energy-saving designs for existing buildings
DESCRIPTION
Dan Watkins of Bornquist, Inc. in Chicago, IL presents Energy-Saving Designs for Existing Buildings focusing on pumping and boiler strategies. Presented at the February 9, 2010 Chapter Meeting & Seminar.TRANSCRIPT
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Energy-Saving Designs for Existing Buildings
Presented by:
Dan Watkins, LEED AP
Bornquist, Inc.
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Topics to Cover
• Designing for Efficiency• System Design Examples
– Variable Speed Pumping– Hot Water Boiler Systems
• Final Tips
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Designing for Efficiency
• Equipment Efficiency• System Efficiency• Payback Considerations
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Equipment Efficiency
• Equipment efficiency does play a role in increasing the overall efficiency of the system. The efficiency of some types of equipment are directly related to the system in which they are installed. Equipment efficiency can also be affected by the geographic area in which it is installed.
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System Efficiency
• System Efficiency plays the biggest role in determining the overall affect of the replacement equipment. Designs should be based on overall system efficiency and not only based on individual equipment efficiency ratings.
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Payback Considerations
• Payback is also a very big consideration, especially in retrofit projects. Sometimes the payback time period can dictate the design chosen. A good payback analysis blends initial cost with system efficiency, not just equipment efficiency.
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System Design Examples
• Variable Speed Pumping• Boiler Systems
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Variable Speed Pumping Applications
• Easy Pump Balancing• Variable Flow Systems
– Hot Water Pumps– Chilled Water Pumps– Condenser Water Pumps– Zone Pumps
• Pressure Booster Packages
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Variable Speed Pumping
• VFD turns down the speed of the pump to match demand.
• HP requirements drop significantly compared to flow rate reduction.
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GPM2 GPM1
HEAD2
RPM2
RPM1
HEAD1
HP2 HP1
=
= =
=
=
RPM2
RPM1
RPM2
RPM1
HP2 HP1
GPM2
GPM1
GPM2
GPM1
HEAD2 HEAD1
22
33
Variable Speed Pumping
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Variable Speed PumpingEasy Pump Balancing
Pump Selected at:1000 GPM @ 100’40 HP required.Duty Point: 30 HP
Oversized by 15%15’ head on TDV
X
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Variable Speed PumpingEasy Pump Balancing
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Variable Speed PumpingConstant Volume Primary - Variable Volume Secondary
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Variable Speed Pumping Example
Pump Selected at:1000 GPM @ 100’40 HP required.Duty Point: 30 HP
Constant Volume Primary - Variable Volume Secondary
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Variable Speed Pumping Example
SENSOR ACROSS COILSENSOR ACROSS COIL
Coil
10 - 15’ P.D.
Control Valve
10 - 15’ P.D.
Typical Total P.D. 20 -30’
Typical Setting Equals
Design Pressure Drop
Across the Coil, Control Valve, and
Circuit Setter.
Constant Volume Primary - Variable Volume Secondary
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Variable Speed Pumping ExamplePump Selected at:1000 GPM @ 100’
Variable Speed andSystem curves shown
20’ Control Head
725 RPM Minimum
Constant Volume Primary - Variable Volume Secondary
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Variable Speed Pumping Example
PE Motor
Constant Volume Primary - Variable Volume Secondary
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Variable Speed Pumping Example
• Savings not as great as compared to closed loop systems
• Still should utilize hydro-pneumatic tanks
• Better for pump life cycle• Does not require booster
pump PRV’s
Variable Speed Domestic Pressure Boosting
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Variable Speed Pumping Example
• Height of building – 12 stories• 150 ft. static lift• 30 PSI City pressure• 30 PSI required at the top• 50’ piping pressure drop at
design flow
Variable Speed Domestic Pressure Boosting
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Variable Speed Pumping Example
Pump Selected at:300 GPM @ 200’30 HP required.Duty Point: 25 HP
2950 RPMMinimum Speed
Variable Speed Domestic Pressure Boosting
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Variable Speed Pumping ExampleVariable Speed Domestic Pressure Boosting
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Efficient Boiler Design
• Boiler Types– What is Efficiency?– Non-Condensing – Condensing
• Maximizing Efficiency– Outdoor Reset– Short Cycle Prevention– Hybrid Systems
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Efficient Boiler Design
• Combustion Efficiency – 100 percent of efficiency minus the percentage of heat lost up the vent.
