As we continue our journey toward electrification and energy efficiency, we must understand the key role played by our capacity to store the energy that we generate for use later. Energy storage goes a long way beyond just bridging the gap between supply and demand. While it has already been a key factor in enabling a stable grid, it continues to gain relevance as we move toward renewable energy generation and the “electrification of everything.”
To understand Energy Storage Systems (ESS), the options available today as well as any future possibilities, we have to start by unpacking the technology in its many types. Dive in to explore from the most conventional to the cutting edge and emerging trends.
Go to:
- Pumped Hydro Storage
- Thermal Energy Storage
- Flywheel Energy Storage
- Battery Energy Storage Systems (BESS)
- Emerging Technologies
Primary technology in mass use today
Pumped Hydro Electric Storage: The Power of Gravity
Pumped hydroelectric energy storage’s importance cannot be understated as it remains the largest-capacity form of active grid energy storage today at >70% of total capacity. Operating on the principle of harnessing gravity’s potential by pumping water to an elevated reservoir during off-peak demand hours, to later release it and generate electricity during peak demand hours.
While these systems represent largest source of energy storage solutions, their high initial costs, substantial footprint, potential environmental impacts and geographical limitations pose significant challenges to implementation. As such, hydro-electric storage solutions tend to be limited to governmental entities only.
| U.S. utility-scale energy storage systems for electricity generation, 2022 | |||||
| Storage system | Number of plants and of generators | Power capacity MW | Energy capacity MWh | Gross generation MWh | Net generation MWh |
| pumped-storage hydro | 40–152 | 22,008 | NA | 22,459,700 | -6,033,905 |
| batteries | 403–429 | 8,842 | 11,105 | 2,913,805 | -539,294 |
| solar-thermal | 2–3 | 405 | NA | NA | NA |
| compressed-air | 1–2 | 110 | 110h | NA | 57 |
| flywheels | 4–5 | 47 | 17 | NA | 0 |
Data source: U.S. Energy Information Administration, Preliminary Monthly Electric Generator Inventory (Form EIA-860m) and Power Plant Operations Report (Form EIA-923), February 2023
Note: Includes facilities with at least 1 megawatt (MW) of total nameplate capacity operational at end of 2022; MWh is megawatthours; NA is not available
Less established technologies in use today
Thermal Energy Storage: Saving the Heat… for Later
Thermal energy storage, including sensible heat, latent heat, and thermochemical storage, offer interesting opportunities due to their energy density and ability to store energy over extended periods of time. These systems operate through heating and cooling methods to manage energy release.
Molten salt, for example, stores heat generated by solar energy to later use during extended periods without sunlight. Ice storage, on the other hand, is a good solution to help buildings minimize the need for compressors to operate air conditioning systems efficiently.
Thermal storage is a versatile solution to energy storage needs; however, efficiency concerns and specialized infrastructure requirements are a significant challenge.
Flywheel Energy Storage: Spinning Power
Flywheel energy storage is a clever marvel of kinetic energy conversion. These systems operate through a mechanical rotor that spins rapidly, storing energy to later release it when needed. Flywheel energy storage can also be found contributing to, for example, the recapturing of braking energy on trains or other vehicles (regenerative braking).
This type of energy storage offers a quick response time and a long operational life, giving them an important role in grid stabilization and balancing fluctuations in power supply. While these systems can absorb and release high power, they are limited to short durations, causing concerns for storage capacity in addition to their elevated costs.
Newer technologies gaining traction
Battery Energy Storage Systems (BESS)
Rechargeable batteries are ubiquitous now. Powering everything from our phones to our cars and our homes and now also established as a reliable bi-directional power source for off-grid, on-grid and micro-grid applications.
As a complementary technology to the rapidly growing renewable energy sources (primarily wind & solar) they provide additional grid stability and come with other benefits such as portability, versatility, and cost savings. They are constantly evolving, bringing higher efficiencies which in turn brings additional cost effectiveness.
However, not all batteries are made the same. There are many different rechargeable battery chemistries each with its own unique set of attributes ranging from popular chemistries such as Lead-Acid, Lithium-Ion, Nickel–Cadmium (NiCd) and Nickel–Metal Hydride (NiMH) to emerging technologies such as Flow and Sodium batteries depending on application power and duration requirements.
Our focus and engineering expertise is with Lithium-ion batteries such as Lithium Iron Phosphate (LiFePO) – often referred to as LFP. We also see a lot of development with Lithium-ion solid-state batteries which eliminate the flammable electrolyte and will be safer but remains as an emerging chemistry today.
Lithium-ion batteries
Lithium-ion batteries have undergone important transformations and enhancements in their lifetime. Once limited to consumer products, this type of battery has evolved and can now be found powering our cars and homes and is also fast becoming a key factor in electrical grid stability.
As lithium-ion batteries continue to spark attention and evolve, their costs continue to plummet, thanks in large part to the economies of scale from the boom of electric vehicles and portable power tools, allowing other industries and applications to tap into the latest technology.
Emerging Technologies: What Does the Future Hold?
While the future of energy storage will continue to develop with further enhancements in the those established technologies, there is also a lot of promise in emerging trends and solutions. Solid-state batteries, for example, promise to increase safety and energy density. Redox flow batteries seem to be a scalable and durable solution for large-scale energy storage. Compressed air, superconducting magnets, underground pumped storage, and hydrogen storage; all at their different stages of development, are all new paths that increase versatility and open up endless options for the unique needs of tomorrow’s applications.
In addition to the emerging technologies, we will certainly continue to see developments in advanced materials, miniaturized technology, software and AI. These advancements could soon be applied to this sector of the industry, optimizing systems, enhancing performance, and offering predictive maintenance and energy forecasting.
