Mapping out hydro’s future

THE UK’s Environment Agency (EA) is keen to show it is championing the cause for hydropower development throughout the country. It states that it strongly supports the UK and Welsh Assembly government’s targets for renewable energy, and further acknowledges the role that hydropower schemes can play in meeting these and greenhouse gas reduction targets.

“Some hydropower schemes have the potential to deliver low carbon electricity and improve the local environment for wildlife, for example by improving fish migration,” says Tony Grayling, head of climate change and sustainable development at the EA. “With the government’s feed-in tariff for renewably generated electricity, hydropower could become an attractive income generator for power developers.”

The first phase of a wider programme to make information available to developers and stakeholders was published in February 2010. In an effort to develop a more strategic approach to sustainable hydro development throughout England and Wales, the EA has identified and mapped potential opportunities. The aim of this is to make it quicker and easier to gain approval for a scheme.

A technical report (Mapping Opportunities and Environmental Sensitivities for Hydropower in England and Wales) was prepared by Entec on behalf of the EA. It gives national and regional level overviews of the potential opportunities available, plus their relative environmental sensitivities to exploitation.

Over 25,000 locations (barriers) were identified with coarse environmental assessments made of each one. In the report the term barrier was used to identify a site where there is sufficient height in river level for hydro production. These are mostly weirs but could be other manmade structures or natural features such as a waterfall. As the EA acknowledges, most new small hydro schemes are usually sited at existing barriers and do not create new impoundments.

The report did not consider the full potential for larger high head schemes as they may have greater environmental impact, and cannot be readily identified using geographic information systems at the scale employed in this project. Small-scale high head hydropower also lies outside the remit of this work, but could be within the scope of future projects. These schemes in particular may be attractive as they present lower risks for fisheries.

The EA is keen to point out that the project and data are not intended to replace any part of an individual site assessment, which is necessary for full scheme appraisals. Its aim is to inform and not replace other assessments. Furthermore, the methodology used in the report is not intended for use in individual site applications.

Opportunity knocks

Once sites had been identified within the mapping project, hydropower opportunity was calculated using height and flow data. Then fishery and protected areas data was used to assess environmental sensitivity. Almost half (46%) of barriers are classified as highly sensitive, mainly due to the presence of migratory fish species such as salmon and eel. About a quarter (26%) of the barriers are medium and low, while the remainder are unclassified due to a lack of data.

However, there are considerably more environmentally compatible opportunities when the EA assumes that a new scheme has a fish pass built on it. As a separate exercise the EA identified what it calls ‘win-win’ schemes. These are defined as providing a good hydropower opportunity and, with the introduction of a fish pass, will increase the status of fish population and improve fish passage. Over 4000 win-win sites were identified, representing about half of the total power potential (580MW). The EA believes that grants for such fish passes could help to unlock this potential.

Results

The opportunity maps showed clear clustering of hydro potential in upland areas of England and Wales. Indeed all regions, except East Anglia, show significant potential. Wales has a theoretical potential of 396MW with the most important English regions being the northwest (196MW) and Yorkshire and Humber (179MW). Particular concentrations of win-win opportunities are available along the Rivers Severn, Thames, Aire and Neath.

Out of an assessment of 25,935 barriers there is a total estimated potential capacity of nearly 1200MW.This could provide up to 3660GWh/yr or 1% of the UK’s projected electricity demand in 2020. However, as the EA stresses, in reality the feasible potential will only be a fraction of this figure due to access to local electricity distribution networks and environmental constraints. The average maximum power generation estimated on a barrier was 45kW.

In the conclusion to its report on the project work the EA says: “We hope that the evidence this project provides will ultimately allow us to develop a strategic approach to the deployment of small scale hydropower in England and Wales, that maximises energy generation whilst ensuring the natural environment is protected and enhanced.”

David Williams, chief executive of the British Hydropower Association (BHA), gave a nod of approval for the EA’s work. “The sensitivity mapping report shows the Environment Agency’s commitment to developing renewable energy whilst protecting the environment,” he said. “The BHA welcomes this stance and looks forward to helping with the development of hydropower at all suitable sites, in conjunction with the installation of fish passes where evidence shows they are necessary.”

Limited but important

Although the Environment Agency believes that small hydro has a limited role to play in renewable energy production, it is still none the less very important. Despite what it calls small figures for theoretical maximum power potential (1178MW), the EA believes hydro offers a number of advantages: it is a reliable and proven technology and is attractive to local communities. Indeed, hydro is also becoming increasingly attractive to those committed to meeting green power demands.

In order to meet ‘extremely ambitious’ government targets of generating 15% of UK energy supplies from renewables by 2020, it has been suggested that 31% of electricity will need to be renewable. “This means,” the EA says, “that we will need to exploit all available renewable energy sources to their sustainable maximum.”

And this is where hydropower can prove its worth. As illustrated by the EA’s mapping study, hydropower could theoretically produce 3% of the country’s renewable energy needs by 2020. In the scale of things this may prove to be a small contribution, but it will pack a big punch in the battle against climate change.