A Comprehensive Guide to the U.S. Codes and Standards for Energy Storage Systems (ESS)

National Fire Protection Association (NFPA)

The first to be organized was the National Fire Protection Association (NFPA), which was organized in 1896 by several men associated with fire insurance companies. Currently, NFPA sponsors over 300 consensus Codes and Standards covering many safety related areas.

International Code Council (ICC)

The second is the International Code Council (ICC). ICC was organized by merging three separate regional code writing organizations. In 1972, the Building Officials Code Administrators International (BOCA), the Southern Building Code Council International (SBCCI), and the International Conference of Building Officials (ICBO) created the Council of American Building Officials (CABO) and published a single cooperative code for residential construction. This code was not well received but led to the formation of a more comprehensive set of building Codes. In 1994, these three organizations merged to form ICC, and created a single set of Codes that had no regional limitations. The first “I-Codes” were published in 2000.

National Fire Protection Association (NFPA)

The first to be organized was the National Fire Protection Association (NFPA), which was organized in 1896 by several men associated with fire insurance companies. Currently, NFPA sponsors over 300 consensus Codes and Standards covering many safety related areas.

Electrical

Electrochemical Double Layer Capacitors (EDLC) – The EDLC is considered a “supercapacitor” or an “ultracapacitor.” It is an electrostatic-based system with two electrodes producing electrostatic effects with activated carbons. These ultracapacitors can store or deliver energy at tremendous rates.
Supercapacitors – This is a general term for electrochemical double-layer capacitors.

Electrochemistries

Sources: Ricardo Consulting, AABC, National Academy of Sciences, and ZincFive estimates

Lead-Acid (LA)

The Lead-Acid battery utilizes the chemical reaction between lead and sulfuric acid. During discharge, lead and sulfuric acid react to form lead sulfate and hydrogen ions. During charging, the lead sulfate and hydrogen ions recombine into lead and sulfuric acid. This cycle of chemical reactions between lead and acid allows the battery to store and release electrical energy.

Nickel-Cadmium (NiCd)

The Nickel-Cadmium battery is based on the redox reaction between nickel hydroxide (NiOOH) and cadmium (Cd). Nickel hydroxide is the anode in the battery, and cadmium is the cathode. When the battery is charging, the reaction is reversed, nickel hydroxide is reduced to metallic nickel, and cadmium is oxidized to cadmium oxide (CdO).

Nickel-Metal Hydride (NiMH)

The Nickel-Metal Hydride battery is based on a chemical reaction between nickel and hydrogen. When the battery is discharged, the nickel is oxidized, and hydrogen is reduced, releasing electrons to provide electrical power. The reversed reaction occurs when the battery is being charged, which causes the hydrogen to oxidize and the nickel to reduce, allowing electrons to be absorbed from an external source.

Nickel-Zinc (NiZn)

The Nickel-Zinc battery is the process of chemical reactions between the anode (nickel) and the cathode (zinc) to produce electrical energy. Specifically, the nickel anode reacts with hydroxide ions during discharge, releasing electrons and forming nickel hydroxide. These electrons then travel to the zinc cathode, which reacts with zinc ions, releasing more electrons and forming zinc hydroxide. This process is reversed during charging.

Zinc-Manganese Dioxide (ZnMnO²)

The Zinc-Manganese Dioxide battery is also known as a zinc-carbon or alkaline battery, a secondary battery that can be recharged and reused multiple times. It is an improved version of the non-rechargeable zinc-carbon battery commonly used in household devices like remote controls, flashlights, and toys. The primary components of a rechargeable zinc-manganese dioxide battery are the anode, cathode, and electrolyte.

• The battery’s anode is composed of zinc metal or a zinc alloy. During the recharging process, an electrical charge is applied to the battery, and the anode’s zinc ions combine with the electrolyte’s hydroxide ions, thus producing zinc hydroxide. The manganese oxide on the cathode is then changed back to manganese dioxide. During the battery operation (and discharge when the battery is in use), the zinc atoms at the anode undergo an oxidation reaction, releasing electrons and forming positively charged zinc ions

Sodium (High Temperature)

The electrochemistry of sodium batteries is based on the intercalation of sodium ions in graphite anodes and the reduction of sodium ions at a metal-oxide cathode. During charge, sodium ions are inserted into the graphite anode, and during discharge, the sodium ions are released and reduced at the metal-oxide cathode. The main advantage of using sodium instead of lithium is cost, as sodium is much more abundant and less expensive than lithium.

• Sodium Sulfur (NaS) – Sodium sulfur batteries are based on the redox reaction between sodium (Na) and sulfur (S). The reaction occurs in a cell with an anode
  of sodium, a sulfur cathode, and a molten lithium and sodium chloride electrolyte. When the battery is charged, sodium ions move from the anode to the cathode and react with sulfur to produce sodium sulfide. During discharge, the reaction reverses, and the sodium sulfide is converted back into sodium and sulfur. The electrochemistry of sodium sulfur batteries makes them very efficient and can store large amounts of energy. They are also highly durable and have a long life span.
• Sodium Metal Chloride (Na NiCl2) – Sodium metal chloride batteries involve the transfer of electrons between the anode and cathode, resulting in the oxidation of sodium at the anode and chlorine reduction at the cathode. The electrolyte is actually a solid beta-alumina that separates the liquid electrodes. This process is reversed during charging.

