The 5th Dartmoor Society Debate Renewable Energy On Dartmoor
Tavistock Methodist Hall, Saturday 19th October 2002
The historical use of water and wind power on Dartmoor from medieval times to the twentieth century, by Dr Tom Greeves.
The experiences of Devon Renewable Energies, by John Oliver & Jeanette Elliott.
South West Hydro’s power installations, by Steve Cryer
The use of commercial-scale wind farms, by Geoffrey Sinclair.
‘Wind power is the only sustainable option’, by Michael Huntingford.
Dartmoor hydro power – practitioners’ experiences:
Cdr George Chapman
Wider national aspects of renewable energy, by Paul Baker
53 delegates gathered at the Methodist Hall in Tavistock on Saturday 19th October 2002 to hear speakers describe various renewable energy schemes on Dartmoor and their wider national context. After the morning and afternoon sessions, a wide-ranging discussion of the issues surrounding renewable energy took place.
Phil Markham of the Dartmoor National Park Authority chaired the morning session and in his opening remarks, he reminded delegates that the UK had committed itself to achieving 10% of its energy needs from renewable sources by 2010.
In the summaries of each speaker’s presentation that follow, the views expressed are those of the speaker and not necessarily those of The Dartmoor Society.
THE HISTORICAL USE OF WIND AND WATER POWER ON DARTMOOR FROM MEDIEVAL TIMES TO THE TWENTIETH CENTURY
The first speaker, Dr Tom Greeves, chairman of The Dartmoor Society, gave delegates a wide-ranging résumé of the historical use of water and wind power on Dartmoor from medieval times to the twentieth century.
He pointed out that water and wind are omnipresent and infinitely renewable on Dartmoor. Dartmoor communities have, until very recently, literally depended on water (and to a much lesser extent on wind) as a source of energy for hundreds of years. The present built fabric of Dartmoor towns and villages, such as Ashburton, Buckfastleigh, Ivybridge, Okehampton and Tavistock, would look very different without the multitude of mill buildings that still survive.
The tinners used energy from water to wash away the waste from their workings and to power the waterwheels, which crushed the ore and drove the bellows of furnaces. The remains of at least 100 tin mills survive in the Dartmoor landscape, some of them dating back to the 15th century or even earlier. That at Upper Merrivale was in use from 1500-1700. From the 18th century until the early 20th century large waterwheels provided the power for stamping mills at mines such as Golden Dagger.
But Dartmoor also has an ancient legacy of corn mills where grain was ground. The most renowned is that at Babeny, which was built by the Forest dwellers largely at their own expense in the early 1300s. Every community had its corn mill from medieval times. Cloth mills for pounding wool (a process known as fulling) are equally ancient. In the 18th and 19th centuries paper, gunpowder, edgetool, leather and sailcloth mills were all parts of the Dartmoor scene. Weirs (or their remains) on the rivers and streams of Dartmoor indicate the take-off point for the water for these mills, which was conveyed in open ditches known as leats. Among the countless surviving leats are the 15th century South Hill Leat and the Bradford Leat (probably of the 16th century), both built to serve tin mills and tinworks.
The newly arrived monks at Buckfast Abbey were quick to recognise the potential of hydro-electricity and installed a turbine in 1901 at West Mill, which lit their temporary church for the first time in March 1902. The Ivybridge Electric Supply Co was established in 1905 and before the end of the First World War, W.G.H. Heath had established plant in Tavistock. All this activity spawned new endeavours, especially on farms. In the Chagford area, Yeo Farm became one of the first in Britain to be lit by electricity on 4 January 1893. Besides lighting the farm, the water powered a sawmill. Other farms followed suit and the remains of plant, weirs and other works can be found in many parts of Dartmoor.
During the 1920s and 1930s more ambitious proposals (most eventually coming to nothing) were made for hydro-generation on Dartmoor, to the alarm of conservationists. But a successful and enduring scheme came into being on the River Tavy, under the control of the West Devon Mining & Power Co., combining old mining leats with a new power station at Mary Tavy, and the old Tavistock Canal supply and a new power station at Morwellham, together forming the largest hydro scheme in England.
Water from four of the large reservoirs on Dartmoor generates electricity from turbines – Avon Dam (at its treatment works), Burrator (at its Crownhill works), Fernworthy and Meldon. There are also turbines at Roadford. Several small-scale operators exist on Dartmoor: Chagford is still a hotbed of innovative activity with turbines at Holy Street Mill, Batworthy Mill and Weeke Brook.
