Transcript Getting the Most out of Energy Modeling

Making the Best Use of Energy
Modeling in Designing
High-Performance Green Buildings
July, 2007
by
Andy Lau, PE, LEED AP
Engineers Are Vital
USGBC’s Core Purpose
To transform the way buildings are
designed, built and operated, enabling an
environmentally and socially responsible,
healthy, and prosperous built environment
that improves the quality of life in
communities.
Reducing Energy Use
1.
Reduce loads
2.
Harmonize with climate
Optimize systems
Use renewable energy
3.
4.
The Heart of the Process –
Integrated Design
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Team-based
Stakeholders engaged throughout
Early goals and team alignment
Expertise engaged early & throughout
Building as organism
Reduce redundancies
Use analysis
Integrated Design Process
Whole System Integrated Process (WSIP)
Discovery
Concept Design
Schematic Design
Design
Development
Front End
(CoVO)- Continuous Value Optimization
Construction
Documents/ Delivery
Back End
Traditional Process
Concept
Design
Schematic Design Design Development
VE
VE
Construction Documents/ Delivery
VE
VE
(VE)- Value Engineering
What is an Energy Model?
A tool for …
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estimating energy
use and savings as
a guide in design,
complying with
standards,
optimizing economic
and energy
performance.
What an energy model is NOT:
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A substitute for
experience &
collaboration
A tool for load
calculations or
HVAC system sizing
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but it can account
for the effect of
building changes on
HVAC sizes
A predictor of
human behavior
Why do we need an Energy Model?
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To inform decisions
Only way to account
for synergistic
interdependencies
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Examples: Daylighting,
Heat Recovery
LEED certification
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Standardizes
measurement of
energy savings
Reduces
“gamesmanship”
Synergistic Interdependencies
Heating &
Cooling loads
Daylighting
Window selection
Electric
Lighting
Energy Use
HVAC Size
HVAC
Energy Use
NOTE:
Eliminate
Perimeter
Heating
=$
Using it effectively
Pre-Design
Design Charrette
Schematic Design
• Climatic analysis
• US EPA Target Finder analysis
• Identify strategies
• Set goals
• Develop base case
• Develop high-performance vision
• Shape, massing
• Windows & Building envelope
• Daylighting
• HVAC type
• Individual EEM’s and combos
Using it effectively
Design Development
• Fine-tune details
• Check progress, LEED points
Construction / Bidding
• “Value” engineering
• Document for LEED
Commissioning
• Calibrate model
• Troubleshoot operation
Start modeling ASAP
When just 1% of a project’s
up front costs are spent…
up to 70% of its life-cycle costs
may already be committed.
Pre-design – climatic analysis
Typical Day Comfort Chart
Williamsport, Pennsylvania
90
Hot and/or humid – avoid sun and air
80
Temperature, °F
70
January
February
March
April
May
June
July
August
September
October
November
December
Approx. Comfort Zone
Mild – manage sun, use ventilation & air movement
60
50
40
Cold & dry – allow sun and humidify
30
20
0
10
20
30
40
50
Relative Humidity, %
60
70
80
90
100
Pre-design – EPA Target Finder
Pre-design – EPA Target Finder
In Schematic Design
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“Easy” via
“wizard’s”
Define base
case
Define
proposed
Analyze EEM’s
Design Development
Fine-tune the design
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Optimization of specific components
Clearview Elementary
0.140
0.120
0.100
Lighting
Energy 0.080
Savings 0.060
($/sq.ft.)
0.040
0.020
0.000
Windows only
Skylight
Clerestory
Clearview, Windows/skylights, 3/21, 11 am, Clear Sky
140
80-100
100
60-80
80
60
40
20
0
Clearview, Windows/clerestories, 3/21, 11 am, Clear Sky
Illuminance (fc)
120-140
100-120
120
80-100
100
60-80
80
60
40
20
0
100-120
120
Illuminance
(fc)
140
120-140
40-60
20-40
0-20
40-60
20-40
0-20
Measurement & Verification
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Proposed energy model is calibrated to
actual post-occupancy operation
conditions and weather data.
Verify that building systems and EEMs
are operating as intended.
Problems can be identified and
solutions analyzed.
Model can be improved next time.
