Energy aspects of vacuum bagging
Vacuum generation

In a positive-displacement vacuum pump (compression by volume reduction), a thermodynamic cycle is described, and compression can only be achieved by expending mechanical energy.

Putting things at their best and assuming that compression is isothermal, the power P required to compress, from suction pressure p_a to discharge pressure p_r a gas flow of volume flow S is given by the formula :$P=p_{\text{a}}S\text{ln}\frac{p_{\text{r}}}{p_{\text{a}}}$

Clearly, in this formula, where p_r is constant, compression power decreases...