A New Hydroelectric Scheme in Ireland
By a “Awake!” correspondent in Ireland
ONE day in 1968, we were motoring up the lovely Vale of Glendassan in County Wicklow. As we reached the 1,567-foot summit of Wicklow Gap, there was an amazing sight! Looking across the barren, boulder-strewn terrain toward Lough (an Irish lake) Nahanagan, instead of observing the familiar scene, we saw that the land was alive with men and machines! Yes, a vast area was being leveled, and a road was being cut. What could it mean?
Subsequent visits revealed that this was the start of a new hydroelectric scheme. But how could this be? The river Glendassan was only a stream. Our curiosity was not satisfied until the summer of 1970, when an engineer from this remarkable site conducted us on a tour and explained to us the basis of the scheme.
Basis of Scheme
Lough Nahanagan is to be used as a natural reservoir. Maps show its level to be 1,378 feet above the sea. But behind, Turlough Hill rises very steeply to more than 2,250 feet, and an artificial reservoir is being constructed at the summit. These two reservoirs will be connected by a tunnel blasted out of the solid rock in the heart of Turlough Hill.
The basic scheme is the modern one of pumped storage. Water is pumped from the lower to the upper reservoir, where it is stored. When generation of electric power is desired, the stored water is allowed to run down the tunnel, through the turbines to turn them, and out into the lower reservoir.
A Tour of the Site
But come and join us as we retrace our steps on the tour of the site, and you will see what is involved.
The level of Lough Nahanagan has been lowered many feet. We are driven in a motorcar through all the outworks that have been established on the lough shores, until we come to the black gaping mouth of a tunnel, bored into the solid rock of Turlough Hill, which towers above us. The car swings into the tunnel, our blazing headlights piercing the blackness. There is almost room for two cars side by side. This is the access tunnel, which is to be lined with concrete. We bump and splash our way gently downhill. At last the tunnel widens out somewhat. Here are lights; it is almost as far as has been excavated. We gaze at the virgin rock faces and ask how far the tunnel is driven at each blasting. It is usually between six and a half feet and ten feet. As we splash around in our gum boots, we notice that at the far end the tunnel narrows, turns, then rises steeply. What is this?
It is the pressure shaft or tunnel that will connect the two reservoirs. The angle of incline is 28 degrees to the horizontal, which means a gradient slightly steeper than one in two, a slope that motorists can appreciate! The length of this gradient will be nearly 540 yards. The diameter is nearly sixteen feet. This pressure tunnel will be steel lined, and concrete will be poured into the space between the steel and the rock wall.
We reenter the car, which turns easily in the wider part of the tunnel. Outside again, we drive to the entrance to the ventilation tunnel. This is of much smaller diameter, and we have to walk. It leads downhill very steeply to what is called The Cavern. This will house the underground generation equipment and will be reached by the access tunnel when all is finished. The excavated dimensions are nearly ninety yards long, about twenty-five yards wide and nearly thirty-three yards high. What a cavern! The main equipment will be four reversible pump turbines that generate power when the force of water turns them in one direction, and which, in reverse, act as pumps for the water. Also included will be two seventy-ton cranes and the control room.
We retrace our steps up the ventilation tunnel and are next driven up that road that we had first noticed being cut on that day in 1968. It winds its way for nearly two and a quarter miles to the top of Turlough Hill. What a spectacle is there! The top of the hill has been sliced off. There are many machines, mainly earth-moving ones, but one machine is enormous. It crushes the rocks and boulders to fragments as they are fed into it. The result: a huge area has been leveled and in the center a great “basin” is being excavated and surrounded by an embankment.
We scramble over the embankment and across the basin. Yes, it is the upper reservoir under construction! The finished height of the embankment will be about sixty-five feet above low-water level. The floor, inner slopes and crest will have an asphaltic concrete lining plus a final mastic sealing coat. What a sight it will be! Why, the distance round the top of the embankment will be more than seven eighths of a mile. And what a marvelous view there is, as we look down upon the Wicklow hills all around,
We start the journey down again. Our tour is at an end. Having seen these things, we now begin wondering about the cost. It will total 14 million pounds. What will be the benefits of spending such a large sum of money?
Perhaps the greatest benefit of the pumped storage system is that it supplies the extra power just when demanded. At the touch of a button, water is released from the upper reservoir, and within minutes this causes the generators to operate. The total capacity available from Turlough Hill will be 280 million watts!
Consider the alternative: other types of power stations operate continuously, and peak demands must be anticipated well ahead of time. This is easily seen in the case of steam-operated power stations, such as those that use coal or oil. (These are known as thermal stations.) Think of a steam locomotive; it takes time to stoke up the fire, and then to have more steam available for planned higher speed or uphill gradient. This is a relatively slow operation when compared with the touch of a button to give extra power; and how much more positive and certain is the latter method! Hence we see that the Turlough Hill Station will be a safeguard against breakdown or shortage of supplies at peak periods.
Another benefit is in minimizing the cost of the supply. Just as there are periods of peak demand for power, so there are periods of minimum demand, the main one occurring during the night. But suppose most of the power stations were shut down each night. Think of the fuel that would be needed to restart them each morning, especially as bigger and bigger stations that require more and more fuel for restarting would have to be built to cope with the increasing peak demand.
Think also of the wear and tear. We might compare this situation with what happens when we run a motorcar: frequent stopping and starting uses more fuel and increases the rate of wear in the engine, whereas keeping the car running steadily is the more economical way and is kinder to the engine. Similarly it is most economical to operate thermal stations continuously at a fairly steady rate, and just add the supply from a pumped storage station at peak periods. But note also that in doing this, the power output from continued operation at night is available to supply the power at a pumped storage station required to pump the water from the lower reservoir to the upper one. In other words, the surplus power output at night resulting from economic round-the-clock operation is transferred to a giant store from where it can be released almost instantaneously just when required.
And costwise these are not the only benefits. The cost of coal and oil needed for thermal power stations is skyrocketing; it has increased by about 50 percent in one year in some cases. No such problem with a pumped storage station, for it runs on water! True, the cost of installation is high, but fixed. And when we compare the 14 million pounds’ cost of the Turlough Hill scheme with the 300 million pounds that Ireland plans to spend in the next ten years on power stations of other types and networks, this cost does not seem to be really significant.
In Ireland at the moment, about one half of the total power is supplied from hydroelectric stations. This supply is independent of imports such as coal and oil. In these days, reliance upon such imports is an increasing hazard. Hence the introduction of the Turlough Hill Station will bring increased security to the country’s power supply.
Thus many persons are going to have an electricity supply that is even more reliable, that remains as economical as possible and is more secure. No doubt great numbers of people have already benefited from the pumped storage scheme in Scotland, the one in Wales, about a dozen in Europe, and a number in the United States. It has also been proposed to build one near Newry in Northern Ireland.
People here look forward to the planned opening of the Turlough Hill scheme in 1973, the first of its kind in this country.
[Diagram on page 17]
(For fully formatted text, see publication)
TURLOUGH HILL SCHEME