How can flywheels be more competitive to batteries?

The use of new materials and compact designs will increase the specific energy and energy density to make flywheels more competitive to batteries. Other opportunities are new applications in energy harvest, hybrid energy systems, and flywheel’s secondary functionality apart from energy storage.

Are flywheel-based hybrid energy storage systems based on compressed air energy storage?

While many papers compare different ESS technologies, only a few research [152,153] studies design and control flywheel-based hybrid energy storage systems. Recently, Zhang et al. present a hybrid energy storage system based on compressed air energy storage and FESS.

What is a flywheel energy storage system?

Flywheel energy storage systems are mainly used for short-term storage application lasting from milliseconds up to minutes such as power quality services . This can also be seen in Table 4.3, where the installed rated power of flywheel energy storage systems is significantly higher than the installed rated capacity.

What is pumped hydroelectric storage?

Pumped hydroelectric storage (PHES) is one of the most common large-scale storage systems and uses the potential energy of water. In periods of surplus of electricity, water is pumped into a higher reservoir (upper basin).

Why are high-strength steel flywheels a good choice?

High-strength steel flywheels have a high energy density (volume-based energy) due to their high mass density. Furthermore, they are superior to composite ones regarding thermal conductivity and design data availability, such as SN curves and fracture toughness.

How long does a flywheel storage system last?

Compared to battery storage systems, flywheel storage systems have a long service life of more than 20 years in most cases. Also, due to their design, they show neither a degradation in round-trip efficiency nor in capacity. However, self-discharge, which mainly results from air and bearing friction, must be considered in the emissions balance.