|
|
Two Taranaki projects – the 200 megawatt gas peaker plant at Stratford and the Ahuroa underground gas storage facility – are about to radically strengthen the country’s gas and electricity industries. By NEIL RITCHIE
The 200MW fast-start gas peaker plant at Stratford will provide the country with greater security of electricity supply than we have ever enjoyed before. When the offshore Taranaki Maui gas field dominated our energy sector it was a key source of fuel flexibility for gas-fired power stations, with field production able to be ramped up or down according to demand from electricity generators that were able to ‘bank’ any unused gas for later use. Maui gas covered by that original flexible supply contract is now gone and has been replaced by more expensive Maui right of first refusal (ROFR) gas and other gas, notably from the near-shore Taranaki Pohokura field, with tight “take-or-pay” provisions that provide virtually no flexibility to store gas at times of low power demand for re-use during peak periods. However, once the Ahuroa storage facility is completed Contact will be able to take gas that it cannot use during periods of low electricity demand (principally spring, summer and early autumn) and re-inject it at Ahuroa for use at the traditional winter times of peak power usage. The gas peaker plant will help Contact manage the increasing volatility of electricity generation as more renewables mean more capacity that depends on the rain falling (hydro stations), or the wind blowing (wind farms). It will perform the critical task of replacing lost generation capacity through any unexpected shutdowns more efficiently and much more quickly. The peaker plant, which is being constructed alongside Contact’s existing 400MW Taranaki Combined Cycle (TCC) plant, will be able to go from cold to full output in less than 10 minutes – something that has never been possible in New Zealand before. Older single cycle gas power stations such as Contact’s now mothballed New Plymouth Power Station used to take 12 hours or so to become fully operational from a cold start. Contact Energy is spending about $500 million on these developments, about $250 million for each, that are the biggest construction projects currently being undertaken in Taranaki.
That first stage will be deemed to have finished once a minimum operating pressure in the reservoir has been reached. Then the second stage will start using full injection and extraction functionality with additional injection compressors and gas processing facilities. Contact is aiming to store up to 10-15PJ of gas from a variety of fields and to be able to inject or extract up to 100TJ/day from next winter. Origin is managing the Ahuroa development and will operate the facility for Contact, which is making all design and construction decisions. The Ahuroa facility will not only be able to provide gas to the nearby 200MW peaker plant but also the 400MW TCC station and even to third parties on demand. Contact communications manager Jonathan Hill says the gas peaker project is making good progress, with United Group New Zealand project managing, engineering and installing the peaking units, as well as procuring and installing the other required equipment. There has also been the recent arrival from overseas of several strategic components starting in June this year with the largest vessel yet to visit Port Taranaki, the 66,635 gross registered tonnage TAMPA which discharged two 100MW peaking generators, each weighing about 165 tonnes and manufactured by Brush in the Czech Republic, that are destined for the Stratford peaker project. The next month the smaller Pantanal vessel arrived at the New Plymouth port with a huge compressor and two 100MW General Electric LMS100 fast-start gas turbines for the project. “We’re well into construction now. There are different streams of work at different stages of completion but most items of major plant are here and are either installed or nearly so,” says Hill. Commissioning of the plant it is due before winter 2010, he adds. “The completion of these two projects will prove to be significant milestones for the company and country – it’s a great story.”
|
It will be ‘back to the future’ with the development of the largely depleted Ahuroa gas field as New Zealand’s first underground gas storage facility as it will allow Contact Energy to choose exactly when it runs its Auckland and Stratford power stations – just as Electricity Corporation of New Zealand (ECNZ) did over a decade ago.
Contact, which is 51.4 percent owned by Australian giant Origin Energy, began injecting gas from nearby fields into Ahuroa last December, using a single production compressor, at the initial rate of about 20 terajoules per day until the reservoir held more than 4.3 petajoules of ‘pad gas’.