Stream engines: small scale hydropower

26 July 2010 | By Ellie Zolfagharifard

When people think of hydroelectric power, they often think of giant dams, swollen rivers, displaced populations and flooded plains. The concept isn’t usually one that sits well with local communities, and even less so with environmental groups.

But behind the negative headlines, hydroelectricity is carving itself a different reputation and this time it’s the communities that are driving the change. Hydro on a small scale is the latest trend to sweep Britain’s villages and it’s providing households throughout the country with a lucrative source of much-needed energy and cash.

The past five years have marked a big increase in interest for microhydro projects among rural populations. ’It’s like all renewable technologies,’ said Steven Harris, head of technology at the Energy Saving Trust. ’We’re just starting to see the obvious and asking, why haven’t we done this before?’

The introduction of the feed-in-tariff (FIT) by the outgoing government in April is likely to be one of the reasons. The scheme provides money in return for domestic energy generated from renewable sources. A medium-sized hydro scheme can cost up to £150,000 and under the FIT would qualify for a maximum of £0.20 for every kilowatt hour of hydroelectricity produced.

Small-scale hydropower schemes are still in their infancy and currently only generate enough electricity to power 120,000 homes in the UK. However, the Environment Agency (EA) believes there is significant potential to produce more. According to its figures, there are around 4,000 areas in England and Wales alone where hydro can be used effectively to tap the power potential of rivers.

It’s like all renewables, we’re just starting to see the obvious and ask, why haven’t we done this?

But doing this means overcoming some major challenges. Like concrete dams, microhydro raises concerns about flooding and damage to fish populations, albeit on a smaller scale. ’These are very real and important issues considering the recent floods we’ve had,’ said Harris. ’But we already have the technology and innovative thinking to address these concerns, it’s just a matter of implementing them.’

In fact, the technologies being developed to address these issues are based on concepts that are thousands of years old. The Archimedes Screw is a classic example. Dreamt up by Archimedes in the third century BC, the design is thought to be one of the earliest pump systems in existence. Back then, it was used by farmers for irrigation, allowing them to move water from lower levels to higher areas. Today, the concept is being reversed to generate electricity.

’Sometimes it’s the simpler solutions that are better,’ explained Steve Welsh, managing director of Water Power Enterprises (h2oPE). ’The Archimedes Screw is very straightforward it only contains two moving parts: the bearings on the top and bottom of the screw. Instead of pumping water out, the screw is reversed to push water down through the tubing, turning it and activating a generator. This design not only protects fish but also limits the amount of water taken out of the river.’ For these reasons, the EA has singled out the Archimedes Screw in its Good Practice Guidelines.

But environmental concerns aren’t the only challenge to widespread microhydro roll-out. Among communities that want to own a microhydro scheme, cost and geological landscape are two of the biggest barriers to installation. Harris believes that the UK should take the lead from countries such as the US, which is paving the way in domestic high-head hydro projects.

’To get one of these going, you need a drop of more than 5m on a river, a hosepipe taken up the stream from a penstock and a small alternator with a pelton wheel to generate electricity,’ said Harris. ’It’s as simple as that. That’ll cost no more than £1,000…In the US, from an off-grid anti-federalist point of view, they’ve been doing this for decades. The technology itself is hundreds of years old and still works just as well.’

What has changed, however, are the materials and control systems used in the hydro systems. Anthony Battersby, director of River Energy Networks, claims that these improvements make hydro far more viable for villages to maintain. ’In an old mill the operators would be nipping in and out, opening the valves a bit, opening the wicket gates, endlessly tweaking the water levels. That is now all done automatically through a processor that can maintain the water level to plus or minus 2mm.’

Up until now, small companies and local people are the ones who have benefited from the re-emergence of hydro technologies. More recently, however, major electricity suppliers such as RWE npower Renewables and Scottish and Southern have been getting involved by announcing projects and community grants of their own. But while the hype surrounding the microhydro industry has increased, so too has a sense of frustration at the speed at which these schemes are getting off the ground.

’Politics is a big issue,’ said Harris. ’I used to live in London; I’ve now moved to a rural village community and boy do the village politics make that lot in Westminster look like amateurs.’ What makes it even more difficult, he claims, is that while the FIT is clear, the operating standards to qualify for the schemes are not. ’This is a small industry and every system is bespoke so any standards written have to be wide enough to cater for that but unlike 10 years ago there is now a big effort in setting these standards.’

Despite difficulties in getting microhydro schemes started, opportunities to get real returns on established projects are proving popular. Welsh heads up h2oPE, a social enterprise that aims to get investors involved in community hydroelectric schemes. The group has recently launched a £1m social share offer to finance three community-led hydroelectric projects. People can invest anything from £250 to £20,000 and the company estimates they will get a three per cent return in the first five years, rising to five per cent thereafter.

’We’ve seen some community groups who are doing things themselves and it’s taken them five years to get planning permission,’ said Welsh. ’We’ve tried to narrow that to two years, from planning a site to producing electricity, by throwing all our resources at it so far it seems to be going well. The FIT has also captured people’s imaginations and on the different sites we’ve been working interest has increased by about 30 per cent.’

Once all the qualifying standards for FIT have been put in place, interest in hydro is expected to grow significantly. The EA predicts that even if all of the potential capacity for microhydro in the UK was captured, it would only amount to one per cent of the UK’s projected electricity demand in 2020. But the sustained interest in hydro proves that it has more to offer than simply small-scale energy generation. Welsh believes that realistically microhydro is just going to be part of a jigsaw of solutions. ’It doesn’t provide scale, but what it does do is allow a community to have sustainable income stream in the long term…quite apart from carbon emission, it’s about community cohesion and community benefit.’