Opened 5 years ago

Last modified 4 years ago

#891 new feature

Ventilation Cooling Model in EnergyPlus

Reported by: shorowit Owned by:
Priority: low Component: Modeling - New Options
Version: Keywords:
Cc: cchriste, ewilson, jwinkler

Description (last modified by shorowit)

From Alea at DEG:

As promised, attached is the nighttime ventilation cooling model in EnergyPlus that we’ve built onto a BEopt generated input file. I recognize you have a lot on your plate and you may not get to looking over this for a while. When you do, I’d be happy to have a call to discuss. Thanks in advance for your time, it would be really exciting to see this technology included in BEopt!

There are two system types that are modeled distinctly and I’ve provided you with idf code for each of these along with example files. The modeling methodology largely follows what has been developed for the 2013 Title-24 California Simulation Engine (CSE); also attached are two document which describes this. The meat of the code is within the EMS group and leverages the Infiltration & DuctLeakage programs that you’ve built. In overview, the system types and general operation are as follows:

  1. Operation:
  1. Ventilation cooling is allowed during the cooling season when there is a temperature difference between indoors and outdoors of 5F, indoor temperatures are above 68F, and outdoor daily average temperatures is greater than 66F.
  1. Systems Types:
  1. Whole House Fan: Per the CSE the fan is sized to 2*CFA (cfm) and is allowed to operate 6am-11pm when conditions allow. Fan airflow is de-rated by 75% to account for non-optimal operation. Exhaust air is rejected to the attic space.
  1. Central Integrated Variable Speed Fan System (i.e. Nightbreeze): A central fan with variable speed capability which is allowed to operate whenever conditions are met. Daily operating airflow rate is determined based on the day’s average outdoor air temperature. Exhaust air is rejected to the attic space.

For complete integration into BEopt there are a few things that have yet to be determined

  • Whole House Fan operation: Users should be able to define fan capacity (without any degradation), fan power, and operating schedule. I see this as most useful for a custom house or case where a particular product and strategy is evaluated. However, for production homes or more generic analyses there should be some representative pre-defined library options that reflect average operation. Perhaps one that’s similar to the CSE assumptions, another that’s morning operation only or evening operation only???
  • Swing season: In climates with swing months where both cooling & heating are allowed the ventilation cooling schedules must be altered. Either we (1) only allow vent cooling during months when heating is unavailable, or (2) lower the heating setpoint and increase the vent cooling setpoint during the swing months. In the example files I’ve included there are no such months.
  • Currently, fan heat and duct gain aren’t included in the integrated vent cool case. I apologize I haven’t gotten around to this yet, but this does need to be included. I would like to get your opinion on how best to include this. The calculations are fairly simple, but it isn’t straight forward how to directly work this into the Infiltration object. One work around would be to reduce the effective airflow according to the temperature increase. Additionally, in the WHF case fan heat should technically be included in the air exhaust to the attic, although the impact of this will be very minor and could probably be ignored.
  • I have been calculating daily average temperatures externally for individual weather files (text file also attached). I’m not aware of any easy way to integrate this in the simulation, if you are please let me know I’d love to learn! For your purposes it may be just as easy to do this with the Python scripts.

Attachments (3)

EnergyPlus Vent (426.0 KB) - added by shorowit 5 years ago.
2013_CASE_R_SEMPRA_NightVentCooling_Sept_2011.pdf (1.2 MB) - added by shorowit 5 years ago.
Update_Central Fan System Method_112013.pdf (231.1 KB) - added by shorowit 5 years ago.

Download all attachments as: .zip

Change History (7)

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