An Examination Of Lead Storage Batteries Environmental Sciences Essay

Introduction

Lead-acid batteries, invented in 1859 by Gallic physicist Gaston Plante , are the oldest type of rechargeable battery. Despite holding a really low energy-to-weight ratio and a low energy-to-volume ratio, their ability to provide high rush currents means that the cells maintain a comparatively big power-to-weight ratio. These characteristics, along with their low cost, do them attractive for usage in motor vehicles to supply the high current required by car starting motor motors. [ 1 ]

Lead-acid battery building

The power features of a lead-acid battery are improved by integrating a scattering of 1 to 10 % by weight of a thermodynamically stable conduction linear, such as conductive Sn oxide coated glass fibres of filamentary glass wool in the positive active bed carried on the grid of the positive home base. The avoiding of positive home base reversal to forestall decrease of the Sn oxide is accomplished by ( a ) using an outsize positive home base and pre-charging it ; ( B ) by pre-discharging the negative home base ; and/or ( degree Celsius ) by puting a circuit ledgeman in combination with the home bases and terminuss to take the burden when the electromotive force of the positive home base falls below a pre-selected degree. [ 1 ]

How lead storage battery plant

Inside a lead storage battery is a series of home bases. One-half of the home bases are made of lead dioxide and the other half are made of a squashy signifier of lead. The home bases are bathed in a solution of sulphuric acid which serves as an electrolyte ( a chemical solution that conducts electricity ) . Two stations extend to the exterior of the battery through sealed gaps in the battery wall. One of the stations — -the negative station — -is connected to the lead home bases, and the other — -the positive station — -to the lead dioxide plates.

Sulfuric acid, chemically, is composed of two H atoms, a sulfur atom and four O atoms. Inside the battery, the sulphuric acid molecules are in solution with H2O and so are dissociated. This means that the S atom with the four O atoms attached to it are in the H2O, separated from the H atoms. The S with the four O atoms is called a sulphate ions and has a dual negative charge. The free H atom is called a H ion and has a positive charge.

The battery performs its map through a series of chemical reactions affecting these ions. In the status described in the introductory paragraph, the battery is charged and has the capacity to provide an electric current through overseas telegrams connected to the two stations. As the battery supplies electric current, the sulphuric acid reacts by giving up its sulphate ions to the lead and lead dioxide plates. This forms lead sulphate that deposits on the home bases. [ 5 ]

Chemical reactions used in lead storage battery

The half-reactions that provide the energy to drive the motor are the same as those that take topographic point during the discharge of a lead storage battery.

Cathode: PbO2 ( s ) + 2e- + 4 H+ ( aq ) + SO42- ( aq ) — & gt ; PbSO4 ( s ) + 2 H2O ( cubic decimeter )

Anode: Pb ( s ) + SO42- ( aq ) — & gt ; PbSO4 ( s ) + 2e-

When a lead storage battery discharges, lead ( II ) sulfate signifiers on both electrodes. When the battery is recharged, the above half-reactions are reversed. However, a new lead storage battery has lead ( II ) oxide on one electrode and pure lead for the other, which is rather different from get downing with two lead electrodes as in this presentation. The half-reactions used to bring forth PbO2 in this presentation are rather different from those in a lead storage battery. Indeed, the coevals of H and O from sulphuric acid instead than take and take ( IV ) oxide from lead ( II ) sulphate is extremely unwanted in a existent battery. If a lead storage battery is overcharged, H and O can be generated. They can organize an explosive mixture in or near the battery, and that mixture can be ignited by a flicker, coffin nail, or lucifer. [ 1 ]

Features

Lead acid batteries were invented in 1859 by Gaston Plante and foremost demonstrated to the Gallic Academy of Sciences in 1860. They remain the engineering of pick for automotive SLI ( Starting, Lighting and Ignition ) applications because they are robust, tolerant to mistreat, tried and tested and because of their low cost. For higher power applications with intermittent tonss nevertheless, Lead acid batteries are by and large excessively large and heavy and they suffer from a shorter rhythm life and typical useable power down to merely 50 % Depth of Discharge ( DOD ) . Despite these defects Lead acerb batteries are still being specified for PowerNet applications ( 36 Volts 2 kWh capacity ) because of the cost, but this is likely the bound of their pertinence and NiMH and Li-Ion batteries are doing inroads into this market. For higher electromotive forces and cyclic tonss other engineerings are being explored. Lead-acid batteries are composed of a Lead-dioxide cathode, a sponge metallic Lead anode and a Sulphuric acid solution electrolyte. This heavy metal component makes them toxic and improper disposal can be risky to the environment.The cell electromotive force is 2 Volts [ 2 ]

Discharge

During discharge, the lead dioxide ( positive home base ) and lead ( negative home base ) react with the electrolyte of sulfuric acid to make lead sulfate, H2O and energy.

