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High unmet cooling hours - OfL Alt systems #24

Open Justin-DeBlois opened 5 months ago

Justin-DeBlois commented 5 months ago

When running the 2023 vintage of the OfL prototype there are 5000+ unmet cooling hours which can be traced back to the spaces served by alt_ systems. I haven't tested other vintages yet. Attached the results summary. results-summary.csv

amine-lazrak commented 4 months ago

The number of unmet hours reported may sometimes not be as alarming as it sounds because EnergyPlus will flag any unmet load from any zone. The impact on energy consumption may be negligible even when the simulations have a significant number of unmet hours. However, 5000+ unmet hours definitely need addressing.

Upon reviewing the Time Setpoint Not Met report table (for OfL-CZ16-2023), it appears that the majority of unmet hours originate from the first-floor zones, specifically MECHELECROOM EL1 CORE SPC (G.C5). Since this is a core zone with zero air infiltration, its cooling loads on the chosen design day are minimal. Hence, EnergyPlus outputs the warning message Calculated design cooling load for zone=MECHELECROOM EL1 CORE SPC (G.C5) is zero. I've made some adjustments to the root file for OfL so that the cooling design day factors in maximum internal loads (lighting, equipment, and occupancy). As a result, the total number of unmet hours has dropped to less than 300 for 8 climates and to less than 1300 overall. The total energy consumption was slightly impacted, with a 0-2% increase/decrease, while cooling and heating were affected by an average of 2-5%. I've already pushed these changes to the fix-UA-issue branch.

The UA value for a couple of coils seems to be off, but this time, EnergyPlus defaults them to probably a more reasonable value rather than 1 W/K. It's definitely something to keep an eye on! Most of the issues we have encountered so far seem to originate from the same issues related to coil sizing and loads at design days. We will continue to search for better solutions. Any recommendations and suggestions are very welcome.

Justin-DeBlois commented 4 months ago

Looks good to me. I have a fix in mind for the UA issue with system-level HW coils. I'm planning on including it in the TRC System Types branch because it overlaps with our system types.

simularis commented 1 month ago

Would it be helpful to attach here some detailed reports of unmet hours by zone for the current version?

We note that the fix-UA-issue branch was not merged.

Justin-DeBlois commented 1 month ago

I think the first commit from that branch is the relevant one, the other two may not be necessary.

Also, are there other root files and schedules with the same issue?