CBECC MF: FluidSys Unmet Demand

[joesinger12]

Issue

When Load Passing was first implemented (For MF WSHP and FPFC) we identified there is an issue that we do not have a mechanism to determine whether the plant equipment can actually meet the load.

Potential Solution

Add E+ hourly output: Output:Variable,,Plant Supply Side Unmet Demand Rate,hourly; Use this output to generate a plant UMLH OR Calculate % of annual load not met And enforce on that

Reported by: joesinger12

Original Ticket: cbecc-com/tickets/3491

[joesinger12]

The E+ hourly output: Output:Variable,,Plant Supply Side Unmet Demand Rate,hourly; can't be used for case of WSHP water loop.

• The Supply Side Unmet Demand Rate is calculated based on the boiler setpoint temperature and the supply outlet temperature.
• In a WSHP water loop the boiler flow rate is usually smaller than the system flow rate, not all the water flows through the boiler in heating mode.
• Then there will always be some mixing of the heated water and the non-heated water before the supply outlet.
• So even when the boiler can heat the water to the setpoint temperature the mixed water at supply outlet will never reach the setpoint temperature.
• Then there will always some unmet demand in heating mode.

An alternative solution is required unless we can control the supply side outlet temperature and not the boiler outlet temperature. An alternative solution is to use post-process calculated values and shows not compliance when:

• sum( positive load ) > sum( boiler output ) * ( 1 + tolerance % )
• - sum( negative load) > sum( cooling tower heat transfer ) * ( 1 + tolerance % )

note: pump heat is not added into the flow so we don't need to consider the pump heat.

Original comment by: joesinger12

[joesinger12]

I've figured out the cause of the WSHP water loop not controlling the water temperature at the supply side outlet but at the boiler and cooling tower outlet. The cause of this behavior is the PlantEquipmentOperation:ComponentSetpoint is added to the PlantEquipmentOperationSchemes in EnergyPlus. We can control the supply outlet temperature by removing PlantEquipmentOperation:ComponentSetpoint from the scheme list. I've done some tests and confirmed it, see attached files. we can also remove the SetpointManagers which are added to the outlet of the boiler and the cooling tower since they are added only for PlantEquipmentOperation:ComponentSetpoint and are redundant after the scheme removal.

Once we can control the supply outlet temperature we can eliminate all the positive "Plant Supply Side Unmet Demand Rate" if the equipment can provide sufficient heating or cooling. So, "Plant Supply Side Unmet Demand Rate" can be a good option for determining UMLH.

Another option is to use the supply outlet temperature to determine UMLH, but beware that the outlet temperature can be out of bounds when there is no demand and we should not count those hours as UMLH.

Original comment by: joesinger12

[joesinger12]

5/3/2023: As per CEC coordination meeting notes o Push to future release o Interim fix: Implement checks for coil to plant sizing in 3.0

Original comment by: joesinger12

[joesinger12]

• Milestone: CBECC2022.3.0 --> CBECC2022.Next

Original comment by: joesinger12