The Archimedes Screw has been used for pumping water for over 2000 years. Applying the principle in reverse, the same equipment now offers a new method for generating power from water, providing a fish friendly and highly efficient alternative to a conventional turbine. Each Archimedean Screw hydropower system is manufactured to be site-specific, with a choice of three designs - steel trough, closed compact and open compact - depending on which is the most appropriate and cost-effective for each individual site.

Click here to see a video of how a scheme can be built.

• High overall efficiency, maintained across large flow variation
• Fish friendly
• Floating objects and debris simply pass through with no need for expensive fine screening
• Robust, simple machinery - low maintenance
• Design life: 25 - 40 years
• No complex control system required - speed is set automatically by the mains connection and the available flow

• Capacity (flow) from 50 to 10,000 litres/second.
• Full capacity maintained with reduced head.
• Hydraulic head from under 1m to 10m.
• No head loss from fine screens or pressure pipes.
• Fully operational down to 15% of maximum flow.

• Achieves an efficiency of up to 87%.
• 'Water to wire' efficiency of up to 77% has been independently verified.
• Highly efficient down to 20% maximum flow.

Reduced initial investment in equipment and installation
+
Annual revenue over varying flows
+
Low maintenance costs
=
Short payback period + High profitability

Archimedean Screw

• Slow rotation = No blade strike damage to fish
• Normal water pressure = No fish swim bladder damage
• Large water chambers = Safe passage for fish of all sizes
• Smooth flow = No disorientation of fish
• No fish screening is required

Conventional Turbine

• Fast blade rotation = High rate of injury to fish
• Pressure changes in water = High rate of injury to fish
• Fine fish screening required - increase installation & running costs.

Video

You can watch a video of Fish and Debris tests here.

Since 2004, Mann Power Consulting Ltd has been supplying the Archimedean Screw as the fish-friendly answer to hydro generation. Although widely in use throughout continental Europe for some time now, the Screw was a newcomer to British rivers, and as such inevitably raised concerns - particularly within the Environment Agency - about the potential environmental and fisheries impact of the proposed installations.

On the basis of previous studies carried out in Europe which supported the claims to fish-friendliness, the Environment Agency permitted the first UK Screw installation (on the River Dart at Ashburton in Devon) to run unscreened for a year whilst monitoring was taking place. During that time, marine biologist Pete Kibel of Fishtek Ltd - in consultation with the Environment Agency and members of the Fish Pass Panel - has undertaken comprehensive live fish trials at the site and the results are extremely positive.

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. 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.

The studies conclude that the Archimedean Screw turbine is indeed fish-friendly with no adverse physical effect on fully grown fish or kelts; at most 1.4% of smolts sustaining limited and recoverable scale loss (NB 'at most' because these were wild fish and quite likely to have sustained some scale damage prior to entry into the turbine) and just 1 out of 160 eels (0.64%) suffered minor and recoverable pinching to the tail. 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 in the UK. 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.