Big power users wait to see effect of savings measures

By CHRIS DANIELS energy writer

Big South Island power users may have to wait till next week to judge the success of new tactics to save their power lines from winter peak overloading.

Transmission constraints on power lines feeding electricity from dams in the lower South Island into the top of the island last month prompted Transpower to warn of the possibility of blackouts for some big users.

Disruption was most likely between 5pm and 7pm on weekdays, when industry and households were both using electricity.

Cold weather over the weekend was not enough to send demand in the region rising to hazardous levels.

Roger Sutton, chief executive of Canterbury electricity lines company Orion, said loads on the system were usually between 10 per cent and 20 per cent lower on weekends than weekdays, since there were far fewer businesses operating.

"We always had at least a 10 or 15 per cent margin over the weekend," said Sutton. "We think with the contingency plans that Transpower and the industry have put into place it's looking increasingly unlikely we are going to get ourselves into difficulty this winter."

Any problems were much more likely on weekdays, and then, on Mondays, when electricity demand was at it highest.

Transpower and South Island lines companies agreed last week on a series of measures designed to save their big customers from blackouts. They included full control of hot water heating by the lines companies, additional use of customer-owned generation, switching Timaru to service from other transmission lines and paying some high-load customers to reduce demand at certain times.

One way of removing the need for an expensive upgrade of transmission lines into Canterbury would be the construction of so-called "dry-year reserve" generation.

The first piece of new, dry-year reserve electricity generation was opened last week at Whirinaki, near Napier. The $150 million diesel-powered station is designed to operate only when inflows into the southern hydro lakes are low.

There is no prospect of that happening this winter, with lake levels at 130 per cent of their average for the time of year. Electricity Commissioner Roy Hemmingway has said that the Whirinaki plant, along with other new generation, such as that from the recent opening of stage two of the Trustpower windfarm near Palmerston North, meant shortfalls were also unlikely next year.

The cost of building and operating Whirinaki will be recovered through a levy on the industry. The construction cost equates to less than $5 a year for the average household.

Once new laws are passed by Parliament, the Electricity Commission will be able to levy the power industry to pay for dry-year reserve generation.

Energy Minister Pete Hodgson last year said that "several hundred megawatts" of reserve generation would eventually be needed, with an annual levy of around $40 being imposed on each household.