Kiwi ingenuity

Engineering’s in the blood of Geoff Henderson, the man behind Windflow Technology’s innovative two-bladed wind turbine.  By Hugh de Lacy.

Finishing high school in the mid-1970s, just a couple of years after the first oil shocks, awakened Geoff Henderson (pictured right) to the possibilities – indeed imperatives – of new forms of renewable electricity generation.

Combining that awareness with a family history of innovative engineering led him to develop the only wind turbine manufacturing company in Australasia, with 90 percent of the machine’s content sourced from within New Zealand.

Henderson is the chief executive and a director of Windflow Technology, the Christchurch-based company that is supplying revolutionary two-bladed wind turbines to a succession of New Zealand wind farms, and which is on the brink of moving into exporting.

Eight years after floating the company on the alternative New Zealand exchange, Henderson has about 50 of his turbines in operation at the Te Rere Hau wind farm in the Manawatu, and is overseeing the gradual gearing up of the Christchurch factory to eventually build 20 a month from the present five a month.

While the car-less days of his high school years provided the inspiration it was Henderson’s father who pointed the way.

“If you actually want to do something about renewable energy you’ll have to become an engineer,” Frank Henderson advised his teenage son.

And Frank was in a good position to offer advice: a Professor of Engineering at Canterbury University, Frank Henderson, with his brother-in-law Arnold France, built the first single-stage axial-flow jetboat in the mid-1950s. This was about five years before William (later Sir William) Hamilton did the same thing, and then went on to commercialise marine jet-power with his Christchurch company C.W.F. Hamilton and Company.

With the example of his father’s contribution to so iconically Kiwi an invention as the jetboat, Geoff Henderson set out to make a comparable input into renewable energy, albeit in a country where two-thirds of the electricity supply was already renewably generated by hydro.

Henderson enrolled at his father’s alma mater and in 1981 graduated with an honours degree in mechanical engineering. He put in three years in Auckland as energy systems engineer with Worley Consultants before setting off on an OE that included two years working on wind farms in California, and four-and-a-half years with the English wind power research and development company Wind Energy Group (WEG).

It was during this time that Henderson invented and patented what was to become the key to his own two-bladed turbine, a power control system called the torque-limiting gearbox. WEG won a £250,000 ($750,000) contract from the United Kingdom’s Department of Energy to build a prototype of the system in a three-bladed turbine.

“It worked well,” Henderson told Energy NZ. “What it does is allow the turbine speed to vary while the generator speed stays constant. To do that there’s a differential stage in the gearbox which is nothing more complicated than the diff  in a lot of vehicle transmissions nowadays.

“It’s combined with a simple hydraulic circuit which bleeds off about three percent of the power on average, with the hydraulics becoming a 15 kilowatt add-on to a 500 kilowatt windmill. It’s a relatively low-cost add-on and between those two things we enable a variable speed capability on the windmill as the key to keeping the torque under control,” he says.

During his time in the UK, Henderson also became project engineer for WEG’s signature commercial wind turbine, the 33 metre high 300 kilowatt MS3. This comprised his managing all the design aspects of the turbine, from the blades and drive-train to the tower and the electrical sub-assemblies. To top off his on-the-job training, he was also made R&D engineer on a project to test the fatigue strength of the critical blade-root joint between the steel studs and wood-epoxy blades.

Ten years after graduation from Canterbury University, Henderson returned to New Zealand with his patents in his back pocket, and set up his own windpower consultancy, Wind Torque. The following year, and with an eye to the future, he bought the chunk of highly windswept land near Palmerston North, on the northern edge of the Tararua Ranges, that is now Te Rere Hau wind farm, the first to feature his two-bladed turbine.

The idea for two blades rather than the usual three had arisen when he was at WEG. After setting up 20 of its three-bladed turbines in California, the company found it was losing out on price in the battle for further orders to the Danish company Vestas, which was heavily subsidised by the Danish Government.

This prompted WEG to dust off some old two-bladed turbine research to see if production savings could be made, and Henderson was in the thick of the project.

“We made a real breakthrough in dealing with some of the dynamic issues of  the two-blader,” he says. “The main advantage is that it results in a significantly lighter machine – about half the weight of a three-blader – with the same power output.”

Today the majority of American and European companies still manufacture three-bladed turbines, but  Henderson saw himself as having no other choice when he set up shop in New Zealand.

“If I thought we could make wind turbines cost-effectively in New Zealand using three-blade technology I would, but it just doesn’t stack up in an unsubsidised environment,” he says. “The Danes have been living off subsidies for 20 years and don’t have the same drivers that we have for really cost-effective technology.”

In 2000 Henderson formed Windflow Technology to produce a prototype 500 kilowatt two-bladed turbine with a 33 metre-diameter rotor and a 30 metre hub height. Within two years he had the pilot machine operating at Gebbies Pass, a turbulent site at the innermost end of Lyttelton Harbour. The project suffered a major setback when a freak storm that had created tornados at Greymouth destroyed the turbine with 50-knot gusts.

“It was a bizarre combination of circumstances and it was a bit hard to see the funny side of it at the time, but the benefit we got out of it in terms of dealing with that Achilles heel was huge,” Henderson says.

The setback was temporary, the investors stuck with the project and Windflow Technology was successfully floated on the alternative exchange. Te Rere Hau was developed by an off-shoot company called NZ Windfarms, listed on the main exchange, which ordered 97 turbines, most of which are now in place. The nacelles are built at the new Christchurch factory in Riccarton while the blades are built in Auckland by Wind Blades, which is wholly owned by Windflow.

State-owned electricity generator Mighty River Power last year took a 19.95 percent cornerstone shareholding in Windflow, with plans to use the Windflow 500 in a new wind farm at Long Gully, west of Wellington. Beyond that there’s another wind farm planned for Otago, and in May Henderson was off to an American Energy Association conference in the windy city of Chicago to launch Windflow turbines into the global powerhouse of the world wind energy market

“Under [US President] Barack Obama the Americans have definitely got the message about renewable energy and climate change, and they’re pouring trillions of dollars over the next 20 to 30 years into wind power,” Henderson says.

And he’s eager to see Windflow Technology getting a slice of that action.