Our project consists of combined cycle power generation, open cycle power generation, and seawater desalination plants located at the Mirfa Complex five kilometers west of the town of Mirfa, about 100 kilometers southwest of the city of Abu Dhabi on the Arabian Gulf coast in the UAE. Our plant is fully operational, having achieved its commercial operation date on October 18, 2017.
TECHNICAL OVERVIEW
Our plant employs combined cycle and open cycle technologies for power generation and MSFD and RO technologies for seawater desalination, which are more particularly described below.
General facility description
The plant consists of combined cycle cogeneration power and desalination facilities based on a cogeneration configuration designed to provide 1,600 MW of annual contracted power capacity and 52.5 MIGD of annual contracted water capacity.
The power plant and the desalination units consist of:
(a) four GE PG9171E open cycle gas turbines of 90 MW;
(b) three Ansaldo AE94.3A gas turbines of 254 MW each connected to a dedicated HRSG;
(c) three Fisia Italimpianti MSFD units, each with a capacity of 7.5 MIGD;
(d) one two-stage RO unit by Degrémont with a capacity of 30 MIGD; and
(e) a dissolved air flotation (“DAF”) unit with a capacity to pre-treat all necessary feedwater for the RO capacity.
In addition, the power plant and the desalination units also include the following components:
(a) an administration, control room and storage building;
(b) connection to natural gas supply, water export and power export systems;
(c) seawater intake and outfall;
(d) backup fuel supply;
(e) a demineralization plant; and
(f) associated auxiliaries.
The Technical Adviser has opined that the plant design, technology and engineering satisfy and are consistent with the operational requirements specified in the PWPA and represent international practices for large CCGT and OCGT power and desalination projects. The Technical Adviser has also opined that the main plant equipment, including the gas turbine generators, steam generators, steam turbine generators, RO plant and MSFD plant, and the major electrical equipment, are sourced from reputed manufacturers who have been supplying equipment to power and water generation plants in the region and worldwide.
Gas-fired power plant
Our plant is a cogeneration facility because it uses excess heat from exhaust gases from the power generation component of our plant in the desalination process. Our plant comprises combined cycle power generation, open cycle power generation and desalination plants.
Combined cycle power generation
The natural gas for our plant is delivered to the gas delivery point, which is managed and operated by ADNOC Gas Processing under the responsibility of EWEC in accordance with the PWPA. Our three CCGT units compress air to a high pressure, which is then mixed with natural gas in the combustion chamber and ignited. The hot combustion gases from the combustion chamber drive the gas turbine that in turn drives a generator that generates electricity. The CCGT units are designed to primarily operate on natural gas as well as with diesel oil as a backup fuel. The hot exhaust gases from each gas turbine are passed via ductwork to a dedicated supplementary fired HRSG. Each HRSG is a dual pressure natural recirculation boiler that generates steam. Each gas turbine/HRSG unit consists of the bypass stack to allow for open-cycle operation. Each HRSG feeds a common high-pressure steam header from which the live steam is distributed to two extraction condensing steam turbines. Each steam turbine is a dual cylinder condensation steam turbine consisting of high pressure (“HP”) and low pressure (“LP”) horizontal split type casings. The three 7.5 MIGD MSFD units are fed by low-pressure steam that is extracted from between the HP and LP cylinders as well as supplied from the HRSG LP drums via an LP common header. The energy produced by the steam generates additional electricity output or water production from the same amount of natural gas input and therefore increases the proportion of the energy in our supply fuel that is converted into useful electricity or heat. This efficiency gain translates into better project economics and a reduced negative impact on our environment.
Open cycle power generation
An additional four OCGT units are installed, each providing the added flexibility of fast generation capacity directly to the grid. The OCGT units are designed to primarily operate on natural gas as well as with diesel oil as a backup fuel.
Cogeneration desalination plant
Our plant employs both MSFD and RO technologies.
MSFD technology
Our MSFD technology desalinates water by heating it with the excess heat from low-pressure steam from our power generation facilities and then sending it through a series of stages, each at a lower ambient pressure than the previous stage. The sudden insertion of the water into an area of lower ambient pressure causes the water to flash or boil almost instantly, converting a portion of it into steam.
