Located at Caversham Weir, our twin-screw Archimedes turbines will generate 320 Megawatt hours of energy per year.
The River Thames at Reading passes over Caversham Weir with a drop of about 1.4 m and an average year-round flow of about 37 m³/second. This high-energy combination was harnessed to power various mills based on View Island for hundreds of years before these were decommissioned and demolished, ending the using of waterpower in Reading by the middle of the the twentieth century. Reading Hydro CBS, identifying this waste of potential energy, has put together a vision to restore this hydro-power tradition for the town and generate clean, green electricity for the benefit of the community.
Hydro turbines & Connection
Our power plant comprises of two SpaansBabcock-built Archimedes screw turbines. Rated together at 46 kW of usable power output, we’ll be generating a total of 320 Megawatt hours per year. Our site is located to the northeast end of the gated weirs, cutting through a causeway linking to lower Caversham. Each turbine will sit in a concrete channel, constructed by Land & Water, at a 22 degree angle from horizontal. The intake channels are controlled by sluice gates and covered by screens; the water flows from the Mill Stream, through the screws and into the Weir pool below.
The turbine house is built from recycled aggregate blocks, wooden roof trusses and insulated steel roof sheeting. It houses core components for the operations of the turbines, including the electrical generators, gearboxes, and electrical control equipment; there are also integrated bat boxes for the local bat population in the roof! Additionally, monitoring equipment and our grid connection (that tunnels under the Thames itself) are also located within the Turbine House.
Hydroelectricity: A brief overview
To generate our electricity, the turbines harness both a drop in water height, or ‘head’, and the speed of the river, or ‘flow’. The head acts as the driving pressure, using the weight of the water to push the turbine. Flow (usually considered on average to account for seasonal variability) dictates turbine rotation speed. These two things are proportional to each other – the higher they both are, the more potential energy there is. Therefore when the water flows, its both the combined push and speed of the water rotating the turbines.
See this link from Community Energy England for more educational details on this process.
Natural Fish pass
Our screw turbines are completely safe for fish, and will be carried downstream through the equipment unharmed. However, the fish cannot swim upstream through the turbines. To remedy this, we will be installing an additional natural fish pass on View Island. Carrying water down from the Mill Leat and throuh the island, the pass emerges adjacent to the turbine channels. With a flow faster than the turbines, the pass will attract and facilitate the upstream passage of fish, eels and lamprey. The fish pass will also provide some new spawning grounds for all fish along its route. Furthermore, we have also built new habitats for other flora and fauna too, with bird boxes, bug hotels and tree planting throughout View Island.
The government set up the Feed-in-Tariff (FiTs) scheme several years ago to encourage renewable generation. We obtained FiT successfully, meaning for each kWh of electricity that we generate, we will receive a small sum in payment. On top of this, we plan to sell our generated electricity to a private consumer and any excess back to the National Grid. By doing so, we generate sufficient income to pay for the installation. This means that once we have paid our Shareholders for their significant support, the whole installation becomes a community asset for the benefit of Reading -for many, many years to come.