One the UK’s oldest — and currently cleanest — forms of renewable energy is making a modern high-tech comeback on a local scale across Britain. Hydropower is providing energy and income for communities but also causing controversy. Jon Herbert reports.

Old mill ponds are being pressed back into service along some of Britain’s fast moving waterways to provide low-cost, almost maintenance-free, very low-carbon sustainable energy. And more local schemes are being planned, with the caveat that concern for fish stocks and wildlife is causing delays.

Hydropower is theoretically one of the simplest forms of renewable energy. It is one end of the scale that includes enormous engineering projects. The Three Gorges dam project on the Yangtze River in China is currently the world’s largest hydropower scheme, with a capacity of more than 10GW.

However, at the modest end of the scale, pico-hydro mini-turbines are being used across the developing world to generate as little as 200–300W to power single homes from weir drop heads that can be as small as just one metre.

Globally, hydro-energy now accounts for some 16% of world electricity consumption, with a rapid expansion seen since the Millennium. More than 150 countries now harness the power of running water. The Asia-Pacific region accounts for one third; China is the world’s largest producer and its hydro sector satisfies roughly a fifth of domestic electrical energy demand.

Paraguay actually generates 100% of its power from hydroelectric dams, exporting 90% of its production to neighbouring Brazil and to Argentina. Norway comes a very close second, producing 98–99% of its electricity from hydro schemes.

In the UK, where almost all suitable large-scale mountain sites are already generating power from established dam water storage and turbine station projects, the Government’s National Renewable Energy Action Plan released in 2010 anticipated an extra 40MW to 50MW of new hydro-energy programmes being commissioned annually up to 2020. However, this ambitious target does not appear to be being met in full. A further 2593MW could potentially be added in Scotland.

Gravity-fed energy

Hydropower falls into three categories. Dam storage schemes use reservoirs to create an artificial high head and flow of pent up energy that can be controlled and released through turbine stations. Run-of-river schemes are more common on local waterways, often linked to weirs to maintain flow continuity.

Meanwhile, pump-storage schemes make use of excess power, often produced during low-demand night time periods from nearby nuclear power plants which run more efficiently under constant load, to recharge a higher reservoir from a lower basin. This is released later to drive the hydro turbines. Tidal power is also a variation of hydropower. Proposals for a series of tidal lagoons to be built around the coast of Wales and northern England were announced in February 2015.

The common principle behind all hydro-energy schemes is turning potential energy (gravity) into kinetic energy, mechanical energy and finally electrical energy with conversion efficiency rates as high as 90%.

Given the energy and carbon involved in manufacture and construction, hydropower is estimated to produce the lowest carbon-footprint of current renewable sources, beating wind.

Opportunities

The Committee on Climate Change has advised the Government that, in theory, hydropower could add up to an extra 8 billion kilowatt-hours (kWh) per year to the UK’s power network. Figures for 2011 show the UK generates circa 1.5% (5700GWh) of its power as hydroelectric, mainly from large-scale schemes in the Scottish Highlands. It is at the smaller end of the scale that the greatest opportunities lie.

Recent studies show that there is a remaining viable hydro potential of between 850 and 1550 MW in suitable parts of the UK, which would represent some 1 –2% of current UK generating capacity and 18% of total renewable capacity.

Hydropower potential is very site-specific and has to be surveyed carefully. Initial installation costs can be high, typically £25,000 for a 5kW small domestic scheme. However, maintenance costs are very low for power that can be generated continuously for 24 hours a day over many decades.

Feed-in Tariffs (FITs) make the economics of projects up to 50kW more attractive — supported by advances in technology that make more sites feasible. Schemes over 50kW are eligible for the Renewable Obligation Certificate scheme (ROCs). Environmental permits are required from the Environment Agency.

Coming to a river near you

While only limited parts of the country have been identified as suitable for potential hydro-energy, a surprisingly large number of schemes are springing up along rivers far from rugged mountain settings. A typical example is a £1 million venture near Abingdon, where the Thames is expected to yield some £120,000 worth of electrical energy annually.

The target for the two 1-tonne hydrodynamic screws installed at Abbey Meadow is to power some 200 homes annually for the next 40 years. One of Abingdon Hydro’s founders, Richard Riggs, commented recently that, “People are looking again at streams running through their villages and old mills beside their houses and are thinking about how to harness the energy.”

Run as a co-operative project by residents, the sale of Abingdon Hydro shares has been designed to provide the necessary investment finance. Although flooding and winter weather have caused delays, this is one of some 15 installations planned along the Thames through Oxfordshire.

The Environment Agency has given permission for hundreds of approved schemes to go ahead. Investors are attracted by the prospect of selling power back to the National Grid for a high rate of return on investment (ROI).

But enthusiasm in some quarters is tempered by concern in others. The Angling Trust’s “Say No To Hydro” campaign has warned that, “Hydropower is coming to a river near you. Be prepared to take action to defend your river and its fish.”

The British Hydropower Association has rejected claims of widespread damage to fish from turbine blades and says that new hydro-electricity could give the UK the equivalent of a giant gas-fired power station and electricity for 1.4 million homes.

In January 2015, the 1.5 tonne Archimedes screw began turning on the Osney Lock Hydro project prior to formal electrical testing by Scottish and Southern Electric, a necessary step before formal power generation can begin. The £650,000 project is again a local investment that will generate 179,000kwh a year, enough to power 50 homes.

Established as a mutual society set up to fund and operate the 49kW power station, the project was reported to have raised £590,700 in just three weeks. After 20 years, the plan is for the investment to be returned to its shareholders.

Osney Lock Hydro says the scheme will generate a local income stream of £50,000 in its first year of operation and £2 million worth of community benefits. A rate of return of 7% is predicted.

Support and objection

However, the largest community scheme on the Thames, Ham Hydro at Teddington Lock, is facing intense opposition. Richmond Council’s planning committee failed to reach a decision recently on plans to install three reverse Archimedean screw turbines on the site.

Supporters say that the £5 million scheme will contribute towards combating climate change and generate decentralised renewable energy. Again, 40% of the necessary capital has been raised by selling shares.

But there are opponents too. One local business has said it will take legal action to stop the scheme because the noise nuisance it would create will severely damage its trade. It believes that the development will cause environmental damage as a result of increased flooding, destroy heritage views, and degrade the special nature of the area.

The project’s supporters include the Green Party’s life peer, Baroness Jenny Jones, local MP Zac Goldsmith, and Former Secretary of State for Business, Innovation and Skills, Vince Cable. A final decision will be taken when new site studies are complete.

The Angling Trust says hydro-electric power can deplete rivers of water, damage fish, and stop many species from moving freely up and down stream. The BHA fears that the Environment Agency has introduced tough new rules following consultations that could severely delay future schemes.

Sustainability is not automatically compatible with serenity, it seems, and local battles could lie ahead before hydropower becomes accepted as a run-of-the-mill part of the UK’s modern energy mix.

First published by Croner-i on 19 May 2015