‘IT ALL depends on the head’ was the message given to participants at the Micro and Community Hydro Training Seminar. The Seminar, held at Wookey Hole Caves in Somerset, UK, on 13 June 2003, was organised by the British Hydropower Association (BHA) and opened with scene setting introduction to the basics of hydro power. The aim was to illustrate the benefits of hydro power, to encourage appropriate hydro development and to educate those at the local level who were involved in the planning and approvals processes for renewable energy projects. The seminar attracted strong participation from local government energy policy advisors, the Environment Agency, micro hydro power owners, community renewable energy developers and members of the BHA.

Paul Baker of the Devon Association for Renewable Energy and Ben Sang of the Severn-Wye Energy Agency outlined the role of the Community Renewables Initiative, a national scheme co-ordinated by the Countryside Agency, that aims to encourage community involvement with renewable energy and maximise local benefits. Grant support for household and community renewable energy schemes is available under the Government’s Clear Skies programme. (www.clear-skies.org)

Low-cost hydro

Ollie Paish of IT Power and Jon Needle of Derwent Hydroelectric Power, made a presentation on the development of low-cost turbines for small, low-head sites. Although high-head sites offer the greatest economic potential, they are the least available in the UK. The Doomsday Book mentioned 10,000 water mills and over the succeeding 900 years many more sites, possibly as many as 30,000 were developed. Many of them could be brought back into use, each generating 5kW-100kW and making a significant contribution to the Government’s target for generation from renewable sources. Few of the abundant, low-head sites have been developed, mainly because of costs. In partnership with GP Electronics, IT Power and Derwent Hydro had spent two years researching and developing a low-cost solution that could see the future development of many more of these sites.

Using a propeller-type turbine they developed a siphonic system, which avoids extensive excavation and has other cost saving advantages. It can be adapted to fit the site and utilises very low falls of water: from 3m down to just 1m. A suction pump primes the siphon by drawing water up the rectangular intake until it begins to flow down through the turbine. The siphon systems means that an intake gate is not required shutdown is achieved simply by opening a valve and breaking the siphon. It also means that the electrical generator is housed above flood water levels giving added security.

Their presentation was illustrated by the 15kW test system installed at Derwent Hydro’s Borrowash Mill in Derbyshire where there is a head of 2.5m. The system uses a variable-speed control system, the first to be installed in the UK, allowing the operating speed of the turbine to be modified to extract maximum power in different hydraulic conditions whilst feeding 50Hz generation into the grid. It is belt driven (another cost saving) using a gear ratio of 3:1. The test system uses variable guide vanes to put spin on the water but the aim is to use fixed guide vanes in future designs (again to reduce costs). So far the test system has been running for three-months and has achieved better than design efficiency. The developers estimate that a commercial siphonic system could achieve cost payback in four years.

On your farm

Miles Fursdon, Old Walls Hydro, described a new hydro power plant he had installed at his farm in the Dartmoor National Park. The family owned farm had been looking for alternative income streams. They had a 7kW Gilkes turbine installed in 1936, before the grid had reached Dartmoor, to meet their own power needs and believed that the farm offered good prospects for hydro power development using the waters of the West Webburn. The plan was to dig a leat an open channel 2.5m wide and 1.5m deep around the side of a hill taking water from above the existing power plant, and dropping it back to the river through 20t of 700mm steel pipe. The channel took 14 weeks to cut and was landscaped as they went. The leat passed through woodland where particular care was taken to drive it in such a way as to avoid damaging trees. It required only three trees to be removed and, as compensation, 800 hard wood trees were planted on 1.2ha of adjacent land. An 89kW cross-flow turbine was installed with a David Brown gearbox and a 100kW transformer. A self-cleaning trash screen was fitted at the pipe entrance and a fish pass for smolts has been built. The leat has been cleaned out once since construction (providing good quality clean gravel). The work, done on a do-it-yourself basis, took eight months to complete and was part funded by a Government grant. The project qualified under the Non-Fossil Fuel Obligation. It has been running for seven years and supplies power to three villages.

Securing planning consent took a lot of work. The primary aim of the Dartmoor National Park is to preserve Dartmoor, and it took some persuading. It was worried that the leat would prevent the movement of wood mice so an arboreal bridge of hazel was planted. It has attracted dragonflies to the area and has been used by the Environment Agency as a source of fish for re-stocking other water bodies. The advice of the Forestry Commission was sought on the potential impact of the leat on the woodland it passed through. In the eight years since it was cut, no adverse effects have been noted. The planning authorities stipulated that the power house should be built of wood but Fursdon hopes to persuade them that a replacement in local stone would be more appropriate (and would reduce noise). The visual impact is very small. Although there is noise intrusion from the wooden power house there have been no complaints about it and it does not appear to have affected wild life a dipper has nested under the power house every year since its construction. Local schools were involved in the project from the early stages.

The project has helped to raise local recognition of the importance of micro-hydro power. From this experience, Fursdon has worked for Devon County Council and the National Trust and helps to maintain five other plants. He is looking to install two more plants.

Fish friendly

Dr Andrew Turnpenny, Fawley Aquatic Research, rounded off the morning session with a presentation on the fish screening implications for micro and small hydro power plants. (A UK guide to intake fish screening policy and best practice with particular reference to hydroelectric power schemes 1998; Ref: H/06/00052/REP is available from the DTI; website: www.dti.gov.uk). All fish are migratory to some degree and any structure on a watercourse can become a hazard or a barrier to fish movement. Screens and passes will help to overcome them. Dr Turnpenny outlined the various methods for fish screening and pointed out that the costs of putting them in place, running and maintaining them can be high so it was important to get it right. Not all hydro power development has negative impacts of fish movement; installations can improve fish access on rivers. Before the construction of the power plant on weir at Beeston on the river Trent the flow of water over the weir had been too strong for fish to pass over it. Now the reduced flow meant that they could swim upstream.

Better than a pension, safer than houses

Workshop sessions in the afternoon discussed public perceptions of hydro power, the risks and rewards and the development process. Image was important and the terms ‘mini-hydro’ or ‘micro-hydro’ were, perhaps, too cold and neutral; ‘mill-power’ with its connotations of rural idyll and urban renewal might help to present a warmer image of these smaller, localised hydro power developments.

The complexity of the planning process and the high up front costs were the main risk factors. Grant schemes disadvantaged hydro power because they failed to take into account the longer design and planning processes. A holistic approach was needed to help get over resistance from other users on watercourses and to ensure that prospective sites were not made redundant by inappropriate development upstream or downstream of them. The rewards were a long life of up to 50-years and, with low running and maintenance costs even taking into account the longish payback of initial costs, hydro power offered a long period of reliable income generation. As one participant pointed out, hydro power plants would be a better prospect than most private pension schemes. More schemes could be financed if funding could be arranged on a mortgage-type basis and it was felt that hydro power facilities would be a far more secure investment than houses.