Current storage options for renewable energy sources include pumped storage hydropower (PSH), Li-ion and redox flow batteries, with a few more technologies down the line. All are crucial to addressing the intermittent nature of wind and solar power and ensuring a viable and reliable transition from fossil fuel-based power production and generation.
PSH has long been in use and accounts for 96 percent of utility-scale capacity in the US. According to the US Department of Energy, it “can help to integrate additional renewable resources, such as wind and solar, with the power system.”
In the electrochemical segment, Li-ion batteries dominate but may be eclipsed by redox flow batteries in the future for power needed for longer durations. The latter type can provide between 10 and 36 hours of energy, according to Larry Zulch, CEO of Invinity, a US company that builds utility-grade energy storage for on-demand renewable power.
Categorized by chemistry, there are vanadium, all-iron, ZnBr, ZnFe, HBr and organic redox flow batteries. The most deployed, vanadium types (VRFBs) are based on water, virtually fireproof, easy to recycle, modular and scalable. In addition, they are less expensive at scale compared to lithium counterparts. VRFBs can handle more than 20,000 charge and discharge cycles or an operating life span of 15 to 25 years with minimal performance decline, according to Hope Wikoff of the US National Renewable Energy Laboratory.
In contrast, Li-ion batteries have about 10,000 cycles in stationary applications or roughly 15 years, Wikoff added. Much older technology lead-acid batteries can withstand 1,000 cycles equivalent to five to 15 years.
Vanadium trove
China accounts for 62 percent of global vanadium production, according to a source quoted by Alex Scott in a 2023 Chemical & Engineering News article. The material is mostly a by-product of iron refining, with the rest derived from petroleum refining processes.
Specifically, Panzhihua, Sichuan and Chengde, Hebei are the two main resource bases of vanadium in China. The former is a highly industrialized city whose economy is almost entirely reliant on mining operations.
With such proximity to an abundant resource, Chinese flow battery manufacturers mainly produce VRBs. The China Energy Storage Alliance said that country will have an additional 1.7GW installed capacity for VRFBs in 2025, bringing the total to 4.3GW or 14 percent of the energy storage field. By CAGR, installed capacity will reach as high as 112 percent from 2021.
In the field of R&D, the latest breakthrough was announced by the Dalian Institute of Chemical Physics, Chinese Academy of Sciences. A VRFB with a higher cell stack power density has been achieved using an innovative design and technique. This new battery delivers 130kW per cubic meter from the current capability of 70kW per cubic meter, or at more than double the power based on the same volume but at 40 percent less cost. It has an energy efficiency of 81 percent, with an efficiency loss of only 1.7 percent after more than 1,200 charge and discharge cycles.
Industrialization underway
The flow battery market has been growing quickly in recent years. Global installed capacity increased from 79.5 to 152.2MW between 2018 and 2021, according to China Times, while China’s rose from 16.1 to 51.6MW. This boom is expected to continue in the coming years.
In the VRFB segment, the worldwide value reached $242 million in 2022 and will hit $720 million by 2028 at a CAGR of 19.9 percent based on Emergen Research’s report. China Times said that this category posted $147 million in 2022 in China and is projected to be in the $3.45 billion scale by 2027 for a CAGR of 87.9 percent.
There are also initiatives on other types of flow batteries. WeView, a leading Chinese supplier of ZnFe flow batteries, announced in late 2023 the beginning of mass production at its new factory in Zhuhai, Guangdong. The facility, with an annual capacity of more than 6GWh, is said to be the world’s first to have breached the 1GWh mark.
ZnFe flow batteries are said to cost as low as $0.028 per kWh in energy storage applications compared to VRFB’s $0.056 and Li-ion’s $0.083.
China vs global players
There are fewer than 100 manufacturers of flow batteries in China and most will try to catch up with international companies in terms of technology, production technique and scale. The major ones include Rongke Power, Huifeng Energy and VRB Energy.
Joining this pool is the Xinzhu Group, which announced its plan to set up a vanadium redox flow battery factory in Neijiang, Sichuan. Once completed, the facility will be the largest production base in West China, adding to Neijiang’s distinction as the country’s second-largest production hub for VRFBs.
Globally, the leaders in flow battery manufacturing include Sumitomo Electric of Japan, Cellennium of Thailand and Cellstrom of Austria. Sumitomo Electric is expanding its VRFB production and installation facilities in the US, with an initial investment of $7.6 million.
China-made redox flow batteries
There are Li-ion and lead-acid types of flow batteries that can also be sourced from Chinese suppliers, but VRFBs are the most widely available. Typical vanadium flow batteries for energy storage applications have 1.2V nominal voltage, 10 to 20Wh/kg power density, over 80 percent charge and discharge efficiency and more than 5,000-cycle life span.
Electrolyte and cell stacks are the key components used in manufacturing flow batteries, respectively accounting for 40 and 30 percent of total production outlay.
The cost of materials decreased slightly in the past 12 months and, along with continuing technology improvements, this has contributed to declining flow battery prices. This trend is expected to continue over the next two or three years.
