Energy storage expands capacity and resilience on the electric grid while helping communities meet localized power demands without incurring additional transmission or distribution line costs. Systems designed for energy storage may also co-locate with renewable energy generators such as community solar arrays or aggregated home and commercial building rooftop solar projects for added flexibility and resilience.
Long-Duration Storage
Prior to recently, energy storage technologies that could reliably deliver power for extended periods were scarce. Lithium-ion batteries represent almost 100% of new energy storage capacities but can only provide six hours or so before needing recharged.
But utilities, states and nations with aggressive clean energy targets require longer duration systems to help smooth out wind and solar power’s fluctuations, and to prevent their curtailment during periods of excess generation due to transmission limitations.
Long-duration storage can play an invaluable role in communities further from the power grid, such as rural areas and islands. Such communities typically pay higher demand charges due to air pollution and climate change – with energy storage solutions (ES) helping reduce demand charges while helping prevent the need for costly fossil fuel peaker plants.
Short-Duration Storage
Short duration energy storage technologies provide many grid services and improve electricity quality and reliability, including fast response ancillary services that help balance supply and demand in real time. They’re well suited to provide fast response ancillary services that help manage supply and demand across the supply/demand curve in seconds rather than minutes or hours.
Frequency control services also can provide frequency regulation services, which reduce power spikes or sags that harm equipment, appliances and end users. They are commonly found in homes or businesses located further from the power grid as well as microgrids or islands fully or partially disconnected from larger electricity transmission networks.
Lithium-ion and flow batteries are widely utilized for residential and commercial applications due to being the most cost-effective and fastest growing technologies in this space. Other storage options available to homeowners and businesses alike are sodium-sulfur batteries designed for specific power or duration needs as well as metal air batteries designed with individual purpose in mind. All of these technologies can be controlled via software for optimal power distribution via grid services.
Flywheels
Flywheels store mechanical energy as angular momentum. They can be used to reduce the speed at which machines continue spinning after power is no longer applied or increase rotational stability.
Flywheels differ from clutches and gears by retaining their energy, which allows them to absorb any sudden spikes in power delivery from utilities or other sources, such as wind or solar energy sources. Flywheels are frequently employed in large power generation systems like these as an energy management device to help ride out fluctuations.
Flywheels can be designed with either a high or low moment of inertia depending on their size and mass, which allows them to store twice as much energy when spinning at equal speed than smaller wheels, though this requires increasing system size and cost; furthermore, most high-speed flywheel systems are optimized for short discharge times which limit their use to power quality applications (Schoenung and Hasselzahn 2003).
Battery Storage
Energy storage systems that connect to the electricity grid offer many value streams for organizations. These include grid services like frequency response, reserve capacity and black start capability; residential battery storage to reduce demand charges for solar customers; or larger scale commercial and industrial energy storage that supports resource adequacy in local communities.
Batteries are an essential technology to support renewable energy and transition towards a cleaner economy. Batteries provide firming services for variable renewables by storing excess generation during times of peak demand, discharging it at times when peak demand arises, stabilizing grid stability, reducing energy bills, and speeding the transition toward cleaner energies.
Energy storage technologies can be found throughout the power grid – at transmission, distribution or generation levels; microgrids; electric vehicles; homes and businesses. Long duration storage techniques available include flow batteries, molten salts and ice storage tanks – they can even be configured to use multiple value streams and meet federal, state and local incentives requirements.