Open loop systems ( i . e . those that draw ground water as opposed to closed loop systems using a borehole heat exchanger ) need to be balanced by reinjecting the spent water.
12.
Assume that the element satisfies a sector condition [ \ mu _ 1, \ mu _ 2 ], and ( to keep things simple ) that the open loop system is stable.
13.
A frequency analysis is performed for a finite number of representative frequencies and a set of " templates " are obtained in the NC diagram which encloses the behaviour of the open loop system at each frequency.