An MSFD unit consists of several consecutive evaporating chambers, which are maintained at decreasing pressures from the first stage which is hot, to the last stage, which is cold. When the seawater enters the first cell it overheats and immediately “flashes” and releases heat, which subsequently produces vapor. The produced vapor is condensed into fresh water in the tubes at the top of the cell. Seawater flows through the tubes of the heat exchangers where it is warmed by the condensation of the vapor produced in each stage. The seawater then flows through a brine heater where it receives the heat necessary for the process of condensing the steam. This process takes place again when the seawater is introduced into the following cell and is repeated until the last and coldest stage. The cumulated water builds up the distillate production, which is extracted from the coldest stage. Seawater also concentrates from stage to stage and builds up brine, which is then extracted from the last stage.
RO technology
RO technology desalinates water using semi-permeable membranes and does not require the use of any steam energy. The RO process includes raw seawater intake, pre-treatment using DAF and dual media filter, filtration through cartridge filters, processing through RO membranes and remineralization. The seawater is first pre-treated through DAF, a pre-treatment process whereby a concentration of air bubbles is passed into the seawater to allow particles to adhere to the air bubbles and float to the surface, which is then mechanically removed. After the DAF pre-treatment, the seawater goes through a flocculation process. The seawater is dosed with certain chemicals, such as ferric chloride and coagulate, and is fed into a flocculation chamber, which has a static mechanical mixer that mixes the treated seawater at a constant rate in order that any particles can coagulate together to form a denser particle for easier removal. From the flocculation chamber, the seawater enters into dual media filters which contain sand and pumice for further filtration of suspended solids.
After this process, the treated seawater is collected in filtered water tanks, which are then pumped through the cartridge filters, which are capable of filtering particles of approximately five microns. The water exiting the cartridge filters is then fed to the RO membranes through a high-pressure pump. As the water enters the first pass of RO membranes, the water molecules pass through the semi-permeable membranes while the salts and other contaminants which are not allowed to pass through are discharged in the reject stream. There are also energy recovery devices that recover energy during the first pass of water through the RO membranes. The water that passes through the first pass of the RO membrane (permeate water) then enters the second pass of RO membranes for further treatment. Any remaining salts and other contaminants are discharged back to the sea, and the permeate water is sent for remineralization where necessary remineralization chemicals such as carbon dioxide, lime, corrosion inhibitor, and sodium hypochlorite are added for safe storage, dispatch, and drinking.
DESIGN OF OUR PROJECT
Our project commenced construction in 2014 and its commercial operation date was achieved on October 18, 2017. Our plant design conforms to international standard requirements for power generation and water production facilities, as well as good engineering practices. The main plant design includes gas and steam turbine generators and an auxiliary plant, as well as on-site fuel handling and metering for natural gas and a TRANSCO‑operated substation for the export of power at our plant’s delivery point. The water production equipment in our plant supports seawater off-take and seawater discharge from the common seawater system. Our plant has specialized forwarding pumps, which are adequately sized in order to transport the water produced from our plant into the water network. The water treatment facilities at our plant include a chemical plant, a re-mineralization plant and a chlorination plant. Our plant also includes control and instrumentation designs, plant mechanical equipment, civil works and environmental monitoring systems required to comply with the Federal Laws and Abu Dhabi law.
Gas turbines
Four of our seven gas turbine generators are open cycle GE Frame 9E (PG9171E) heavy-duty outdoor units rated at 90 MW. The remaining three combined cycle gas turbine generators are Ansaldo AE94.3A units rated at 254 MW gross at reference site conditions. These technologies are considered to be proven and are widely used for similar IWPPs in the region.
Heat recovery steam generators
Our plant contains three single-pressure HRSGs. The hot exhaust from each of our plant’s gas turbines is fed into an HRSG to generate steam, which in turn drives a steam turbine. This combination produces electricity more efficiently than either the gas turbine or steam turbine alone. The HRSGs are dual pressure natural circulation units with horizontal gas flow. The HRSGs are manufactured by Ansaldo Caldaie, an internationally recognized supplier of HRSGs of the type and capacity required for our project and with the necessary experience in the design of supplementary firing systems. There are also several of these HRSGs in the GCC region, many of which are owned by our Sponsors, which lead to the availability of common parts and experience, and also the interchangeability of people, parts and knowledge.
Steam turbines
Our plant contains two condensation steam turbines, which accept the steam output from the three HRSGs via the common HP header. The steam turbines are dual cylinder condensation steam turbines, each providing a rated gross output of 287.4 MW. The steam turbines receive steam from the gas turbines at 104 bar and at a temperature of 563°C, which is within the typical range of steam conditions used by steam turbines. The steam turbine HP cylinder exhaust feeds the LP turbine with additional extraction to the LP common header (for supply to the MSFD plant). The steam turbines are manufactured by Ansaldo Energia, an internationally recognized leader in steam turbine technology, with a large fleet of such turbines operating worldwide.
