ENERGY MANAGEMENT
IN A CHILLED WATER PLANT
USING THERMAL STORAGE
The Tenth International Conference
on Thermal Energy Storage
ECOSTOCK 2006
Stephane Bilodeau, PE, Ph.D.
[email protected]
Scope
• Overview of the project
– Storage Approach
– Operating Schematic
– Implementation
• Results
– Monitoring Results
– Economical Results
• Conclusion
TES Project in IBM Bromont
TES Project in IBM Bromont
• Chilled Water Production Optimisation using Thermal
Energy Storage
• Dismantling 2 Old Chillers (1000 tons each)
– Over a total of (7000 tons) of installed capacity in the Plant
• Using Thermal Storage to reduce Peak Load as well as
improving plant efficiency
– Integrated in a closed loop using water-glycol solution as a
thermofluid (250 l/s or 4000 usgpm)
• Improved control strategy
– To secure the chilled water supply to the plant
– To simplify operation
TES to Improve the Performance
of the Facility
Novanergy works to
maximise efficiencies
17 000.0
16 500.0
16 000.0
Fluctuations In Energy Consumption
Novanergy works
to reduce this...
2950.0
2450.0
15 500.0
15 000.0
1950.0
Série1
Série2
14 500.0
14 000.0
1450.0
13 500.0
13 000.0
950.0
12 500.0
12 000.0
450.0
2004-06-02 2004-06-03 2004-06-04 2004-06-05 2004-06-06 2004-06-07 2004-06-08 2004-06-09 2004-06-10 2004-06-11
00:00
00:00
00:00
00:00
00:00
00:00
00:00
00:00
00:00
00:00
Storage approach
• The Preferred Storage Approach
• Partial storage
–
–
In the partial-storage approach, the mechanical equipment runs to meet part of the peak
period cooling load, and the remainder is met by drawing from storage. The equipment is
sized at a smaller capacity than the design load. Partial storage systems may be run as loadleveling or demand-limiting operations.
In a load-leveling system, the equipment is sized to run at its full capacity for 24 hours on
the severe days. The strategy is most effective where the peak cooling load is much higher
than the average load.
• Partial-storage load-leveling operating strategy
–
In a load-leveling system the equipment runs at its full capacity for 24 hours on the design
day. When the load is less than the equipment output, the surplus energy is stored. When
the load exceeds the capacity, the additional requirement is discharged from storage. A
load-leveling approach minimizes the required equipment and storage capacities as well as
GHG emissions for a given load.
Operating Schematic
MCP2
NV1
Ech2
Po (VFD)
MCP1
Discharge
Vref
Discharge
Charge &
Plant
Vech2
1
2
4
3
Cooling
Tower
Operating Schematic
1
MCP2
2
NV1
Ech2
MCP1
Discharge
Plant Load
Vref
Discharge
Charge &
Chilled
Water
Vech2
3
4
Po (EFV)
Energy Efficiency
• The recharge is driving the energy efficiency of the process:
– NV1: High Efficiency Compressor Operation
• Charge the cold storage tank at low outside temperature
• Reducing part load improves kW/ton
– Free cooling: night free cooling may be moved to follow day loads
• NFC: by charging the system directly with a cooling tower at night – during mid
•
season –
QFC: by precooling the cold side to improve overall efficiency [Quasi-Free
Cooling approach]
– Energy recycling: exploiting plant energy rejection
• DER: Direct recovery of rejected energy (condenser side)
• IER: Using the differential between the Part load and the nominal operating
condition of heating or cooling equipments to recharge at high efficiency
eliminating part load operation (reducing energy consumption and equipment
wear)
Implementation
Operation
2 Storage Tanks
•PCM with 30 F and 40 F melting point
•Useful capacity respectively of
•2226 tons-h
•and 1995 tons-h
LOG(p),h-DIAGRAM
QSGHX : 0 [kW]
5
2
4
T2 : 39.7 [°C]
3
T4 : 26.5 [°C]
QC : 4348 [kW]
T5 : 26.5 [°C]
TC : 28.5 [°C]
T3 : 39.7 [°C]
Thermodynamic cycle
with TES
W : 597.7 [kW]
m : 23.14 [kg/s]
QE : 3780 [kW]
6
TE : -1.5 [°C]
7
X6 : 0.19 [kg/kg]
T7 : 2.0 [°C]
8
1
T8 : 3.0 [°C]
T1 : 3.0 [°C]
REFRIGERANT : R134a
COP : 6.324
COP* : 6.364
η CARNOT : 0.703
Monitoring Results
• Peak Shaving (kW)
– Reduction of Peak loads
• Up to 1 250 kW
• Compressor’s efficiency improvement
– Average kW/tons improvement from 0.9 to 0.5 kW/tons
• « Free cooling » during mid season
Solar Rad.
