In the pursuit of net zero, global efforts to bolster renewable energy capacity has made energy storage technologies essential. One of the main challenges to the large-scale deployment of renewable energy, particularly wind and solar, is its intermittent nature. As such, achieving both safe and low-cost energy storage is crucial. Battery technology holds the key, and sulfur-based flow batteries are becoming an alternative choice in this market dominated by lithium-ion batteries.

The International Energy Agency forecasts that installed grid-scale battery storage capacity will expand 35-fold between 2022 and 2030, reaching nearly 970 gigawatts. It’s expected that around 170GW of capacity will be added in 2030 alone, a significant jump from 11GW in 2022.

Lithium-ion batteries are the most widely used energy storage solution, primarily due to their mature technology and robust economic performance. They dominate consumer electronics, electric vehicles, and energy storage systems. However, lithium-ion batteries come with certain risks, particularly their flammability, which raises safety concerns. Additionally, their recycling process is complex and environmentally unfriendly, involving toxic metals and organic electrolytes. If not recycled properly, these materials can cause significant environmental harm.

However, flow batteries, which use liquid electrolytes – typically water-based – offer higher safety levels by avoiding the risk of combustion. This makes them a safer choice for large-scale applications.

“Future energy storage technologies need to meet two conditions: absolute safety and lower costs than lithium-ion batteries. Only then can the market truly open up,” Yi-Chun Lu, co-founder and chief scientist of Luquos Energy, tells The Asset in an exclusive interview. Luquos Energy is a Hong Kong-based start-up focusing on cutting-edge energy storage technology.

Promising alternative

While vanadium redox flow batteries (VRFBs) are currently the most mature water-based battery technology, they remain limited by high costs, particularly of electrolytes.

In this case, sulfur-based flow batteries present a promising alternative due to its much lower cost and huge production. With an average lifespan of up to 15 years, they offer a longer service life than lithium-ion batteries and can compete with vanadium flow batteries. Although their energy density is relatively lower than lithium-ion batteries, this is not a critical factor for fixed energy storage applications.

However, sulfur-based flow batteries face two primary technical challenges. The first involves membrane selectivity. “We have been developing new ion-selective membranes and are now capable of mass-producing highly selective, non-fluorinated ion-exchange membranes. This is a key advantage that sets us apart from other flow battery companies,” Lu notes.

The second challenge is the development of catalysts. “We have independently developed a catalyst that does not require precious metals, which improves the battery’s energy efficiency. Our catalyst design focuses on environmental friendliness, low cost, and scalability,” she explains.

In July 2024, Towngas Smart Energy and Luquos Energy launched the first demonstration project featuring a sulfur-based flow battery energy storage system in Shenzhen. This system was connected to a charging station for electric trucks. The power demand of such charging stations is particularly high, especially in regions where there is a significant difference between peak and off-peak electricity prices. Even without using renewable energy, the battery system allows operators to store electricity during off-peak hours when prices are lower, and sell it back during peak demand, saving over 70% in electricity costs.

Energizing Hong Kong farm

Building on the success of this project, Luquos Energy is now working on a new project at a smart farm in Hong Kong’s Yuen Long district. The farm will use its battery system for energy storage, combined with solar power, to provide stable electricity. Looking forward, the company plans to focus on industrial applications, where the demand for energy storage is particularly high.

 “Once we achieve large-scale production, the cost of sulfur-based flow batteries could be reduced to at least half that of lithium-ion batteries, and to one-quarter of the cost of vanadium flow batteries,” Lu predicts. The price advantage of sulfur, along with its global abundance, makes it a highly attractive solution for meeting future global energy storage demands.

Luquos Energy is currently raising funds and negotiating with local governments for policy support. The company is looking for investors, and initially aims to raise around HK$100 million (US$12.87 million) in a pre-A-series funding round.

“Lithium-ion technology is already very mature, and the market is mainly focused on price competition. If we can improve safety and reduce costs, we will have an opportunity to capture market share,” says Lu.

The company is looking to overseas markets, especially Europe, Southeast Asia, and countries along the Belt and Road Initiative, where demand for energy storage is rapidly increasing.