Energy Storage Systems

  • A wide range of Energy Storage technologies exist and are available for selection based on the User’s load requirements:
    • Historically they involved Electrochemical battery systems, often with conventional lead-acid batteries, even conventional type vehicle batteries.  The life cycle costs of these battery systems were sensitive to depth of discharge and charging patterns.
    • There were also very good stored energy systems like (1) Pumped hydro storage (using electricity in low demand periods to pump water to a higher elevation where it can be drained down later in high demand periods to power generators) but they needed certain topographical features not available everywhere; and (2) Compressed air energy (where compressors store the air in underground caverns) but they needed certain geological features not available everywhere.

Electrochemical battery storage systems have been undergoing significant development over recent years, expanding from Lead Acid into Lithium ion and Redox flow technologies:

Lithium-ion Battery System

Chemical storage technologies have included Hydrogen being produced with surplus power then available subsequently in peak energy demand periods using fuel cells.

The duration of energy storage is an important consideration.  Shorter duration ESS technologies like Lithium ion batteries are well suited to intra-day variation of Renewable energy sources.  Longer duration ESS technologies are also required for extended intermittency of Solar or Wind energies over several days.  Extreme weather events can also disrupt reliable energy supply without increased energy storage.  The US Department of Energy (DOE) Advanced Research Projects Agency – Energy (ARPA-E) has been supporting the development of Long-Duration Electricity Storage (LDES) solutions for 10 to 100 hours of energy storage.

Energy Storage

  • Battery Energy Storage Systems (BESS)
    • Lead Acid;
    • Nickel / Nickel metal hydride (NiMH)
    • Lithium ion (Li-ion)/ Lithium Iron Phosphate (LiFePO4) – most common now
    • Redox Flow – longer durations and load cycles than Lithium batteries
  • Energy Storage Systems (ESS)
    • Hydrogen – no issues with capacity, duration, or cycles – only a function of storage amounts