Battery and Fuel cells

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In this article at OpenGenus, we have explored the concept of Battery and Fuel cells including different types of batteries, performance requirements, hydrogen-oxygen fuel cells and much more.

Table of contents

  • Battery
  • Types of batteries
  • Primary batteries
  • Secondary storage or accumulator batteries
  • Performance Requirements of a battery for commercial requirements
  • Fuel Cells
  • Characteristics of Fuel Cells
  • Requirements for successful functioning of a fuel cells
  • Hydrogen-oxygen Fuel Cell
  • Molten Carbonate Fuel Cell
  • Solid Oxide Fuel Cell

Battery

  • Device that stores energy
  • That energy is converted from chemical energy to electrical energy
  • Portable source of electrical energy

Types of batteries

  • Primary batteries
  • Secondary storage or accumulator batteries

Primary batteries

  • Disposable batteries as cannot be recharged
  • Source of dc power
  • Convenient to use
  • Cost efficient

Secondary storage or accumulator batteries

  • Can be recharged after partial or complete discharge
  • Source of dc power
  • Supply to large, short-term(or small, long-term) power requirements as in automobiles and airplane batteries
  • Capacitance is large which is beneficial to circuits as in telephone exchanges

Performance Requirements of a battery for commercial requirements

  • Long shelf life
  • Reliability
  • High energy efficiency
  • Tolerance to different environmental conditions such as variation in temperature, vibration, shock, etc.
  • High capacity

Fuel Cells

  • Similar to other electrochemical cells
  • Only difference is that chemical energy is provided by fuel and oxidant is stored outside the cell
  • Capable of supplying current as long as the reactants are supplied
  • Primary cell

Characteristics of Fuel Cells

  • Noise levels are low
  • High efficiency
  • Free from vibration , heat transfer and thermal pollution
  • Modular and hence can be built in a wide range of power requirements
  • Emission levels are far below the permissible limits

Requirements for successful functioning of a fuel cells

  • Fuel and oxidants must be cheap and readily available
  • To promote high rate of electrode processes, high temperature and suitable catalyst is required
  • Fairly concentrated aqueous solutions of the electrolytes should be used to have good conductivity and minimize the effect of concentration polarization
  • Suitable fuel design so that there is a stable interface between solid electrode, liquid electrolyte and gaseous fuel which promotes high rate of electrode processes

Hydrogen-oxygen Fuel Cell

  • Consists of two inert porous electrodes(made of either graphite saturated with finely divided Platinum or a 75/25 alloy of Pd with Ag or Ni) and an electrolyte solution of 25% KOH solution.

  • Hydrogen gas is bubbled through anode

  • Oxygen gas is bubbled through cathode

  • Following are the reactions:

  • At anode:

  • At cathode:

  • Net:

  • The product discharged by the cell is water

  • Standard emf of cell is found to be 1.23V(Eox+Ered=0.83V+0.40V)

  • In actual practice, emfof cell is 0.8 to 1.0V.

  • A number of fuel cells are stackedtogether in series to make a Fuel cell battery or fuel battery.

Uses of Hydrogen-oxygen Fuel Cell

  • Auxiliary energy source in spce vehicles
  • Product water is a valuable source of fresh water for astronauts
  • Preferred for space craft due to their lightness

Molten Carbonate Fuel Cell

Advantages

  • Higher efficiency
  • No noble metal catalyst
  • No negative effects from CO or CO2(High temperature increases O2 kinetics)
  • Internal reforming(H2 OR CH4)

Disadvantages

  • Material is resistant to degradation at high temperature.

Solid Oxide Fuel Cell

Advantages

  • Internal reforming
  • Solid electrolyte eliminates leaks
  • CO and CO2 are not problematic
  • H2O management, catalyst flooding, slow O2 kinetic are not problematic

Problems

  • Material constraints due to high temperature

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