Allow water plant to access equipment operating capacity for plant dispatch management

[rraustad]

Issue overview

The plant manager uses a design or rated capacity to dispatch equipment based on plant loads. This capacity can also use a multiplier to define a capacity higher than rated. However, if the plant load is larger than the specified maximum capacity the plant manager limits/caps the load passed to the equipment model. This can mean the equipment is meeting a load less than that possible for current operating conditions. For example, a cooling tower operating at a much lower wet-bulb temperature than design has much more capacity than at the rating point. This cooling tower appears to be undersized, but investigation shows that the load passed to the cooling tower is less than what the cooling tower can actually provide. This results in the cooling tower outlet temperature missing the set point temperature and also results in a higher return water temperature and even higher cooling tower outlet temperature on subsequent plant iterations. In some plants this can lead to runaway plant temperatures.

The plant needs a worker function to get actual maximum operating capacity during the simulation so that the plant manager can properly manage the plant load. This worker function would be added to plant equipment that can change capacity based on current operating conditions. For example a boiler has a fixed capacity and a plant heat pump capacity varies based on load/source side conditions. The boiler would continue to use a fixed capacity for plant dispatch while the heat pump would provide a current maximum operating capacity.

Issue provided by Trane North America.

Details

Some additional details for this issue (if relevant):

• Platform (Operating system, version)
• Version of EnergyPlus (if using an intermediate build, include SHA)
• Unmethours link or helpdesk ticket number

Checklist

Add to this list or remove from it as applicable. This is a simple templated set of guidelines.

• Defect file added (10803-CoolingTower-MissSetpoint.idf.txt)

• Ticket added to EnergyPlus Defect Complexity (Github Project)

• Pull request created (the pull request will have additional tasks related to reviewing changes that fix this defect)