When built, the scheme will incorporate three reverse-engineered Archimedean screws with a total output of 492kW.
The annual yield is projected to amount to approximately 1.6GWh, i.e. 1,600,000 units of electricity supplied to the national grid.
The yield figure is based on a range of data including recordings made at 15-minute intervals over a period of 100 years: this data was supplied to us by the Environment Agency.
Data on the river flow and head (the distance the water falls over the weir) have been collected since 1883. The readings are collected at 15-minute intervals and we have analysed this data to determine the potential yield of our scheme. The “Duration curves” document shows the proportion of each year that the flow and head at Teddington Weir exceeds certain levels. The “Flow Chart” document shows the average flows for every day from the beginning of 1970 to the end of 2010.
Teddington Weir is at the end of the Tidal Stretch of the Thames. This tidal effect on the project has been accurately modelled using two different methodologies. We have used the 15-minute data to model the yield for a range of years, such that we can see what the yield of the scheme would have been if it had been installed at that time. The results are perfectly in line with our estimated average yield of 1,600,000 kWh per annum: for an example of the yield calculations based on 2010 flow and head figures, see Teddington nov 13. The alternative methodology models the impact of the tidal variation on the overall efficiency of the scheme: Tidal effect on levels methodology.
All of Teddington and Ham Hydro’s technical calculations and designs have either been carried out by or reviewed by relevant experienced consultants.
Detailed analysis of the projected sound of the scheme and the mitigation measures have been undertaken by independent consultants. In brief, the turbines themselves will each be enclosed in a transparent, semi-circular tube: this will mitigate any hydrodynamic noise (possible splashing sounds); in addition, the generators housings will be equipped with sufficient noise muffling to enable the scheme to be operated within the constraints placed upon it by Richmond Council planning department.
We have commissioned three noise reports, with subsequent work in response to consultees’ feedback. The analysis has identified that the noise produced from the generators and the turbines will be no noisier than the weir.
Entec UK Ltd carried out a flood risk assessment in 2011 and updated it in 2013 to account for our design changes. It is available below – it demonstrates that the scheme will have a negligible flood risk:
Consultants have since carried out further work on flood events with a higher frequency, such as 1 in 1o year, 1 in 20 years and 1 in 50 year events, with particular reference to the 2km upstream reach which includes Trowlock Island. The report is below – it confirms the flood risk assessment’s findings:
Health & Safety
The safety features to be constructed within the overall project fall into two categories:
- safety features for maintenance purposes; and
- safety features for river users.
Please review the “16 Designed Safety Features Word Doc” for full details.
Please note that we have been working with the RNLI to model and design the upstream screen of the scheme to ensure that persons in the water who inadvertently end up alongside it are able to exit the water, especially when currents are strong. We will be continuing to develop the specfics of the solution during detailed design post planning approval.
River Users and River Flow
River users include canoeists, sailors, skiffers and rowers. In addition, anyone who is advertently in or on the water must be taken into consideration in the design of the scheme’s safety features. Therefore, we have consulted extensively with organised river users and associated organisations. We have specifically set up a consultation River Users Group which includes representatives from Tamesis Sailing Club, Lensbury Watersports Centre, Lensbury Sailing Club, The Skiff Club (Teddington) Environment Agency and The Teddington Branch of the Royal National Lifeboat Institution (RNLI).The following features have been
The River Users Group raised concerns that the scheme may materially impact the flow profile of the river such that it would affect their activity on the water and could provide a health and safety impact both to them and indeed others who may in the water. As a result the Group scoped a study that Teddington & Ham Hydro commissioned (undertaken by Turnpenny Horsfield Associates) to analyse the river flow profile. The scope of this study was discussed with and agreed by the River Users Group. The results showed that the flow profile changes within the reach “are expected to be minor (in the region of several tenths of a meter per second) and not discernible to a river user in any place in the river more than a few meters from the new structures.” Reflecting on the results, the River Users Group were comfortable that the flow profile of the river reach is not materially affected by the scheme and therefore there will be no impact to the way in which they undertake their respective activities on this river stretch. The full report can be found here [insert THA’s report here]