While batteries are the most common, there are other methods for storing wind and solar power:  

Thermal Energy Storage — For solar energy, water or molten salt is used to store heat that is then stored in an insulated tank until the energy is needed. The energy can be used directly for heating or cooling or can be used to generate electricity. 

Compressed Air Storage — For both solar and wind energy, a compressor system pumps large tanks or caves full of pressurized air, which can be released to drive a turbine that produces electricity. 

Pumped-Storage Hydropower — Wind and solar energy are used to pump water up into a reservoir when demand is low, then the water is released to flow when needed, turning a turbine to generate electricity when demand is high. 

Flywheel Storage — Expanding solar energy makes the wheel turn faster and that energy can be extracted by attaching the wheel to an electrical generator, which slows down the wheel due to electromagnetism, producing energy. 

Virtual Storage — Solar energy can be stored by heating or cooling a building before the energy is needed, then the building stores the thermal energy so more power is later available during peak demand. 

Fuel Cells — Solar and wind power can be used to create new fuels that can be burned or consumed to provide energy, effectively storing the solar energy in the chemical bonds.  

Electrochemical Storage — Similar to batteries in laptops and mobile phones, electricity is fed into a battery, causing a chemical reaction that stores the energy. While lithium-ion is the most common, others include lead-acid, sodium and nickel-based batteries. 

While all of the above have their benefits, the best storage option—batteries—we saved for last. Batteries are one of the key solutions to effectively integrate high shares of renewable solar and wind power around the world. This is especially true for populations that have long relied on fossil fuels. The efficiency and cost of batteries makes them more viable for the foreseeable future. 

Currently, utility-scale battery storage systems are being used around the world in places such as the United States, Australia, Japan, and throughout Europe. One of the larger systems is the Tesla 100MW/12MWh Li-ion battery storage project at Hornsdale Wind Farm in the Australia. Another notable high-level demonstration project is in New York. Using a 4 MW/40MWh battery storage system, it reduced nearly 400 hours of congestion in the power grid, saving more than $2M in fuel costs.  

Behind-the-meter (BTM) batteries that are connected behind the utility meter of commercial, industrial and residential customers aim to reduce electricity bills due to the falling cost of battery storage technology and the growing demand for electric vehicles. In Germany, 40% of recent solar panel applications have been installed with BTM batteries, while Australia aims to reach 1M BTM battery installations by 2025.  

Globally, energy storage deployment in emerging markets is expected to increase by more than 40% each year until 2025.