• Thermal Efficiency – The combustion efficiency minus the jacket losses of the boiler. Based on ANSI Z21.13. For boilers 300,000 to 12.5 million Btu.
• A.F.U.E. – The measure of annual efficiency of a boiler that takes into account the cyclic on\off operation and associated losses as it responds to changes in load. For boilers under 300,000 Btu
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Efficient Boiler Design
• Non-Condensing– Cast Iron– Steel Tube– Copper Fin– Modulating
• 75-88% Efficiencies
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Efficient Boiler Design
• Condensing– Cast Aluminum– Stainless Steel– Cast Iron– Dual Heat Exchanger
• 85-99% Efficiencies depending on operating conditions
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Efficient Boiler Design
120oF return water
100% input 87% efficiency Where is the
condensation?
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Efficient Boiler Design
80
82
84
86
88
90
92
94
96
2001801601401201008060
130oF Dew Point of Natural Gas
Condensingmode
Non-Condensingmode
Ste
ady
stat
e boile
r effi
cien
cy %
Boiler returnwater temp oF
98
80
82
84
86
88
90
92
94
96
2001801601401201008060
130oF Dew Point of Natural Gas
Condensingmode
Non-Condensingmode
Ste
ady
stat
e boile
r effi
cien
cy %
Boiler returnwater temp oF
9898
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Efficient Boiler DesignCondensing Boiler Design Guidelines
• Design system for lower water temperatures – Use larger delta T’s– Radiant floor heat / snow melt– Water Loop Heat Pumps
• Select boiler plant for small turndown capabilities
• Save initial cost by using both condensing and non-condensing boilers when possible
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Efficient Boiler Design
• Outdoor Reset– Designing a Reset Curve
• Cycle Efficiency– How the cycle suffers– Adjusting the differential– Buffer Tanks
• Hybrid Systems
Maximizing Efficiency
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Efficient Boiler Design – Outdoor Reset
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Efficient Boiler DesignCycle Efficiency
No
min
al
Bin
Tem
p
Gre
ater
T
han
Th
is
Tem
p
Les
s T
han
o
r E
qu
al T
o
Th
is T
emp
JUL
AU
G
SE
P
OC
T
NO
V
DE
C
JAN
FE
B
MA
R
AP
R
MA
Y
JUN
To
tal H
ou
rs
% o
f T
ota
l H
ou
rs in
T
his
Bin
Cu
mu
lati
ve
% o
f T
ota
l H
ou
rs
% o
f M
ax
Th
eore
tica
l L
oad
65 64 66 54 53 73 43 3 0 0 0 1 14 27 51 269 4.34 4.34 2.78
63 62 64 39 54 47 55 3 0 0 0 8 18 34 38 259 4.18 8.51 5.56
61 60 62 26 26 45 34 3 0 0 0 6 26 60 48 227 3.66 12.17 8.33
59 58 60 11 9 19 21 3 0 0 0 2 17 21 12 104 1.68 13.85 11.11
57 56 58 7 14 49 42 11 0 0 0 3 35 45 29 207 3.34 17.19 13.89
55 54 56 6 16 32 41 23 0 0 0 3 28 47 41 197 3.18 20.36 16.67
53 52 54 1 9 37 44 29 1 3 1 4 36 54 17 220 3.55 23.91 19.44
