Changes the heatpumps behaviour to operate at minimum with lowerActivationLimit of the nominal thermal power.
The variable is currently ignored by pycity_scheduling and this would give it some effect. Fully turning the heatpump off would be not allowed here as it is in pycity_base, because this would turn the optimization problem into an integer problem.
The parameter lowerActivationLimit is descriped here in pycity_base https://github.com/RWTH-EBC/pyCity/blob/master/pycity_base/classes/supply/HeatPump.py#L42