The steam turbine model has adequate operational experience, is a conventional and proven design and is low-risk technology. There are also several of these steam turbines in the GCC region, many of which are owned by our Sponsors, which lead to the availability of common parts and experience, and also the interchangeability of people, parts and knowledge.
MSFD desalination units
Three 7.5 MIGD MSFD units are included in our project. These have been manufactured by Fisia Italimpianti, which is one of the major suppliers of large capacity MSFD units and has significant references for projects in the GCC region. Our project’s desalination units are of a conventional single deck, cross tube, design that has been developed over many years with numerous installations worldwide. The desalination units used in our plant have sufficient capacity required for our project. There are also several of these MSFD units in the GCC region, many of which are owned by our Sponsors, which lead to the availability of common parts and experience, and also the interchangeability of people, parts and knowledge.
RO desalination units
A single two-stage RO unit is included in our project. It has a capacity of 30 MIGD and has been manufactured by Degrémont (now branded SUEZ). Degrémont has over 30 years’ experience using the RO technology. A DAF unit pre-filters the seawater required by the RO plant.
The Technical Adviser has opined that our main plant equipment, including the gas turbine generators, steam generators, the RO plant and the MSFD plant, and the major electrical equipment, have been sourced from reputed manufacturers that have been supplying equipment to power and water generation plants in the region and worldwide. See the Independent Technical Due Diligence Report in Annex C for further information.
Shared Facilities
Our main project contracts anticipate that (i) new generation/desalination plants might be developed in proximity to our project in the future, and (ii) in such case we will share certain facilities with those new projects. For example, a new independent water project (Mirfa 2) with a capacity of 150 MIGD is currently being procured by EWEC which is expected to be located in close proximity to our plant. The shared facilities would include (among others): the seawater intake structure and wave breaker; the oil bubble barrier system; navigation buoys; a fire station; and common roads, entrance facilities, fencing and lighting. These facilities are currently owned by the SF Company.
The premises on which the facilities are situated are owned by ADPower, and leased to the SF Company for an initial term of 30 years, with the initial term being automatically extendable to cover the useful life of the facilities. This lease includes the right to extract from the Arabian Gulf for supply to our plant and any plants to be owned by the SF Company’s other shareholders in the future all seawater required by the plants. These premises have been leased to the SF Company at nominal annual rent set for the entire period, without provision for rental increases. The lease agreement has been submitted to Abu Dhabi Municipality for its approval and will be executed once that has been obtained.
We and ADPower each hold a 50% share in the SF Company. The Mirfa Shared Facilities Shareholders’ Agreement (the “SF Shareholders’ Agreement”), which governs the management of the SF Company, the operation and maintenance of the shared facilities and the provision by the SF Company of user services to its shareholders, was entered into by us and ADPower on October 2, 2014. ADPower has the right to sell its shares in the SF Company to the developers of any new generation/desalination plants that will benefit from the shared facilities.
Connection to Abu Dhabi’s power and water networks
The electricity and water that we produce is transmitted by TRANSCO which is the licensed system operator for the power and water transmission facilities in Abu Dhabi. The terms of our transmission are governed by a Connection, Use of System and Interface Agreement with TRANSCO. See “Certain Relationships and Related Party Transactions” and “Summary of Principal Project Documents—Connection Agreement”. TRANSCO transmits our water and power to Abu Dhabi’s electricity and water distribution networks, which are managed by Abu Dhabi Distribution Company (“ADDC”) and Al Ain Distribution Company (“AADC”). We do not have any contractual agreement or direct contact with ADDC or AADC.
To transport the electricity produced from our plant into the main electricity transmission network, our plant has connection equipment that includes metering systems, which are owned, operated and maintained by TRANSCO.
The water produced at our project is pumped out of our plant by the TRANSCO pumping station and subsequently connected into the existing water transportation infrastructure.
Our Offtaker
EWEC is our sole offtaker under the PWPA and a wholly-owned subsidiary of ADPower. EWEC purchases from us, and we deliver to EWEC, the electrical power generated and the desalinated water produced by our plant through the connection equipment that TRANSCO (a wholly-owned subsidiary of TAQA) operates and maintains. TRANSCO, on behalf of EWEC, transmits the output of our plant to the power and water distribution networks operated and maintained by ADDC and AADC. TRANSCO, ADDC and AADC are all wholly-owned subsidiaries of TAQA.