attached to leading edge of the Archimedean Screw

Rubber bumper attached to leading edge of turbine blade

 

Photographs copyright  Fishtek and Mannpower Consulting Ltd.,

Please Note: All the reports are copyright and may not be used for commercial purposes without the prior consent of Mannpower Consulting Ltd.