There was a windmill in or near Plympton St Mary in 1561 or earlier and one at Bere Ferrers in 1637, and there may have been medieval examples on or near Dartmoor. Devon is known to have had at least 37 operating windmills.
The 20th century has witnessed the most conspicuous use of wind power on Dartmoor, with several small wind pumps and, in the last part of the century, a wind turbine at Holwell near Widecombe and another at Wheal Lucky near Princetown. Both these operated for a number of years but no longer function. The current proposal for two tall wind turbines at Beech Farm, Lamerton, is the first large-scale scheme to have been submitted in the Dartmoor area. So far, nothing on the scale of the Cornish wind farms has yet been proposed.
Tom pointed out that it had been one hundred years since all these pioneering developments on Dartmoor – a long time to wait for a new phase of imaginative and progressive thinking about water on Dartmoor. He hoped that ‘the dead hand of authority’ would not obstruct clear and innovative ideas.
THE EXPERIENCES OF DEVON RENEWABLE ENERGIES
The second talk of the morning was presented by John Oliver and Jeanette Elliott, who set up Devon Renewable Energies (website address www.devonrenew.com), based at Bideford, to promote and educate people about the potential and options for small-scale renewable energy schemes.
They felt that there was a part to be played by small-scale wind turbines, as distinct from the large-scale wind farms. They had frequently quoted Dartmoor and Exmoor as examples to other local authorities of examples of how small wind turbines can be incorporated into the landscape and work efficiently. Sometimes a compromise has to be reached on the location, such as by siting a turbine in front of a tree to diminish its visual impact, but increasing its height to catch sufficient wind. Other practical aspects included using lattice towers instead of tubular poles to carry the wind turbine, as these are preferred as perches by birds of prey.
John and Jeanette moved on to describe the latest development with photo-voltaic (PV) cells in the exploitation of solar power to generate electricity. PV cells are now available as a flexible roof covering or as tiles, both of which can look very similar to traditional roof coverings, such as slate. PV cells are also available in a glass panel fixed to reconstituted slate. On a bright day PV cell roof coverings can generate a maximum of 5 kilowatts, but on a dull day, output can be as low as ½ kilowatt. However, despite their low power output, PV roofs can be very effective for buildings in environmentally sensitive locations. John cited the example of a remote exhibition centre building that was previously powered by a Lister generator that ran for 20 hours per day. Now its power comes from PV roofing and a 6kW wind turbine, with heating being assisted by passive solar heating from glass. These renewable energy sources of course require no fossil fuels and generate no noise.
John was critical of the Government’s scheme for grants towards PV roofs. Grants are only available for buildings that are already connected to the national grid and not for buildings in places that are isolated from the mains electricity network. He quoted a modern factory in Spain as another example of weakness in Government policy. The factory is powered entirely by a wind turbine, which was partly funded by a 50:50 grant from the EU and Spanish government. Unfortunately the British government did not adopt this grant scheme, because it did not wish to commit itself to match EU funding with its own like-for-like funding.
SOUTH WEST HYDRO’S POWER INSTALLATIONS
Our third speaker was Steve Cryer, who is South West Water’s Hydro Manager. Steve is also chairman of the British Hydropower
Association and a member of the European Hydropower Association. He described how Christy Brothers & Co Ltd of Chelmsford, an enterprising firm who brought mains electricity to many small villages and towns in the first part of the twentieth century, had built Mary Tavy hydro power station between 1932 and 1936.
An intake in Tavy Cleave takes water from the Tavy along a leat to Wheal Jewell reservoir, the top water level of which is 1000ft (305 metres) above sea level. The reservoir holds 6½ million gallons (29,500 cubic metres) of water and provides an operating head of water of 500 feet (152 metres) for the Mary Tavy power station. This system comprises three Pelton wheel driven generators, each of 650 kW capacity.
The power station at Mary Tavy also has three Francis turbine generators, each of 230kW capacity. They are driven by water from Bennett’s Reservoir, which in turn draws water from the River Tavy at Hillbridge Weir. The Mary Tavy station is shortly to be refurbished with electronic controls to replace the existing manual controls, which are inefficient.
The total power output from Mary Tavy is sufficient to provide the electricity needs of 5000 houses. Steve explained that, like all hydro schemes, Mary Tavy relies on the pressure of water and velocity of flow to power the turbines. The potential energy of the water is converted into electrical energy and the generated power increases with the head of water on the turbine. Water taken from the river to generate electricity is returned to the river after use, so hydro power is essentially non-consumptive of water. In general hydro power installations are long-life schemes.
