Lanes Merge

Coast perfect for hydro generation

0 Comments | Press, The; Christchurch, New Zealand, Jun 22, 2010 | by HARDIE Norman

NORMAN HARDIE makes the case for hydro-electric power development on the West Coast.

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Ninety-nine per cent of Norwegian electricity is generated from hydro-electrical sources. The remainder is from wind farms and a small experimental tidal scheme in one of the fiords.

The railway locomotives are electrically powered, in spite of the country having an abundance of North Sea oil. For several years electricity has been exported to Denmark.

In 2008 an under-sea cable was placed, giving Holland access to surplus power that Norwegian hydro plants have to offer.

Our West Coast has a rainfall greater than any equivalent area of Norway and the mountain ranges are some 1000 metres higher. Yet the West Coast imports most of its electricity over Arthur’s Pass and via the Buller Gorge, sourced from the Waitaki lakes.

The line losses in such great distances, to Fox Glacier and Karamea, exceed 50 per cent. Domestic electricity charges in that part of the country exceed most other districts. Why does this situation exist?

In 1982 an official assessment of annual rainfalls was done in a section that extended from Hokitika to Rakaia headwaters, Mount Hutt and Rakaia. Very long rain gauges were delivered by helicopter and men were flown to them every month or so. The published results for the total year appeared in 1983.

Very large falls were indicated, frequently above eight metres and in places going up to 12m. There are few places in the world that have so much rain. Most of the rain falls on the west side and there are rain shadows in the Rakaia basin and the Canterbury Plains.

Since the decision in December 1983 to build the Clyde high dam no other large hydro schemes have been built. Some minor upgrading has been done. The permanent flooding of the arable flats from Cromwell for 18km towards Tarras gave hydro-electricity a bad odour.

Unfortunately hydro- electricity is often associated in New Zealand with the permanent flooding of agricultural or highly scenic river valleys. This need not be so.

In Europe hydro construction has continued and not one major valley has been lost in the last 50 years.

Dozens of schemes exist where water is diverted from a high valley through a tunnel and at the exit point penstocks and a generating station are constructed.

In some circumstances a similar purpose is achieved by building canals along ancient glacial terraces and then dropping down in steps. Each step includes generators. At the Waitaki this has been done at stations Ohau A, B and C.

In the daily pattern of domestic use of electricity there are two major peaks. One is at the beginning of the day and a longer, bigger one each evening. These peaks are higher in winter when more heat and light are required.

Electricity supplied from coal, gas, tides, wind or geothermal sources is unsuitable to meet these short-term peaks. It is just hydro-electricity which can be turned for an almost instantaneous boost.

Most Westland valleys fall very steeply to the west from the main divide, so they cannot be diverted easily to the Canterbury side. One can see this when driving from Arthur’s Pass to Otira.

However, further south there are two western valleys which, with a tunnel, could make considerable contributions to the storage at Lake Pukaki and hence to the six stations further downstream in the Waitaki
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