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Windflow Technology Ltd
An interview with Geoff Henderson and Dr Neil Cherry
Dorothy - 25/05/01

Windflow Technology Ltd

New Zealanders are complaining about the increases in their power bills and after the recent drought conditions they are anxious about the low levels in South Island lakes on which the large South Island hydro-electric power stations depend for their water supply. The present government supports the Kyoto Agreement and is making a push for renewable energy.

Americans are seriously concerned about their power shortages and President George W. Bush's plans for improving the power supply are upsetting ecologists and conservationists.

What more appropriate time for launching Windflow Technology Ltd, a company that will produce windmills for the development of electric power from the wind and increase the electricity supply from an alternative source of energy?

New Zealand an appropriate country
New Zealand is located in the Roaring Forties and the airstream is accelerated through narrow gaps in the mountains of the South and North Islands, and sea breezes blow across its long coastlines. These factors make this country an appropriate area for the development of windpower.

Expertise in engineering and in meteorology and wind energy essential
For Windflow Technology Ltd to succeed it needed a mechanical engineer highly skilled in the design of the machinery involved, and a scientist skilled in meteorology and knowledgeable about wind energy resources.

Fortunately in 1985 two people with these specialisations met when working in the United States - Geoff Henderson engineer, and Neil Cherry meteorologist.

Geoff Henderson
Geoff Henderson
Geoff Henderson
Geoff Henderson's ambition from his student days was to work in renewable energy. After he graduated from the University of Canterbury with a Bachelor's Degree in mechanical engineering he worked for a consulting engineer for three years on energy-related projects, and then was appointed to manage a wind farm in the Altamont Pass in California - a dream come true.

From there Geoff moved to work in England for the Wind Energy Group - the leading firm in the field owned 50/50 by Taylor Woodrow and British Aerospace. As a senior engineer he was responsible for the design and development of wind energy technology and was project engineer for the flagship machine MS3 which produced 300 kilowatts. It was a two-bladed machine prototyped in 1987-88. His appointment to such a senior position at such an early stage in this career reflected New Zealanders' reputation for being hard working and multi-skilled - both qualities needed in his position.

A three-bladed machine developed previously had not been sufficiently cost-effective and had been subject to wear and damage, but the two bladed machine eradicated the fatigue loads.

Dr Neil Cherry
Dr Neil Cherry
Dr Neil Cherry
Dr Cherry's specialisation and experience fitted him ideally for involvement in the development of Windflow. He was responsible for the wind energy survey of New Zealand in the 1970s. At that time the Government's policy was to fund only the survey - their plan was that they leave the development of the technology to overseas firms.

Neil was invited to review the United States wind energy programme run by Battelle Laboratories, the leading group in the US wind survey programme. His appointment was as an independent reviewer. In 1980 he spent six months in Richland, Washington. Again there was a need for multi-disciplinary skills as he was kept on at Battelle and asked to correct previous research and extend the wind profiles.

At the end of 1991 the United States wanted to be world leaders in wind research, and commissioned a World Survey of Wind Energy Resources. Dennis Elliott had continental experience and surveyed the United States. As Neil had experience in surveying winds over the oceans he did the rest of the world. This research confirmed Neil's belief that New Zealand had massive potential for wind power development.

Modern wind turbines
Modern wind turbines capture the wind's energy by turning in the wind and driving an electric generator. Modern windmills consist of:

a rotor driving a generator generally through a gearbox
a tower
auxiliary systems including yawing, braking and hydraulics and often blade pitching and variable speed
a computerised controller

Windflow Rotor
Windflow Rotor
The two-bladed Windflow windmill has the blades mounted on bearings so that they can be "pitched" to control power and/or speed. In order to reduce any imbalance in the wind forces on the two blades and therefore reduce the stresses on the mechanisms the "teeter" hinge lets the rotor rock back and forth. Importantly the blade pitching is coupled to the pitching motion (through the pitch mechanism) so that the blade moving down-wind feathers and the blade moving up-wind goes to fine pitch. This stablilises the teeter motion.

The other important aspect of the design is the Torque Limiting Gearbox which Geoff invented while he was working in England. It allows the rotor speed to vary while keeping the torque constant. It provides a soft connection to the grid to absorb the gust energy and send it smoothly into the grid as it has a fluid step in it.

The use of the Torque Limiting Gearbox means that it does not have to be designed to cope with the heavy loads carried by fixed speed machines. This means that it saves money. Similarly the teetering rotor enables lighter construction, which reduces costs. The design is more robust in turbulence as it allows the rotor to move in response rather than resist gusts.

Hydro power in New Zealand provides a backup
Because the wind varies, a backup is needed and this normally limits the amount of wind power that can be economically installed in an electrical network or "grid". In New Zealand lake water can be stored while wind power is available and used in calm weather. This means that a higher proportion of wind power can be used economically.

Wind power can be low cost energy
If wind farms can be sited close to cities they avoid expense of long cabling to connect with the hydro power. There are suitable windy sites close to all the main centres in New Zealand which makes wind power a source of low cost energy as the fuel is free and the line cost and the energy losses are minimal.

Recent work in New Zealand
Since Geoff returned to New Zealand he has been employed to survey wind resources, and for several years he has been a consultant for The Power Co Ltd in Southland.

Geoff and Neil were invited by ECNZ to participate in a research project which led to the Brooklyn Wind Turbine in Wellington. ECNZ took a conservative approach and wanted to use "proven technology and a guaranteed manufacturer" for the machines and any needed repairs, so in 1993 they imported from Denmark a machine developed in 1984-6.

Windflow machines will be manufactured in New Zealand
For the Windflow machines the work will be done locally under sub-contract by a Christchurch engineering firm and an Auckland boat builder, and will use local expertise and factories already here. At present the windmills operating in New Zealand are all imported - seven German mills in the Wairarapa and 48 Danish mills near Palmerston North. Local production must be beneficial for New Zealand, creating work for New Zealanders and saving costs from shipping and the extra expense incurred with the present exchange rate. Local manufacture also means local accountability and quick cheap servicing.

The first site
The first wind farm will be at Gebbies Pass close to Christchurch. The site is in an area with highest mean winds in winter, when the spot price for electricity is highest. There is a ten-year agreement with Orion to connect to the network, and the Christchurch City Council has agreed to buy all the output of the first turbine to cover the initial investment over a long period.

The stages of development projected by Windflow Technology Ltd
The first stage for Windflow Technology Ltd will be the building of one windmill, the second stage the building of another ten, and the third building up to sixty per year by year 5.

The use of wind power world wide as a source of energy grew six to sevenfold in 1990-2000. With increasing interest in wind power in both New Zealand and Australia the future for the production and sale of the windmills looks promising, especially with CER facilitating trade with Australia.

Investment in Windflow Technology Ltd
The Company is seeking to raise three million dollars in the Stage 1 Offering. This offer closes on Friday, 1 June, 2001.

If you are interested in investing in the company go to and download the Investment Statement.

Neil Cherry as Chairman of Directors and Geoff Henderson as Director and Chief Executive Officer and the other Board members were delighted to receive a substantial investment from Teddy Goldsmith, the UK environmentalist and founder of the Ecologist Magazine.

Those interested in preservation of New Zealand's clean green image will support the development of wind power as a source of renewable, clean and competitive energy.

To read more about Neil Cherry and his work, please visit his website for more information.

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