Pictures of the Future    Spring 2006

Energy for Electricity and Water

Persian Gulf countries want to expand their energy and water infrastructures. A power and desalination complex built by Siemens in Abu Dhabi is the most powerful facility of its kind worldwide.

When oil pumping operations began in Abu Dhabi in the early 1960s, the emirate, which is practically all desert, had a population of only 50,000. Today, one million people live in Abu Dhabi—more than half of them in Abu Dhabi City, the capital of the emirate and of the entire United Arab Emirates (UAE).

Abu Dhabi City is a modern metropolis with futuristic buildings and many green areas and shady parks. However, pass the city limits and you’re in the desert—under which is the country’s main source of wealth. 8 % of the world’s petroleum resources and 4 % of its natural gas are located beneath the deserts of the UAE. Of this total, more than 90 % is located in Abu Dhabi.

But although oil is plentiful, water is scarce in Abu Dhabi. The country has no rivers or lakes and hardly any rain (33 mm per year). Moreover, what little groundwater it possesses has been almost entirely depleted, while demand for water is rising rapidly. Abu Dhabi already has the world’s third-highest per capita drinking-water consumption. And according to the Abu Dhabi Water and Electricity Authority (ADWEA), daily water consumption is set to increase to 3.57 mill. m³ by 2015. The main reasons are population growth and a growing number of ambitious agricultural and forestation projects. The huge need for water can be met only through seawater desalination.

But water isn’t the only resource in short supply; the emirate also requires electrical energy to power its growing industrial base and the population’s air conditioning needs. Average peak electricity consumption in Abu Dhabi will reach approximately 8,000 MW in 2015. As a result, the emirate is investing a substantial portion of its oil income in the creation of effective water and energy supply infrastructures. Within the framework of this initiative, Abu Dhabi has launched a privatization program that is exemplary in the Gulf region. New facilities for power generation and seawater desalination are being privately planned, built and operated. In each case, the operating company is a joint venture between ADWEA and a foreign holding.

Siemens’ "Shuweihat S1" turnkey facility is a perfect example of how this innovative approach works. In August 2004, the state-of-the-art combined cycle power plant, which is closely linked with a high-performance desalination facility, went into operation some 250 km west of Abu Dhabi City. Siemens served as the consortium leader and was therefore responsible for building the entire complex, which is located beside the sea. Italimpianti, an Italian company, built the desalination plant.

Power and Water for the City. Even at the high ambient temperature of 46 °C, the facility generates 1,500 MW of electricity (more than one block of a nuclear plant) and also produces 450,000 m³ of drinking water each day. Based on the current per capita water-consumption level in Abu Dhabi of 500 l per day, that’s enough water to supply 900,000 people. The water is mainly used for irrigation projects, however.

Over the long term, the complex will undergo two further expansion phases, creating a power generation park that can generate 5,000 MW and produce 1.4 mill. m³ of drinking water per day. According to the Shuweihat CMS International Power Company, which operates the complex, the facility is already the largest combined power/desalination plant in Abu Dhabi —although it is still in its first expansion phase. In terms of output, it is the most productive complex of its kind worldwide.

"Just the sheer size is impressive," says project manager Dr. Martin von Hassel from Siemens Power Generation. "The first expansion phase alone encompasses an area of 4 km², the equivalent of 560 soccer fields." One technical highlight, according to Hassel, is the plant’s net efficiency of 54.4 % —which means that more than half the energy released through gas combustion is converted into electricity. "Up until now, it wasn’t possible to achieve such a high efficiency rating with a combined power/desalination plant," says Hassel. "The fact that we succeeded is due to our innovative turbine technology and our ability to optimize the steam cycle. For example, we use special materials in our gas turbines. This —in combination with a very effective cooling system —enables the turbine blades to withstand extremely high gas temperatures. What’s more, the unit is designed so that water production can be flexibly decoupled from power generation." This means the facility can produce the maximum amount of water possible even in periods of low electricity demand.

The Shuweihat facility consists of five power plant blocks, each of which is equipped with one turbine, a generator, and a waste-heat steam generator. Natural gas that is extracted in Abu Dhabi is burned in the gas turbine. The hot gas is used to generate electricity, as well as steam in the waste-heat steam generator. The steam, in turn, is used to drive two turbines that also produce electricity. The turbine exhaust steam, which has a temperature of between 140 and 180 °C, provides the energy needed for the desalination process.

The desalination unit functions according to the principle of multi-stage flash evaporation. The unit consists of six identical units operated in parallel. The units are actually the largest and most powerful such devices ever built. Salt water taken from the sea runs through several chambers in the units; with the help of the waste heat from the power plant, the salt water is partially evaporated under reduced pressure. The steam thus created is condensed to give distilled water, which is captured, collected and then enriched with minerals. The result is top-quality potable water.

"The design will ensure that fuel costs remain as low as possible throughout the facility’s entire service life," says Hassel. "The main objective is to produce a reliable supply of as much drinking water as possible. This is a very promising concept for the Persian Gulf region in particular, as the area’s primary problem is water scarcity." Seawater along the Gulf coast has such a high salt content that other desalination procedures, such as reverse osmosis, are generally of little use. The distillation of seawater is therefore a key method for obtaining potable water in the region.

Siemens has built similar facilities in other parts of the Gulf, including the Jebel Ali plant in Dubai and the second stage at Al Taweelah in Abu Dhabi. In addition, contracts have been signed for the first successor projects in the UAE, Qatar and Saudi Arabia. One of these involves a power/desalination plant to be built under the direction of Siemens some 110 km south of Jeddah at a cost of 1.8 bill. €. As a result, Siemens will further expand its position as the market leader for turnkey power/desalination plants in the Middle East.
                                                                                                               Björn Gondesen