This step adds a controller that disables the heat pump when the supply water temperature exceeds 45°C. The simple controller has a large impact on the heat pump's COP.
The temperature sensor in the storage tank serves as an input to the hysteresis controller. The controller is configured such that it switches to a false signal below 45°C and to true above 50°C.
The output of the hysteresis controller is thus true when the
tank temperature is high enough and false otherwise. This Boolean
signal has to be converted in a real control signal that can be
accepted by the heat pump model using the
BooleanToReal block. The heat pump already has a
control signal. Since blocks cannot be removed from an extension of
a model, the heat pump model input type is set to
enable_variable_speed=true. This configuration allows the model to
accept any real signal while ignoring connections to the other
control signal.
The figure below shows the operative zone temperature
recZon.TSensor, the heat pump condenser
temperatureheaPum.con.T and the radiator heat flow
rate rad.Q_flow in the north-oriented zone with (red)
and without (blue) hysteresis control. We see that the supply
temperature is indeed reduced significantly. This causes the zone
temperature to be slightly lower, up to about 0.2°C.
However, the COP increases to around 4-5 and the electrical
energy use decreases from 28.1 kWh to 17.4 kWh.