What is Peltier Effect? How to produce cooling effect from current?

Peltier effect is a thermoelectric effect in which electricity converts into heat. It is completely opposite to Seebeck effect. In this effect temperature difference across the junctions is generated by applying voltage across the junctions. 

When current flows through the semiconductors heat from one electrified junction is transferred to the other electrified junction producing active refrigeration on one side and heat dissipation on other side. If heat sink is applied on the hot side, it increases the cooling on cold side.
However, despite having fast and pollution-free refrigeration this phenomenon is not used for making big refrigerators because it is highly expensive, so that only freon-12 is used for this purpose.

This phenomenon can be utilised for small cooling purposes.

Calculation for obtaining amount of heat absorbed:-
heat absorbed at hot side, Q=P*I*t
where P is Peltier Coefficient, I is current flowing through semiconductors
and t is time interval till the current flows