As the world moves towards adopting more renewable energy sources like solar and wind power, energy storage solutions become increasingly important to overcome the intermittent nature of these technologies. Energy can be stored during times of excess generation and utilized during high demand, leading to a more reliable and resilient grid. Several promising energy storage technologies today are vying to power our future energy infrastructure.
Batteries
Batteries are electrochemical devices that convert chemical energy into electrical energy. Lithium-ion (Li-ion) batteries have long been used in consumer electronics and electric vehicles. Now, utility-scale Li-ion batteries are also gaining traction for grid-level energy storage. Compared to other mainstream batteries, Li-ion batteries have higher energy density, low self-discharge, and high cycle life. However, they still face challenges like degradation over time and safety issues related to thermal runaway. Alternatives like lithium-sulfur, solid state, and flow batteries aim to improve upon the limitations of Li-ion technology. Ultimately, battery chemistry and manufacturing advancements will determine if batteries realize their full potential for large-scale, long-duration energy storage.
Pumped Hydro Storage
Pumped hydro storage (PHS) is a mature technology that has been used since the 1890s. It stores energy by pumping water from a lower reservoir to an upper reservoir when electricity demand is low. Then, when high demand, water is released from the upper reservoir through a turbine to generate electricity. Over 90% of all grid storage today is provided by PHS because of its high storage capacity and cost-effectiveness. However, suitable geology and negative environmental impacts limit sites for new PHS plants. Recent innovations use seawater instead of freshwater to open up more coastal and island locations for PHS. Enhanced PHS designs also increase generation capacity within existing reservoirs.
Compressed Air Energy Storage
Compressed Air Energy Storage (CAES) stores energy by using electricity to compress air in an underground cavern or container. To discharge, compressed air is released, heated, and expanded through a turbine to generate electricity. CAES can provide large-scale, long-duration storage comparable to PHS at a lower cost and with less environmental impact. Geographic limitations for underground storage sites and reliance on natural gas to heat the released air are key barriers to expanding this technology. Innovations like adiabatic CAES aim to make the process more efficient without natural gas. Pairing CAES plants with renewable energy could provide days of storage to mitigate wind and solar intermittency.
Hydrogen Storage
Hydrogen is emerging as an exciting option for long-term energy storage. Excess renewable electricity can be used to produce hydrogen through water electrolysis. This green hydrogen can then be stored and used later to generate electricity in a fuel cell or used as a transportation fuel in hydrogen vehicles as an alternative to gasoline and diesel. Hydrogen provides a unique solution to integrate renewable energy across the entire energy system. However, most hydrogen today is produced from natural gas, which nullifies environmental benefits. Cost declines in electrolyzer technologies and dedicated support for green hydrogen infrastructure can realize hydrogen’s full decarbonization potential across the power, transportation, buildings, and industrial sectors.
Thermal Energy Storage
Increasing the efficiency of renewable generation is equally important as energy storage capacity itself. Thermal energy storage (TES) is a cost-effective technology that avoids dumping excess heat and maximizes energy utilization over time. Excess thermal energy is stored in materials like molten salt or water at high temperatures and later dispatched to drive a generator. Sensible, latent, and thermochemical TES techniques store heat at various temperatures for heating and cooling needs in buildings and industry. For concentrated solar power plants, TES with molten salt stores heat to keep generating electricity for hours after sundown. Advancing TES solutions in combination with renewable energy sources provides a pathway for round-the-clock clean energy.
Conclusion
energy storage serves a pivotal role in overcoming intermittency challenges and aligning supply with demand across all sectors and time periods. Exciting innovations are underway across battery, thermal, hydrogen, and hydro-based storage solutions to meet economic targets and deliver environmental sustainability. Unlocking versatile, large-scale energy storage will ultimately empower the full transition to a decarbonized energy future.