Navigating Long-Duration Energy Storage

The current landscape of non-lithium long-duration storage technologies continues to grow and change. On Tuesday morning at POWERGEN 2025, Megan Reusser, Technology Manager at Burns & McDonnell, shed some light on this ever-changing market in her session, Navigating the Current Landscape of Long-Duration Energy Storage (LDES) and highlighted the advantages and disadvantages of technologies in the space, such as:

• thermal storage
• pumped hydro
• mechanical energy storage
• gravity storage
• compressed air energy storage
• liquid air energy storage

Currently, legislation supports LDES, but the new administration may change that. The Office of Clean Energy Demonstrations (OCED) is funding five to 15 projects at $20 million each.

“To achieve net-zero emissions goals, different forms of energy storage are going to be required due to several factors,” Reusser said. “Number one is the intermittency of renewables. As we know, there is an increase when the wind is blowing or the sun is shining but having the energy storage in place to follow that can also help enhance the grid’s stability and reliability. So, really focusing those two things together in the form of energy storage. Decarbonization across industries is another factor as is energy cost optimization—storing when costs are low, selling when costs are higher. Energy storage could also help reduce the need for grid expansion by allowing power and access in remote areas.”

Types of Energy Storage

There are four main types of LDES: mechanical, thermal, electrochemical, and chemical. Each type of LDES technology has its own set of challenges and advantages.

Mechanical LDES converts electrical energy into potential or kinetic energy. This category has many technologies under its umbrella, and Reusser said it’s really for the longer duration. Some examples include:

1. Compressed air solutions, which store air at high pressures (geology-based)
2. Liquid air solutions, which store air at cold temps but require a high energy demand

Mechanical LDES technologies are used for grid balancing, backup power, and industrial microgrids. Some challenges with mechanical LDES are its high capital expenditures (CapEX) and inefficiency compared to other forms of energy storage. Plus, it has geographical limitations.

Thermal LDES technologies store energy in the form of heat, including latent heat, sensible heat, and electrothermal. Heat is transferred to working fluids to produce steam via a turbine at a later point. Thermal LDES applies to industrial heating but not industrial power.

It is scalable for long durations and decarbonizes hard-to-abate sectors. Potential heat loss and higher CapEx are challenges.

Electrochemical LDES technologies include flow batteries, metal anode batteries, and static batteries—they may look like lithium batteries, but they have a different chemistry. There are 40 different chemistries of flow batteries. What makes it a flow battery and differentiates it from a static or lithium battery is electrolytes are stored in tanks and flow through the cells to create the current.

Flow batteries are good for integration with renewables. They are scalable, have long lifespans, and have a low risk of thermal runaway. However, costs can be high, and due to configurations—several tanks with pumps, etc.—they have a lower energy density, and it takes up more space to have the same amount of energy storage in comparison to lithium. It also has a lot of moving parts, so it will require regular maintenance for some of the pumps, valves, and other components. Also, batteries tend to struggle in low-temperature conditions.

Chemical LDES technology solutions are hydrogen, ammonia, or LNG. For example, you could use renewable power to create hydrogen and then store that hydrogen, and that could technically be your form of energy storage. The same goes for ammonia and LNG. This is a good fit if you’re more interested in utilizing the molecule rather than the electron, Reusser. This works to transport fuel, in industrial processes, and energy export so that you’re moving the molecule and not the electron. They can also be used to decarbonize hard-to-abate sectors.

These technologies also have high energy density. Similar to thermal and mechanical LDES, they are complex systems, so you could have high CapEx, and you have to deal with storing and transporting the molecules.

Choosing the Right Solution

Choosing the right type of energy storage depends on the use case and lifecycle. Reusser recommends assessing operating conditions and cycling frequency and evaluating CapEx and financial planning.