Indie mix is a hit

Siemens and Fisia Italimpianti have successfully completed the construction of the Shuweihat IWPP, the largest power and water plant in the Middle East. Now fully operational, the plant is making an important contribution to the region’s power and water needs and further projects at the site seem a likely prospect.

Nigel Blackaby, Features Editor

The wealthy Emirate of Abu Dhabi is dominated by the city of the same name. This “garden city”, located on the Arabian Gulf, is enjoying an unprecedented boom and period of growth. As the number of new hotels, office blocks, shopping malls and residential areas increases, so does the requirement for electricity and, perhaps even more importantly in this part of the world, the need for clean drinking water. The new Shuweihat S1 independent water and power plant (IWPP) is satisfying this demand and is the latest in a series of IWPPs commissioned by the Abu Dhabi Water and Electricity Authority (Adwea).

Set on an otherwise largely deserted and remote coastal peninsular close to the resort of Jebal Dhana, and surrounded by a huge expanse of sand, the $2.5bn Shuweihat S1 project is an impressive site. Everything about it is on a large scale. The availability of land allows for a spacious and well-designed site layout, which includes a fire-fighting station, a Mosque and an oil discharge station for tankers with a pipeline extending 1km into the sea, which had to be routed around a coral reef. Despite the remoteness of the location the site maintains a high level of security.

Award winning

Shuweihat also boasts notable credentials. The plant has now been fully operational for around a year and a half and is capable of operating with a capacity of over 1500 MW and 455 million litres per day. It is the world’s biggest independent combined power and water plant and features the largest desalination units ever built. It achieves a power generation efficiency of 42 per cent and an overall efficiency of just below 55 per cent. “The desalination facility was awarded Plant of the Year by Global Water Intelligence in London in 2005 and the plant is the first in the Gulf to simultaneously achieve ISO certifications for safety, quality and environmental excellence,” explains Dave Price, managing director of Shuweihat CMS International Power Company (SCIPCO), the project company established by the owners of Shuweihat.

Remote location

Alongside the completed Shuweihat S1 plant the ground is cleared in preparation for future expansion
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Jebal Dhana is located 250 km west of Abu Dhabi city and is therefore well away from the main load area. This has necessitated the building of power transmission substations and transmission lines at 220 kV and 400 kV as well as a water transmission pumping station and pipelines. It is interesting therefore to examine the drivers for Adwea’s decision to locate its biggest IWPP three hours drive from the capital in its remote western region. Certainly the physical conditions at Shuweihat were suitable with access to the sea enabling seawater intake and discharge for up to three plants with an ultimate capacity of 5000 MW and 1400 million litres/day. Water saline conditions were suitable and environmental impact minimal. With the site just 100 km from the Saudi Arabian border Shuweihat is the chosen location for the future power grid interconnection with its western neighbour, envisaged as part of the GCC Grid Interconnection Project. The then ruler of Abu Dhabi, Sheikh Zayed Bin Sultan Al Nahyan, was most keen to promote the geographical diversification of Abu Dhabi’s infrastructure and in particular growth in the Western Region. Another suggestion is that a territorial dispute with Saudi Arabia might have been a motive for establishing a major element of infrastructure in this region.

If the location of Shuweihat requires some explanation then the need for its power and water capacity needs little. In 2001, Adwea forecast electricity demand to rise from 3723 MW to 4320 MW by 2004 with the need for a further 700 MW by 2006. Abu Dhabi currently has a capacity of around 6000 MW and expects to have to increase this to over 8100 MW by 2015. “Sheikh Zayed’s vision of transforming the desert into a green country has meant an almost infinite demand for water,” says Price. “Adwea forecasts a doubling in demand between 2001 and 2015.”

A brand new Mosque was built on the water’s edge at Shuweihat
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Shuweihat is effectively 60 per cent owned by the Abu Dhabi government through The Abu Dhabi National Energy Company (Taqa). The remaining ownership is equally divided between the joint developers CMS Energy of the USA and the UK’s International Power. The consortium successfully bid for the project and signed a power and water purchase agreement with Adwea on 31 July 2001. The EPC contract was awarded to Siemens Power Generation for the power elements and Fisia Italimpianti for the desalination plant. PB Power was appointed SCIPCO’s owner’s engineer. On 1 November 2001 Notice to Proceed was issued.

