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Here in North Wales we are “blessed” with an abundance of all weather! We have some spectacular lakes and rivers which are well supplied with a superb amount of annual rainfall, as such it's an area, like many, that has throughout, harnessed the power of water.
There are many spectacular valleys in the Snowdonia region but I want to focus on just two, the Ogwen Valley and the Llanberis Valley, two adjacent valleys separated by the Glyderau mountain range. The Llanberis Valley is well visited, many of the paths up Eryri or “Snowdon” begin here and as such it hosts lots of visitors. On the opposite side of the Llanberis valley from Eryri you see the huge UNESCO world heritage site of the Dinorwic Quarry. The scale of this endeavour is huge and well worthy of exploration with a good start being a visit to the National Slate Museum where we can find a great historical use of Hydro power. One half of this astonishing museum is formed by huge workshops, foundries and furnaces, if you are interested in machine tools like, lathes, milling machines, shapers and more, it's a spectacular visit. As you wander through room after room you'll notice that all of this heavy equipment was driven from a, still rotating, line shaft.
When you reach the end of the main shaft you find that it is water driven using a pelton wheel which was fitted in 1925, however, in an act of uncanny forward thinking in terms of industrial heritage, the original large water wheel and it's housing remain in place and still turn. It's a fascinating example of harnessing the power of water.
Jumping forward in time and operational to this day the Dinorwic power station is a close neighbour of the National Slate Museum. The Dinorwic power station is a large hydro electric station that came online in 1984. To this day it is the largest scheme of it's type in Europe. It's impressive in all aspects, from it's dynamic ability to quickly ramp up and down production, the amount of power it can produce, to the incredible civil engineering that largely hid all this facility deep inside a mountain.
Starting in 1974 the total excavation inside the Elidir Fawr mountain totalled a mind-boggling 1 million cubic meters with the complete site excavating over 12 million tonnes of material. The site was chosen as it had a lake above the site, Marchlyn Mawr, and Llyn Peris below the site. Inside the mountain the power stations workings are spread between 9 caverns, the larger two being the turbine hall which is 180m long and 51m high and the transformer hall which is 160m long and 17m high, both much longer than a full-size football pitch. The turbine hall is the photograph at the head of this article. When electricity is needed, water is released from Marchlyn Mawr and flows through a series of 10m diameter tunnels to drive 6 turbines. These turbines are actually reversible and therefore are more correctly classed as pump turbines. Each turbine has a generation potential when running at full load of 288MW, a spectacular amount of power, and that's before you multiply it by 6. The water used by the system then passes into the lower Llyn Peris, at full flow the volume of water passing through the turbines is around 390M^3 per second, for context that's close to an Olympic size swimming pool of water every second.
Dinorwic is an example of a “pump storage” hydroelectric facility, and this is why the turbines are reversible and can be used as pumps. This means that when power demands by the national grid are high, and therefore power stations can sell units of electricity at a higher price, Dinorwic will operate in generator mode using the pump turbines as turbines to generate electricity. When demand is low on the grid, and the unit price for electricity is lower, Dinorwic can become a consumer of energy reversing its turbines into pumps and pumps water back through the system up into Marchlyn Mawr. Being able to replenish its water stocks in this manner means that Dinorwic is always ready to produce power and indeed it's seen as a critical part of UK power infrastructure as it has the fastest response time; it can ramp up to full production in a mere 16 seconds.
It's hard not to be impressed by the Dinorwic Hydro Electric power station, but if we take a short journey over to the Ogwen valley, there's another really interesting Hydro Electric project that, in my mind, is just as interesting, unique and exciting. The village of Bethesda is a fascinating place, it's home to the Penrhyn Slate quarry which is still operational to this day, it also hosts, within a disused section of the Penrhyn Slate quarry “Zip World” Europe's longest zip line at over a mile long. This all sits alongside the Afon Ogwen river which in turn, quite subtly holds its own hydro electric power station. This Hydro Electric project “Ynni Ogwen Hydro” is completely community owned and run by a dedicated team of volunteers. It's a fantastic achievement for the village, but before we start I should also declare that I am (albeit in a very modest way) a shareholder in this amazing scheme! In fact all the, not insignificant, amount of cash needed to set this up was gathered largely in this valley from individuals, families and small businesses buying shares. The shares cannot be freely traded, and can only be sold back into the scheme, so most people entered into this in the spirit of supporting a local initiative rather than reaping huge profits or dividends. In fact Ynni Ogwen Hydro is a not for profit organisation and under the guidance of an elected board, spends its profits back into the community in various ways via a charitable arm of the company.
I met up with Gareth Cemlyn Jones who is a seasoned Hydro engineer and is also the current Chair of Ynni Ogwen Hydro. The whole operation takes place over roughly 100 meters of the Afon Ogwen and we started by looking at the grid connection transformer mounted on poles that acts as the connection to the 3.3kV Scottish Power Energy Network (SPEN). Whilst perhaps not the most inspiring part of the system it was the very fundamental of the project as this had to be bought, installed and commissioned before Ynni Ogwen Hydro could even begin the conversations around planning and applying for the feed-in tariffs and meet all the other criteria of being able to set up this project. At this point, the main fundraising for the project wasn't finalised so indeed this humble pole signifies quite the leap of faith for the community.
