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Widecombe History Group Talk on The Hydroelectric Project at Old Walls


Old Walls Hydro-electric Project

This was a most interesting and exciting project. A family’s dream of producing electricity for their home from a re-usable energy source. This has been achieved through inspiration, dedication, enthusiasm and a determination that has to be seen to be believed. Miles Fursdon, his wife Gail, their two children Yvette and Luke and their parents were all involved and they all contributed to the success of the project.

Firstly let us reflect upon the history of Old Walls. Built in 1936 by Mr Biggs, a jeweller from Exeter, who owned the land, now comprising Old Walls Estate. He decided to install a water powered generator for the house. This was a 7 kilowatt 240 volt direct current plant, driven by a water turbine. Taking water from the West Webburn river that ran along the western edge of the of his property. He built a weir just South of Jordan and the power house was built about midway between Ponsworthy and Jordan. From the weir he laid a 20 inch diameter pipe about 300 yards underground to a turbine and the water then returned to the river. This must have been one of the first properties on Dartmoor to have electricity. In 1946 when Miles’s grandfather bought Old Walls, William (Bill), Miles’s father moved there. In 1974 the plant was updated to produce alternating current, the original turbine was used to drive the new generator. By 1984 the pipes which had been used originally by clay pits in Cornwall, needed replacing. Miles was very much involved with this and the experience had a lasting effect on him. He was deeply influenced by the whole concept of re-usable energy particularly Hydro power. He spent several years measuring the water flow in the Webburn, the rainfall of the area, calculating the rise and fall of the river and much more regarding the river as it travelled the length of the boundary of the farm. Some eleven years of measuring and calculating and during that time he also became aware of the diversity of wildlife that was on the farm and particularly in the woods and river. He decided that an open channel, a leat, 4 feet deep and 9 feet wide, would be the most economical way of doing this, as a pipeline, due to friction, would result in a loss of power. To get the water as near to the power house as possible in an open channel and a comparatively short length of pipe to transport the water from the leat to the turbine was the most efficient method and, this would also be the ultimate wildlife friendly method of getting the water as near as possible to the necessary ‘power house’. He calculated that this could increase the power generated by about eleven fold over the original piped system. By taking water from the northern most point of the farm and returning it at the southern most end of the farm he could make use of the maximum fall of the river over the full length available to him. A further 3 years was spent in the planning of the project and getting it accepted by The Dartmoor National Park, the N.R.A. and National Grid

The next decision was that he would use as much as possible local products, local labour and local suppliers to assist him with the scheme.

After much surveying he found that the ideal route would mean the removal of only 5 trees and to compensate for their removal he would plant 800 trees on a 3 acre plot on a steep part of the farm . close to the site. After successfully obtaining the necessary planning approval, work began in April 1995. A 15-ton swing shovel was hired from John Baker of Ilsington and work continued for four months constructing the leat. Due to the fact that the side of the valley was so steep the leat had to be constructed accurately as they progressed down the valley, there was no going back to do remedial repairs. It was important that the leat only dropped a few inches in it’s whole length of five hundred yards. This was achieved by the "schoolboy method of water finding its’ own level" by the use of a hose pipe, the success can be seen today as the actual drop of the leat is only four inches from the source at the weir to the forebay at the power house end. Rocks up to eight ton had to be removed as they cut the leat along the valley side and on occasions Michael Mudge of Huccaby was called in to drill and blast some of the bedrock. To make sure that the levels were holding correctly, each Friday evening water was let in to that part of the completed leat to check for level. To everyone’s’ joy the calculations were working accurately. The water was then allowed to drain out ready to start work again on Monday morning.

One action that the whole family must be congratulated on was that they involved the junior class of Widecombe Primary School. The children witnessed the excavations, the drilling of the rocks and saw how with feathers and tares and a three-pound hammer huge rocks could be drilled and cut and, in one case, the making of a gatepost. Thirteen weeks and the leat was dug! A couple of bridges were constructed over the leat as the farm was now virtually cut in half, and there had to be a way of crossing from one part to the other. The leat terminated some 54 feet above the level of the river, next the power house had to be constructed and a large pipe, technically known as the ‘penstock’ was laid from the ‘forebay’, the catchment tank, to the turbine in the power house below. 115 yards of pipe 2ft 3 inches in diameter was needed and it was located in Essex. Brian Harris, a local haulier, was employed to bring this home and using two lorries the 30 tons safely arrived at Old Walls. Starting at the power house the pipes were laid from the bottom upwards. Each pipe had a steel collar welded on one end and the next pipe would slot into the other.

The forebay, catchment tank, had to be built very carefully and according to careful calculations. The top of the pipe needed to be 14 feet below the surface of the water so as to stop a vortex forming as the water goes down the pipe. A sump was required before the pipe mouth to catch any heavy objects that may fall into the forebay and a good screen had to be in place to prevent any foreign material going down into the turbine which would damage the whole system.

At the top of the leat another catchment tank had to be constructed to stop rubble and other material getting into the leat, this also acted as a defence against over flooding to let surplus water return to the river at scource

Ever conscious of the needs of the wild life in the woods and the river, various actions had to be taken.

1. Due to the migratory senses of the fish when coming up the river to spawn, a method was devised to stop them coming up the outlet channel from the turbine, this was achieved by a large cylindrical rotating grill.

2 Similarly, when the young fish decided to head for the sea, they followed the course of the water and on reaching the end of the leat, a method was devised to stop them going down the pipe into the turbine by means of a pipe which bypassed the power house.

3. The Fursdons interest in the natural habitat of the area has been borne out by the fact that ever since this has been constructed a breeding pair of the small riverside bird, the Dipper, has successfully reared a brood under the floorboards of the power house, this in spite of the noise generated by the turbine.

A series of sluices and cleaning screens are all features of this scheme. The turbine needs to be geared up to increase the speed to drive the generator and the base of the power house had to be built with great accuracy so that all the equipment fitted perfectly. All power cables involved are laid underground. Sad to say the British turbine first purchased was inefficient, producing only 64 kilowatts when all the calculations projected 85 kilowatts of energy should have been achieved. This was installed and up and running in December 1995, just eight months after the commencement of the project. By the Spring of 1996 it became obvious that this turbine was not up to the task and no adaptations could be made to it. Reluctantly they had to look abroad for an alternative turbine and near Prague in Czechoslovakia they found a factory that could produce what was needed. Miles and Gail travelled to Eastern Europe and placed an order in April 1996, this would take five months to build, and in September 1996, they hired a lorry, sharing the driving, covering one thousand miles in 22 hours. After a couple of days break, they made the return journey in about the same time, and after several minor adjustments were delighted when they realised that the 85 kilowatt turbine newly installed was producing a hefty 89 kilowatts of power. The satisfaction they now have is of producing all their own electrical needs and being able to sell their surplus electricity to the National Grid. The meters from the generator to the national grid are read 48 times a day, and SWEB phone the recording house connecting the power house to the grid once a day for these readings. A very successful conclusion to an environmentally friendly means of producing electricity from a renewable source of energy that needs encouraging.

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