The new Darling Downs Power Station will take advantage of the rich source of coal seam gas (CSG) reserves held by Origin Energy in southwest Queensland, predominantly in the area around Roma and Chinchilla. The $780 million 630 megawatt (MW) gas-fired power station will be located near Braemar, 40 kilometres west of Dalby and will be the biggest combined cycle power station in Australia.

Providing a myriad of environmental benefits

In November last year, construction started on the gas-fired power station, which Queensland Premier Anna Bligh says will emit about half the greenhouse emission of a conventional power station.

“Coal seam gas is a clean energy source and when this station is online, it will produce 2.5 million tonnes per annum less than a conventional power station of its size – which is the equivalent of taking 600,000 cars off the road,” she said.

The environmental benefits of the gas-fired power station also extend to saving water. Since the power station uses air cooled technology, it will use less than 3 per cent of the water a conventional water cooled coal-fired power station would use, or about 200 megalitres (ML) versus 8,000 ML a year.

Additionally, unlike natural gas, which is trapped by specific geological conditions, since CSG is held in place by water, pumping out water is part of the CSG production process. Origin plans to develop a 9 ML day reverse osmosis water treatment plant as part of the broader project.

One of the project’s bigger challenges has revolved around the pre-treatment of this water, which has high coal fine loads.

Pre-treatment involves micro- and ultra-filtration, with a settling pond prior to the reverse osmosis reaction that exposes the water to the atmosphere and allows some heavier minerals to precipitate out. There are a range of different markets for this water, from supplying local councils with potable supplies to nearby industrial markets, including coal washing. Ultimately however, the projects’ broader environmental benefits are particularly important given the considerable impact of the drought on Queensland in recent years.

Spurring the development of ‘economic powerhouses’

Premier Bligh said that CSG projects, including the Darling Downs Power Station, have yielded approximately $1 billion worth of development across Queensland, with clear benefits to the regional economy.

“We expect this investment to continue at more than $160 million a year and this means local jobs and a further boost to our regional economy,” Ms Bligh said. “This Origin power station and associated CSG developments alone will create an average of 440 jobs during the construction phases, and up to 55 jobs when operational.”

“Many of these regional communities have been hit hard by drought in recent years and the rich source of energy in the Surat Basin has the potential to turn towns like Dalby, Miles and Chinchilla into economic powerhouses.”

Promoting CSG development

In order to achieve this lofty aim, Origin is planning two separate but parallel activities alongside construction of the power station.

Firstly the company plans to invest a further $360 million to expand its CSG production at Spring Gully, which is located 80 kilometres north of Roma. This supply source will later be supplemented by the development of Origin’s CSG Walloons fields, which are located near Chinchilla.

Fuel for the power station will be processed at the Spring Gully CSG gas processing plant and then transported through an existing gas pipeline to Wallumbilla. A new $90 million 200 kilometre pipeline will be constructed from Wallumbilla to the new Darling Downs Power Station site.

In February this year, Origin secured $900 million for the development of the Darling Downs Power Station and ongoing CSG projects. The development will become one of the lowest cost power stations in the National Electricity Market, in part because Origin directly owns the CSG reserves that will fuel the power station, but also because, the power station is expected to have a low life cycle cost, including both construction and long-term maintenance costs.

When completed in 2010, the power station will not only complement Origin’s existing power stations at Roma, Mount Stuart and Wambo, but will also boost CSG projects in the Surat Basin. The environmental benefits of CSG and gas-fired power stations will not only tackle greenhouse gas emissions, but will significantly reduce water consumption, both of which are required for a sustainable energy future.