A table based combined heat and power (CHP) model. Depending on the user choice, this model can be both heat and electricity driven.
When controlled by heat demand, the CHP is controlled either by flow temperature or by return temperature. When electricity control is activated, an electricity profile needs to be connected to the model. During electricity controlled operation, heat controllers act as emergency systems.
A complete On/Off controller is implemented which takes charge of the timing of each turning on and off command. For example it can be set that between each on and off command, the CHP needs 300 seconds (set in parameter SD_delay) to be able to execute the other command. During this time a PI controller controls the temperature continuously.
Minimum possible capacity can be set to prevent the CHP working in lower capacities. If the timing does not allow a shut down at times lower capacities are required, the CHP works on minimum capacity until the shut down is permitted. This can result in the rise of water temperature higher than setpoint and may in some cases result in temperatures higher than boiling point of water.
The dimension of thermal and electrical power outputs and fuel input as well as the electricity profile should be in kW. The dimension of fuel consumption depends on the user's data.
The combustion temperature T_sorce is at the moment set to a constant value of 1748 K. The value is relevant for exergy analysis.