South West Hydro also owns the Chagford Power Station, originally built in 1891 by G.H. Reed, a local millwright and machinist, to power his factory. Chagford was refurbished in 1911 and again in 1950. The station is currently closed, but further refurbishment is shortly due to take place to replace the old switchgear, which under present regulations is no longer suitable for supplying energy to the national grid.
The third hydro power system owned by South West Hydro is the equally well-known Morwellham scheme, which draws water from lower down the River Tavy. The station was another built by Christy Brothers and was commissioned in 1934.
THE USE OF COMMERCIAL SCALE WIND FARMS
Next to speak was Geoffrey Sinclair, who is the Principal of Environment Information Services, based in Narberth, Pembrokeshire. Geoffrey outlined the various factors affecting the use of commercial-scale wind farms. He pointed out that Devon has no such installations, unlike Cornwall, where there are currently 105 turbines between 45 and 50 metres in height and located on several wind farms.
Generally turbines are becoming ever larger and of greater output. If the blade diameter is doubled, then the power output is quadrupled. The higher the turbine, the greater and less turbulent is the wind speed and the turbine is more efficient. In fact turbines can now be 75 metres to 130 metres high, with blades of diameter 50 metres or more and generating 2 megawatts of power – which is big! This illustrates the conflict surrounding commercial wind farms – the turbines need to be large to provide a useful output, yet their impact on the landscape can be substantial.
At present, 3% of the UK’s energy needs come from renewable energy sources and, as mentioned by session chairman Phil Markham at the start of the debate, the target is for this to rise to 10% by 2010. Generally, the achievement of this target may now be more difficult, because the price of electricity has been driven down by moves by the electricity regulators towards more competition in the market. The lower unit price makes renewable energy sources less viable.
However, wind turbines are currently very competitive, because of subsidy schemes. There are currently four ways in which to implement wind turbine schemes:-
- a) Small turbines for individual properties through the local authority planning system.
- b) Larger scale wind turbines – again through the planning system.
- c) Through the National Wind Power scheme ‘Windwork’, to help farmers diversify into power generation with ‘smaller’ large-scale turbine schemes.
- d) Proposals for really big schemes (of output greater than 50 megawatts – approximately 25-30 turbines) are dealt with through the Electricity Act and approved by the government’s Department of Trade and Industry. A scheme at Romney Marsh in Kent is currently progressing through this route. Geoffrey pointed out that this scale of project would not be suited to Dartmoor!
Geoffrey provided figures that illustrated the magnitude of the task of obtaining 10% of energy needs from renewable energy sources by 2010. If this were to be achieved through wind power alone, it would require, say, an additional 3590 on-shore turbines (2MW each) and 1644 off-shore turbines (4MW each). The ‘zone of visual influence’ of these would be between 22 and 25 miles, compared to 12 miles for a typical present-day wind farm.
Just how massive the impact of these would be is illustrated by the fact that each turbine would be 2 to 3 times the height of typical present-day machines. The numbers required would be equivalent to constructing one 400 ft high on-shore turbine every quarter of a mile from Land’s End to John o’ Groats and one 500ft high off-shore turbine in every 2½ miles of the UK’s open coast!
Geoffrey stated that the Countryside Agency favours wind turbines on brownfield sites before any others. One such scheme being progressed is at Teesside, on the east coast. Interestingly, he pointed out that west coast schemes generally have more visual impact, because they are most prominent at sunset when more people are awake, compared to east coast schemes, which are most prominent when the sun rises.
Geoffrey Sinclair’s talk was followed by a wide discussion among delegates and speakers. The debate was then adjourned for lunch.
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Oz Osborne of West Den chaired the afternoon session, which was an interesting mix of practitioners’ experience of hydro power on Dartmoor and more consideration of the wider issues surrounding renewable energy.
‘WIND POWER IS THE ONLY SUSTAINABLE OPTION’
The first speaker of the afternoon was Michael Huntingford of Farm Energy Ltd (www.farmenergy.co.uk), a firm based at Barnstaple and specialising in wind power on a scale for small communities. Much of their work is in the Orkneys (from where Michael had just returned), the Western Isles and offshore locations.
