Beyond the range

Queensland's 630MW Darling Downs Power Station
Queensland's 630MW Darling Downs Power Station

Final testing of Queensland’s 630MW Darling Downs Power Station is now underway. Australia’s largest CCGT project will become a key link in Origin Energy’s integrated strategy.

For early settlers attempting to explore Queensland’s Darling Downs, the Toowoomba range proved a barrier for horse-drawn carts looking to travel west. One-hundred-and-seventy years later the Great Dividing Range continues to test the pioneering spirit, proving a logistical and safety challenge for transportation of the generators and turbines intended for the region’s newest power station.

Situated near the Braemar site in the Darling Downs region and near completion, the gas-fired power station has an approximate 630 MW base load plant capacity from three 120 MW Frame 9E gas turbines and a 270 MW steam turbine. Construction began in August 2007 and was headed by Origin project director, Paul Farnworth. The new power station will take advantage of CSG reserves held by Australia Pacific LNG (APLNG) and Origin in south west Queensland, predominantly in the area around Roma and Chinchilla.

Origin Energy executive general manager major development projects, Andrew Stock develops and delivers the company’s large greenfields capital projects in Australia and New Zealand. The acquisition of Sun Retail in 2007 provided a permanent site in Darling Downs for the possible construction of the power station, he explains.

“(The purchase of Sun Retail) was terrific, because, having bought a retail business, we wanted to be able to back that retail business with generation, at least in part,” Mr Stock said.

With the emergence of coal seam gas in Queensland, the site was ideally situated for burning the available fuel. Even though coal seam gas was just a “pipedream” a decade ago, Origin sees itself as a pioneer in leveraging the new source of energy.

“We like to think we helped unlock the potential for the resource. We have seen over that decade now become a very, very large source of gas for Australia and potentially overseas countries through the developments which are going on,” Mr Stock said.

Commissioning commenced in fourth quarter 2009 and is currently periodically dispatching into the grid during operating trials, with the ramp up to full commercial operation to take place in the second quarter of 2010.

“The station is a very flexible station in the way it is designed, so it has a very substantial amount of turn down. (It gives us) that flexibility to adjust load and also to deal, if we need it to, with production variations or the needs of customers on our retail supply portfolio,” Mr Stock said.

“Another thing which was pretty important was fuelling it with gas, so it has a low environmental footprint, particularly around greenhouse. The power station can produce electricity with less than half the greenhouse emissions per megawatt hour produced by conventional coal power.”

Darling Downs’ combined cycle generates more energy and produces less emissions through its steam cycle. The station’s efficiencies are over 50 per cent, with less than 0.4 tonnes of CO2 per megawatt hour compared to conventional black coal power stations running on 0.8 tonnes.

“The flexibility and the low environmental footprint, they are really important features to us. And obviously we can marry up the low environmental footprint with the ability to develop and add value to our coal seam gas resources by fuelling the station on coal seam gas.”

Unusual for a power station, Darling Downs is air cooled, using less than 3 per cent of the water used in a conventional water cooled power station.

“Given the trends for what looks like a drying climate, although that obviously varies from year to year, it’s getting tougher, so we thought given the power station is going to have a long operating life, it’s very important to us that it can operate at times when water is maybe less available for other generators,” Mr Stock said.

Providing engineering and construction activities and supply of the balance of plant were CH2M Hill, with the steam turbine delivered from GE USA and the gas turbine supplied by GE France. Located six floors about the ground, installing the steam turbine proved an interesting challenge.

“Because of the way it is designed we had to carefully jack that very large unit which weighs several hundred tonnes six storeys up.”

As Australia’s largest CCGT plant, the station represents a significant part of Origin’s integrated development strategy around coal seam gas in Queensland.

“In terms as a transition pathway to a lower carbon future, whichever regulatory regime we have in place, technologies like combined cycle have a key role to play because the technology is proven, operates all over the world today and by using natural coal seam gas combining it with technology to make power, you can achieve very significant cuts in emissions,” Mr Stock said.

“Even with the best coal technologies, modern combined cycle plants like this one and others are able to generate power with substantially less emissions. It’s a way we can meet our future energy needs with a lower environmental footprint.”

With a 50 per cent ownership of APLNG alongside ConocoPhillips, Origin is developing coal seam gas resources for domestic, as well as potential export. A 200 km pipeline from Wallumbilla to the site has been constructed and has been connected to the Queensland electricity grid. The power station is critically important to this strategy as it provides an assured load for the ongoing development of the coal seam gas in advance of the gas project getting approval.

In the event of future needs, a 77 ha block adjacent to the current power station has also been purchased for possible expansion.

“We are looking at how we might do that, we are still in the evaluative phases there. Clearly as the CSG resources are developed that will potentially increase demand for electricity in Queensland and obviously Queensland is a growing economy. I’m sure there will be opportunities in the future to grow our business,” Mr Stock said.

Darling Downs will prove a key link to Origin’s integrated strategy to develop coal seam gas, invest in renewable technology, bring APLNG forward through development and expand throughout Queensland and other states.

“The power station will benefit Origin and its retail business and that integrated story of finding resources, taking them to markets (either directly as gas or converted into products like electricity or LNG) and then being involved in the retail interface as we are in Queensland,” Mr Stock said.