modelThermalElectricalFollowing

Information

This model for combined heat and power device uses empirical data contained within a "performance map" to represent device-specific performance characteristics coupled with thermally massive elements to characterize the device's dynamic thermal performance. It was developed based on the specification described in Beausoleil-Morrison (2007).

Model applicability

The model is primarily intended to predict the energy performance of combustion-based cogeneration devices, such as internal combustion engine and Stirling engine units. However, the general model specification makes it applicable to any device simultaneously producing heat and power from which heat is recovered as hot water, as long as recalibration is undertaken. Fuel cell based micro-cogeneration technology is outside of the modeling scope.

The parameters required to define the governing equations can be determined from bench testing with only non intrusive measurements (e.g. fuel flow rate, cooling water flow rates and temperature, electrical production). The ability to reuse and recalibrate the component models or sub-models ensures that they are applicable to future generations of cogeneration devices.

Model topology

Three control volumes are used to model the cogeneration unit dynamic thermal characteristics.

• The energy conversion control volume represents the engine working fluid, combustion gases and engine alternator. It feeds information from the engine unit performance map into the thermal model, see Buildings.Fluid.CHPs.BaseClasses.EnergyConversion.
• The thermal mass control volume represents the aggregated thermal capacitance associated with the engine block and the majority of the heat exchanger shells, see Buildings.Fluid.CHPs.BaseClasses.EngineTemperature.
• The cooling water control volume represents the cooling water flowing through the device and the elements of the heat exchanger in immediate thermal contact.

Depending on the current mode, control signals and plant boundary conditions, the CHP unit switches between six possible operating modes: off mode, stand-by mode, pump-on mode, warm-up mode, normal operation mode, cool-down mode. The mode switch control is implemented in Buildings.Fluid.CHPs.BaseClasses.Controller.

References

Beausoleil-Morrison, Ian and Kelly, Nick, 2007. Specifications for modelling fuel cell and combustion-based residential cogeneration device within whole-building simulation programs, Section III. [Report]

Parameters

Connectors

Components

Revisions

• April 30, 2021, by Michael Wetter:
  Reformulated replaceable class to avoid access of components that are not in the constraining type.
  This is for issue #2471.
• April 8, 2020, by Antoine Gautier:
  Refactored implementation.
• February 14, 2020, by Jianjun Hu:
  Added documentation.
• June 1, 2019, by Tea Zakula:
  First implementation.