Located in the heart of Snowdonia, in one of the most beautiful
landscapes in Great Britain, Dinorwig (or Dinorwic) power station is
quite an oddity. The location was carefully chosen out of hundreds of
different areas surveyed, and consequently the power station was built
near Llanberis, North Wales. Except this was an area of such
astounding natural beauty that the entire power station had to be built
underground, inside the mountain.
Construction
The station became operational in 1984, but construction work had
started ten years previously. It was a huge process, 12,000,000 tonnes
of earth1 had to be removed and thousands of jobs were created in an
area much in need of employment after the collapse of Wales' slate and
coal industries. In total 6,000 man years of labour were used.
Why go to Such Lengths?
In England and Wales electrical power is distributed throughout the
country by a network of power lines owned and controlled by The
National Grid. It is their job to ensure that electricity is available
when and where it is needed. In the UK, most of the electrical
energy is generated by large fossil fuel power plants, or by nuclear
power stations.
The demand for electricity varies through the day - far less power is
used during the night hours than during the day. While it is possible to
match this variation in demand by varying the output of the large
power plants, to do so is uneconomical. It would be much better if the
excess electricity generated at night could somehow be stored for use
during the day.
Dinorwig is an example of a pumped storage hydroelectric plant (there
is another at Ffestiniog, also in Snowdonia). During the day
Dinorwig's six turbines supply energy to the National Grid, and during
the night power is fed from the grid to recharge the reservoirs.
In addition, Dinorwig can be brought from standby to peak capacity in
approximately twelve seconds, making it ideal for coping with sudden
unexpected 'spikes' in demand.
How Does it Work?
The basic idea behind Dinorwig is quite simple. The power station
consists of two lakes, Marchlyn Mawr high in the hills behind Elidir
Fawr, and Llyn Peris on the valley floor. The lakes are one and a half
kilometres from the other, with a height drop of 500 metres separating
them. The two are connected by a series of pipelines. Inside the
mountain between the two lakes is the largest man made cave in Europe,
and inside looks remarkably like the set for a James Bond
movie. Inside this cavern are the turbines.
When there is a need for power water is allowed to flow out of the
upper lake, down through the pipes into the turbines, at immense
pressures, the force of gravity acting on the water forces the
turbines round and once the water has passed through, it drains down
into the lower lake. This in itself is an excellent system, but can
only be used once; if the top lake is empty then no more power can be
produced. The solution is simple. During the night when there is an
excess of power in the National Grid, the turbines are reversed, and
used to pump water from the lower lake back to the top lake, ready for
the next peak in demand.
Take a Tour!
The power station has an accompanying museum in Llanberis, the museum
is excellent and from there for a small fee a minibus will take you
inside the power station and you will be given a guided tour through
the insides of the mountain. The tour is well worth it, the main
cavern where the turbines are is quite spectacular, but be warned -
take a jumper, you will go a long way underground and it gets quite
cold down there, even in summer.
Dinorwig is owned and run by First Hydro Company, a subsidiary of Edison Mission Energy. Further information, including pictures and statistics for both Dinorwig and Ffestiniog can be found at the FHC website
1 approximately 4 million cubic metres, equivalent to two Millennium Domes or over 36,000 double-decker buses
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