Osney Lock Hydro is a 49kW run-of-river hydroelectric generator located on the small island adjacent to Osney Lock in Oxford.
It is based on an Archimedean screw hydropower system, chosen for its efficiency, robust design, low noise, and ‘fish friendliness’. You can read more about this technology at www.mannpower-hydro.co.uk. An Archimidean screw is particularly well-suited for low head applications (where the ‘head’ is the difference in water level between the entry and exit). At Osney Lock this is typically around 1.6-1.8m.
With an initial lease of 40 years on the Environment Agency land, generation began in 2015. With a 25-40 year lifespan, the screw within the concrete hydro casing should only need to be replaced once during this time.
The amount of electricity generated at any one time depends on the flow of the river and on the head. The hydro typically runs consistently from late Autumn to late Spring, when there is sufficient flow in the Thames, but the annual generation can vary significantly from year to year depending on levels and timing of rainfall. The target generation for a ‘typical’ year is 179,000kWh. In summer 2021 our cumulative generation surpassed one million kWh.
Electricity generated by the hydro and the solar PV panels in the roof is sold in the first instance to the Environment Agency’s Osney Yard maintenance depot, and any surplus beyond their demand is exported to the local grid. The installation benefits from the Small-Scale Feed-In Tariff support scheme for the first 20 years of its life.
Maximum power output 47.8kW
Target annual output 179MWh (excluding solar array)
4-bladed screw blade
Width 3m; length 4.35m
Head height 1.7m
Capacity 4000 l/second
Angle 22 degrees
Variable rotation (maximum 23 rpm)
Screw weight 11 tonnes
The scheme has been designed so there is no negative impact on the Thames during high flow conditions, and therefore it does not increase flooding risk in any way.
The scheme design included construction of a new fish pass parallel to the turbine house, thus expanding the environment for fish. As part of the process to secure planning permission and Environment Agency support for the scheme, we commissioned an independent environmental study to investigate any potential negative impact on local biodiversity, including impact on fish. The study concluded ‘Currently the weir represents an impassable barrier to all fish species and therefore it is not anticipated that the proposed scheme will have any adverse impacts on the river from a fish upstream migration perspective. Installation of the fish pass associated with the proposed scheme is likely to significantly improve fish migration opportunities past the barrier.’
The fish pass
As part of the construction of Osney Lock Hydro, a new fish pass has been installed, allowing fish to move freely up river for the first time in two hundred years.