51 50 52 0 0 30 56 11 10 4 1 9 46 62 7 230 3.71 27.62 22.22
49 48 50 0 0 29 64 46 23 7 9 27 63 66 7 335 5.40 33.02 25.00
47 46 48 0 0 8 41 27 3 9 18 17 83 40 1 247 3.98 37.00 27.78
45 44 46 0 0 4 39 42 4 17 29 15 79 31 4 261 4.21 41.21 30.56
43 42 44 0 0 1 34 54 9 9 24 36 42 16 0 226 3.64 44.86 33.33
41 40 42 0 0 2 15 18 9 2 9 31 20 3 0 110 1.77 46.63 36.11
39 38 40 0 0 0 30 43 24 7 28 34 63 6 0 236 3.81 50.44 38.89
37 36 38 0 0 0 38 74 54 32 35 68 43 5 0 350 5.64 56.08 41.67
35 34 36 0 0 0 16 54 70 62 36 97 30 2 0 368 5.93 62.01 44.44
33 32 34 0 0 0 6 64 63 42 21 85 30 0 0 312 5.03 67.04 47.22
31 30 32 0 0 0 15 107 88 87 87 67 26 0 0 478 7.71 74.75 50.00
29 28 30 0 0 0 8 46 40 43 44 67 2 0 0 251 4.05 78.80 52.78
27 26 28 0 0 0 0 22 42 63 48 48 0 0 0 224 3.61 82.41 55.56
25 24 26 0 0 0 0 18 44 29 72 31 0 0 0 195 3.14 85.55 58.33
23 22 24 0 0 0 0 5 20 23 29 20 0 0 0 98 1.58 87.13 61.11
21 20 22 0 0 0 0 0 44 27 34 27 0 0 0 133 2.14 89.28 63.89
19 18 20 0 0 0 0 0 45 46 29 23 0 0 0 144 2.32 91.60 66.67
17 16 18 0 0 0 0 0 48 36 21 6 0 0 0 112 1.81 93.41 69.44
15 14 16 0 0 0 0 0 31 30 17 2 0 0 0 81 1.31 94.71 72.22
13 12 14 0 0 0 0 0 26 36 27 0 0 0 0 90 1.45 96.16 75.00
11 10 12 0 0 0 0 0 7 14 17 0 0 0 0 39 0.63 96.79 77.78
9 8 10 0 0 0 0 0 3 12 13 0 0 0 0 29 0.47 97.26 80.56
7 6 8 0 0 0 0 0 4 21 14 0 0 0 0 40 0.64 97.90 83.33
5 4 6 0 0 0 0 0 1 6 1 0 0 0 0 9 0.15 98.05 86.11
3 2 4 0 0 0 0 0 4 11 7 0 0 0 0 23 0.37 98.42 88.89
1 0 2 0 0 0 0 0 4 21 1 0 0 0 0 27 0.44 98.86 91.67
-1 -2 0 0 0 0 0 0 5 12 0 0 0 0 0 18 0.29 99.15 94.44
-3 -4 -2 0 0 0 0 0 4 9 0 0 0 0 0 14 0.23 99.37 97.22
-5 -6 -4 0 0 0 0 0 14 24 0 0 0 0 0 39 0.63 100.00 100.00
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Efficient Boiler DesignCycle Efficiency
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
Ener
gy U
se P
er U
nit o
f Loa
d (e
.g.,
HD
Ds)
Ener
gy U
se (T
herm
s, D
ecaT
herm
s, e
tc.)
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Efficient Boiler DesignCycle Efficiency
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
New
Ene
rgy
Use
Per
Uni
t of L
oad
(e.g
., H
DD
s)
Old
Ene
rgy
Use
Per
Uni
t of L
oad
(e.g
., H
DD
s)
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Efficient Boiler DesignCycle Efficiency
New
Ene
rgy
Use
Per
Uni
t of L
oad
(e.g
., H
DD
s)
Old
Ene
rgy
Use
Per
Uni
t of L
oad
(e.g
., H
DD
s)
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
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Efficient Boiler DesignCycle Efficiency
New
Ene
rgy
Use
Per
Uni
t of L
oad
(e.g
., H
DD
s)
Old
Ene
rgy
Use
Per
Uni
t of L
oad
(e.g
., H
DD
s)
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
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Efficient Boiler DesignCycle Efficiency
Ener
gy U
se P
er U
nit o
f Loa
d (e
.g.,
HD
Ds)
Ener
gy U
se (T
herm
s, D
ecaT
herm
s, e
tc.)
