Technical Visit to RWEs Dolgarrog Hydro Site - May 2016

The visit began with a short induction and a presentation by Deiniol Williams Operations Shift team leader on the history of Dolgarrog power station from its early beginnings to the recent upgrades and improvements. Originally built in 1920 providing power for aluminium production using DC power, the station now houses 4 Francis turbines delivering a total of 33 MW to the grid.

The aluminium works has long since closed with the site now occupied by the recent Surf Snowdonia tourist attraction.

Mention was made of the dam disaster of 1925 when the Eigiau dam failed and flooded the village. 16 people were killed in this tragedy which led to the Reservoirs Act requiring statutory inspection of dams and structures. The Eigiau reservoir remains as a natural lake although the dam is no longer in use.

Dolgarrog is now effectively two power stations within one building comprising a high head scheme (units 2, 3) as well as a low head scheme (units 4, 5). Water for the low head (240m) scheme comes from the Coedty reservoir through a 3km pipeline whilst the high head (360m) scheme is fed from the Cowlyd reservoir through a 5km pipeline.

Dolgarrog is one of several hydro stations within the RWE Hydro fleet which in total delivers 80 MW to the grid. Most of the fleet is in Scotland but all controlled from Dolgarrog as the principle site. Cwm Dyli in Snowdonia is another 8.5 MW site which is effectively Dolgarrog’s Unit 1.

Following the presentation we were taken up to the Coedty reservoir and the Marble Arch site where the pipelines come together before descending into the power station. We were shown the auto closing penstock protection valve on the low head scheme and enjoyed fantastic views across the Conway valley in glorious sunshine.

On descending to the power station we were given a tour of the power station and control room. The control room engineer has sight of the operational situation for the full RWE UK hydro fleet and can arrange support technicians to visit as required.

The Dolgarrog high head Gilkes Units 2 & 3 were installed in 1992 and each rated at 11 MW. Unit 4 was recently replanted and comprises a Kossler 10MW unit which together with Unit 5 rated at 5MW represents the low head scheme. The tour of the power house ended with a visit to a small museum housed on the site with equipment dating back to the early operational days of the power station.

We finished the day with refreshments in the main office block where we met with Dave Bevan, Production manager. The possibility of a visitors centre being established at the site was suggested. The neighbouring Surf Snowdonia has brought a lot of additional tourism to the area which could be of benefit to the power station.

The opportunity was taken to present Deiniol and Dave with IMechE certificates of appreciation for arranging such an excellent visit. Also thanks to John and Nathan for giving up their time and helping with the driving and the tour of the catchment area. We are very appreciative of RWE for allowing their team to facilitate such a visit.

Excellent feedback received from all who attended what proved to be a very informative visit.

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