In a clear and uncompromising talk which, said Michael, would ‘invade the comfort zone of many people’, he stated that climate change is the greatest threat to mankind. It has been caused by man-made emissions of ‘greenhouse’ gases, to the extent that each person in the developed world produces 5 tonnes of carbon dioxide (CO2) per annum. If every person on earth produced this much CO2, the result would be a runaway global warming. Michael’s view was that it was now imperative that man-made CO2 emissions should be reduced to zero, if global warming was to be solved.
Nuclear power is not a solution because, in a fully liberalised energy market, it would not be financially viable. In addition there is the problem of dealing with spent nuclear fuel. The only viable solutions were:-
- Hydro power – limited by the need for suitable topography
- Energy from waste – largely exploited already
- Solar power – only suitable for smaller scale development
- Wind power – the cheapest new-build power generation
Michael went on to explain his view that massive deployment of wind power as soon as possible is the only viable solution to global warming. It is the only technology capable of producing clean energy in sufficient volume to replace fossil and nuclear energy. Hydrogen technologies and energy storage would allow wind power to supply all the energy markets, i.e. power, transport and heating.
Wind is the most benign of the renewable energy options. The downside was its visibility, but Michael believed that visibility was an aesthetic human consideration and not one that had truly adverse environmental impact.
Michael concluded by saying that Dartmoor contains a high proportion of the area in the south-west that could be exploited for wind power. As he had predicted, his talk had indeed ‘invaded our comfort zones’!
DARTMOOR HYDRO POWER – PRACTITIONERS’ EXPERIENCES
Next Miles Fursdon, of Old Town Farm, Poundsgate, described his project to construct a new leat, pipeline and hydro power plant at his family’s Old Walls Farm, near Ponsworthy. The farm, where Miles grew up, had had a small 7kW hydro plant for many years, but more power was needed and Miles decided to build an entire larger scheme. It soon became clear what remarkable enterprise and persistence he had shown in tackling such a major project, not just in the construction work itself, but in obtaining all the necessary licences and permissions. This ‘red tape’ on its own took three years to cut through; Miles had to obtain an abstraction licence to take water from the West Webburn into a new leat, and then to obtain planning permission for a new weir in the river, the new leat, the entry chamber, the pipeline and finally the turbine house. He also needed a discharge consent to pass spent water from the turbine back into the river.
When all the paperwork had been completed, work could finally begin on the ground. He and his family did most of the work themselves and did not use any design consultants. The first step was to build the new weir on the West Webburn on the site of the original one near Old Walls Farm; then came the new leat, which had to be constructed at a very flat gradient of generally 3 inches fall in 500 ft (i.e. 1 in 2000). To test the accuracy of excavation, water was allowed into the new leat regularly to check that it ran downwards throughout the length of the works completed to date. Part of the route lay through woodland, but followed an existing track, requiring the felling of only one tree. The completed leat soon encouraged wildlife not previously seen there to the new aquatic habitat.
Finally Miles imported two new turbines from the Czech Republic and erected a new turbine building to house them next to the river near Ponsworthy. Surplus electricity is sold to the national grid via a metered connection near the turbine house.
All this work involved the local community in a number of ways. Wherever possible, Miles used local suppliers for materials and plant hire. He also invited local schoolchildren to watch construction in progress. This gave the opportunity to demonstrate some of the skills needed, such as splitting large rocks found in the excavation by the ‘feather and tare’ method to allow the resulting smaller pieces to be removed. Thus was an old Dartmoor skill demonstrated to the youngest generation.
All this showed just what could be achieved through mastery of labyrinthine bureaucratic procedures and use of engineering skills. Miles managed all this and ran his farm at the same time!
[Editor’s note: in conversation during the day, Miles revealed two more key facts about his hydro scheme; first that it had paid for itself in 4½ years and second that the surplus electricity that he sells to the national grid [National Power] is sufficient to supply the whole of Widecombe, Ponsworthy and the adjacent area!]
Our next hydro ‘practitioner’ was Sonia Newton of Sowton Mill on the River Teign, near Dunsford. Sonia taught art and music for many years, but said she now divided her time between gardening and turbine maintenance! Her father had bought Sowton Mill in 1945, largely because it already had hydro power and in fact the mill had been supplied originally by a leat dating from the 1580s, drawing water from a weir on the Teign. The original turbine generated 7 horsepower (5.2 kW).
In 1986, the Sowton Mill turbine was given a complete re-vamp. An important improvement was the provision of a new wooden weir gate which could be raised and lowered to provide the correct flow of water by remote control from Sonia’s kitchen a quarter of a mile away! Previously Sonia had had to walk out to the old weir gate, often in bad weather, and operate a mechanism that was not very user-friendly.
