Drive for Energy Efficiency
Roger S H Lai
23.04.2007
Why need to pay attention to
energy efficiency?
1. Try to arrest the runaway increase of
carbon dioxide. If the world does not do
anything now and let business as usual, then
by 2050, there will be so much climate
change that the situation would be
irreversible. (El Gore, IEA study: Energy
Technology Perspectives 2006 :Scenarios and
Strategies to 2050)
2. Fossil fuel is finite
Reference Scenario:
Implications for CO2 Emissions
50
Gt of CO2
40
30
Increase = 14.3 Gt (55%)
20
10
0
1980
1990
Coal
2004
2010
Oil
2015
2030
Gas
Half of the projected increase in emissions comes from new power
stations, mainly using coal & mainly located in China & India
Global Savings in EnergyRelated CO2 Emissions
42
Increased nuclear (10%)
Increased renewables (12%)
Power sector efficiency & fuel (13%)
Electricity end-use efficiency (29%)
38
Gt of CO2
Reference Scenario
Fossil-fuel end-use efficiency (36%)
34
Alternative Policy Scenario
30
26
2004
2010
2015
2020
2025
2030
Improved end-use efficiency of electricity & fossil fuels is accounts for
two-thirds of avoided emissions in 2030
Ways to save energy and
reduce emission (1)
Use a different way of energy generation rather than
fossil fuel: e.g. by 2030, contributions of reduction
from: Renewable energy (12%), nuclear (10%)
Improve the fuel to energy conversion of fossil fuel.
Improve the loss of energy transmission to end use:
Improve energy efficiency at end-use: potential of
contributing up to 65% of the projected growth
reduction
CO2 sequestration (probably not mature enough to
be significant)
Compounding losses…or savings—so
start saving at the downstream end
What other countries are
doing? (1)
Advanced countries have set ambitious
goals. One scenario studied in Germany is:
a) maintain current level of total energy
consumption while maintaining economic
growth, build no more fossil fuel power
stations;
b) phase out existing nuclear stations
c) build renewables to replace (b)
d) improve energy efficiency by 50% by
2050 to meet new energy needs
What other countries are
doing? (2)
UK: similar consideration. Carbon tax
introduced. Aim to reduce carbon
dioxide by 50% by 2050.
USA: e.g. Government buildings to save
energy of 2% per year from 2005 to
2015: that is 20% in ten years.
China: Laws for RE and for EE established
in recent years.
Are these energy efficiency
targets realistic?
With innovative approaches, and changes in
conventional installation practices, such
targets are realistic.
Cases quoted by Rocky Mountain Institute:
over 50% energy eff. improvement achieved
Case quoted by Scientific America in 9/2006
issue: factory in Germany 43% improvement.
Our studies : A simple novel project at BATCX
achieved 16% improvement
Let’s see some examples
Lighting
T5 tubes much more energy efficient
“Plug and enhance” devices now
available
Electronics ballasts incur less loss
Use of reflective luminaires
Much of the existing lighting systems
could be retrofitted
Suitable de-lamping
Fluorescent Tubes Lighting (1)
Power (lamp only)
Length
(mm)
T8
600
900
1200
1500
18W
30W
36W
58W
T5
14W
21W
28W
35W
Fluorescent Tubes Lighting (2)
Coating
Halo-phosphate (standard T8)
Tri-phosphate (standard provision for T5)
Halo-phosphate
Tri-phosphate
1200 mm T8
2850 lumen
3250 lumen
1150 mm T5
N. A.
2600* lumen
Electronics ballasts
Potential Energy Saving
Take 1200mm system as an example
Standard T8 EMB to Standard T8 EMB to Standard T8 EB to T5
T8 EB
T5 EB
EB
44W to 36W
44W to 31W
36W to 31W
Save 18%
Save 30%
Save 14%
Plug and Enhance (7)
PnE not using QEB
It use tri-phosphors T8 tube with shorter than standard length and lamp
power together with an additional EMB
11% reduction in energy consumption
Use of LED Exit Signs
Conventional Exit Sign
LED Exit Sign
 18W
 3W
 2-year service life
 5-year service life
 Estimated savings:
kWh/annum
24,800
Replacement of Incandescent Lamps
Incandescent lamps
CFLs
Incandescent lamps
CFL
40
9
Total circuital power (W)
1,672
264
Lighting level (lux)
1,300
1,600
Lamp wattage (W)
Estimated Savings
10,000 kWh/annum
A/C system (1)
Design
Water-cooled a/c system more energy
efficient than air-cooled a/c system (more
than 15%, up to 30% possible). Use of fresh
water cooling towers.