Measurement & Verification
DEP Cambria, Ebensburg, PA: LEED Silver
Electric Use Measurements
TABLE 1
Comparison of Measured Power Levels with
PowerDOE Model (prior to calibration)
Measured
(kw)
Modeled
(kw)
Difference
(%)
Pumps-ground loop
4.06
2.60
-36.0
Fans-HVAC
8.60
9.23
7.3
Heat Recovery Ventilators
13.00
5.22
-59.8
Lights
21.90
18.64
-14.9
Equipment (plug)
17.80
17.80
0.0
Item
Occupancy Comparison
DEP Ebensburg Occupancy Schedule - Weekday
1
0.9
0.8
0.7
0.6
Fraction 0.5
0.4
0.3
WD Modeled
WD Measured
0.2
0.1
0
1
2
3
4
5
6
7
8
9
10 11 12
13 14
15 16
17 18
Time of Day
19
20
21
22
23
24
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
WD Modeled
743 per-hr modeled vs. 706 per-hr reported (+5.1%)
0
0
0
0
0
0
0.1
0.8
0.5
0.7
0.7
0.6
0.6
0.6
0.6
0.3
0.2
0.1
0.1
0.1
0.1
0.1
0
0
WD Measured
0
0
0
0
0
0
0.04 0.5 0.58 0.58 0.58 0.58 0.42 0.58 0.58 0.58 0.5 0.25 0.08
0
0
0
0
0
Lighting Comparison
DEP Ebensburg Lighting Schedule - Weekdays
1
0.9
0.8
0.7
0.6
Fraction 0.5
0.4
0.3
WD Modeled
WD Measured
0.2
0.1
0
1
WD Modeled
2
3
4
5
6
7
8
9
10 11 12
13 14
15 16
17 18
Time of Day
19
20
21
22
23
24
226 kwh modeled vs. 310 kwh measured (-27%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
0.1
0.1
0.1
0.1
0.1
0.1
0.3
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.8
0.6
0.6
0.2
0.2
0.2
0.2
0.2
0.1
0.1
WD Measured 0.13 0.13 0.13 0.15 0.24 0.72 0.9
0.92 0.94 0.94 0.94 0.94 0.93 0.93 0.94 0.9 0.83 0.66 0.4 0.11 0.12 0.14 0.14 0.13
Plug Loads Comparison
DEP Ebensburg Equipment Schedules - Weekday
1
0.9
0.8
0.7
0.6
Fraction 0.5
0.4
0.3
WD Modeled
WD Measured
0.2
0.1
0
1
1
WD Modeled
0
2
2
3
3
4
4
5
5
6
6
7
8
7
9
8
10 11 12
13 14
15 16
17 18
Time of Day
19
9
10
11
12
13
14
15
16
17
18
20
19
21
20
22
21
23
24
22
23
24
138 kwh modeled vs. 292 kwh measured (-53%)
0
0
0
0
0
0.1
0.8
0.5
0.7
0.7
0.6
0.6
0.6
0.6
0.3
0.2
0.1
0.1
0.1
0.1
0.1
0
0
WD Measured 0.404 0.403 0.402 0.404 0.405 0.422 0.527 0.732 0.801 0.796 0.797 0.751 0.742 0.779 0.771 0.635 0.507 0.443 0.418 0.411 0.407 0.405 0.405 0.406
Comparison of Actual Energy Use in 2002 with
Calibrated PowerDOE Model
Model
Actual
Model/Actual
Energy
Demand
Energy1
Demand
(kwh)
(kw)
(kwh)
(kw)
Jan
33,095
82.7
35,111
Feb
29,147
83.3
Mar
32,260
Apr
May
Month
Energy
Demand
82.9
0.943
0.998
34,777
78.6
0.838
1.060
83.5
35,247
75.4
0.915
1.107
29,894
86.1
34,761
74.3
0.860
1.159
30,688
84.5
34,531
77.0
0.889
1.097
Avg
0.889
1.084
HVAC Energy use is underpredicted by about 16%
Predicted Savings
Case
Total
(kwh)
Bill
($)
Bill
($/sq.ft.)
Savings
(%)
ASHRAE Budget
624,302
64,556
1.87
Baseline
Proposed Original
253,814
26,561
0.77
-58.8
Proposed w/M&V Adj.
343,418
35,246
1.02
-45.5
Economics of Green Bldg’s
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Holistic approach needed
Uses team knowledge
 Emphasis on reducing redundancies
 Comprehensive accounting
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BIG SAVINGS
can cost less than
Small Savings
Traditional Economic Approach
(+)
STOP
Added
Cost
Diminishing
Returns
Cost Effectiveness Limit
(payback, ROI, capital budget)
Cumulative Savings
(-)
Rocky Mountain Institute
Tunneling through the
Cost Barrier
DETOUR
(+)
Diminishing
Returns
Cost Effectiveness Limit
Cumulative Savings
(-)
Rocky Mountain Institute
Reduced
Costs
Neptune Township Community School
NJ Elementary School/Community Center ● 145,600 GSF ● SSP Architectural Group
EEM’s
 solar orientation
 R27 wall w/ blown
cellulose
 R30 roof insulation
 triple pane windows
 LPD 0.92 W/sf
 solar shading
 light shelves
 daylight dimming
 ground source heat
pumps
 underfloor air
 demand controlled
ventilation
 energy recovery units
Energy Modeling Results
EEM
Lower Lighting Power
Density
Cost
Savings
Payback
-$123,887
$12,549
NA
Daylighting
Wood Triple Pane
Windows
$90,350
$16,584
5.45
$69,896
$9,117
7.67
Extra Wall Insulation
$46,302
$9,240
5.01
R30 Roof Insulation
$41,789
$5,186
8.06
40% load reduction
Energy Modeling Results
EEM
EEM Combination
Cost
$124,450
Savings
$36,912
Payback
3.37
HVAC System:
Ground Source Heat Pumps
40% load reduction = 10% cost reduction
10% cost reduction = $400,000
Holistic Effect
Cost
-$275,550
Savings
$80,166
Payback
??
Conclusions / Recommendations
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Start early
Allow adequate time for the analysis
Communicate regularly and effectively
Recognize design integration issues
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Danger of line item “Value” engineering
Use your head too!
Thank You