Next generation turbines turn wind power on its axis

Posted on 4 Mar 2014
The 4N-55 wind turbine claims to be more efficient than a comparable horizontal axis turbine, is easier to maintain and is radar and bird friendly.

A new company in Blackpool is turning heads with its next generation vertical axis wind turbines. Always efficient performers, new composite materials have helped these turbines to overcome the physical shortcomings of previous designs. Will Stirling reports.

You may not be a lover of wind power, but the facts speak for themselves: wind generated electricity in the UK is growing at a rate of knots.

A total of 2,841,080 MWh of electricity was generated in December 2013 – supplying 10% of the UK’s electricity demand. In 2012 it was about 5.3% of the UK’s needs, demonstrating the vast amount of wind power capacity that was brought online during 2013. That’s good news for the government, which has said that 15% of the UK’s total electricity should be from renewable energy in just six years.

But, whether onshore or offshore, these turbines are almost exclusively the windmill-like, horizontal axis wind turbines or HAWTs, and are all imported into the UK, with some turbine towers and certain components manufactured here.

Now commercial grade vertical wind turbines are now appearing in the UK and, refreshingly, they are being manufactured in Britain.

Designs for vertical axis wind turbines, VAWTs, have been around for years. VAWTs are more efficient that horizontal axis turbines. This is according to the Darrieus concept, which demonstrates that the amount of wind force needed to cause a vertical turbine blade to “lift” is lower than that required to turn an equivalent horizontal blade, ceteris paribus. The US government was excited enough about this to commission research group Sandia National Laboratories to investigate and prove the concept in 2012.

Most of the early research into VAWTs terminated in the 1990s due to physical shortcomings in the early designs. “Due to a lack of suitable technology, i.e. the wings were manufactured out of aluminium, early VAWTs suffered from fatigue failures, but modern composite technology means that fatigue is no longer an issue,” says Dominic M’Benga, managing director of 4Navitas in Weeton just outside Blackpool.

Here, the three-year old company is making 55KW vertical axis wind turbines with a nearly all-British supply chain. “It was part of the business plan, to keep it British, although this has not been easy,” says Mr M’Benga, referring to certain problems with suppliers sharing the ‘spirit of partnership’ that the company required.

The directors who formed the company were convinced that, as composite materials improved in weight and strength, the old problem of blade fatigue with VAWTs would become redundant. They were proved right, teaming up with marine carbon fibre experts Green Marine to make lighter blades that generate the right force to turn the turbine without developing stress defects.

Now many VAWT designs are coming on to the market, such as McCamley’s MT01 Mk2, developed with research help from Warwick Manufacturing Group. Big companies including e.On and Ericsson are pouring money into their development.

A key advantage of a vertical axis wind turbine over its more familiar cousin is maintenance.

The main moving parts – the gearbox, motor / alternator and controls – are located at ground level, meaning quicker and cheaper maintenance than a comparable HAWT. The hub is still located at the top of the tower, which is 25 metres in the case of the 4N-55 model, but this is merely a spindle, converting the horizontal rotation into a vertical drive.

As well as maintenance, the 4Navitas turbine is environmentally friendly. “The low rotational speed of VAWTs means that they can operate below radar Doppler, meaning that they are “radar friendly” or do not interfere with aircraft radar,” says Yorkshireman M’Benga. The horizontal plane of rotation makes them visible as a sold object from all angles, making them bird and bat friendly,” a feature the horizontal turbines do not share.

Also, the screw design pile means no concrete foundation is necessary for this model, reducing costs further.

Getting to this market-ready stage has been a struggle, starting the business in zero-growth 2010 and finding that the banks were as risk adverse for new manufacturing ideas in practice as by reputation. The company could not get any funding before proof-of-concept and decided to self-fund, raising further capital by selling equity.

With the first orders delivered, and more interest from markets including Italy, South Africa and the US, 4Navitas intends to develop a supply chain in the UK capable of manufacturing one 4N-55 per week. “We also have a licence agreement with [fabricator] Collinson plc, which is setting up a manufacturing plant north of Preston to manufacture a variant, the 4NC-55,”M’Benga says. “This will be a light steel frame tower, with the same mill and control system as the 4N-55.”

Despite the noble intention, M’Benga has fought with selling the vision to potential partner suppliers. “British manufacturing companies cannot seem to grasp the partnership principle. They want to make huge profits on their individual component of the machine without, it would seem, wanting to invest in winning orders of the end product.”

Conversely, he says, “European companies want to invest time and therefore money, working to develop a solution and even prototyping their components. They seemed to better equipped to understand that building a complex product like a wind turbine required teamwork and the necessity to provide engineering resource and consultancy.”

Ringspan (UK) Ltd, a division of German company Ringspan, became more of a “relationship supplier” for 4Navitas, sharing some of their risk, and now provides many component parts for the turbines.

Other key suppliers include Green Marine for the blades, Parker SSD and Emerson Industrial Automation who provide the drive and control system, gearboxes and motors, prototype gearboxes from Radicon in Huddersfield and fabrication from Collinson.

With a proven technology, the means to build it, a healthy list of enquiries and plenty of wind, 4Navitas is confident about the future and expects to hit that one unit per week rate by end of 2014.

Despite the government’s about turn on Feed-in Tariffs in 2012 for residential and small business renewable generated power, trade body RenewableUK expects more companies to invest in onsite power as energy prices continue to rise above inflation and more of the hitherto dubious technology of some green energy becomes, like these VAWT blades, proven. The government will hope that they do.

Dominic M’Benga will talk about 4NAVITAS and VAWT technology at the Global Manufacturing Festival at the Advanced Manufacturing Research Centre with Boeing near Rotherham on June 25.