Imagine a single energy storage system capable of serving all potential needs, from a short burst of high power to keeping the lights on for many hours. Such a system could greatly improve the overall economics of energy storage by removing limitations on the amount of revenue a single system can generate.
This is the focus of several leading companies that are looking to develop hybrid energy storage solutions, combining multiple different technologies in a single system. Energy storage technologies all have their ideal applications; some, such as flywheels, ultracapacitors, and certain lithium-ion chemistries are best at delivering high power over shorter periods of time. Others, such as compressed air and flow batteries, are ideally suited for applications that require a lower level of power to be delivered over a longer period of time. Combining technologies into a single system with the flexibility to perform multiple tasks, could greatly improve not only the economic returns on investment, but also the overall lifetime of storage systems.
Many hybrid energy storage systems are currently available or have already been deployed. Power grid giant ABB has been actively developing its flywheel business and is looking to hybrid systems to fully realize the benefits that flywheels can provide. The company has installed a hybrid flywheel/battery system on remote Kodiak Island, in Alaska. In this installation, two 1 MW flywheels handle the grid’s frequency regulation and high power needs, while the batteries provide the energy density required to fill in the gaps of local wind power generation. As short duration/high power needs are more frequent, this hybrid system reduces the number of times the batteries must be discharged, greatly extending the overall life of the system.
Hybrid systems involving ultracapacitors are also finding promising applications. A leading company in this space is the Spanish firm Win Inertia, which has partnered with ultracapacitor manufacturer Maxwell Technologies to offer an integrated hybrid storage system. The ultracapacitors handle the frequent, intense power requirements, allowing the batteries to be discharged less often. This allows the optimal use of high energy density storage technologies, as well as a rapid response to short term issues. Win Inertia is primarily focusing on the software, controls, and system-integration challenges to make this technology as effective as possible.
Beyond Single Applications
Integration with existing electrical grids presents a major software challenge for energy storage system integrators. When multiple types of storage technologies are integrated into a single system, these challenges become even more complex. The overarching goal of energy storage system integration is to ensure the longevity of a system and its constant availability in the market, thus maximizing the return on investment for system owners.
If these challenges can be overcome, the potential for hybrid storage systems is enormous. Standard storage systems are often designed for only one application, for example frequency regulation, which limits the potential revenue they can generate. Hybrid systems with the ability to meet multiple grid needs and capture multiple revenue streams can be much more economical. While advanced hybrid storage systems are only beginning to emerge, they could one day lead the energy storage market.