Iron-vanadium mixed-acid flow batteries offer better performance in extreme temperatures. They are also safer, more scalable, and provide power for longer periods.

By Ali A. Al Meshari, Aramco Senior Vice President of Technology Oversight & Coordination

Solar and wind energy will be critical to meeting net-zero targets across the world, but to have an impact, renewable energy facilities will have to be paired with battery storage that can provide power when the sun is not shining, or the wind is not blowing. Lithium-ion batteries are currently the storage technology of choice, but they have limitations. However, new innovative alternatives are being developed.

Global renewable generating capacity is growing apace. In 2024, the world added 530 GW of renewable generating capacity, according to the International Renewable Energy Agency. And renewable output is set to grow by 21% every year to 2030, spurred by costs that — according to Bloomberg New Energy Finance have fallen to record lows.

Energy storage capacity has also been growing fast. Installations almost tripled in 2023, the largest year-on-year gain yet. But matching storage capacity to renewable generation will not be an easy task.

Lithium-ion batteries only store power for short periods — about four hours at the most. In addition, the amount of energy they can hold decreases over time if it is not used.

And there is another problem —most batteries’ performance declines at temperatures above 40°C. Such temperatures are not uncommon in Saudi Arabia, the wider MENA region, and the Global South.        

These factors pose a challenge one that Aramco is seeking to overcome as part of our aim to achieve net-zero Scope 1 and Scope 2 greenhouse gas emissions across our wholly owned and operated assets by 2050. To support solar energy deployment and our ambitions to reduce the carbon emissions of our power consumption, our scientists have been researching a new type of flow battery that can cope with our region’s high temperatures without loss of performance, and also overcome some of the other shortfalls of lithium-ion and lead acid batteries such as their limited cycle life, prone to overheating, and their recycling challenges.

The benefits of flow batteries

Flow batteries have been around for almost 150 years. Structured differently from 

conventional batteries, they store energy in the form of liquid electrolytes (one positive, one negative) in external storage tanks that are separate from the battery cells. They turn chemical energy into electricity when the electrolytes are pumped into the battery cell/stack.

This technology offers several advantages over other electrochemical batteries. As the electrolyte is separate from the battery cells, the energy capacity and duration of the system is controlled by the size of the electrolyte storage tank, rather than being limited by the size of the battery. Meanwhile, the amount of power produced is determined by the size of stacks or number of battery cells. Another advantage of flow batteries is their ability to be repeatedly discharged up to 100%, and then fully recharged. Lead-acid batteries have a 60% discharge limit, while lithium-ion batteries have a maximum discharge of 80%

In addition, flow batteries can be almost instantly recharged, simply by replacing the electrolyte and recovering the spent material. Flow batteries have enhanced safety over other batteries, with no chance of exploding. And they are easier to repair because of their modular structure, which means that, for example, a non-functioning battery cell could be simply replaced without replacing the whole system. Moreover, flow batteries offer low-cost energy storage that is safe, non-toxic, non-flammable, and easy to scale up from kilowatt hours (kWh) to gigawatt hours (GWh).

A new era for flow batteries

Commercially available all-vanadium flow batteries suffer irreversible damage at the high temperatures that Saudi Arabia often experiences — above 40°C. But Aramco’s Technology team has developed and scaled up a new flow battery electrolyte (iron-vanadium mixed-acid) that can be used in the harsh climate of the Middle East and beyond. The energy storage system was developed in collaboration with Aramco’s strategic partner in flow battery technology, Rongke Power. The key benefits of the new iron-vanadium mixed-acid flow battery include higher electrolyte utilization, lower vanadium use, an operating temperature window ranging from -8°C to 63°C (which eliminates the need for cooling), less stringent requirements in materials selection, and potential utilization of hydrocarbon-based membranes that can be implemented at scale.

The batteries have already been put to the test. In 2023, a 50 kWh unit was commissioned at Aramco’s facility in Abu Ali island. The battery system, in conjunction with solar panels, was used to supply energy to the cathodic protection system protecting pipelines from corrosion.

Aramco is now deploying a MWh-scale battery to provide power to unconventional gas wells at Wa’ad Al Shamal, and looking at other applications for the flow batteries, including helping to power direct air capture facilities and data centers.

In addition, Aramco is working on creating new hydrocarbon-based membranes  essential to the performance of flow batteries that are cheaper and more durable. Membranes enable the exchange of ions, which creates electricity, while at the same time keeping the different electrolytes separate.

To reduce carbon emissions in our electricity use, renewables will be essential. But for wind and solar to have maximum impact, they will need the help of batteries that can handle the heat of a Saudi Arabian summer.