Speedy construction

Construction of Shuweihat took 36 months from EPC award to COD at a capital cost of $1.6 billion. It involved 26 million construction man-hours and a peak workforce of 6000. Commercial operation of Unit 1 began on 16 May 2004 and by the end of August the project had been fully tested, including a test on back-up oil fuel and was shown to be performing above guarantee levels. Full production commenced in October 2004. “Just a few years ago a plant such as this would have taken five years to build,” says Dr Martin von Hassel, Siemens project director for Shuweihat. The short construction time was made possible through the use of a Siemens standardized system, the core of which is the Econopac. This is made up of the gas turbine, generator, air intake, exhaust gas system, fuel system, electrical package, gas auxiliaries and fire protection. “By basing Shuweihat on a standard design albeit with a different air intake and boiler pipework, we were able to reduce delivery times,” says von Hassel.

Siemens was responsible for the turnkey erection of the plant and supplied five SGT5-4000F (formerly V94.3A) gas turbine generators, two steam turbine generators and all the ancillary systems. Each gas turbine has a gross rating of 222 MW at reference site conditions (46à‚°C ambient and 42 per cent relative humidity). Siemens also supplied the five Marcegaglia dual-pressure heat recovery steam generators (HRSG). The steam turbines have a gross rating of 254 MW. The HRSGs feature supplementary firing to provide a degree of control in steam production independent of gas turbine firing.

The six multi-stage flash (MSF) desalination units are 30 per cent larger than the previous largest units built. They are supplied with steam from the steam turbine exhaust or from the bypass if the turbines are out of service. The desalination element of the plant using 70 MW of the power capacity to achieve production of the 455 million litres per day. The distillers are supplied with seawater from seawater pumps ten per cent of which is converted to potable water, with the rest returned to the sea as brine. The resulting distilled water is remineralized to produce palatable potable water that is stored in six storage tanks, which represent 24 hours of water production, by the plant. The water is delivered to the water transmission system via a pumping station.

Optimizing efficiency

Although based on a standard design, the desalination element at Shuweihat and consequential need for process steam is a key difference. From a very early stage in the project Siemens, Fisia and PB Power, along with CMS Energy and International Power sought to implement wide-ranging optimization of the water/steam cycle in order to attain improved efficiency levels for the entire plant. “This is a unique project because of the power to water ratio,” says Jens-Peter Saul, VP sales and new plants and services for Siemens in the Middle East. “Close collaboration between developers and Siemens is the basis for the success,” says Saul.

The air intakes were one of the variations to the standard design
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An example of the integration of power and MSF cycles was the approach to the high condensate return temperature from the MSF process that restricted recovery of heat within the HRSG. In a combined cycle gas turbine power plant stack temperatures of 90-100à‚°C are typical, whereas on a combined cycle supplying steam to a MSF plant it is not normally feasible to achieve temperatures below 140à‚°C. A modification to the cycle was introduced to recover the excess heat in the condensate back into the MSF cycle reducing both stack loss and MSF steam consumption. The costs associated with the modification were modest yet it achieved a six per cent reduction in steam demand from the MSF process and a fuel saving of up to two per cent with corresponding reductions in emissions.

Future expansion

With its first year of operation under its belt a planned winter outage is scheduled at Shuweihat during which each gas turbine will be inspected. “With everything on such a large scale you would expect any problems to be big but we have had very few teething problems during our first year of operation,” says Price.

A mark of the success of the project and the undoubted need for more power and water in the region is the large cleared and floodlit area alongside the Shuweihat S1 plant, ready and waiting for the expected announcement of a S2 and possibly a S3 project. These projects are again expected to be IWPPs and likely to be tendered during 2006 or early 2007. “SCIPCO would very much like to take on the expansion of Shuweihat,” said Price. With the sites already cleared and easy access for EPC contractors, competition is likely to be keen.

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