Global
Temperature (C)
Nbr Hrs
Nbr Hrs
Dry
Bulb
Wet
Bulb
Amplitu
de
Std
Tmp
Wet
Bulb
Twb<10C
(50F)
Twb>18C
(64F)
Jan
5,66
-10,9
-11,5
12,8
2,7
11,3
741,0
0,3
Feb
8,9
-10,7
-11,5
14,0
2,3
11,3
671,4
0,7
Mar
12,72
-3,3
-4,8
12,2
2,3
23,4
732,1
2,2
Apr
16,16
3,6
1,0
12,0
1,6
33,8
698,1
13,4
May
18,4
11,1
7,6
14,0
1,7
45,7
506,7
102,2
Jun
19,76
16,2
13,1
14,2
1,0
55,6
108,5
220,3
Jul
19,93
18,3
15,4
13,6
1,1
59,7
37,9
289,6
Aug
17,04
16,8
14,4
13,4
1,1
57,9
67,9
257,7
Sep
12,7
12,2
10,1
13,7
1,3
50,2
352,6
142,7
Oct
8,79
6,6
4,7
12,1
1,7
40,5
632,9
39,4
Nov
4,84
0,1
-1,0
9,2
1,8
30,2
705,0
0,9
Dec
4,25
-8,1
-8,7
10,5
2,6
16,3
737,9
0,1
12,6
1,8
5992,0
1069,4
Global
Monitoring Results
• Reduction in energy consumption (kWh)
– Reduction of part loads
• Performance increase by more than 15%
– Reduction of winter consumption
• Improvement of winter free cooling by extending from September to May
with a « Quasi Free Cooling » with storage at nignt : + 3000 hrs
• Allowing for Higher return temperature from the Free cooling Exchanger
– Reduction in condensing temperature
• Recharge at night/lower outside temperatures (with average daily
amplitude, it represents an improvement of 15 % to 21% in kW/tons);
• Condensing temperature optimization is a net thermodynamic improvement
of more than 10% over the year.
Monitoring Results
General results
Energy production and storage for the chilled
water loop
Before (2004)
After (2005-2006)
Chiller water Production
18 728 tons-h/day
37 537 tons-h/day
Daily Consumption
16 706 kWh/day
15 572 kWh/day
Average Instaneous Consumption
696 kW
648,8 kW
Average Production (MCP + VFD
Chiller)
--
1564,1 tons
Average Production (before)
780,3 tons
--
Free Cooling
750 tons (for 90% of time)
945 tons (average)
Total Chilled Water Production
1455 tons
2509 tons
Efficiency
0,892 kW/tons
0,415 kW/tons
Efficiency (including Free Cooling)
0,478 kW/tons
0,259 kW/tons
Energy Management
– Novanergy – MCP1+MCP2 :
• Improvement in operating conditions for all the
•
– 5 300 MWh per year
– 45 % in GHG Emissions for Ch.Water
2400
700000
2100
600000
1800
500000
1500
400000
1200
300000
900
200000
600
100000
300
Energy consumption for Chilled Water
1500000
1000000
kWh
800000
Free Cooling
(number of hrs)
500000
0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Month
Free Cooling Hrs
Mois
Ju
ly
Au
gu
Se
st
pt
em
be
r
O
ct
ob
er
No
ve
m
be
De
r
ce
m
be
r
0
Reduction in consumption
Ja
nu
a
Fe ry
br
ua
ry
M
ar
ch
Ap
ril
M
ay
Ju
ne
Consumption (kWh)
Reduction in energy consumption
0
chillers in the plant
Reduction of 6 % in the overall electrical energy
consumption of the Plant
Economic Analysis
• Comparison with standard design (Common Chillers) show an important
improvement in the Return on Investment with the Novanergy system.
–
–
–
–
–
Interest Rate: 4%; Present Worth Factor: 3%
Marginal energy cost: 0,0253 $/kWh
No Cost reduction considered (due to the elimination of a 1000 tons chiller)
The dollar value of the kWh savings was $134,400.
Additional savings from peak load shaving (kW) was $162,400 for a grand total
of $296,800.
– The net present value NPV =
$3.9 M.
• Payback with 400 k$ in grants : 3,7 years
– The “Life Cycle Cost Analysis” do not consider the impact of maintenance cost
reductions as well as the future price fluctuations of the energy sources which
would seriously improve the numbers.
Conclusion
• TES Implementation Results in:
–
–
–
Reduction of the Peak Load
Reduction of the Energy Consumption
Simplification the operation and the maintenance
• It Follows loads from 100 tons to 2500 tons;
• It Reduces the Stop and Start to a minimum
• It Reduces unefficient part loads to the mechanical units and
corrects the original « Overdesign »
– Chilled water supply more stable and safe
• In case of power shortage or mechanical failure, two pumps are sufficient
to operate the chilled water plant
– Reduction in refrigerant needs (½ of the original design)
– Reduction in GHG emissions by 45 %