A tip gate was added to deal with the higher flows when the Teign was in spate and a new footbridge was built to span the leat where it was widened at the exit chamber. Most dramatically, the turbine itself had to be anchored to the underlying rock to resist flotation whenever water levels in the river were really high. Watertight doors also had to be fitted to the turbine house; a pump in a floor sump removes any water that might seep in. A new washout gate was provided to allow accumulated silt to be flushed away from time to time.
Finally the old turbine was replaced with a new cross-flow turbine and an automatic control was added to the turbine inlet to adjust the flow according to the operating head of water. The condition of Sonia’s water abstraction licence prevents her from taking water and using the turbine when dry weather causes the flow in the Teign to fall below a certain amount. At such times she has to switch to mains electricity.
Sonia had clearly been keen to improve an already useful facility and, like Miles Fursdon, had taken on major work to bring this about.
Commander George Chapman of South Brent was the last practitioner to speak to delegates. He installed his micro hydro plant on the Avon above South Brent in 1980 to supply his house with electricity. In 1986 he became Hon. Secretary of the then National Association of Water Power Users (later to become the British Hydropower Association) and in the same year, he joined the committee of the Association of Independent Electricity Producers (AIEP) to represent hydro users. Over the next 10 years, he was involved in the successful campaigns for the abatement of abstraction charges for hydro generators under 5MW and for local authority rates for independent generators to have parity with the Central Electricity Generating Board’s rating.
George’s plant, which cost £12,000 to install in 1979/80, comprises a waterwheel generating 4 to 5 horsepower (3 to 3.7 kW). The turbine’s rotation is transmitted through a gearbox, which drives a belt connected to a generator. George said that the gearbox came from an old Fordson Major tractor and after 22 years of use the wear on it is negligible! The equipment is installed in a small stone building with a slate roof.
The weir on the Avon is hand-operated. George measures the river level meticulously – he showed one particular graph that demonstrated that the River Avon at South Brent can be very ‘flashy’, i.e. flow can increase dramatically and suddenly after heavy rain.
George had estimated that his hydro power unit had paid for itself after 8 years of use and thereafter had provided useful savings in electricity costs. Like Sonia Newton, George has the ability to switch to mains electricity if for any reason he cannot operate his waterwheel.
THE WIDER NATIONAL ASPECTS OF RENEWABLE ENERGY
Our final speaker in the debate was Paul Baker of the Devon Association for Renewable Energy (DARE – website address www.devondare.org). Paul switched our attention from the fascinating details of individual hydro installations on Dartmoor back to the wider national issues associated with renewable energy. DARE’s aim is to promote the achievement of European targets for renewable energy production and of renewable sources providing 10% of our energy needs by 2010. In the last six months, DARE has helped more than 50 individuals and organisations with renewable energy schemes, including solar panels and wind farm development.
Paul reiterated the message of earlier speakers – that renewable energy is needed because of the threat of climate change, pollution of the environment and the finite nature of fossil fuels. A switch to renewable energy is needed urgently, said Paul. A developing economy will require still more electricity than we are currently using and the major issues for renewable energy are the technology that should be used, its scale and its location.
There is a whole range of options and there is a need to encourage work to improve the cost effectiveness of some technologies. The UK target of 10% of energy coming from renewable sources by 2010 is very modest compared to other European countries. For instance, we lag significantly behind Austria, which has a target of 100% renewable energy sources within the next 30 years.
Looking more locally, the south-west’s share of our own national renewable energy target is between 11 and 15%. The Government Office of the South West (GOSW) has started work on its strategy. Consultation on the framework for the strategy would be closing on 31st October 2002. GOSW’s approach is to have a top-down strategy, rather than a bottom-up community-based approach, and this has attracted criticism. The challenge is therefore to participate in the strategy for the south-west and exert influence to bridge the inevitable gap.
The debate was then thrown open again to delegates. It was pleasing that Graham Wall, the DNPA’s senior planner, was present throughout the debate. Graham said that he was excited by what he had heard and hoped that the DNPA’s Sustainable Development Fund could be used for worthwhile sustainable energy projects.
Oz Osborne thanked speakers and delegates and also thanked Tom Greeves and The Dartmoor Society for initiating the debate. In reply Tom echoed Oz’s thanks to all who had contributed to the debate.