Power hardware in the loop-based lifetime assessment of hybrid energy storage systems: A novel realistic approach

Reliable and cost-effective energy storage is essential for grid applications, but lithium-ion batteries face lifetime limitations due to cycling stress, temperature effects, and high power ramping. This paper presents a novel Power Hardware-in-the-Loop (PHIL) approach for experimentally assessing battery aging in Hybrid Energy Storage Systems (HESS) that combine batteries with flywheels. The proposed setup enables realistic emulation of field conditions and long-term degradation testing. Two configurations are experimentally evaluated: a standalone battery system and a hybrid flywheel–battery system with equivalent energy capacity. Results show that the HESS configuration significantly reduces power ramping and depth of discharge, resulting in lower degradation rates than a standalone battery. Furthermore, a Levelized Cost of Storage (LCOS) analysis confirms that the HESS achieves superior lifetime economics under realistic operating conditions, particularly under end-of-life criteria.