$500m plant could delay power line

State-owned power company Genesis Energy is drawing up plans to build a $500 million gas-fired power station on the shores of the Kaipara Harbour.

If built, a new station north of Auckland could delay Transpower's plan for new power pylons running through the Waikato.

Transpower says new lines are needed by 2010, before a critical shortage of electricity bites in the upper North Island.

Demand for power in the Rodney district is growing at 4 per cent a year, while fears for security of supply for the whole Auckland region are also growing. Power use across Auckland has reached records in the past two weeks.

Genesis has been investigating potential sites for a power station in the Helensville and Wellsford areas. The two locations' proximity to both a natural gas pipeline and electricity transmission lines makes them attractive.

The Rodney District Council is understood to have been approached about the need for changes to its district plan to allow construction of a new power station.

A new gas-fired station would also affect plans by Mighty River Power to reinstate the Marsden B power station as a coal-burning plant.

Genesis chief executive Murray Jackson said the project was not yet at the "build stage" as the company was working on developing gas reserves.

A number of regions for gas turbine generation were being assessed, with none predetermined.

Genesis was working with district councils on site selection.

Progress on a Kaipara station is dependent on good results coming from testing at the Cardiff natural gas well in Taranaki, which is 40 per cent owned by Genesis.

Combined Cycle Gas Turbine (CCGT) stations are a popular way of converting gas into electricity. They are essentially a large jet engine sitting on the ground driving a generator.

Exhaust gases are passed through a boiler to produce steam that in turn drives a turbine coupled to a generator.

Genesis says a Kaipara station would have an "ultimate capacity" of 360MW, but current gas pipeline capacity would allow initial output of 240MW.

Getting resource consent to build a new station should be relatively straightforward, as they do not take up much land and, apart from CO2 emissions, do not emit much pollution.

By comparison, Mighty River, as it seeks to fire up Marsden B, needs permission to discharge hundreds of kilograms of mercury into the sea, as well as lead, cadmium and arsenic.

If local gas supplies run dry, CCGT stations can run on imported liquefied natural gas (LNG).

Genesis and Contact are in the early stages of planning for LNG, which they say could be easily injected into the national gas pipeline system.