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
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Efficient Boiler DesignCycle Efficiency
Total HDD x Best Therms/HDD = What’s Possible
Total Therms – What’s Possible = What Was Wasted
The E/L Curve Fast Calculation…
Billing Period Therms HDDs Therms/HDD
December
January
February
March
etc
Total Therms Total HDD
Best ?
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Efficient Boiler DesignCycle Efficiency
Se
aso
n
Mo
nth
Th
erm
s N
ow
He
atin
g D
egre
e
Da
ys (
HD
D)
Th
erm
s /
HD
D
HD
D a
s %
of
Pe
ak M
on
th
Th
erm
s /
HD
D
Th
erm
s F
utu
re
Th
erm
s /
HD
D
Th
erm
s F
utu
re
OCT 12,614.86 399 31.62 28.30 13.71 5,469.29 12.20 4,867.67
NOV 38,831.88 940 41.31 66.67 32.29 30,355.75 28.74 27,016.62
DEC 63,143.90 1148 55.00 81.42 39.44 45,276.10 37.07 42,559.54
JAN 68,300.44 1410 48.44 100.00 48.44 68,300.44 45.53 64,202.41
FEB 52,692.62 1003 52.54 71.13 34.46 34,561.07 32.39 32,487.40
MAR 41,710.14 832 50.13 59.01 28.58 23,781.10 25.44 21,165.18
APR 25,161.45 587 42.86 41.63 20.17 11,837.54 17.95 10,535.41
302,455.29 219,581.29 202,834.23
82,874.00 99,621.06
27.4 32.9
83.2 16.8Percent of savings due to each measure
Winter '96 - '97
TOTAL FUEL USE (THERMS)
HISTORICAL DATA
Measure #1: IMPROVE LOAD
MATCHING PLUS FIX CYCLE
Measure #2: IMPLEMENT
MEASURE #1 PLUS IMPROVE BOILER
EFFICIENCY
TOTAL FUEL SAVINGS (THERMS)
Total fuel savings as percent of current fuel use
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Efficient Boiler DesignHow the Cycle Suffers
BOILER 800 MBH Output
10 GPM 10 GPM 60 GPM
20 Gallons in boiler at 170 °F. At 10 GPM and 100 MBH loadAt 800 MBH firing, boiler will hit 190 °F in about 20 seconds.
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Efficient Boiler DesignHow the Cycle Suffers
Added piping increases boiler volume…but to what extent?Adding 20 Ft. of 3” pipe adds 7.6 gallonsFiring increases from 20 seconds to 25 seconds!
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Efficient Boiler DesignHow the Cycle Suffers
Using a buffer tank to add 200 gallons will increase firing to almost 3 minutes for a 20 °F delta T. Using reset on the system loop could allow for a 50 or 60 °F delta T. Using a 60 °F delta T would mean a minimum run time of over 8 minutes!
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Efficient Boiler DesignHow the Cycle Suffers
180
140
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Efficient Boiler DesignHow the Cycle Suffers
180
140
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Efficient Boiler DesignHybrid Systems
Condensing Boiler
Non-condensing Boilers
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Efficient Boiler DesignHybrid Systems
Non-condensing Boilers
BufferTank
Condensing Boiler
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Efficient Boiler Design
• Utilize Buffer tanks and water temperature reset
• Design for long on/off cycles• Boilers do not need to be same size/style• Use small, modulating boilers as a “jockey”
boiler• Design for efficiency during light loads
General Guidelines
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Final Thoughts
• System design is typically more important than individual equipment selections.
• Energy retro-fits should be based potential savings and initial cost.
• Every building and every system is different, so there is no one-size-fits-all approach to Energy Saving Design.
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Questions?