Baglan: cooking with gas

The Baglan Bay power project, which got the go-ahead despite the Government’s restrictions on new gas-fired plants, sets new standards in efficiency for gas turbines, says Andrew Cavenagh

The go-ahead this summer for the development of a medium-sized gas-fired power station in south Wales is likely to have far-reaching implications for the power generation industry in the first decade of the next century.

Industry secretary Stephen Byers’ announcement that he had granted consent for the construction of the 500MW plant at Baglan Bay, near Port Talbot, seemed at odds with the stricter planning regime for gas-fired projects introduced by the Government late last year.

The plant, to be developed by BP Amoco and General Electric of the US, is not a combined heat and power (CHP) project, several of which have been exempted from the moratorium because their higher generating efficiency will help to reduce greenhouse gas emissions. It was widely assumed that the prospect of creating 6,000 jobs in a deprived area (the plant will be the catalyst for the development of an energy park) had taken precedence, with elections to the Welsh Assembly looming.

Byers conceded that this had been a factor, noting that the `potential benefits, particularly in terms of employment and economic regeneration, are such that I have decided not to use my powers to defer or halt this project’.

But another factor – that the project would be the first commercial exploitation of General Electric’s new H system gas turbine – is of much greater significance to the power generation market.

Originally announced in 1995, the H system has been developed to set new standards in turbine energy efficiency and environmental cleanliness. The project has been a collaborative effort between GE Power Systems, GE Aircraft Engines and the GE corporate research and development centre.

While broadly based on proven turbine technology, the H system uses advanced materials and a new steam cooling system that enables it to operate at a much higher firing temperature, 1000C hotter than the previous F series.

Jim Lowe, GE’s project manager for the scheme, says the use of steam has overcome the law of diminishing returns reached with air-cooled turbines, where more of the compressed air had to be diverted for cooling as the firing temperature increased. `With steam cooling you can use all the air in the combustion system,’ he says.

This improvement enables the H system to achieve an energy conversion efficiency of 60%, compared with 58% for the most efficient combined-cycle plant now in operation. This may sound marginal, but with fuel the biggest single cost in running a gas-fired power plant the saving over a station’s lifetime is likely to be considerable – each percentage point in efficiency gain is reckoned to reduce lifetime operating costs by £9m-£12m for a plant in the 500MW range.

The system’s higher efficiency also gives it the highest electrical output – 500MW – for a single combined-cycle unit.

More importantly, the use of nozzle steam rather than air cooling means efficiency gains can be made without the usual drawback of high-temperature firing: increases in emissions of nitrogen oxides (NOx).

Using data published by the Department of the Environment, Transport and the Regions, GE says the system cuts emissions of NOx by 80% and carbon dioxide by 16%.

Baglan Bay already has an old 100MW oil-fired heat and power plant that serves BP Amoco Chemicals’ isopropanol production facility on the site. BP Amoco gave a commitment to keep this plant open, retaining 60 jobs, if the new plant was approved.

The project will also use waste heat to increase the power plant’s efficiency to over 70%. Although it does not qualify as a full-blown CHP scheme, its CHP element will account for 185MW of output. Initially, it will provide steam as well as power for the isopropanol plant. Later it will offer the same service to large industrial users who are attracted to the energy park. When the station comes on line, it will boost total generating capacity in South Wales by 300MW, which closely matches the region’s present supply deficit.

Lowe says the H system has completed tests in rig conditions but will face further extensive testing during the commissioning phase following the 18-month construction period. The plant is not expected to start continuous operation before the end of 2002.

GE has high hopes for the technology over the next 10 years, as deregulation of power markets and mounting pressure to minimise environmental damage puts an ever greater premium on low-cost, high efficiency plants.