Nearby the pole is a large cabinet that contains some final metering at the point where the power is inserted into the grid. Of course, occasionally the system may be shut down so this is also where the small amount of power the system would require can be drawn down from the grid, but a quick inspection of the panels shows that the system is exporting near constantly to the grid. I also noticed in the cabinet a brilliant collection of brooms and scraping devices attached to various poles and a couple of personal floatation devices. We were about to grab these to walk to the other end of the system but, with impeccable timing, two volunteers arrived from the far end of the system and informed us that all was well and the screens (more on those later) didn't require cleaning.
A short walk up a beautiful tree-lined bridleway brings us to the lovely old bridge at Ogwen bank. The water flows smoothly under the bridge before darting down a spectacular set of waterfalls and, unless you are really looking, you'd struggle to see that one side of these falls has been adapted to take water into the hydro system. Our first technical spot is a small box mounted to the side of the bridge, here Gareth explains that it's a sensor monitoring the river level. The whole hydro system is essentially under a PID control system that is constantly adjusting and reacting to the river conditions to keep both the system performing as efficiently as possible, but also to protect the river and wildlife by not taking water when the river is too low. One of the problems that Gareth had to overcome was that the lightning/surge protection for this first sensor had been burnt out a couple of times in storms and it was felt that it wasn't an adequate device, wonderfully the new surge protector they had specified and fitted was from RS electronics! Gareth even sent over these before and after pictures of the old burnt-out circuitry that has now been replaced in the second picture with a Phoenix Contact, LIT 1X2-24 Surge Protector 24 VDC Maximum Voltage Rating 20kA Maximum Surge Current Surge Arrester.
Moving 10 meters or so down from the bridge we inspect the “screens”. These screens at a shallow angle allow water to drop through into a 1.2m diameter pipe which in turn is connected to a forebay structure, essentially a large tank acting as a sump, built at the edge of the river. The forebay structure acts to allow air bubbles to disperse before introducing the water into the pipe that will descend down to the power house. Again the forebay structure is monitored for water levels and this data is fed into the PID control calculations.
From the forebay the water is fed into a 900mm diameter pipe to begin its journey down to the power house. These pipes are often referred to as “penstock” pipes and that term can be used for any artificial pipe system serving a water-powered device from an old water wheel attached to a mill or our more cutting edge usage here. The penstock pipe is a good example of the large civil engineering work that this project needed. It's been completed to an amazingly high standard and they have really minimised the impact on the surrounding environment. Following the path back and down to the power house you can, when looking, see the route of the last 20 meters or so of the penstock and it's amazing how they have threaded it through established woodland without having to remove many trees.
The penstock drops down into the power house which is a block built structure that's been clad in nice timber and roofed with slates from the neighbouring Penrhyn Slate quarry and as such is a very attractive and fitting little building. On my crisp winter morning visit the warmth of the turbine room hits you, and is welcome, as you step inside. At the back of the room, the penstock comes into the building and is reduced to 800mm diameter through a butterfly valve which acts as the main inlet valve. The water then hits the turbine which is an Ossberger crossflow design and the water entering the turbine is controlled by 2 guide vanes which are actuated with an oil-filled hydraulic system connected back to the control system still reacting to the PID values. Gareth explains that the two guide vanes are different in size and they can be used individually or in combination giving a wide range of input conditions, and allowing flexibility for the system to respond to current water levels. The whole control system centres around the vane activity and the monitoring of the forebay levels with the control system PID always aiming to maintain the level in the sump by opening or closing the vanes.
At maximum the turbine flow capacity is a healthy 850 litres per second. The turbine is coupled to the generator via an oil cooled gearbox, which isn't running hot but is definitely a nice source of warmth for the power house at around 55C. The gearbox receives the turbine input which operates up to 400 rpm but outputs to the generator at 1000 rpm. The generator is a 100kW induction generator and it's fair to say that it all purrs along very nicely and quietly. Gareth checks some details on the panels on the wall and shows me that, on the day I visited the total generated power at the power house to date is 749558.9kWh, which seemed a lot, but then he added, “oh you have to add a “2” to the front of that number as it's been round the clock twice!”. Whilst the main control panel has a small LCD screen with lots of system information on it, Gareth and the team of volunteers are more likely to check in with the system online. The system is packed with sensors which are all web connected and the whole software control system is online. This means that the volunteers can monitor and check the state of the system using their smartphone or a laptop with Gareth and others able to interact with, and if needed close down the system quickly, from anywhere with a data connection.
Finally, the water passes through a sump and an outflow pipe and falls through a screen back into the river a few meters below the power house. My visit is rounded out with a task, I proudly got to grease the bearings on both the turbine and the generator and logged the maintenance in the log book. This gives some insight into the weekly and monthly regime of maintenance and inspection all carried out by the well trained and organised volunteer team. I left the site feeling pretty inspired, whilst the massive machinations of the Dinorwic power station are astonishing the fact that the Ynni Ogwen Hydro started as an unfunded idea, was brought into existence by community fundraising, and is kept running by community volunteers with profits going back into the community, shows not only excellence in engineering but shows us what we humans can achieve with a little organisation and passion.