Technical Article

An Overview of Energy Storage for PV Systems

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Energy storage systems have been around for centuries in the form of hydro dams,

Applications

Military and critical facilities, and remote locations really driving energy storage forward. Cost of generator fuel and transporting fuel in the event of emergency is extremely high.

Services

• Microgrid Parallel Operation

• Backup Power

• Increased PV Self-consumption

• Demand Management

• Demand charge reduction 

• Peak load shaving

• Time-of-use Bill Management

• Distribution Deferral

• Transmission Deferral

• Transmission Congestion Relief

• Resource Adequacy 

• Black Start

• Voltage Support

• Frequency Regulation

• Spin / Non-spin reserve

• Energy Arbitrage

• Grid battery charging

Fully Integrated Systems

Benefits: system and components all designed to work together, warranties are all under one company, makes design much easier.

Some companies offer fully integrated energy storage systems

• Dynapower NEC energy solutions

• Switch (LG Batteries + CPS inverter + Gelli Controls)

• Princeton Power Systems

Batteries

Lots of options, may be

Lithium ion (Li-ion)

• Dominant battery technology, accounted for 94.2% of US energy storage market in Q2 2017 (1)

Lithium Ferro Phosphate (LFP-type Li-ion): 

Attributes:

• chemically stable

• thermally stable

Manufacturers:

 

Lithium Nickel Manganese Cobalt Oxide (NMC-type Li-ion):

Attributes:

Manufacturers:

• LG CHem: 

  • 4.2 MW PV, 7MW / 3MWh energy storage system in Village of Minister, Ohio S&C developed in 2016

• Kokam

• Panasonic

• Tesla

• Samsung

Lead-acid

Flow

• 5% US energy storage market in Q2 2017 (GTM Research)

• Safe: not flammable, negligible short-circuit potential, no thermal runaway

• long lifespan, no degradation

• Some O&M required for replacing pumps and balancing electrolyte

All-iron hybrid redox:

Vanadium redox flow battery

• Avalon Battery

Zinc-bromine hybrid redox

Zinc-iron hybrid redox

Sodium-sulfur batteries

Zinc-air batteries

 

Inverters

 

 

Controls & Monitoring

Software to control all equipment, for very large storage system may be worth having a custom built software system.

Geli

 

Resources & References:

1. US Energy Storage Monitor: Q3 2017, GTM Research and the Energy Storage Association, September 2017

   1. Latest version can be found at www.energystoragemonitor.com

2. "Advanced Battery Technologies for Stationary Energy Storage Applications" by David Brearley, SolarPro Magazine, November/December 2017