Charge

During bear downing, the rhythm is reversed: the lead sulfate and H2O are electro-chemically converted to take, lead oxide and sulfuric acid by an external electrical bear downing beginning. Many new competitory cell chemical sciences are being developed to run into the demands of the car industry for EV and HEV applications.Even after 140 old ages since its innovation, betterments are still being made to the lead acid battery and despite its defects and the competition from newer cell chemistries the lead acid battery still retains the king of beasts ‘s portion of the high power battery market. [ 2 ]

A

Advantages

Low cost.

Reliable. Over 140 old ages of development.

Robust. Tolerant to mistreat.

Tolerant to soaking.

Low internal electric resistance.

Can present really high currents.

Indefinite shelf life if stored without electrolyte.

Can be left on drip or float charge for drawn-out periods.

Wide scope of sizes and capacities available.Many providers universe broad.

The universe ‘s most recycled merchandise. [ 4 ]

Defects

Very heavy and bulky.

Typical coulombic charge efficiency merely 70 % but can be every bit high as 85 % to 90 % for particular designs.

Danger of overheating during bear downing

Not suited for fast charging

Typical rhythm life 300 to 500 rhythms.

Must be stored in a charged province once the electrolyte has been introduced to avoid impairment of the active chemicals.

Gasing is the production and release of bubbles of H and O in the electrolyte during the bear downing procedure, peculiarly due to inordinate charging, doing loss of electrolyte. In big battery installings this can do an explosive ambiance in the battery room. Sealed batteries are designed to retain and recombine these gases. ( See VRLA below )

Sulphation may happen if a battery is stored for drawn-out periods in a wholly dismissed province or really low province of charge, or if it is ne’er to the full charged, or if electrolyte has become abnormally low due to inordinate H2O loss from soaking and/or vaporization. Sulphation is the addition in internal opposition of the battery due to the formation of big lead sulfate crystals which are non readily reconverted back to take, lead dioxide and sulfuric acid during re-charging. In utmost instances the big crystals may do deformation and shorting of the home bases. Sometimes sulphation can be corrected by bear downing really easy ( atA low current ) at a higher than normal electromotive force.

Wholly dispatching the battery may do irreparable harm.

Sheding or loss of stuff from the home bases may happen due to inordinate charge rates or inordinate cycling. The consequence is balls of lead on the underside of the cell, and existent holes in the home bases for which there is no remedy. This is more likely to happen in SLI batteries whose home bases are composed of a Lead “ sponge ” , similar in visual aspect to a really all right froth sponge. This gives a really big surface country enabling high power handling, but if deep cycled, this sponge will rapidly be consumed and autumn to the underside of the cells.

Toxic chemicals

Very heavy and bulky

Lower temperature bound -15 A°C

[ 2 ]

Charging

Charge instantly after usage.

Stopping points longer with partial discharges.

Charging method: changeless electromotive force followed by float charge.

Fast charge non possible but charging clip can be reduced utilizing the V Taper charge control method. [ 3 ]

Application

Automotive and grip applications.

Standby/Back-up/Emergency power for electrical installings.

Submarines

UPS ( Uninterruptible Power Supplies )

Lighting

High current drain applications.

Sealed battery types available for usage in portable equipment.

Costss

Low cost

Flooded lead acid cells are one of the least expensive beginnings of battery power available.Deep rhythm cells may be up to duplicate the monetary value of the equivalent flooded cells.

Assortments of Lead Acid Batteries [ 2 ]

Lead Calcium Batteries

Lead acid batteries with electrodes modified by the add-on of Calcium supplying the undermentioned advantages:

More immune to corrosion, soaking, gassing, H2O use, and self-discharge, all of which shorten battery life.

Larger electrolyte reserve country above the home bases.

Higher Cold Cranking Amp evaluations.

Little or No care. [ 1 ]

Lead Antimony Batteries

Lead acid batteries with electrodes modified by the add-on of Antimony supplying the undermentioned advantages:

Improved mechanical strength of electrodes – of import for EV and deep discharge applications

Reduced internal heat and H2O loss.

