World’s largest solar-storage microgrid goes online in Saudi Arabia

Saudi Arabia’s Red Sea multi-utility project has entered full commercial operation, completing a large-scale renewable-powered off-grid utility system designed to supply an entire tourism destination and its supporting infrastructure.

SEPCOIII, a PowerChina subsidiary and the engineering, procurement and construction (EPC) contractor for the project, said on Aug. 21 that the full utility complex had reached commercial operation. The company signed the EPC contract with ACWA Power in February 2021.

Developed for Red Sea Global’s tourism destination on Saudi Arabia’s western coast, the project operates independently of the national transmission network. ACWA Power lists 358 MWac of installed solar PV capacity and 1,225.4 MWh of battery energy storage, alongside 112.5 MW of backup internal-combustion generation. Earlier project documentation typically referred to about 340 MW of solar and 1.2 GWh of storage.

Huawei, which supplied PV inverters and the battery storage system, previously described its package as comprising 400 MW of PV and 1.3 GWh of storage.

The battery system performs functions beyond those typically required of storage connected to a conventional transmission grid. As the Red Sea network is isolated, the microgrid must establish and maintain its own voltage and frequency while balancing variable solar generation with demand. Grid-forming battery storage provides voltage and frequency support and supplies electricity when solar generation is unavailable.

Project disclosures indicate that the system has also demonstrated black-start and fault-ride-through capabilities during operation, providing a utility-scale example of grid-forming storage deployed in an isolated network.

In May 2025, Guinness World Records certified 1,125.18 MWh of the installation as the world’s highest-capacity off-grid battery-based energy storage facility. Construction on the facility began in October 2021 and the storage unit started operating in September 2023.

The Red Sea development differs from a conventional solar-plus-storage project in the range of infrastructure connected to its microgrid. The multi-utility system includes seawater desalination, drinking-water distribution, wastewater treatment, district cooling, solid-waste management and communications infrastructure.

ACWA Power lists three reverse-osmosis desalination plants with a combined capacity of 32,500 cubic meters per day, wastewater treatment capacity of 16,000 cubic meters per day and 32,500 refrigeration tons of district cooling capacity. Red Sea Global has said the renewable-powered utility infrastructure supplies operational resorts, the airside facilities at Red Sea International Airport, employee accommodation, electric-vehicle charging, 5G infrastructure, district cooling and the destination’s water systems.

The project operates under a 25-year utility concession. Rather than financing and owning the individual utility assets, Red Sea Global purchases electricity, water and other services from the project consortium. The project was developed under a public-private partnership structure, with Saudi Arabia’s Public Investment Fund (PIF) supporting the long-term offtake agreement.

SEPCOIII carried out the EPC work, while Chinese suppliers involved in the energy package included Huawei and PV module manufacturer Longi.

The transition to full commercial operation marks completion of the wider multi-utility package rather than the start of operations for the solar and storage assets, which have been progressively commissioned since 2023.

The project provides a large-scale operating example of solar and grid-forming battery storage supporting an isolated utility network rather than supplying electricity to an interconnected grid. Its performance could offer technical and operational lessons for similar systems on islands, at remote industrial sites and in new developments where extending conventional transmission infrastructure is difficult or uneconomic.