Flow

Flow batteries are electrochemical cells that use two different liquid electrolytes stored in separate tanks and pumped through the cell. The electrolytes are typically held in flow cells and separated by a membrane that allows ions to pass through. During operation, the two electrolytes react in the cell, generating electrical energy. This energy can power various loads, including motors, pumps, and lights. The process can be reversed, allowing a flow battery to act as a generator and store energy for later use.

• Vanadium Redox (VRFB) – Vanadium redox flow batteries are electrochemical energy storage systems that use a vanadium-based electrolyte solution. The vanadium electrolyte is stored in two tanks and is circulated through a cell stack. The cell stack consists of a series of electrochemical cells where oxidation and
  reduction reactions take place. During charging, oxidation occurs in the cell stack, causing the vanadium in the electrolyte to be oxidized. During discharge, the vanadium is reduced. This cycle allows the battery to store and release electrical energy as needed.
• Zinc-Air (ZnO₂) – The zinc-air flow batteries use zinc metal as the anode and air-breathing cathodes. The zinc metal is oxidized at the anode, releasing electrons that travel through the external circuit to the cathode. Oxygen from the air is reduced at the cathode, forming hydroxide ions. The hydroxide ions react with zinc ions in the electrolyte to form zincate ions, which are then released into the electrolyte. The zincate ions are then re-oxidized at the anode, and the cycle is repeated. This process is powered by the flow of electrons from the anode to the cathode, generating electrical energy.
• Zinc-Bromine (ZnBr) – Zinc-Bromine flow batteries are based on the redox reaction between zinc and bromide ions in an aqueous electrolyte stored in two tanks separated by a membrane. During charging, zinc is oxidized at the anode, and bromide is reduced at the cathode, forming a zinc bromide complex. During discharge, the reaction is reversed. The energy is stored in the zinc bromide complex, which can be recharged several times.

Lithium

Lithium batteries are rechargeable batteries that utilize lithium metal or compounds’ electrochemical properties to store energy. They are the most common type of rechargeable battery used in consumer electronics such as cell phones, tablets, and laptops. Lithium batteries are also used in electric vehicles, medical devices, and military applications. The electrochemistry of lithium batteries is based on the redox reaction between lithium and an electrolyte solution. In a lithium battery, lithium ions are stored in the cathode material and are released into the electrolyte solution during charging. As the lithium ions travel through the electrolyte solution, they react with the anode material to form lithium metal, releasing electrons. During discharge, the lithium ions travel back to the cathode and take electrons from the anode, creating an electric current. (There are over 20 “lithium” chemistries. These are the most widely used in stationary applications.)

Lithium Iron Phosphate (LFP) – Lithium Iron Phosphate (LFP) batteries rely on a reversible redox reaction between the active materials, lithium iron phosphate (LiFePO₄), and carbon. Upon charge, lithium ions (Li+) are inserted into the anode (negative electrode) while electrons are supplied to the cathode (positive electrode). When the battery is discharged, the lithium ions are extracted from the anode and travel through the electrolyte to the cathode. This is where the electrons are recombined to form the LiFePO₄ compound. During this process, the battery releases energy in the form of electricity.

• Lithium Nickel Manganese Cobalt Oxide (NMC) – Lithium Nickel Manganese Cobalt Oxide (LiNiMnCoO₂ or NMC) batteries are rechargeable lithium-ion batteries that have become increasingly popular recently. In these batteries, the positive electrode, or anode, is made of lithium cobalt oxide (LiCoO2). The negative electrode, or cathode, is made of a combination of nickel, manganese, and cobalt oxides (NMC). Lithium ions move from the anode to the cathode during charging, depositing onto the negative electrode. During discharging, the lithium ions move from the cathode to the anode in the opposite direction. This process of shuttling lithium ions back and forth between the anode and cathode provides power for the battery.
• Lithium Nickel Cobalt Aluminum Oxide (NCA) – Lithium Nickel Cobalt Aluminum Oxide (NCA) is a rechargeable lithium-ion battery that utilizes a specific combination of materials in its cathode, including lithium, nickel, cobalt, and aluminum oxides to store and release electrical energy. During discharge, lithium ions move from the anode to the cathode through the electrolyte, creating an electric current. Nickel and cobalt are known for their high energy densities, while aluminum helps stabilize the cathode structure. The NCA cathode chemistry offers several advantages, including increased energy density, a long life cycle, high operating voltage, quick charging, and thermal stability. NCA batteries are commonly used in electric vehicles, power tools, and portable electronics.
• Lithium Titanate (LTO) – Lithium Titanate anodes have been known since the 1980’s. The cathode can be lithium nickel manganese oxide (LMO) or nickel manganese cobalt oxide (NMC) compound, while the anode replaces the graphite with lithium titanate formed in a spinel arrangement. During charging, lithium ions move from the anode to the cathode. During discharge, lithium ions move from the cathode to the anode. This movement of ions creates an electric current, which is used to power a device. Lithium titanate has good fast charge characteristics and performs well at low temperatures but exhibits lower energy density than other technologies and is safer than most lithium batteries. LTO is expensive when compared to other lithium batteries.