Focus on Middle East | DEWA focuses on solar and gas
Commissioning is well underway at DEWA IV, aka fourth phase of the Mohammed bin Rashid Al Maktoum (MBR) solar park (and, somewhat confusingly, also called Noor Energy 1), in Dubai, a 950 MW hybrid project consisting of 100 MW of central-tower CSP (concentrated solar power), 600 MW of parabolic-trough CSP (in three tranches of 200 MW) and 250 MW of bifacial PV. Noor Energy 1, jointly owned by DEWA (Dubai Electricity and Water Authority), Saudi Arabia based ACWA Power and Silk Road Fund (state-owned investment fund of the Chinese government), is the project company established to implement this fourth phase, under a 35 year power purchase agreement.
The 700 MW of CSP is thought to make it the world’s largest single site concentrated solar power facility, while the 262.44 m high central solar tower is believed to be the world’s highest such tower. The DEWA IV project, which will occupy an area of 44 square kilometres, was awarded to an ACWA Power led consortium in 2017. Shanghai Electric is the EPC contractor and NOMAC (First National Operation & Maintenance
Company, a wholly owned subsidiary of ACWA Power) is the O&M contractor.
Thanks to significant molten salt thermal energy storage capacity – 15 hours of operation – the plant is said to have “the ability to deliver reliable and dispatchable solar generated power round the clock.”
The 950 MW 4th phase is based on the independent power producer (IPP) model with investments totalling AED 15.78 billion. The levelised cost of electricity (LCOE) is USD 7.3 cents per kWh for the 700 MW of CSP capacity and USD 2.4 cents per kWh for the 250 MW of PV. The plant will support the Dubai clean energy strategy goal of increasing the share of clean energy in Dubai to 25% by 2030.
Central-tower CSP
Above: Molten salt receiver prior to installation in central tower
Simplified schematic of central-tower CSP (source Siemens)
The basic principle of the central-tower CSP plant is to convert primary solar energy into electrical energy using a field of 70 000 heliostats (flat mirrors on mounting poles with tracking capability), a molten salt solar receiver located at the top of a high tower in the centre of the solar field, a system for transferring and storing the thermal energy, based on molten nitrate salts, and a steam cycle with a turbo-generator, rated capacity 100 MW. The John Cockerill designed and supplied solar thermal receiver includes a wall of pipes, which
Site of DEWA IV (aka fourth phase of MBR (Mohammed bin Rashid Al Maktoum) solar park, also known as Noor Energy 1)
acts as a heat exchanger. The solar radiation directed to the receiver heats the working fluid, molten nitrate salts, from 300°C to 565°C. John Cockerill signed a contract in 2018 for the design and supply of the receiver with Shanghai Electric Brightsource Solar Energy Limited for the owner Noor Energy 1.
The ‘cold’ salt is held in a storage tank at around 300°C. The receiver’s circulation pump pumps the salts from the cold salt storage tank to the receiver, passing through the Inlet vessel. At the receiver outlet, the hot salts (at 565°C) enter the outlet tank, which acts as a buffer for the hot salt system.
From the receiver’s outlet tank, the hot salts descend from the tower to the hot salt tank, where they are stored. From this tank, the circulation pump pumps the flow required for steam generation, which consists of a group of salt/water-steam heat exchangers.
On cloudy days, and at nights, the operation of the solar field stops, but discharge of the storage system can begin. The receiver’s salt circulation pump stops, the receiver empties, and the salt circulation pump supplies hot salt to the steam generator.
To keep the salt from solidifying, the plant includes electric resistance elements submerged in the salt storage tanks.
Molten salt system Generator HP turbine Receiver HP steam
Receiver tower
Hot salt
Reheat steam
Superheater Reheater Steam gen./evaporator Cold salt Helliostats
Steam generation system
Thermal storage system Feedwater preheaters
Condensate tank
Power block IP/LP turbine
Condenser
36 | October 2022|
www.modernpowersystems.com
300°C 565°C
Molten salt loop
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55
