Battery Technologies for Small Scale Embedded Generation.

by Norman Jackson, South African Energy Storage Association (SAESA)Content Provider – Wikipedia et al

Small Scale Embedded Generation - SSEG• SSEG is very much a local South African term for Distributed

Generation under 10 Mega Watt.

Internationally they refer to:Distributed generation, also distributed energy, on-site generation (OSG) or district/decentralized energy

It is electrical generation and storage performed by a variety of small, grid-connected devices referred to as distributed energy resources (DER)

Types of Energy storage:• Fossil fuel storage

• Mechanical• Compressed air energy storage• Fireless locomotive• Flywheel energy storage• Gravitational potential energy• Hydraulic accumulator• Pumped-storage

hydroelectricity

• Electrical, electromagnetic• Capacitor• Supercapacitor• Superconducting magnetic

energy storage (SMES, also superconducting storage coil)

• Biological• Glycogen• Starch

• Thermal• Brick storage heater• Cryogenic energy storage• Liquid nitrogen engine• Eutectic system• Ice storage air conditioning• Molten salt storage• Phase-change material• Seasonal thermal energy

storage• Solar pond• Steam accumulator• Thermal energy

storage (general)

• Chemical• Biofuels• Hydrated salts• Hydrogen storage• Hydrogen peroxide• Power to gas• Vanadium pentoxide

• Electrochemical (Battery Energy Storage System, BESS)• Flow battery

• Rechargeable battery

• UltraBattery

History of the battery

A voltaic pile, the first battery1800

Italian physicist Alessandro Volta demonstrating his pile to French emperor Napoleon Bonaparte

This was a stack of

copper and zinc

plates, separated by

brine-soaked paper

disks, that could

produce a steady

current for a

considerable length

of time.

Although early batteries were of great value for experimental purposes, in practice their voltages fluctuated and they could not provide a large current for a sustained period. The Daniell cell, invented in 1836 by British chemist John Frederic Daniell, was the first practical source of electricity, becoming an industry standard and seeing widespread adoption as a power source for electrical telegraph networks. It consisted of a copper pot filled with a copper sulfate solution, in which was immersed an unglazed earthenware container filled with sulfuric acid and a zinc electrode.

How do chemical batteries work?• Electricity, as you probably already know, is the flow of electrons through a conductive path like a

wire. This path is called a circuit.

• Batteries have three parts, an anode (-), a cathode (+), and the electrolyte. The cathode andanode (the positive and negative sides at either end of a traditional battery) are hooked up to anelectrical circuit.

The chemical reactions in the battery causes a build up of electrons at theanode. This results in an electrical difference between the anode and thecathode. You can think of this difference as an unstable build-up of theelectrons. The electrons wants to rearrange themselves to get rid of thisdifference. But they do this in a certain way. Electrons repel each other andtry to go to a place with fewer electrons.In a battery, the only place to go is to the cathode. But, the electrolyte keepsthe electrons from going straight from the anode to the cathode within thebattery. When the circuit is closed (a wire connects the cathode and theanode) the electrons will be able to get to the cathode.

Primary cells or non-rechargeable batteries

• A primary cell is a battery (a galvanic cell) that is designed to be usedonce and discarded, and not recharged with electricity and reusedlike a secondary cell (rechargeable battery). In general,the electrochemical reaction occurring in the cell is not reversible,rendering the cell unrechargeable. As a primary cell is used, chemicalreactions in the battery use up the chemicals that generate thepower; when they are gone, the battery stops producing electricityand is useless.

A variety of standard sizes of

primary cells. From left:4.5V

multicell battery, D, C, AA, AAA,

AAAA, A23, 9V multicell

battery, (top) LR44, (bottom) CR2

032

Secondary cells or rechargeable batteries

• A rechargeable battery, storage battery, secondary cell, or accumulator is a type of electrical battery which can be charged, discharged into a load, and recharged many times, as opposed to a disposable or primary battery, which is supplied fully charged and discarded after use. It is composed of one or more electrochemical cells. The term "accumulator" is used as it accumulates and stores energy through a reversible electrochemical reaction.

