Energy storage: Delivering reliable, sustainable performance in long-duration applications

Reliable, efficient and low-emission pumps and compressors are fundamental to long-duration energy storage (LDES). As renewable energy generation expands and output becomes more variable, operators rely on energy storage systems that remain stable, responsive and available when the grid needs support.

Mechanical seals, couplings and filtration support the rotating equipment behind these systems, helping LDES reduce reliance on fossil fuels, enhance resilience during outages and deliver clean, consistent power.

Energy storage and its impact on system stability

Energy storage refers to technologies that absorb energy and release it later to balance supply and demand. In the context of the energy transition, storage is increasingly necessary to integrate higher proportions of solar, wind and hydro into power grids. These technologies support operational flexibility, reduce curtailment and improve system resilience.

LDES stores energy for several hours to several days. There are several applications of long-duration energy storage (LAES, CAES and CCES), which will be discussed in more detail below.

The key requirement driving LDES adoption is the need to reduce intermittency from renewables and provide resilience during extended power shortages. In regions with limited transmission access, LDES can also provide vital backup during long outages caused by extreme weather or equipment failures.

In recent years, the value of energy resilience has become increasingly evident in global events where sustained power outages have impacted industries, communities and critical infrastructure. Energy storage provides a pathway to mitigate these disruptions by offering reliable power during emergencies, enabling black-start capabilities and supporting microgrids in remote areas.

Barriers slowing wider LDES deployment

While LDES technologies continue to advance, the path to wider commercial deployment remains challenging. These obstacles affect both developers and the OEMs responsible for supplying rotating equipment:

• Limited commercial track record for newer LDES designs
• Need for high efficiency to improve overall system economics
• Demanding operating conditions, including high pressures, cryogenic temperatures or long thermal cycles
• Complex permitting and integration requirements for large-scale projects
• Growing expectations for reduced emissions and environmental impact
• Pressure to lower lifecycle costs and extend operational life

For OEMs building compressors, pumps, turbines and related equipment, reliability remains the defining expectation. LDES assets must be ready to operate whenever needed, often under variable cycling conditions. Unplanned maintenance or efficiency losses can significantly reduce the value and performance of the entire system. As a result, sealing solutions must provide long-term stability with minimal intervention.

Types of energy storage technologies

Different storage technologies employ distinct methods to charge and discharge energy, each generating unique operational pressures on rotating equipment.

Liquefied air energy storage (LAES)

LAES stores energy by compressing and cooling air until it liquefies at extremely low temperatures. When electricity is needed, the liquid air is evaporated and expanded through a turbine to generate power.

LAES Technologies include:

• High-pressure compressors
• Cryogenic pumps
• Cryogenic turbines
• Heat exchangers and thermal recovery
• Expansion turbines

For OEMs, LAES presents challenging operating conditions. Compressors must manage high-pressure ratios, while cryogenic pumps must handle very low temperatures without losing integrity or performance. Mechanical seals must maintain stability across extreme temperature changes and prevent leakage of cryogenic air during repeated charge and discharge cycles.

Compressed air energy storage (CAES) and compressed carbon dioxide energy storage (CCES)

Compressed air and compressed carbon dioxide systems store energy by using electricity to compress gas into underground caverns or artificial chambers. During discharge, the stored gas is heated and expanded through a turbine to produce electricity.

They depend on:

• Multi-stage compression
• Thermal management during charge and discharge cycles
• Gas-tight containment to prevent losses
• Handling of variable operating pressures

Compressors in CAES/CCES operate across a wide range of pressures and temperatures, so sealing solutions must remain stable under cyclic loading. Rotating equipment must also tolerate thermal expansion and contraction without losing alignment or efficiency.

Thermal energy storage (including molten salt systems)

Thermal energy storage converts electrical energy to heat, storing it in a working medium such as molten salt or high-temperature fluids. When power is required, the stored heat is used to drive an engine or turbine.

These systems often involve:

• Heat pumps
• High-temperature circulation pumps
• Heat exchangers
• Thermally demanding operating conditions

Mechanical seals used in thermal storage applications must withstand long-term exposure to elevated temperatures and thermal cycling. They must also handle fluids with varying properties, ensuring no leakage occurs even during transitions between heating and discharge phases.

How mechanical seals, couplings and filtration support energy storage

Across energy storage applications, rotating equipment drives the conversion of thermal, mechanical or compressed energy back into power. Mechanical seals play a critical role in this process by maintaining equipment integrity operating under demanding conditions.

Mechanical seals in energy storage systems must provide:

• High-pressure containment for compressor stages
• Cryogenic performance for LAES applications
• Chemical and thermal compatibility with storage media
• Resistance to thermal shock and rapid cycling
• Extended mean time between repairs to limit maintenance needs
• Low emissions and minimal leakage

Couplings support shaft alignment and reduce vibration while transmitting power and speed between equipment. Filtration maintains the cleanliness of the working fluid, protecting seal faces and limiting wear on pumps and compressors.

Together, these components support:

• Greater equipment uptime
• Safe, efficient operation
• Lower total cost of ownership
• Reduced environmental footprint
• Higher system efficiency and reliability

For OEMs, integrating appropriate sealing technology early in the design process ensures that energy storage equipment is prepared for the full range of operational demands.

Filtration protects pumps, compressors and auxiliary systems by keeping working fluids and gases clean and preventing contaminants from entering critical components. In LDES applications, where equipment often operates under high-pressure, cryogenic temperatures or long thermal cycles, clean process media directly improves performance and reduces wear.

Effective filtration helps:

• Maintain media cleanliness for compressors, heat-transfer circuits and cryogenic loops
• Protect mechanical seal faces from particulate damage
• Reduce the risk of fouling in thermal systems, improving heat-transfer efficiency
• Extend equipment life by limiting erosion and contamination-related failure
• Support consistent operation across frequent charge and discharge cycles

By improving equipment reliability and reducing maintenance interventions, filtration contributes to the overall efficiency, safety and sustainability of LDES systems.

Connecting energy storage to the broader energy transition

LDES plays an essential role in supporting a cleaner, more resilient energy system. As renewable projects scale and electrification continues across industries, LDES technologies will help balance the grid, limit curtailment and provide dependable energy when other sources are unavailable.

For OEMs serving this sector, the opportunity is clear. Rotating equipment (such as pumps and compressors) designed for efficiency and longevity are the backbone of these storage systems. Mechanical seals, couplings, and filtration ensure reliable operation in the environments characteristic of LDES technologies.

Working together, these components help energy storage operators:

• Maintain performance across varied operating cycles
• Support continued expansion of renewable generation
• Strengthen system resilience during long disruptions
• Reduce dependence on high-emission backup generation
• Move closer to net zero goals

As the energy transition accelerates, LDES technologies will expand their role in electricity markets, industrial operations and remote energy systems. Mechanical seals and supporting technologies will remain essential to their success, enabling reliable performance and supporting sustainability objectives across the entire system.

Supporting OEMs in energy storage

As grids adapt to higher shares of renewable generation, energy storage presents OEMs with significant opportunities to improve reliability and enable cleaner, more flexible power systems. Mechanical seals, couplings and filtration will continue to shape the performance of these assets. John Crane will remain a trusted partner in helping OEMs bring robust, efficient and sustainable energy storage technologies to market.