Improved piping and ductwork design,
minimize bends, use larger size pipes and
ducts.
Do not excessively oversize the pumps and
motors.
A/C systems (2)
New design and retrofit
Automatic tube cleaning device
Use of PROA to reduce scaling on the
refrigerant side of the heat exchanger
VSD for the air flow control and liquid flow
CO2 sensing and control
Operational control: water temperature reset,
air temperature reset, air duct static pressure
reset
Typical areas for big savings
Thermal integration
Power systems
Designing friction out of fluid-handling systems
Water/energy integration
Superefficient and heat-driven refrigeration
Superefficient drivesystems
Advanced controls
Let’s look at one example: pumping systems
(information from Rocky Mountain Institute
www.rmi.org)
Why focus on pumping? examples
Pumping is the world’s biggest use of motors
Motors use 3/5 of all electricity
A big motor running constantly uses its
capital cost in electricity every few weeks
RMI (1989) and EPRI (1990) found ~1/2 of
typical industrial motor-system energy could
be saved by retrofits costing <US$0.005
(1986 $) per saved kWh—a ~16-month
payback at a US$0.05/kWh tariff. Why so
cheap? Buy 7 savings, get 28 more for free!
Downstream savings are often bigger and
cheaper—so minimize flow and friction first
Then minimize piping
friction
EXAMPLE
optional
vs.
99%
1%
Boolean pipe layout
99%
hydraulic pipe layout
New design mentality
• Redesigning a
standard
(supposedly
optimized)
industrial pumping
loop cut power from
70.8 to 5.3 kW (–
92%), cost less to
build, and worked
better
 Just two changes
in design mentality
New design mentality,
an example
1. Big pipes, small pumps (not the opposite)
No new technologies,
just two design
changes
2. Lay out the pipes first, then the
equipment (not the reverse)
No new technologies, just two
design changes
Fat, short, straight pipes — not skinny, long, crooked
pipes!
Benefits counted
92% less pumping energy
Lower capital cost
“Bonus” benefit also captured
70 kW lower heat loss from pipes
Additional benefits not counted
Less space, weight, and noise
Clean layout for easy maintenance access
But needs little maintenance—more reliable
Longer equipment life
Count these and save…~98%?
This case is archetypical
Most technical systems are designed to optimize
isolated components for single benefits
Designing them instead to optimize the whole
system for multiple benefits typically yields ~3–
10x energy/ resource savings, and usually costs
less to build, yet improves performance
We need a pedagogic casebook of diverse
examples…for the nonviolent overthrow of bad
engineering (RMI’s 10XE (“Factor Ten Engineering”
project—partners welcome)
Which of these layouts has less capex & energy use?
Condenser water plant:
traditional design
return from tower
to
chiller
return from tower
to
chiller
return from tower
…or how about this?
return
from
tower
to
chiller
to
chiller
return
from
tower
• Less space, weight, friction, energy
• Fewer parts, smaller pumps and
motors, less installation labor
• Less O&M, higher uptime
Summary of improved piping
and ductwork
Reduce bends to minimize obstructions
to flow
Use larger diameter pipes and smaller
pumps/motors
Power proportional to v3
Layout the pipe and duct first before
laying out the components
Trial of the concept at BATCX
BATCX as the trial site for “big pipe small pump’concept
BATCX was commissioned in 1999
2 x 330kW sea water-cooled ammonia chiller
1/F sea water pump room pumping cooling water to 4/F
chiller plant room
BATCX – Sea Water Flow Schematic Diagram
Proposed Modification
Existing Configuration
Water
Path
No. of fittings
1
2 x 90o
2 x branches
2 x 45o
2
2 x branches
2 x 45o
3
2 x 90o
2 x branches
2 x 45o
Proposed Design
Water
Path
1
No. of fittings
2 x 90o
1 x branch
2
2 x 90o
2 x branches
3
2 x branches
Proposed Modification - 1/F Pump Room
some bends eliminated
Before
After
Proposed Modification - 4/F Chiller Plant with one section of
pipe enlarged
After
Before
Impeller Trimming (1)
The operating point is
shifted to the right after
the pipe work
modification as
frictional loss is reduced
and the flow is
increased
Impeller Trimming (2)
The impeller should be
trimmed down as to
reduce the flow back to
the point before the pipe
work modification
Impeller Trimming (3)
The distance between the
original pump curve and the
one extrapolated from the
new operating point dictates
how much the impeller
should be trimmed down
Impeller Trimming (4)
The impeller was
trimmed down from
228.6mm to 221.6mm
(7mm) in diameter
Improvement recorded
~8%
12. High Efficiency Motor
P er f o r m a n ce Cu r v e
90.0%
EFFI
of
ECMEMP
88.0%
86.0%
Efficiency
84.0%
82.0%
80.0%
78.0%
76.0%
74.0%
72.0%
50% Load
75% Load
Loading
Existing Motor
High Efficiency Motor
Full load
Power Consumption of Sea Water Pump #2 at Different Stages
4.00
3.50
Power Consumption (kW)
3.00
2.50
2.00
1.50
1.00
0.50
0.00
Before Pipe Work Modification
After Pipe Work Modification
After Impeller Trimming
After Installation of High
Efficiency Motor
Conclusion from the trial
project in BATCX
Energy saving from the modified changes in
reducing pipe bends, and enlarging one
section of the pipe gives about 8%
improvement in energy efficiency.
