For reasons that escape me, we have been asked to do more small scale hydro power projects this year than ever before. Hydro projects are a personal favourite of mine because they are the most bespoke of any renewables, and because they often involve the most interesting local issues. History comes into it a lot as well: there were 30,000 active hydro power schemes in the UK several hundred years ago, because our ancestors knew very well where to get cheap and clean energy. Today there are only around a 100.

One of the projects we are working on at the moment is the restoration of an Edwardian scheme in Warwickshire. Turbines were installed on this site in 1902, and decommissioned just before the second world war. This is a great site, because all the water management and civil engineering has already been done, so the project costs are all about the mechanical and electrical systems (and much lower than they might have been as a result).

The best thing about it is that the original turbine manufacturer, Gilkes, is still very much in business. We were able to phone them up, give them the 1902 order number, which we retrieved from the county archives, and they were able to find the original drawings and details of the project, 107 years later! The only sadness was that their machine wasn’t still in place – not beyond the bounds of possibility, as some hydro power schemes do last many decades.

On good sites, hydro has among the best financial and carbon paybacks for renewables. This is because water is more dense than air, so carries more energy at the same speed. You should be looking at paybacks of four to 10 years on sensible schemes.

The big challenge and cost uncertainties lie in civil engineering costs and regulatory compliance, as the Environment Agency (EA) now has so many interests to balance (from many varieties of wildlife, to downstream neighbours and river users, to flood defence and water supply) that it can take years to get approval for even modest schemes. The EA is getting much better at streamlining its processes, but project developers still have to be realistic, and budget for some upfront costs and risks if they expect long-term project success.

About the author:

Matthew Rhodes is chief executive of Encraft

If you have a question about anything in the above blog, please ask it in the comments section below.