China’s solar and wind power generating capacities are the largest in the world, accounting for more than 35 per cent of the global total. As demand continues to grow to meet its climate goals, the need for storage facilities has also become critical to ensure a ready and consistent supply. Lithium battery output, for example, surged 70 per cent last year to 957 gigawatt-hours (GWh), according to a report published by sustainable energy research house EVTank and China Yiwei Institute of Economics, more than enough to feed the domestic electric-car industry. About one-sixth of excess output ended up in storage systems. China is fast-tracking its renewable-energy installation capacity in its five-year plan through 2025. Here’s what you need to know about energy storage in Asia’s biggest economy. Why does China need many more power storage facilities? By 2060, surging production of weather-dependent solar and wind power will result in daily output fluctuation of up to 40 per cent of peak demand, according to Shu Yinbiao of Chinese Academy of Engineering and former president of State Grid Corp and China Huaneng Group. “Prolonged overcast, windless and frigid periods present major uncertainties for energy output,” he said. This dilemma mirrors the problem in the hydro, coal, natural gas and nuclear capacities combined, making it a tremendous risk to the stability of supply in China’s power system, Shu added. Seasonal variations are also substantial. China’s national wind capacity utilisation averaged 555 hours in the first quarter last year, while solar farms averaged 300 hours, according to China Electricity Council. This compares with 462 and 373 hours respectively in the third quarter. Are there novel solutions to keep up with energy storage requirements? Lithium-ion batteries are not a practical solution for long-duration energy storage (LDES) needs, due to design limitations, rising raw material prices and safety concerns. Pumped storage hydro plants are currently the industry’s mainstay storage solution . It works by pumping water from a reservoir to another at a higher elevation, using power generated in excess of demand. The water in the higher reservoir is later released to generate hydropower - when the sun is not shining or when the wind is weak. Emerging technologies have one advantage over pumped hydro: they are not limited by the geographical locations of the energy sources. They can be deployed and scaled up wherever they are needed. How soon can new storage technologies become competitive and viable? “Pumped hydro is the only truly large-scale, long-duration storage technology deployed and will continue to dominate [through] to 2030,” said Kevin Shang, principal analyst for energy storage at Wood Mackenzie, a consultancy. Most LDES technologies are struggling to scale up in cost-efficient ways, he added. The only technology that could rival pumped hydro is compressed-air energy storage, which takes more than five years to develop, according to Jackson Cutsor, senior analyst, clean energy technology at S&P Global Commodity Insights. Heat generated during compression can be stored, and used during expansion, he added. “But those technologies each serve different purposes and only indirectly compete against each other,” he said. “Pumped storage projects take significantly longer to develop and are more capital intensive to deploy.” Flywheels storage, which maintains rotational energy via a rapidly spinning rotor, are unlikely to be a notable part of the solutions before 2030, Cutsor said. Sodium-ion, meanwhile, can be a viable alternative in the next three to five years, he added, because of the abundant and cheap supply of required materials. Since sodium-ion batteries’ design is nearly identical to those of lithium-ion packs, factories could be converted or designed to manufacture both to achieve cost savings. Which countries are supporting emerging storage technologies? Where does China stand? Last May, the US Department of Energy launched a US$505 millionfour-year initiative to support small pilots and large utility-scale demonstrations. The UK government unveiled a £32.9 million (US$40.7 million) funding in November to support new energy storage projects. Driven by strong policy support, the deployment of vanadium redox flow batteries and compressed air energy storage has increased rapidly in China. Last year, the world’s largest redox flow battery energy storage system with 400 megawatt-hours of capacity was connected to the grid in Dalian, northeast China. The world’s largest compressed air energy storage project with the same capacity came on stream in Zhangjiakou of northern China, Shang of Wood Mackenzie noted.