Use of high-efficiency motor gives another
8%
More energy reductions could be achievable if
the pipework is designed from scratch.
Water-cooled a/c system
Government conducted a study in 1999,
water-cooled a/c much more efficient
than air-cooled a/c
Launched the pilot scheme for using
fresh water cooling towers for watercooled a/c systems
Some installed systems have achieved
good results
Development
Year
2000
2001
2002
2003
2004
2005
6
11
28
45
57
71
Non-domestic Gross
Floor Areas (m2)
9M
16 M
28 M
40 M
52M
70 M
Coverage of Territorial
Non-domestic Gross
Floor Areas
12%
18%
30%
41%
53%
70%
Pilot Scheme
Designated Areas
Private Sector Participation
November 2005 figures
46 Applications from New Development
1,489,556 m2 (51% of newly constructed buildings)
107 Applications from Existing Development
3,538,083 m2 (5% of existing buildings)
Achievement (1)
Year
2000
2001
2002
2003
2004
2005
Total
No. of Application
4
4
7
37
79
53
184
No. of Applications
approved by WA in
principle
4
4
4
27
37
25
101
No. of completed
installations
0
2
3
2
15
12
34
Achievement (2)
Completed cooling capacities: 362,533 kW
Annual energy saving: 35,120,000 kWh/yr
Annual emission reduction:
CO2
24,584 tonnes/yr
NOX
63 tonnes/yr
SO2
49 tonnes/yr
Particulate
3 tonnes/yr
Benefits of Pilot Cases
1.
Lower heat rejection system energy cost for replacing aircooled dry radiators by cooling towers : 88%
2.
Lower condenser water temperature : 8oC in summer
3.
Improve chiller plant efficiency : 23%
A shopping mall
12 x 2,333kW cooling towers
(total heat rejection: 27,996kW)
Annual energy saving: 4,870,000
kWh/yr
A commercial
complex
9 x 3,336kW cooling towers
(total heat rejection: 30,024kW)
Annual energy saving: 4,650,000
kWh/yr
Benefits
Savings of three pilot cases
as compared with air-cooled
plant –
9, 520 MWh/yr
Equivalent to 9 HEC wind
turbines in Lamma Island
Automatic Tube Cleaning System
Condensing Water
Shell and Tube
Condenser
Tube Cleaners
Collector and
Injector
PLC Controller
To drain
Common Configuration of Ball Type Automatic Tube Cleaning System
Tube cleaner Trap
Tube cleaners
Injection pressure
(from pump, air compressor, or
dynamic pressure of
condensing water)
Automatic Tube Cleaning System
Ball type tube cleaner
Brush type tube cleaner
Results of using automatic
tube cleaning system
One Grade A office building in Eastern
District with a water-cooled A/C system
using cooling towers has improved the
COP of the A/C system from
0.76 to 0.8 kW/ton -> 0.72 kW/ton
EMSD is trying out this in some venues
New initiatives in Improvement of Energy
Efficiency for Air-conditioning Systems
Topics
Static Pressure Reset Controls for Variable Air
Volume Supply Systems
All Variable Speed Chilled Water Plant Controls
High Efficiency Centrifugal Compressor Systems
Air-cooled Chillers Condensing Temperature
Controls
Constant Static Pressure Controls
Conventional, Constant Static Pressure (CSP) VAV,
A/C System Design:
Maintain static pressure in main air duct at
constant pressure
Area of Concern:
Unnecessary high duct static pressure occurs in
partial load condition and results in energy
wastage
RSP VAV A/C Controls
Reducing Static Pressure (RSP) VAV A/C Controls:
 Resetting of duct static pressure set point according
to actual on-line condition of the VAV boxes within
the zone
 Reduction of duct static pressure results in
reduction of fan speed
 Accomplishment of energy saving as a result of fan
speed reduction of variable speed drives (VSD)
RSP VAV A/C Controls
Required fan pressure
reduced without
change of flow rate
Operating points with and without RSP control