Longer service life than Calcium batteries.

Easier to reload when wholly discharged.

Lower cost. [ 5 ]

Lead Antimony batteries

hold a higher self discharge rate of 2 % to 10 % per hebdomad compared with the 1 % to 5 % per month for Lead Calcium batteries.Valve Regulated Lead Acid ( VRLA ) Batteries

Besides called Sealed Lead Acid ( SLA ) batteries.This building is designed to forestall electrolyte loss through vaporization, spillage and gassing and this in bend prolongs the life of the battery and eases care. Alternatively of simple blowhole caps on the cells to allow gas flight, VRLA have force per unit area valves that open merely under utmost conditions. [ 4 ]

AGM Absorbed Glass Mat Battery

Used in VRLA batteries the Boron Silicate fiberglass mat which acts as the centrifuge between the electrodes and absorbs the free electrolyte moving like a sponge. Its intent is to advance recombination of the H and O given off during the bear downing procedure. No silicon oxide gel is necessary. The fiberglass flatness absorbs and immobilises the acid in the flatness but keeps it in a liquid instead than a gel signifier. In this manner the acid is more readily available to the home bases leting faster reactions between the acid and the home base stuff leting higher charge/discharge rates every bit good as deep cycling.

This building is really robust and able to defy terrible daze and quiver and the cells will non leak even if the instance is cracked.

AGM batteries are besides sometimes called “ starved electrolyte ” or “ dry ” , because the fiberglass mat is merely 95 % saturated with Sulfuric acid and there is no extra liquid.

About all AGM batteries are sealed valve regulated “ VRLA ” .

AGM ‘s have a really low self-discharge rate of from 1 % to 3 % per month [ 3 ]

Gel Cell

This is an alternate recombinant engineering to besides used in VRLA batteries to advance recombination of the gases produced during bear downing. It besides reduces the possibility of spillage of the electrolyte. Prone to damage if gassing is allowed to happen, therefore bear downing rates may be limited. They must be charged at a slower rate ( C/20 ) to forestall extra gas from damaging the cells. They can non be fast charged on a conventional automotive courser or they may be for good damaged.

Used for UPS applications. [ 2 ]

SLI Batteries ( Get downing Lighting and Ignition )

This is the typical automotive battery application. Automotive batteries are designed to be to the full charged when get downing the auto ; after get downing the vehicle, the lost charge, typically 2 % to 5 % of the charge, is replaced by the alternator and the battery remains to the full charged. These batteries are non designed to be discharged below 50 % Depth of Discharge ( DOD ) and dispatching below these degrees can damage the home bases and shorten battery life. [ 1 ]

Deep Cycle Batteries

Marine applications, golf roadsters, fork lift trucks and electric vehicles use deep rhythm batteries which are designed to be wholly discharged before reloading. Because bear downing causes inordinate heat which can falsify the home bases, thicker and stronger or solid home base grids are used for deep cycling applications. Normal automotive batteries are non designed for repeated deep cycling and usage dilutant home bases with a greater surface country to accomplish high current transporting capacity.

Automotive batteries will by and large neglect after 30-150 deep rhythms if deep cycled, while they may last for 1000s of rhythms in normal get downing usage ( 2-5 % discharge ) .

If batteries designed for deep cycling are used for automotive applications they must be “ oversized ” by about 20 % to counterbalance for their lower current carrying capacity. [ 1 ]

A Uses of lead storage battery

Lead-acid batteries are genuinely the power behind mundane life.A They keep those systems we depend on-cars, boats, public transit -running as we move through the day.A However, possibly even more of import is the map these batteries play in those times when normal life is halted-such as during a blackout or brownout.A In these state of affairss, when all other power is cut, lead-acid batteries guarantee our safety by supplying necessary back-up power for everything from computing machines to hospital exigency lighting.A

In a power outage, lead industrial batteries are what back up radio and wired telephones and computing machine systems so that phones stay on no computing machine informations is lost.A They power the bulk of nomadic vehicles both on land and sea.A Lead-acid batteries start and power vehicles, back up uninterruptible operations like infirmaries, railway signals, arms systems, and air traffic controls, and assist electric public-service corporations shift tonss among grids.A On the H2O they start engines, back up critical systems in pigboats, and power navigational signals and devices in boats.A