Different Types of Rechargeable Batteries.Aluminium-ion batteryFlow battery

Vanadium redox batteryZinc–bromine batteryZinc–cerium batteryLithium based battery

Lead–acid batteryStarter batteryDeep cycle batteryVRLA battery

AGM batteryGel battery

Glass batteryLithium air batteryLithium-ion battery

Lithium ion lithium cobalt oxideLithium ion manganese oxide batteryLithium ion polymer batteryLithium iron phosphate batteryLithium–sulfur batteryLithium–titanate batteryThin film lithium-ion battery

Magnesium-ion battery

Molten salt batteryNickel–cadmium battery

Nickel–cadmium battery vented cell typeNickel hydrogen batteryNickel–iron batteryNickel metal hydride battery

Low self-discharge NiMH batteryNickel–zinc batteryOrganic radical batteryPolymer-based batteryPolysulfide bromide batteryPotassium-ion batteryRechargeable alkaline batteryRechargeable fuel batterySilicon air batterySilver-zinc batterySilver calcium battery Sodium-ion batterySodium–sulfur batterySuper iron batteryUltraBatteryZinc ion battery

Lead–acid battery• The lead–acid battery, invented in 1859 by French physicist Gaston Planté, is the oldest type of rechargeable

battery. Despite having a very low energy-to-weight ratio and a low energy-to-volume ratio, its ability to

supply high surge currents means that the cells have a relatively large power-to-weight ratio.This technology contains liquidelectrolyte in an unsealed container,requiring that the battery be keptupright and the area be well ventilatedto ensure safe dispersal ofthe hydrogen gas it produces duringovercharging.Its low manufacturing cost and its highsurge current levels make it commonwhere its capacity (over approximately10 Ah) is more important than weightand handling issues.

Starter vs Deep Cycle battery

A deep-cycle battery is a lead-acid battery designed to be regularly deeply discharged using most of its capacity. In contrast, starter batteries (e.g. most automotive batteries) are designed to deliver short, high-current bursts for cranking the engine, thus frequently discharging only a small part of their capacity.

VRLA battery (Sealed Lead-Acid)

The sealed valve regulated lead–acid battery (VRLAbattery) is popular as a replacement for the lead–acidwet cell. The VRLA battery uses an immobilized

sulfuric acid electrolyte, reducing the chance ofleakage and extending shelf life.VRLA batteries immobilize the electrolyte. The twotypes are:Gel batteries (or "gel cell") use a semi-solid electrolyte.Absorbed Glass Mat (AGM) batteries absorb theelectrolyte in a specialfiberglass matting.

A VRLA battery utilizes a one-way, pressure-relief valve system to achieve a “recombinant” technology. This means that the oxygen normally produced on the positive plate is absorbed by the negative plate. This suppresses the production of hydrogen at the negative plate.

Lithium-ion battery (Li-ion Battery) - LIB1980 - The electrolyte, which allows for ionic movement of ions(electrically charge particles of an atom), and the two electrodes arethe constituent components of a lithium-ion battery cell. The cathodeis typically made from a lithium material. The anode is generally madefrom carbon (graphite).

Li-ion Battery Comparison – One to anotherLithium-ion battery

TypesPower Energy Safety Lifespan Cost Performance

Lithium Cobalt Oxide

L H L L L M

Lithium Manganese Oxide

M M M L L L

Lithium Nickel Manganese Cobalt

OxideM H M M L M

Lithium Iron Phosphate

H L H H L M

Lithium Nickel Cobalt Aluminum

OxideM H L M M M

Lithium Titanate M L H H H H

Lithium Iron Phosphate – LFP (LiFePo4)1996 – LFP can be produced by heating a variety of iron and lithium salts with phosphates or phosphoric acid.

The major differences between LFP batteries and ordinary lithium batteries are that LFP batteries do not have safety concerns such as overheating and explosion, that they have 4 to 5 times longer cycle lifetimes than lithium batteries and 8 to 10 times higher discharge power.

Flow Batteries

• Concept 1930’s maindevelopment in the 1980’s

• A flow battery, orredox flow battery (afterreduction–oxidation), is atype of electrochemical cellwhere chemical energy isprovided by two chemicalcomponents dissolved inliquids contained within thesystem and separated by amembrane.

