Come wind or rain
By Mark Venables

25th January 2008

The UK may not have sunshine on its side as far as large-scale power generation goes, but our soggy islands have plenty of scope for harnessing the power of water.

Hydropower - mostly large-scale dams in Scotland - currently supplies the greatest proportion of renewable electricity, delivering some 4,605 gigawatt hours in 2006, or about 40 per cent of total generation from renewable sources.

And while a massive expansion of wind power is expected, industry experts believe hydro can still have a role to play as a well-established conventional energy source.

The Scottish Government and the Department for Business are currently funding reviews into what extra capacity hydropower generation can supply, but British Hydropower Association (HPA) chief executive David Williams estimates there is another two to three gigawatts that could be exploited - equivalent to the total capacity of our existing wind farms.

Most of the potential would be projects with generating capacity of less than 20MW and would not involve dams but would be "run of river" schemes diverting water through turbines. Microgeneration water schemes could also contribute a small part.

Even with wind capacity increasing, it is estimated that almost 30 per cent of renewable electricity will be coming from hydropower in 2010, a mix which he believes provides a stability of supply.

The more different technologies we have, the more stable your supply is. When the wind's not blowing, it might be raining. Hydro is not as intermittent as wind and you can predict it a lot more easily than wind and that's a big advantage.

Scientists and energy providers are also looking offshore to the power of waves and tides to generate electricity.

There are two types of power that can be generated by tides: tidal streams create energy through fast-flowing currents usually in channels, while tidal range power exploits the difference in water height between high and low tides.

Together it is estimated the two resources could supply at least 10 per cent of the UK's electricity if fully exploited - about 5 per cent each. But the most high-profile proposal for a tidal project is also highly controversial: a barrage across the Severn which could alone generate about 4.4 per cent of UK electricity supplies.

The Severn Barrage - with an estimated cost of some £15 billion - could generate large quantities of low-carbon electricity for 120 years but would destroy some 11,000 hectares of natural habitat in the Severn Estuary.

Last October, the Sustainable Development Commission gave backing to the scheme, tempered by a warning it must be a public project complying with environmental laws, just days after the Government announced a multi-million pound feasibility study into a barrage.

However, environmentalists - who support renewable energy - are critical of the proposed barrage because of the threat it poses to wildlife.

Announcing the details of the feasibility study into the barrage yesterday, Business Secretary John Hutton said the potential scale of the project and the impact it could have on securing energy supplies and tackling climate change was breathtaking.

Tidal barrages and lagoons will be looked at in the study, which will analyse the potential environmental, social and economic impacts of possible projects.

Friends of the Earth welcomed the examination of a "tidal lagoon" system in the estuary, which would generate electricity from tidal water captured in lagoons to flow through turbines around a mile offshore and which they say would be cheaper and less damaging.

Another form of renewable power is wave technology, which can generate electricity in a number of ways - for example through floating structures producing power through movement or through turbines driven by water.

While wave power is a technology in its infancy, with only a handful of demonstration projects up and running in the UK, our waters have some of the best potential in the world.