Transcript TDV Workshop Presentation Dec 14, 2000

Redefining Equipment
Performance Curves
Charles Eley
Randy Karels
Eley Associates
CASE Initiative Project
Copyrighted © 2000 PG&E All Rights Reserved
Overview


Non-residential standards use DOE2 or other software for wholebuilding trade-off procedures
Requires two energy simulations
• proposed design
• budget building.



The rules for creating the models and making the simulations are
tightly regulated by the ACM manual.
The default curves were developed in the late 1970s before scroll
compressors and more modern equipment unloading techniques
came on the market; some were updated with the 1993 supplement.
Propose changes to the ACM manual:
• allow users to input data for particular HVAC equipment
• update of the default curves to reflect performance of modern equipment.
CASE Initiative Project
Copyrighted © 2000 PG&E All Rights Reserved
We examined the five curves that describe unitary
performance.
wet, dry bulb
temperature
COOL-CAP-FT
cooling capacity
wet, dry bulb
temperature
COOL-EIR-FT
cooling energy
input ratio
part load ratio
COOL-EIR-PLR
energy input ratio
dry bulb
temperature
HEAT-CAP-FT
heating capacity
dry bulb
temperature
HEAT-EIR-FT
heating EIR
CASE Initiative Project
Copyrighted © 2000 PG&E All Rights Reserved
Our Initial Approach

Initially investigated the technologies for 150 different
rooftop package units from several manufacturers
• Tried to draw conclusions between the technologies and
performance.
• No statistically robust methods of predicting an actual performance
curve based on the data available.
CASE Initiative Project
Copyrighted © 2000 PG&E All Rights Reserved
Our Current Approach

Therefore, we looked at the entire data set and compared:
• The current DOE default.
• Best-fit curves.
– These curves are the most accurate representation of the data set for
each particular equation.
– Determined with least-squares regression
• P15 curves.
– Lowest performing 15% of the data set..
– In general, equipment that performed poorly did so at all
temperatures.
– Chose a set of temperatures more demanding than ARI testing
conditions and found the equipment with the worst performance. We
collected enough individual equipment performance data until we had
collected 15% of the total population. We then performed a leastsquares regression on this subset to create the P15 curves.
CASE Initiative Project
Copyrighted © 2000 PG&E All Rights Reserved
Recommended Changes to ACM


Found divergences between the current defaults and the
actual performance
Users will be given the option of inputting the performance
data of their particular equipment directly into the
compliance software and generate unique performance
curves.
• This method would best capture the details of the unit’s
performance

If the user does does not input data then the performance
curves would revert to the P15 curves.
• Because these units represent the worst performers in the
population, the user is motivated to use equipment with better
performance and input it into the model.

The reference building will use the best-fit performance
curves for each piece of equipment.
CASE Initiative Project
Copyrighted © 2000 PG&E All Rights Reserved
COOL-CAP-FT is a 3-dimensional surface dependent on
outside dry- and entering wet-bulb temperatures …
CASE Initiative Project
Copyrighted © 2000 PG&E All Rights Reserved
… but to aid discussion, we reduce it to two dimensions as
shown below.
COOL-CAP-FT Current Defaults
1.1
Normalized capacity
EWB = 72
1
EWB = 67
0.9
EWB = 62
0.8
0.7
0.6
85
CASE Initiative Project
Copyrighted © 2000 PG&E All Rights Reserved
95
105
Dry bulb temperature
115
125
As expected, P15 Curves diverge from the current defaults
and best-fit at higher temperatures.
COOL-CAP-FT Comparison of Curves
EWB = 72
1.1
EWB = 67
Normalized capacity
1
Current Default
Best Fit
EWB = 62
0.9
P15
0.8
0.7
0.6
85
95
CASE Initiative Project
Copyrighted © 2000 PG&E All Rights Reserved
105
Dry bulb temperature
115
125
COOL-EIR-FT is the normalized cooling efficiency as a
function of dry and wet bulb temperatures.
worse
worse
COOL-EIR-FT Current Defaults
1.8
1.7
1.6
Normalized EIR
1.5
EWB = 62
1.4
EWB = 67
1.3
EWB = 72
1.2
1.1
1
0.9
better
better
0.8
85
95
CASE Initiative Project
Copyrighted © 2000 PG&E All Rights Reserved
105
Dry bulb temperature
115
125
Actual equipment performance is much worse than the
current DOE2 defaults at high temperatures.
P15
COOL-EIR-FT Curve Comparisons
worse
worse
1.8
1.7
1.6
Normalized EIR
1.5
best fit
1.4
current
defaults
1.3
1.2
1.1
1
0.9
better
better
0.8
85
95
CASE Initiative Project
Copyrighted © 2000 PG&E All Rights Reserved
105
Dry bulb temperature
115
125
HEAT-CAP-FT is the normalized heating capacity as a function of
outside dry bulb temperature. There is little divergence in the data for
this curve.
HEAT-CAP-FT Curve Comparison
1.2
Normalized capacity
1
0.8
0.6
0.4
17
27
37
47
Dry bulb temperature
Current Defaults
CASE Initiative Project
Copyrighted © 2000 PG&E All Rights Reserved
Best Fit
P15
57
HEAT-EIR-FT is the normalized heating efficiency as a function of dry
bulb temperatures. The worst performers significantly higher EIRs
below 37°.
HEAT-EIR-FT Curve Comparison
1.9
1.8
worse
Normalized EIR
1.7
1.6
1.5
1.4
1.3
1.2
1.1
better
1
0.9
17
27
37
47
Dry bulb temperature
Current Defaults
CASE Initiative Project
Copyrighted © 2000 PG&E All Rights Reserved
Best Fit
Proposed Defaults
57
COOL-EIR-FPLR defines the normalized cooling efficiency
as a function of part load.


We are not recommending any changes to the current
defaults
Lack of scientific data
• Current manufacturer and scientific data was either non-existent or
unavailable for study. We attempted a proxy based on Integrated
Part Load Values (IPLV), but we did not have the defendable
research to justify our modeling assumptions.

DOE2 modeling issues.
• Losses due to the cycling of compressors is a large factor in the
overall part load performance of the equipment.
• Losses could not be quantified due to a lack of data
• Losses could not be modeled due to the non-linear discontinuities
in the performance curve that are formed when a compressor
cycles on or off.
CASE Initiative Project
Copyrighted © 2000 PG&E All Rights Reserved
Conclusions


Changes to the ACM manual and default curves are
needed to most accurately model present-day HVAC
equipment
Recommended approach is the best compromise
between usability, accuracy, and consistency
CASE Initiative Project
Copyrighted © 2000 PG&E All Rights Reserved