Hey group,
I wrote a message asking what variables to use for extracting hourly loads on the heating/cooling system, but haven’t heard back yet. I’ve been digging in further and am still getting some confusing results. I want to extract the hourly
(or monthly) load on the system so I can use this in another modeling program (GLHEpro), but I need to make sure these are the loads on the whole system. As I understand it:
Air System Total Heating Energy is the heat addition to the air loop for all components
Zone Predicted Sensible Load to Setpoint Heat Transfer Rate is the predicted load for the zone, not including load due to ventilation air. (negative is cooling, positive heating)
As a test of whether my results make sense, I summed the monthly load for each of these variables and took the ratio to the energy use for heating/cooling respectively (all converted to the same units). I called this ‘actual COP,’ and would
want it to roughly correspond to the nominal COP for the equipment with some variation due to performance curves. I’m doing this on the Stand-alone Retail Reference building (AC COP 3.8 and gas AFUE 0.78).
I would expect that the ‘Air System Total Energy’ variable would provide the actual load that the use of gas is inputting. But, the actual COP for this variable is way too high. The Zone Predicted.. variable seems reasonable – slightly
lower than the nominal COP, because the denominator (gas usage) includes some energy to heat up the outdoor air.
At the end of the day, all I’m looking for is the all-in heating and cooling loads for the whole building. What am I missing??
|
|
Heating:Gas (MWh) |
Zone Predicted Sensible Load to Setpoint (all zones, MWh) |
Total Heating Load (air system total energy, MWh) |
Actual COP (Zone Predicted / Gas usage) |
Actual COP (Air system / gas usage) |
|
January |
76 |
50 |
69 |
0.7 |
0.9 |
|
February |
58 |
39 |
54 |
0.7 |
0.9 |
|
March |
20 |
12 |
25 |
0.6 |
1.2 |
|
April |
7 |
4 |
14 |
0.5 |
2.0 |
|
May |
1 |
1 |
10 |
0.5 |
7.0 |
|
June |
0 |
0 |
9 |
|
|
|
July |
0 |
0 |
9 |
|
|
|
August |
0 |
0 |
9 |
|
|
|
September |
1 |
0 |
9 |
0.4 |
15.8 |
|
October |
5 |
3 |
13 |
0.5 |
2.5 |
|
November |
29 |
18 |
31 |
0.6 |
1.1 |
|
December |
58 |
39 |
55 |
0.7 |
0.9 |
NEAL HUMPHREY | Senior
Associate | 919.449.6879 | nhumphrey@xxxxxxxx
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