Counting the kilowatts

Assumptions are easy to make. When assessing the untapped hydro power potential around the world it is easy to assume that growth in areas like the UK is very limited. It may well be so if you are look-ing at megawatts, but if you are counting kilowatts, a different story unfolds.

With a commitment to sustainable development, people in and around Gloucestershire’s Stroud Valley in western England are determined to make small hydro plants a recognised part of the landscape. This is not new for the region: its has a long history of hydro.

Ossie Goring, who operates a 25kW hydro power plant on the river Cam in the adjacent Dursley Valley, says that the Stroud Valleys as they are today are not a natural phenomenon — they were shaped by the development of hydro power for nearly three centuries between 1540 and 1830. The wealth of the region used to rely on milling industries which utilised the gradient of the river Frome, Slad Brook and Painswick and Nailsworth streams. The result was over 100 mill sites in the Stroud Valleys.

As the milling industries died out attempts were made to develop the sites for power production. Unsophisticated technology and cheap grid electricity meant that little development occurred. By 1970 many sites were neglected. Goring says that inoperative sluice gates and uninterested owners led the local river authority to remove or raise the sluice gates. Many of the mill ponds dried out and in some examples the available head of water was reduced from 3m to 1.5m, with an associated loss of power potential from 45kW to 25kW. Over the next two decades general interest in the mill sites declined.

The 1992 Earth Summit in Rio was a turning point for the Stroud Valleys. This commitment to sustainable development asked many governments to assess their priorities. As Mike Simpson from Gloucestershire County Council says, governments were urged to think globally but act locally. The UK government told local authorities that they had to play a leading role in sustainable development and Gloucestershire realised that a key aspect to sustainability was energy.

‘Hydro was the most obvious choice for us,’ says Simpson. ‘Although quite a small percentage is available for development in the UK it was recognised that this could play a significant contributory role in meeting carbon dioxide reduction targets. In 1994 when we started to assess the situation, landfill gas electricity was not available, wind was controversial and other renewable technologies were still in their infancy. But hydro was available.’ Gloucestershire County Council commissioned a scoping study to assess the hydro power potential in the Stroud Valleys. Ossie Goring of Water Power Engineering, along with Hebe consultancy, undertook the task. A conservative estimate put the untapped hydroelectric potential at 1.3MW, enough for 2-4% of industrial and commercial power needs in the region. The annual production of 5.9GWh would be sufficient for 9-14% of domestic properties in the Stroud Valleys.

Fourteen of the most promising sites on the river Frome were selected by the study and it was recommended that the most effective way to develop them would be to combine adjacent sites, giving heads of 3-5m. A tiltgate could be used to raise the water level upstream which could be combined with regrading the river by lowering the bed between the sites. Such hydro power installations could operate as stand-alone units, but the simplest approach would be to run the stations in parallel with the mains supply. This would use the existing low voltage network to distribute power and would also mean power was available when demand exceeded hydroelectric supply.

Gloucestershire County Council believes that there is a place for small hydro generators embedded in the electricity supply system in the UK. ‘Our electricity supply industry seems very big from the top down but every kilowatt of power helps,’ Simpson says. He believes that local hydro generation may also help to improve energy conservation. ‘If people recognise that their energy supply is from a local source they may learn to respect it more. Energy supplies in this country are now just regarded as bottomless pits.’ Five years on from publication of the Stroud Valley report, little progress appears to have been made and only one scheme is under way. Does Gloucestershire County Council still believe in hydro? ‘Our view of developing and supporting hydro in the Stroud Valleys has not changed,’ Simpson says. ‘The lack of progress is partly to do with the financial climate but I also believe that we have missed opportunities in developing these sites. If you look to the continent,’ he added, ‘small hydro opportunities are not missed there. It’s not such a problem. The attitude to small hydro is very different.’ So if problems have hampered development of small hydro sites in the Stroud Valleys, what are they? Some would point the finger of blame at the Environment Agency. A government organisation responsible for regulating hydro power in the UK, it has been accused of being anti-hydro, being inconsistent in its regulating duties, and not being open to discussion with the industry. ‘We have to take a rounded view in any hydro power development,’ Paul Bailey from the Environment Agency says. ‘People generally appreciate our duty to regulate through the issue of abstraction licences, impounding licences and land drainage consents but are not so aware that we are bound to consider these impacts on fish, conservation, recre-ation, public rights of way and navigation as part of these determinations.’ The Environment Agency says that there clearly is some potential for hydro power development in the Stroud Valleys and that it is not opposed to hydro. ‘I am disappointed if the industry feels we are anti-hydro,’ says Bailey. ‘Some people think our role includes that of a renewable energy agency, but it doesn’t. Our role is to protect and enhance the environment principally through regulation. In our wider remit we do support hydro power in its contribution to reducing greenhouse gases, but we cannot make exceptions for hydro just because it’s a green energy.’ Bailey says that following on from the 1994 study of the Stroud Valleys, the agency looked at the 14 sites itself to assess potential environmental impacts. ‘We have some difficulties with what the original report proposes and would prefer to look at each site individually,’ he says. ‘Although the report was a scoping study assumptions have been made about combining sites to create larger heads and regrading the river beds. By adjusting the available head this will create environmental impacts. We’re not saying that hydro development can’t proceed,’ he adds, ‘but just that the developers must look at these things.’

