Noor power station in Morocco is the largest concentrated solar power plant on the planet, and uses molten salt storage to produce electricity at night. Built on an area of more than 3000 hectares - the size of 3500 football fields – the Noor-Ouarzazate complex produces enough electricity to power a city the size of Prague. Situated at the gateway to the Sahara Desert, the whole complex provides 580 megawatts – saving the planet from over 760 000 tonnes of carbon emissions every year.
Known as the gateway to the Sahara, the city of Ouarzazate is located in southern Morocco, where the region has some of the highest levels of sunlight in the world – up to 2635 kWh/m2 annually. A few kilometres north of the city a dazzling ring made from hundreds of thousands of mirrored surfaces makes up a sprawling 2500 hectare solar power plant. Called Noor, after the Arabic word for ‘light’, the gigantic solar complex provides nearly half of Morocco’s energy from renewable sources. The site is able to power more than a million homes.
The Noor-Ouarzazate complex is made up of three distinct facilities which were introduced in phases: Noor I, Noor II and Noor III. The fourth phase, Noor IV accounts for 70 MW, and comprises three plants at different sites producing solar power using a hybrid photovoltaic technology.
The first two phases of the project produce energy using concentrated solar power (CSP) technology and 12-metre-tall mobile parabolic mirrors. The Noor I site alone features 537 000 of these cylindrical parabolic mirrors that are controlled by computers so that they constantly face the sun. Unlike conventional solar panels which deliver energy direct to the grid, curved mirrors focus the sun’s rays and concentrate the radiation to heat a special thermal oil that runs through stainless steel pipes throughout the facility. This synthetic oil, which can be heated to around 390°C, is channelled to the central power plant, where it produces steam to drive the main turbine and generate electricity.
Storing sunshine with steel and salt
In a variation of the CSP technology, the third power plant to come online, Noor III, combines a concentrated solar power tower with a central receiver that superheats molten salts to more than 500°C. The 243 metre tower, the tallest in Africa, houses molten salt which has been melted to create energy. A cylinder full of salt is melted by the heat from the mirrors during the day, and stays hot enough at night to store heat and allow the plant to produce power at full capacity, even during hours of darkness.
For this to work, huge quantities of these special salts, which are a mixture of potassium and sodium nitrate, are held in massive steel tanks. Special grade stainless steel is used throughout the site’s heat exchangers, pipework, generators and energy storage facility. Each of the 19 400 m3 tanks is made from specialised UR347 stainless steel. Due to the highly corrosive nature of the salts contained within, it would be impossible to operate this innovative heat storage method without this niobium-stabilised austenitic steel.
Steel underpins the entire facility as it is used for the production of the heat exchangers, steam generators, high-temperature pipes and molten salt storage tanks. This is due to its incredible corrosion resistance, combined with its flexibility of use, as this special grade can be easily formed and welded.
ACWA Power Ouarzazate, a consortium comprising ACWA Power, the Moroccan Agency for Solar Energy (Masen), Aries and TSK, constructed the project under the build, own, operate, and transfer (BOOT) strategy. A consortium led by an ACWA Power subsidiary and Masen manages and maintains the Noor complex.
This fourth phase of the project is the 70 MW PV portion of the 580 MW Ouarzazate Solar Power Station (OSPS), a CSP-PV solar power complex located in the Drâa-Tafilalet region, central Morocco.
While the scale and output of Noor I and II are impressive, Noor III represents a significant technological leap that heralds a bright future for sustainable energy generation. With the molten salt storage tanks able to provide enough heat to maintain operation of the plant for seven hours after dark, the Noor complex is able to provide 24-hour energy and represents a game-changer for solar as part of the future renewable energy mix. Noor represents a vision of the future, where glistening steel mega structures are able to renewably power entire regions round the clock.
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