Osbaston Hydropower Turbine and fish pass ~ Revisited!
On one of our recent visits to Wales we visited the Osbaston hydropower project on the river Monnow. The project consists of two 3.6m diameter Archimedes Screw hydropower turbines. The turbines were designed to rotate at a speed of 28rpm, which produce a maximum power output of 150kW. The estimated annual power output is 670,000kWh enough electricity to power over 150 homes and gives an estimated annual CO2 saving of 288 tonnes.
A small percentage of the power generated is used to power the owners home and the remainder is sold to the National Grid. The fish pass and hydropower scheme was offically opened in 2009.
An earlier hydroelectric power station had been on the site from 1896 and provided Monmouth with electricity, using the weir and water channels of the forge, until 1953, shortly after the nationalisation of the power grid in 1947. Landowner Ronald Kear unearthed the foundations of a 110 year old hydropower station whilst working on his property and this prompted him to consider the prospect of building a new power station as a source of renewable energy.
Alongside the hydropower scheme is the Osbaston fish pass, built in 2008 by the Environment Agency Wales so that salmon could avoid the weir and spawn upstream. The following year migratory salmon were found 20 miles (32 km) above the fish pass. The fish pass allows river-spawning fish, such as salmon, to access an extra 125 miles of river – something which they had not been able to do since Osbaston Weir was put in place in the 18th century.
The new fish pass also provided an opportunity to significantly improve the ecological quality of the water. Additional work completed by the Agency helped reduce the build up of sediment and provide freedom of movement for other species of fish, upstream and downstream. Environment Agency Wales is working to bring all rivers in Wales up to a ‘good’ standard by 2027 as required by the Water Framework Directive, a major environmental initiative to make Wales’ natural waters even better.
The fish counter has recorded several species of fish using the pass, including salmon which have not been observed in the Monnow upstream of Osbaston Weir in living memory. Not only is this positive in terms of biodiversity, but the establishment of a river as a salmon fishery can also bring major benefits to local communities through a growth in the leisure industry supported by angling.
Once again we see the Ancient power of Archimedes being used for hydropower generation because if it’s fish-friendly credentials. The Archimedean Screw turbine provides a fish-friendly alternative to conventional turbines, ideally suited to low-head (1m-10m) sites, and sites with fish protection issues. 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.
