It seems that We could get enough power by just heat one side of An Free Piston Stirling Engine.
NASA researched .And Sunpower also.
Could it be used as cellphone(or laptop) charger.So we can use Gasoline for power.
A definite yes. But why use gasoline?, a stirling engine can use low grade heat from the sun/ burning wood. The example you show I presume was designed by NASA? ( for use in zero gravity), because the piston and the shunts are all supported by springs if you use this configuration, then you should use it vertically so the springs are only required to centralize the assembly.
Frank