The generation of electrical energy from thermal energy was originally discovered by Thomas Johann Seebeck in 1822 when he first demonstrated that a thermoelectric voltage was produced after providing a temperature difference across two materials. Jean Charles Athanase Peltier then demonstrated in 1834 that the application of a current could be used to pump heat, an effect with great potential for refrigeration. It was not until the 1850s that Lord Kelvin worked out the physics of the Seebeck and Peltier effects attributing the reversible heat flow discovered by Peltier must have an entropy associated with it and the Seebeck coefficient was a measure of the entropy associated with the electric current. Further developments in the theoretical understanding of thermoelectrics required quantummechanics. The efficiency of the thermoelectric generation process was derived in 1911 by Edmund Altenkirch.