A new low-head river hydroelectric power plant has opened in Yorkshire today.
The new 500kW Kirkthorpe hydro scheme on the River Calder is built next to a Victorian weir which drops around 3m in height.
Water flowing into the plant above the weir drops by around 7m and is then channelled through a turbine to generate enough electricity to supply 800 homes.
The £5.3M plant was built within a 100m long cofferdam formed by 10m high sheet pile walls which extend 7m into the river bed to toe into the rock. Eric Wright Civil Engineering operations director Gavin Hulme told New Civil Engineer that the design of the plant was complicated by having to bend the water channels around the weir. This made the cofferdam more difficult to build. Eric Wright Civil Engineering is the main civil engineering contractor for the project
“Traditional rectangular cofferdams are much easier to support as there is usually a wall directly opposite and parallel that can be used to prop off and equally distribute the active pressures from the ground,” said Hulme.
“At Kirkthorpe the propping could not do this due to the shape, so extensive angled propping and shear connections were needed along with ground reduction and tie back anchors to create a composite temporary works design.”
The design was also complicated by the need to incorporate a salmon run to allow them and other migratory fish to travel up and down stream without being caught in the turbine blades. Two channels adjacent to the turbine run have been incorporated into the design and large grilles at the entrance and exit stop fish from swimming through the wrong waterway.
Changes to the programme had to be built in around the severe floods which took place in 2015.
“In the winter of 2015 there were repeated storms,” said Hulme. “We were subjected to quite a lot of flooding as we were right on the river, but we managed to plan and phase the works so all of the disruption was kept to a minimum. It did flood us out on a number of occasions, but we’d included that in our programme.”
To allow the water to flow through the channel opening, water was allowed into the channel to balance the pressure on both sides of the wall and then the sheet piles were burned at their base by specially trained divers and removed.
National Infrastructure Commission deputy chairman Sir John Armitt who opened the plant said: “I’m delighted to have been given the opportunity to open Kirkthorpe and see another fine example of British engineering. It is particularly welcome to see further investment in the nation’s permanent energy infrastructure as this is a priority for both the government and the National Infrastructure Commission.”
Barn Energy, the owner of the scheme said that there were over 29,000 weirs in England and Wales and so there was huge potential to use the technology to increase sources of renewable energy generation.