The UK's Rocksavage combined cycle gas turbine IPP power station, just officially opened, is designed to cope with some 200 stops and starts per year rather than baseload operation.

Flexibility is likely to be one of the issues exercising the UK government’s energy people this summer as they consider the desirability of continuing the current moratorium on new gas-fired power plants. One criticism levelled at gas-fired plants built in the first “dash for gas” of the early 1990s, immediately following the path-breaking privatization of the UK electricity supply industry, is that they operate predominantly in baseload mode. They give no thought to flexibility, load following, frequency response, security and the greater good of the whole electricity system. It is flexible coal plants, so the argument goes, operating in mid merit order that take on the burden of these security services – but fail to receive a proper reward for their efforts.

However, in what has been dubbed “the second dash for gas”, a new generation of flexible gas-fired plant is emerging. Exemplifying the new generation is InterGen’s 770 MWe Rocksavage combined cycle power plant, which was officially opened by the Queen on 31 July – two years from the project’s financial closure, in June 1996. (Financial closure itself was also very fast, taking only 12 months from signature of a development agreement with ICI.)

The Rocksavage IPP plant is designed to provide 300 MWe to ICI’s adjacent Runcorn chloro-alkali facility (saving approximately £20 million per year compared with other supply options), 400 MWe to utility Scottish Hydro Electric and the rest to the National Grid. Fuel is supplied to the plant on a “tolling” basis. The gas is procured and provided to the plant by ICI and Scottish Hydro, and processed through the power plant which then provides them with electricity. Whether the plant operates or not depends on whether the two main customers need the electricity and whether it is their cheapest option. “It is not a baseload plant that runs regardless of pool price”, says InterGen’s George Grant. “It is the first UK IPP developed specifically for the mid merit market, and is not designed to just be switched on and run continuously.” This flexibility was built in from the outset, he points out. The design basis of the plant assumes around 200 stop/start sequences per year.


Rocksavage, which employs 42 people for day-to-day operation and represents a £375 million investment by InterGen, claims to be the most efficient power plant in the UK, at 58 per cent. It is the first commercial application of ABB’s new GT 26 turbine (one of which has been operating at the Birr test facility in Switzerland since 1996).

The plant has two GT 26s, which use low NOx sequential combustion technology, and an ABB steam turbine with a totally enclosed water-to-air cooled (TEWAC) generator (for further information see MPS, November 1996).

The entry into commercial operation of Rocksavage is a milestone for InterGen, the power plant (and related fuel infrastructure) development and operating company jointly owned by Bechtel and Shell. The first kWh generated by Rocksavage was also the first electricity to be generated by a wholly InterGen-owned plant, and marks the company’s transition from a developer to an operator of power plants. Rocksavage is seen as a flagship plant launching what it hopes will become a “a national energy company in the UK.” The setting up of what it calls national energy companies, which handle all aspects of electricity production, from power project financing to electricity marketing is a key element of the InterGen strategy. Elsewhere in the UK, the company is developing a salt cavern gas storage facility (under North Yorkshire) and gas-fired power plants at Spalding and Coryton – but these projects remain uncertain pending the final outcome of the government’s current review of energy sources for power generation.

InterGen is proving to be no slouch when it comes to getting power plant projects moving. Established in 1995, and now employing 311 people worldwide, it currently has the 770 MWe Rocksavage in operation, some 2100 MWe of generating capacity and a 700 km gas pipeline under construction, eight projects (6450 MWe) at an advanced stage of development and “two dozen projects in early development being pursued in 15 countries.” A recent success was finalization of the contracts for the Sidi Krir 2 x 325 MWe build-own-operate-transfer gas-fired power project in Egypt, where InterGen is consortium leader.