Life without lead-acid batteries would intend everything but muscle-powered transit would stop.A There would be frequent power outages as electric public-service corporation companies could n’t manage rapid fluctuations in the demand for electricity.A Every major telephone company in the universe uses lead-acid batteries as back up power, maintaining telephone systems working during storms, power outages, and earthquakes.A They besides provide quiet, pollution-free exigency power for critical operations in installations like air traffic control towers, infirmaries, railway crossings, military installings, pigboats, and arms systems.A Lead-acid batteries maintain pollution control systems runing during blackouts and blackouts in environmentally sensitive fabricating operations until the works can be shut down.A These batteries besides back up cell phones and bipartisan wireless systems.A [ 3 ]

Types of Lead Acid Batteries

Despite the scope in battery types and applications, the features peculiarly of import in PV applications are the care demands of the battery and the ability to deep charge a battery while keeping a long life-time. To advance long rhythm life with deep discharge, deep rhythm batteries may be either of the open-flooded type with an surplus of electrolytic solution and midst home bases, or of the immobilized electrolytic type. Sealed gelled batteries may be rated as deep rhythm batteries, but they will normally defy fewer rhythms and lower discharges than the specially designed afloat home base or AGM batteries. Shallow-cycle batteries typically use dilutant home bases made from lead Ca metals and do non typically have a deepness of discharge above 25 % [ 3 ] .

Batteries for PV or remote country power supplies ( RAPS )

The stringent demands for batteries used in photovoltaic systems have prompted several makers to do batteries specifically designed for PV or other distant power systems. The batteries most normally used in stand-alone photovoltaic systems are either deep-cycle lead acid types, or shallower rhythm maintenance-free batteries. Deep-cycle batteries may be unfastened flooded batteries ( which are non maintenance-free ) or confined electrolyte AGM batteries which are maintenance-free ( but which do necessitate attention in regulator choice ) . Particular shallow-cycle maintenance-free batteries that withstand infrequent discharging may besides be used in PV applications, and provided that the battery bank is suitably designed, ne’er require a DOD of more than 25 % . A long-life battery in an suitably designed PV system with right care can last up to 15 old ages, but the usage of batteries which are non designed for long service life, or conditions in a PV system, or are portion of a hapless system design can take to a battery bank which fails after merely a few old ages.

Several other types of specific purpose batteries are available and these are described below.

Get downing, illuming ignition batteries ( SLI ) .These batteries are used in automotive applications and have high discharge and charge rates. Most frequently they use electrode home bases strengthened with either lead Sb in a afloat constellation, or lead Ca in a certain constellation. These batteries have a good life under shallow-cycle conditions, but have really hapless life-time under deep cycling. SLI batteries should non be used in a PV system since their features are non optimized for usage in a renewable energy system because life-time in a PV system is so low. [ 3 ]

Grip or motor power batteries.

Grip or motor batteries are used to supply electric power for little conveyance vehicles such as golf carts. Compared to SLI batteries, they are designed to hold a greater ability to be deep-cycled while still keeping a long life-time. Although this characteristic makes them more suitable to a PV system than one which uses SLI batteries, motor power batteries should non be used in any PV systems since their self discharge rate is really high due to the usage of lead Sb electrodes. A high ego discharge rate will efficaciously do high power losingss from the battery and do the overall PV system inefficient unless the batteries experience big DOD on a day-to-day footing. The ability of these batteries to defy deep cycling is besides far below that of a true deep-cycle battery. Therefore, these batteries are non suited to PV systems. [ 3 ]

RV or marine batteries.

These batteries are typically a via media between SLI batteries, grip batteries and true deep-cycle batteries. Although they are non recommended, both motor and marine batteries are used in some little PV systems. The life-time of such batteries will be restricted to a few old ages at best, so that the economic sciences of battery replacing mean that such batteries are typically non a long-run cost effectual option. [ 3 ]

Stationary batteries.

batteries are frequently used for exigency power or uninterruptable power supply applications. They are shallow-cycle batteries intended to stay close to to the full charged for the bulk of their life-time with lone occasional deep discharges. They may be used in PV systems if the battery bank is sized so that it ne’er falls below a DOD of between 10 % and 25 % .

Deep-cycle Batteries. Deep-cycle batteries should be able to keep a rhythm life of several thousand rhythms under high DOD ( 80 % or more ) . Wide differences in rhythm public presentation may be experienced with two types of deep rhythm batteries and therefore the rhythm life and DOD of assorted deep-cycle batteries should be compared. [ 3 ]