What a fantastic piece of technology is the archimedes screw turbine. It’s simple, works in situations where other hydro power turbines aren’t much use, has a very low environmental impact and is even safe for fishes.

The archimedes screw is a type of water pump which has been known since ancient times, and may well have been used to water the hanging gardens of Babylon. It was certainly familiar to Roman engineers.

Archimedes Screw (c)Siberwolf at Wikipedia 2009 (click image to see original and licence)

To pump water from the bottom to the top, the pump needs to be twisted, either by hand, perhaps a windmill or someone running on the casing, as an ancient treadmill.

A few years ago, a genius engineer unknown to google or wikipedia, figured out that if you turn it upside down and let the water drive the turbine, you could stick a generator on top and make electricity, being careful not to let the generator get wet.

The big advantage of these turbines over others used for small hydro schemes is that they work well when there is a low head of water so can be used over an existing weir, or in outflow pipes.  That configuration means they don’t need much pipework either, making the civil engineering component of the scheme much smaller.  Debris in the river just passes through (at least up to a point), so there’s no need for trash screens

A 48kW scheme installed on the river Dart in Devon in 2008 consistently produces 35-48kW, enough to power visitor facilities, a conference centre and two bungalows in the River Dart Country Park.

Another in Osbaston, Wales provides 150kW, and powers 152 homes.  The environment agency cite it as an example of good sustainable practice in their guidelines for small hydro schemes.

Osbaston Hydro Scheme and Fish Pass

Osbaston Hydro Scheme and Fish Pass

Most importantly, it doesn’t bother the fish.  Because its open to the air, and large, the fish just swim up it.  The water is going at the same speed as it would be over a weir, and so it makes little difference to them.  The one in the photo above is actually a fish pass as well as a hydro scheme.

Environmentally friendly, low maintenance and robust – it’s an ideal technology