The phrase "an external energy source" is correct and usable in written English.
You can use it when discussing energy systems, technology, or any context where energy is supplied from outside a system.
Example: "The solar panels serve as an external energy source for the building, reducing its reliance on the grid."
Alternatives: "a foreign energy supply" or "an outside energy provider".
Two approaches are provided for the supplementation strategy: adding heat to the waste mass using an external energy source to increase waste temperatures and cooling the waste mass using an external energy source to decrease waste temperatures.
The calculated flame-front velocity can also be used to describe the transient flame-front dynamics after ignition by an external energy source.
The developed method for synthesis of graphene does not require an external energy source, since it occurs in a self-sustained synergetic manner.
In operation as single-effect mode, the prototype is driven by solar energy, whereas in operation as a double effect mode, an external energy source may be used.
This paper investigates the ability of MPM, a continuum approach, to reproduce the evolution of a granular slope destabilised by an external energy source.
An industrial heat pump can upgrade heat from a low temperature level to a high temperature level with the aid of an external energy source.
This result depends on the physical characteristics of PU and the initially charged energy and has no relation with any external energy source.
If hydrogen is to be produced at scale as part of a sustainable cycle, external energy source(s) are then required.
In some systems, the syngas and oil can actually be used as a fuel to run the pyrolysis reaction, meaning it requires no external energy source beyond the organic waste itself.
In the absence of external energy source, these waves can only propagate with the strain energy that flows into the crack front.
Due to the inclusion of the electric-driven mechanical compressor, no other external energy source is needed in the SEE/MEE system.