Vanadium Redox BatteryThe vanadium redox battery (VRB), also known as the vanadium flow battery (VFB) or vanadium redox flow battery (VRFB), is a type of rechargeable flow battery that employs vanadium ions in different oxidation states to store chemical potential energy. The vanadium redox battery exploits the ability of vanadium to exist in solution in different oxidation states, and uses this property to make a battery that has just one electroactive element instead of two.

The oxidation state, sometimes referred to as oxidation number, describes degree of oxidation (loss of electrons) of an atom in a chemical compound. Conceptually, the oxidation state, which may be positive, negative or zero.

How to compare different battery Technologies in a BESS ?

We will concentrate on the Following:1) Temperature.2) Capacity – SIZE3) DOD – Depth of Discharge4) Cycles – How Often.5) C Rate – Discharge or Charge Rate6) Cost –Battery & System Cost

Typical Battery Technology

Spider Chart

Temperature – Operating condition of the batteries - OCNominal battery performance is usually specified for working temperatures somewhere between 20°C and 30°C. The performance and indeed life of a battery can be seriously affected by the onset of extreme temperatures and, despite many consumer beliefs, heat is as big a cause of battery failure as is cold.

Capacity. – In BESS we measure it in kilo Watt hours (kWh)Storage systems can level out the imbalances between supply and demand. Because we are looking at the demand side when planning a BESS we measure capacity in kWh.

A battery's capacity is the amount of electric charge it can deliver at the rated voltage, and is measured in units such as (A·h).

Typically a lead Acid battery would be 105Ah at 12V which is 1,260VAh.

If we assume a system power factor of 1 that would be 1.26kWh, and if you times that by the energy efficiency of your system (to compensate for conversion losses) you would get your BESS capacity.

Depth of discharge (DOD) is normally stated as a percentage of the nominal ampere-hour capacity;0% DOD means no discharge. As the usable capacity of a battery system depends on the rate ofdischarge and the allowable voltage at the end of discharge, the depth of discharge must be qualifiedto show the way it is to be measured. Due to variations during manufacture and aging, the DOD forcomplete discharge can change over time or number of charge cycles.Vanadium Flow Batteries have a 100% DoD with no change to its Cycle life.

Depth of Discharge. – (DOD) Measured in %

If batteries are used repeatedly even without mistreatment, they lose capacity as the number ofcharge cycles increases, until they are eventually considered to have reached the end of their usefullife. Different battery systems have differing mechanisms for wearing out. For example, in lead-acidbatteries, not all the active material is restored to the plates on each charge/discharge cycle;eventually enough material is lost that the battery capacity is reduced. In lithium-ion types, especiallyon deep discharge, some reactive lithium metal can be formed on charging, which is no longeravailable to participate in the next discharge cycle. Sealed batteries may lose moisture from theirliquid electrolyte, especially if overcharged or operated at high temperature. This reduces the cycling

life.

Cycles – Lifespan or Cycle Stability – Measured in # of Cycles

C Rate - Charging and Discharging.

You need to calculate or measure what is the Maximum Load or Supply that your BESS should work on.

Once you know what is the maximum demand or charge rate is in kW’s you can calculate your C Rate.

C Rate = Capacity / Max Charge or Discharge Power

Example 1: 20kWh Usable Capacity / 10kW max Discharge is a C2 or C/2 or 0.5C – That means it is possible to discharge the battery fully over 2 hours.

Example 2: 20kWh Usable Capacity / 40kW max Charge is a C0.5 or C/0.5 or 2C – Which means that the battery can last for 30 minutes.

It is possible to have a different charge C Rate and a Discharge C Rate.

Cost – Battery and Balance of System

Cost – Battery cost US$ /kWh

According to the latest Bloomberg New Energy Finance’s forecast – New Energy Outlook 2018 – falling battery prices will significantly affect the energy market.

It’s estimated that lithium-ion battery prices decreased by 80% between 2010 and now.

DoD and Cycles have to be taken into account when comparing costs of Technologies.

Cost – Balance of System (BOS) Cost US$/ kW

Cost –Balance of System Cost US$/ kW