A molten salt leak has forced Noor Ouarzazate III’s solar power plant to shut down again, just months after it returned to service following a similar problem. The latest leak was found during checks before the plant was due to restart. Engineers discovered molten salt leaking from the south side of the hot storage tank. The plant is expected to remain offline until October.
According to Le Nouvelliste, before the leak was found, operators had noticed the plant was losing molten salt much faster than expected. Temperature sensors under the tank also recorded a sudden rise in heat in the same area. But when engineers reviewed two months of operating data, they found no warning signs. Pressure, vibration and flow rates had all remained normal.
Molten salt is used to store heat so the plant can keep producing electricity after sunset. But storing salt at very high temperatures puts heavy stress on the steel tanks.
Engineers say these failures usually happen because different parts of the tank heat up and cool down at different speeds. This can make the steel floor bend, crack welded joints and allow molten salt to leak.
The latest incident follows a major molten salt leak at Noor Ouarzazate III solar power solar back in February 2024. The 150MW plant remained out of service for 14 months before restarting in April 2025.
ACWA Power, the plant’s main shareholder, said the earlier shutdown caused direct revenue losses of between $47 million and $51 million. The company also reported an asset impairment of $51.1 million.
Repairing this type of damage is slow and complex. Engineers must first drain the molten salt and cool the tank very slowly before they can replace damaged steel plates, insulation and, if needed, parts of the concrete foundation.
