Giddens, N.Z., at top in hydro schemes

Press, 24 October 1989, Page 13

Giddens, N.Z., at top in hydro schemes

KEN COATES

talks with an engineer who has spent

many years of research in developing . compact microhydro power plants suited to the do-it-yourself expertise of most high-country farmers.

PEOPLE IN REMOTE areas who fear a return to unreliable diesel generators for electricity because of deregulation need not despair. A Christchurch research engineer, Peter Giddens, has come up with an alternative which he believes could be just the answer — small, custom-made hydro plants, reasonably priced and reliable.

The jargon term is microhydro power, and Peter Giddens is one of the most knowledgeable men in the world in this field.

He recently retired after 38 years at Canterbury University’s School,of Engineering where he carried out exhaustive research into this form of alternative energy over 15 years. It has significance for developing countries, particularly isolated villages in the Pacific islands, and in Africa and Asia. A post-graduate engineering student at the university is working on a standardised microhydro system and a Christchurch manufacturer is interested in producing packaged units. The compact microhydro plants developed by Peter Giddens seem well suited to the do-it-yourself expertise of most high-country farmers. With neighbours and friends they are well able to construct components and install equipment, apart from work that is required to be done by an electrician. The concept is simple, as so many good ideas are. Take a water pump, reverse its direction, force water through it and it becomes a power source, or turbine, for an electricty generator.

Provided there is a handy and reliable water source, such as a spring, stream or river, and sufficient fall, an electricity supply more than adequate for the average householder can be installed for between $20,000 and $40,000. “This is not big money — for many landowners, only the price of another vehicle,” says Peter Giddens.

He estimates that the cost of power supplied in this way to the average remote consumer is about three times that paid by an urban householder.

Small hydro-electric plants are nothing new. The South Island has many schemes, some of which have been operating for about a century.

But the research at Canterbury University, linked with findings elsewhere in the world, has established the viability of small, domestic plants, providing electricity at urban standards at an acceptable cost. The average life of such a plant is estimated at 20 years. The oil crisis of the early 1970 s stimulated work on the project, which included testing water intakes, pumps and other equipment in the university’s fluid mechanics laboratory.

Peter Giddens explains that a realistic output for a domestic plant is five kilowatts, a generous power supply by average standards.

A key factor is the fall available for the water rersource — the greater the fall,- the less flow is needed to power the turbine

and generator. For example, a fall of 100 metres calls for a flow of only 15 litres a second, while a 15-metre fall needs 100 litres a second. The pipeline is the most expensive item, and wether of asbestos, concrete or plastic, the cost averages $lO,OOO, depending on length and diameter. Centrifugal pumps, in common

use and easily adapted to act as a turbine, cost between $lOOO and $l5OO. Generators and electric control equipment each take a similar share of the total cost. Peter Giddens - has tested something like 100 pumps, some of which have been adapted and used on a variety of schemes. An experimental five-kilowatt

hydro plant has been operating for six years on a sheep station near the Lewis Pass. Two houses are supplied with electricity by a hydro plant tapping a stream on a bush-clad hillside 92 metres above. Another test plant, with an 11kilowatt output, has been installed on a sheep farm near Omarama, and vital information

has been obtained on its performance during icy winter weather.

Water from a river intake passes along two kilometres of canal before entering a steeply sloping pipeline of 60 metres to a powerhouse.Equipment was tested in Canterbury University’s fluid mechanics laboratory for a larger, 35kilowatt plant installed by an Ashburton engineer at Erewhon sheep station. The latest work being done at the university includes fine tuning of a New Zealand-made pump to upgrade the performance of a 10-kilowatt microhydro scheme designed for a hosptial in Zaire, Africa. This is at Luanza, on the shore of Lake Mweru.

Depending on the nature of the land, and the type of water intake, microhydro power is competitive with diesel-powered plants, according to Peter Giddens.

It is much more convenient, as power is available around the clock (with a reliable water supply), and “it is certainly preferred by the people who have it.”

The majority of New Zealanders are used to having a seemingly unlimited supply of electricity at the flick of a switch. The limit is the main house fuse, but seldom is enough power used — about 15 kilowatts — to blow it.

A microhydro power user will not have the same access a city user has to a large draw-off of electricity at one time. But by spreading the load, peaks can be avoided and consumption kept within the five-kilowatt output. This supply, available continuously, is luxurious in terms of average residential consumption, according to Peter Giddens.

But it does mean careful management. It opens the way for house design that provides for concrete under-floor heating and The cost of power from a microhydro plant is estimated at 25 cents a unit (one kilowatt an hour) for an average household, though it reduces the more electricity used. This compares with 8.25 cents a unit in residential Christchurch.

The man who has spent years researching this alternative energy system suspect that many people in isolated areas will be interested in installing means of generating this form of power. “I know the electricity supply authorities are interested in getting remo(e consumers to make a change so these long fingers of radiating power supply — expensive to maintain — are got rid of,” Peter Giddens says.

Due to the work he has headed at the university, New Zealand is at the forefront of microhydro power development. And the man who has guided the work will prepare a code of practice in designing and installing small hydro schemes, using as far as possible, commercially available equipment. This will be produced in booklet form so that detailed guidance in planning and construction will be readily available to all who want to go the microhydro way.