We are going to deal with few instances where energy stored in the bonds of atoms or molecules are converted to energy due to the movement of charged particles i.e., example of chemical energy to electrical energy.
- Galvanic Cell
- Fuel Cell
- Electric eel
- Coal-fired power plants
- Leclanche dry cell
- Button batteries
- Lithium-iodine battery
- Nickel-Cadmium battery
- Lead-acid battery
- Natural gas power plants
Galvanic cells are electrochemical cells that convert chemical energy in the electrolyte to electrical energy through a chemical reaction known as a redox reaction, which is an oxidation-reduction reaction. A galvanic cell contains two electrodes made of different metals kept in contact with an electrolyte.
An example for a galvanic cell is the combination of electrodes of lead and lead oxide in an electrolyte of sulphuric acid. The spontaneous redox reaction generates electricity.
Fuel cells are one of the efficient and cleanest forms of energy conversion devices that have a wide variety of applications in several sectors. A hydrogen fuel cell has the end products as water, heat, and electricity, none of which are hazardous.
In addition, there is no need to recharge a fuel cell.
The electric eel is a kind of freshwater fish that is capable of converting chemical energy into electrical energy and the electricity produced is used to shock its prey. Eels contain a battery-like array of cells that make up almost 80 percent of its body. These cells are known as electrocytes. The collective discharge from each electrocyte present in the eel releases around 860 volts.
These creatures use this property as a defense against its predators too.
Coal-fired power plants
Coal-fired power plants are the largest source of generation of electricity where coal is burned to produce electricity. Initially when the fuel (here coal) is burned, chemical energy is converted to thermal or heat energy. Apart from heat, light energy and sound energy are also produced but they get dissipated. Of all these, thermal energy is only used to generate electricity.
The thermal energy rotates the turbines; the rotating turbines possess mechanical energy and hence the thermal energy is converted to mechanical energy. These turbines turn the generators and finally electrical energy is produced.
Leclanche dry cell
Leclanche dry cell is a type of cell widely used in flashlights and other devices, where chemical energy to electrical energy conversion takes place as a result of redox reactions. The electrolyte of this cell consists of a mixture of manganese oxide solution, ammonium chloride solution, zinc chloride, graphite and starch.
Calculators, watches and cameras contain miniature batteries known as button batteries. In these, the anode is a zinc-mercury amalgam, the cathode is either mercury oxide or silver oxide. The main disadvantage is the disposal of the battery since it contains mercury or silver as well as the expense.
As the name suggests, the main elements of this battery are lithium and iodine. Lithium metal acts as the anode, a solid complex of iodine acts as the cathode and lithium iodide is the electrolyte. The redox reactions convert chemical energy to electrical energy.
Since this kind of battery has proven to be long-lived, it finds application in cardiac pacemakers or other medical implants since frequent replacement of batteries are impossible in these equipments.
Small electrical appliances like portable vacuum cleaners contain nickel-cadmium battery, which is another type of battery that converts chemical energy to electrical energy. It consists of cadmium anode and highly oxidized nickel as the cathode.
Since cadmium is highly toxic to the environment, significant disposal problems arise due to its use.
The lead acid battery is also known as lead storage battery. Its anode comprises of spongy lead metal, the cathode is made of powdered lead dioxide. An aqueous solution of sulphuric acid acts as the electrolyte in this battery. The oxidation-reduction reaction transforms chemical energy to electrical energy.
This battery is widely used in automobiles and it can be discharged and recharged a large number of times.
Natural Gas Power Plants
The energy conversion in a natural gas power plant is not direct. There is a sequence of steps to transform chemical energy of natural gas to electrical energy. Initially the combustion of fuel (here, natural gas) transforms the chemical energy to thermal energy and light energy. Then, the thermal energy rotates the turbines (similar to the process in coal-fired power plant) and hence is converted to mechanical energy. The turbines turn the generators and finally, electrical energy is produced.
The major disadvantage of these power plants is their hazardous emissions.
It is a point worth to be noted that all the energy conversion mechanisms in the universe (in general) follow the law of conservation of energy.