Cost effective combined axial fan and throttling valve control of ventilation rate

The proportional-integral-plus (PIP) control of ventilation rate in mechanically ventilated agricultural buildings is investigated. In particular, a fan and throttling valve control system for a 22 m/sup 3/ test chamber that represents a section of a livestock building or glasshouse that is housed at the Katholieke Universiteit Leuven is presented. The throttling valve is used to restrict the airflow at the outlet, thereby generating a higher static pressure difference over the control fan. In contrast with previous approaches, however, the throttling valve is directly used as a second control actuator, utilising airflow from either the axial fan or natural ventilation. The proposed combined fan/valve configuration is compared with a commercially available PIDbased (proportional-integral-derivative-based) controller and a previously developed scheduled PIP design, yielding a reduction in power consumption in both cases of up to 45%.