Tyn Y Waun is a water treatment works located at Treherbert in South Wales. It is the main water supply to the Rhondda Fawr valley. Its supply is derived from the Nant Garreg source and the Llyn Fawr reservoir (pictured opposite) which impounds surface water from the Rhigos mountains. After further settlement in the raw water reservoir at the site, the water is treated prior to distribution to the 35,000 industrial and domestic customers in the Upper Rhondda Fawr.
The impounding reservoir top water levels are at 385m and 369m AOD for the Nant Gareg and Llyn Fawr sources respectively. This results in a maximum static pressure at the turbine location of 12.7barg.
The scheme maximised the use of as much of the existing infrastructure as possible. The new turbine building was constructed in GRP and houses a in line strainer, two jet vertical Pelton turbine, fixed speed asynchronous generator, control system and grid connection equipment.
There were a number of environmental, technical and commercial challenges that were successfully overcome to allow the scheme to progress to the construction stage, namely:
- Permitted development was not allowed; therefore full planning consent was required.
- Domestic dwellings were located within 40m of the new turbine house; thus the solution had to include acoustic insulation measures to negate any possible noise pollution.
- To ensure that treated water processing would not be compromised an automated bypass facility was incorporated within the new turbine house.
- In all modes of operation the scheme has to regulate flow into the water treatment works and maintain the level of the raw water reservoir.
The scheme annually offset over 200 tonnes of carbon and generates in the region of 400 MWh per year, which is approximately 85% of the total site usage of the water treatment works.
The contract was executed under AMCO's Hydro Generation Services Framework with DCWW.