Obeying the second law of thermodynamics (there ain't no perpetual system), energy has to be generated physically. In meditation, as discussed in my previous post Entropy and Meditation, the power source is one's breathing energy.
As in any energy system, a source is not sufficient, it needs stations where energy is to be directed, stored, enhanced and relayed. In meditation, the energy is chi, the channels are called Chi-channels and the stations are called Meditation Points.
In chakra meditation, the first step is to build up meditation points (stations) at (roughly) the places of chakras as depicted at chakra-diagrams that can be easily accessed freely through the Internet.
The second step is to transform these meditation points into Pumps. The best metaphor of such pump is the mechanism of a Spring. Master Wang XianZai (王芗斋) put is succinctly in his famous phrase below, as one of the key requirements of a good Zhang zhuang: Everywhere inside one's body are springs. 無處不彈簧. When one exerts force to compress a spring, the original force doesn't change the spring's location, instead the energy is stored in the compressed spring ready to be used when the compressing force is released.
Through the action of controlled spring suppression and managed release, energy can be stored, enhanced and redistributed for other uses.
In internal martial art, the key pumps (or springs) are located at the joints (in particular the ball-and-socket joints) whereas in Tibetan Buddhism, the chakras serve as key pumps.