On 28 July a ceremony was held at the Senoko plant in Singapore to mark handover of the second of three combined cycle plants being constructed in the course of the Stage 1 repowering project. Modern Power Systems was there.
The formal handover by Alstom to Senoko Power of the CCP4 360 MW combined cycle unit was a key milestone for both parties. For Alstom it is a mark of the progress it has made in restoring confidence in its GT24/26 gas turbine technology. For Senoko Power it represents the completion of a further major step towards what president and CEO Roy Adair called “overhauling the business base” of the company, particularly in conjunction with its receipt of ISO 14001 environmental management accreditation – also celebrated on the same day.
Benefits of repowering
CCP4, which was handed over well ahead of the contractual date of September 2004, is the second combined cycle unit to be completed as part of the programme to repower the Senoko Stage 1 power plant, which originally consisted of three 120 MWe oil fired units, commissioned in 1976.
The end result of the repowering project will be 1080 MWe of new natural gas fired combined cycle capacity at Senoko, with an efficiency of about 50% (HCV) compared with 36% for the old oil-fired units. (This 1080 MWe is in addition to five 250 MWe oil/gas steam turbine plants at the site commissioned over 1978-83 (the first two comprising Stage 2 of the station and the subsequent three Stage 3) plus a Siemens V94.2 based 2×425 MWe combined cycle plant (completed in 1994) – amounting to an eventual total installed capacity of 3180 MWe.)
CCP4, like CCP3 (handed over February 2002) and CCP5 (due for handover December 2004, three months ahead of schedule), consists of a GT26B gas turbine exhausting into a CMI vertical heat recovery steam generator (triple pressure with reheat). Steam from the HRSG drives a steam turbine retained from the original plant, with the same bearings and foundations. But the steam turbine has been very extensively upgraded, with new rows of blades skilfully added to accommodate the greater steam flow, with no increase in length. Also retained from the old plant is the condenser, which was retubed a few years ago (with titanium substituted for the original cupro-nickel) and has sufficient margin to
accommodate the significantly increased cooling water flow rate. A good deal of the existing civil structures are also re-used.
The cost of the repowering, which adds a total of 720 MWe, is put at S$600 million (about US$350 million), while the benefits, in addition to the higher efficiency already mentioned, include: substantial cost savings relative to new build; reduced NOx; faster start up (from standstill to full load in 3 hours instead of the 9 needed for the old plant; greater automation, with no increase in manpower and a tripling in productivity in terms of electricity output per man; effective use of land; and increased fuel flexibility, with the ability to use gas from either Malaysia (Petronas) or Indonesia (South Sumatra).
The prudence of this dual gas supply strategy was amply demonstrated during the 29 June Singapore blackout, when Senoko was unruffled by loss of the West Natuna gas supply, and in fact able to respond by increasing its generation to 50.5% of Singapore’s total load.
Senoko Power, which Roy Adair described as “lean, keen and green”, aspires to be, in his words, “a genuine triple bottom line company”, the three prongs being finance, environment and community, and the repowering project is seen as very much a part of that underlying strategy, positioning the company well to be a key player in the Singaporean electricity market.
Another goal is for Senoko Power to become self sufficient in water supply, an issue of no small importance in Singapore. The company has recently moved further towards this objective with installation of a 2400 m3/d desalination facility at the power station.
In the course of commissioning CCP3, a number of problems were encountered, including the well known “introductory issues” associated with the GT24/26 – the most significant being deformation of the second stage blade shroud of the low pressure turbine – as well as several others, as might be expected in a repowering project of this complexity.
The package of modifications designed to address GT24/26 issues has been installed at site on the CCP3 gas turbine and this has been performing well. In the case of CCP4 and CCP5, the gas turbines have been delivered to site with the modifications already installed.
CCP4 performance to date has proved to be better than contract levels, with NOx emissions of less than 10 ppm.
Now that the GT24/26 introductory issues have been resolved, users are beginning to experience the benefits inherent in the design, which include very low emissions and small footprint (the same as a 13E2) – a particularly attractive feature at the congested Senoko site.
Senoko Power does seem to be a genuinely satisfied customer. At the handover ceremony Roy Adair went out of his way to acknowledge Alstom’s role in the success of the project, noting the company’s willingness to take ownership of problems and saying it was “to be congratulated for delivering CCP4, not only ahead of schedule but also at performance levels in excess of guaranteed contractual levels.” He was also impressed by the way the problems posed by the small and congested site were dealt with, a “tremendous achievement”, he said, involving “shoe-horning” new equipment into a very constricted space and requiring a number of “tailor-made engineering solutions to be devised.”
New orders needed
After the challenges of introducing the GT24/26 technology such unsolicited testimonials must be most welcome to Alstom, and a great help in its efforts to win new customers for the technology.
As well as the CCP4 handover another important milestone for the GT24/26 was also passed in July when the fleet, now totalling 16GW, clocked up a million operating hours. The next key stage in the evolution of the GT24/26 will be winning of further orders beyond those recently placed for the Cartagena plant in Spain. Such orders are understood to be in the pipeline.
Icreasing carbon efficiency, even without Kyoto
While Singapore feels it is unable to accede to the Kyoto protocol, it still has ambitious plans to improve carbon efficiency. As explained at the Senoko CCP4 handover ceremony by environment minister, Lim Swee Say, the Senoko repowering project is seen to be in line with this national effort.
Lim Swee Say explained, “we have not been able to accede to the Kyoto Protocol because of our unique circumstances. As a small city state, we are dependent on the burning of fossil fuels to meet the
energy needs of our growing population and economy. Unlike other countries, we are unable to tap on renewable sources of energy or non-carbon alternatives in a big way to reduce our dependency on fossil fuels. We do not have the natural endowments to tap hydropower or geothermal energy. Even solar and wind energy present little scope due to our cloudy skies and slow wind speeds. We are therefore unable to cap, much less, reduce carbon dioxide (or CO2) emissions.”
Nevertheless, he noted, between 1990 and 2002, Singapore managed to contain growth in CO2 emissions to about 5% annually, slower than real GDP annual growth of 6.3% – a 15% improvement in carbon efficiency.
“Our carbon efficiency is better than the world average, and we are more carbon efficient than some advanced economies such as Canada and Australia,” he said. Looking ahead: “Our aim now is to improve our carbon efficiency by another 10 percentage points or more as compared to 1990 levels, so that our carbon efficiency in 2012 will be at least 25 % better than 1990.”
For further information on the Senoko repowering project, see Modern Power Systems, August 2002