Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
The output processor currently averages or sums time all series data without qualification. There are some variables where any aggregation beyond a single timestep is not meaningful. COP is a particularly tricky one, because even an average COP during on times is not exactly what most users want to see. For this particular output variable, this is discussed in the Input Output Reference:
Chiller COP [W/W] This output is the coefficient of performance for the chiller during cooling operation. It is calculated as the evaporator heat transfer rate (Chiller Evaporator Cooling Rate) divided by the “fuel” consumption rate by the chiller. For the constant COP and electric chillers, the “fuel” is electricity so the divisor is Chiller Electric Power [W]. For the absorption chiller, the “fuel” is steam so the divisor is Steam Consumption Rate [W]. Note that this variable is reported as zero when the chiller is not operating. When reported for frequencies longer than "detailed" (such as timestep, hourly, daily, monthly or environment), this output will only be meaningful when the chiller is operating for the entire reporting period. To determine an average COP for a longer time period, compute the COP based on total evaporator heat transfer divided by total electric or fuel input over the desired period.
Output:Table:Monthly (and soon Output:Table:Annual in v8.4) offer additional aggregation rules for custom output reports.
| | 2 | No.2 Revision |
The output processor currently averages or sums all time all series data without qualification. There are some variables where any aggregation beyond a single timestep is not meaningful. COP is a particularly tricky one, because even an average COP during on times is not exactly what most users want to see. For this particular output variable, this is discussed in the Input Output Reference:
Chiller COP [W/W] This output is the coefficient of performance for the chiller during cooling operation. It is calculated as the evaporator heat transfer rate (Chiller Evaporator Cooling Rate) divided by the “fuel” consumption rate by the chiller. For the constant COP and electric chillers, the “fuel” is electricity so the divisor is Chiller Electric Power [W]. For the absorption chiller, the “fuel” is steam so the divisor is Steam Consumption Rate [W]. Note that this variable is reported as zero when the chiller is not operating. When reported for frequencies longer than "detailed" (such as timestep, hourly, daily, monthly or environment), this output will only be meaningful when the chiller is operating for the entire reporting period. To determine an average COP for a longer time period, compute the COP based on total evaporator heat transfer divided by total electric or fuel input over the desired period.
Output:Table:Monthly (and soon Output:Table:Annual in v8.4) offer additional aggregation rules for custom output reports.