Detrimental impacts

Bailey claims that the gradient of the river may have to be flattened to combine two sites, while hydraulic research in the Stroud Valleys has shown that regrading will not always add additional head. Bailey also voiced concern over the self-cleaning ability of the river, saying the gradient needs to be kept as near to natural a level as possible to allow the flow to clean the river.

Ossie Goring does not believe that regrading the river bed will have detrimental environmental impacts. He says that many mill sites have lowered head because they were levelled down and are full of rubble and waste.

In the 1980s a three-mile stretch of the river Cam was regraded for flood control improvements. Removing 1.5m of black sludge and waste from the river bed meant that in six months aquatic plants which had not grown for 30 years were estab-lished. Fish species which had not been seen in the river before also appeared.

Furthermore, Goring says that hydro power sites contribute to the cleaning abilities of the river. The pollution control division of the National Rivers Authority acknowledged that his Coaley Mill site on the river Cam aids water pollution control by aerating the water, removing waterborne litter and monitoring pollution. Water quality downstream of Coaley Mill has improved.

One thing which both Bailey and Goring agree on is that the economic side of small hydro schemes and the long pay back periods are not always attractive to potential investors. ‘People get the impression that vast fortunes can be obtained from small hydro,’ Goring says. ‘But those of us who do it are committed to sustainable development. We don’t make a lot of money. It’s just one of those things that gets better and better the longer you operate it.’ Bailey’s belief is that if this can be demonstrated to mill owners through the successful develop-ment of ideal sites, small hydro in the region may flourish.

Ideal sites

The Environment Agency speaks about ideal sites but what exactly does it mean? Those which it would be happy to see flourish in the Stroud Valley must use the available head and flow of the river, without altering the river level upstream or regrading downstream. Environmental impacts such as fish safety must also be considered and the mill owner must be willing to progress with the development.

Ebley Mill is one of the agency’s preferred sites and is the only one of the 14 being developed at present by Energy 21 — a non profit, community-based, renewable energy organisation. ‘Ebley Mill is the site with the best hydro power potential,’ Jackie Carpenter from Energy 21 says. ‘In the past the river was divided into streams for the mills but at Ebley it all flows together.’ Carpenter admits that the 2m head at the site is not very good but says the intention is to show that even by using this head, 50kW of power can still be generated. Theoretically, the head can be increased with tiltgates and regrading to produce 100kW but Energy 21 wants to look at development in the real world.

‘Since Ebley was built,’ she said, ‘there has been substantial development. Upstream there is a rugby club which wouldn’t appreciate us flooding its ground while we also have to consider the main roads nearby. We know there will be challenges but we are willing to work with others to overcome them.’ The Environment Agency sees one great challenge at Ebley Mill — it has a flow measuring gauge upstream of the weir. Bailey says that small hydroelectric developments would render this ineffective and remedying the problem may be costly. Both Energy 21 and the Environment Agency are keen to work together on the problem.

‘We want to work with the Environ-ment Agency,’ says Carpenter, ‘as this has the potential to be a worthwhile partner-ship. It is very much a learning curve for them as the development of UK small hydro has been very limited recently. We believe that Ebley Mill can be a good example of how the Environment Agency can work with small hydro developers.’ Forming partnerships and creating mutual understanding may be the only way forward for small hydro in the Stroud Valleys. Goring admits that in the past he has offered to develop some of the sites but did not receive much backing. The overwhelming opinion of those involved with small hydro in and around the Stroud Valleys is that it is not under-stood or appreciated. And this seems to be a reflection of the UK as a whole. The government is criticised for putting more resources into exporting hydro than developing schemes locally for the benefit of local people. ‘Unfortunately,’ Mike Simpson from Gloucestershire County Council says, ‘hydro power is still regarded as being an energy source which is generated abroad and not in the UK.’ Energy 21 is optimistic that Ebley Mill may change attitudes, at least within the vicinity of the Stroud Valleys. As Carpenter says: ‘We are sufficiently stubborn and have the determination to see this through.’

Sign up for our weekly news round-up!

Give your business an edge with our leading industry insights.

Sign up