Relationship Between Supply Air
Pressure and Fan Speed
Relationship between supply air pressure and fan
speed
Pressure (Pa)
Pressure (Pa)
300.00
250.00
200.00
150.00
100.00
50.00
0.00
254.33
224.00
174.22
76.85
20
25
91.74
30
128.52
35
40
Frequency (Hz)
45
50
Relationship Between Fan Power
Consumption
and Fan Speed
Relationship between fan power consumption
and fan speed
Power Consumption
(kW)
Power Consumption (kW)
12.00
10.00
8.00
6.00
4.00
2.00
0.00
10.22
8.72
6.34
2.16
20
25
3.15
4.42
30
35
40
Frequency (Hz)
45
50
Comparison of Hourly Average Static
Pressures Between RSP and CSP Modes
Average Static Pressure under RSP and CSP
Average static pressure under RSP
Average static pressure under CSP
300
Supply air pressure (Pa)
250
242
256
248
244
225
200
255
251
250
249
253
252
234
196
181
150
179
161
169
166
157
159
145
151
144
132
114
100
73
50
0
07:30
08:30
09:30
10:30
11:30
12:30
13:30
Time
14:30
15:30
16:30
17:30
18:30
19:30
Comparison on Daily Performance
with same Cooling-degree Hour
CSP mode
RSP mode
27.6
27.4
0730 – 1900hrs.
0730 – 1900hrs.
No. of Daily Coolingdegree Hours (CDH)
147.65
145.60
Total kWHr
90.86
66.65
kWhr/CDH
0.62
0.46
Averaged outdoor
temperature (deg.C)
Operating Schedule
Saving
25.8%
Preliminary Findings on Energy
Performance
CSP mode
RSP mode
No. of sampling days
25
7
Total No. of Coolingdegree Hours (CDH)
4,044
968
Total kWHr
2,225
415
kWhr/CDH
0.55
0.43
Saving
21.8%
All variable speed chilled
water plant control
Existing practice, chiller pumps are not
variable speed. Chiller motors are large, and
VSD expensive. Moreover, chiller variable
speed control are not common.
All variable speed system means that the
chiller pump is variable speed, the chiller
water supply is variable speed, the cooling
water circulation is variable speed.
With all these variables, the problem is how
to optimize the control.
Theory
1.
Natural Curve Sequencing
Methodology for determining the
best operation sequence and loading
of equipment with respect to kW/ton
Equipment is operated as close as
possible to its natural curve
2.
Equal Marginal Performance
Principle by means of Demand
Based Control
Methodology for determining the
operation speed of each piece of
equipment so that the chiller plant is
operating at its most efficient
configuration
Operation of the all-variable speed
chiller plant is optimized based on
the actual demand for cooling
Existing
CCMS
VFD
F
F
T
T
T
F
Johnson
Control
DDC
T
F
Condenser
T
F
VFD
VFD
T
F
T
F
VFD
VFD
VFD
T
F
Hartman
Loop
Optimum
Energy
Controller
Energy Saving
Existing chiller plant power consumption :
0.8 kW/TR
Estimated power consumption of chiller plant with
Variable Speed Control at 50% load and 70oF
condensing water temperature: 0.65 kW/TR
Around 20% improvement in chiller efficiency is
expected
Estimated energy saving : 500,000 kWh/year
High Efficiency Centrifugal
Compressor System
Features
Turbocor compressor system claims to be an
energy efficient technology for air-cooled and
water-cooled chillers. The system mainly
comprises:
VSD-controlled magnetic bearing compressors
Control program to control the chiller operation
including load sharing among compressors
Electronic expansion valve
Oil free operation
69
Components of the Compressor
Inverter Speed
Control
2-stage Centrifugal
Compressor
Pressure and
Temperature
Sensors
Synchronous
Brushless DC
Motor
Motor and
Bearing Control
Inlet Guide
Vanes
Variable speed nature of the high efficiency
centrifugal compressor
Operating speed ranges from 18,000
to 48,000 RPM
Inverter is built into the compressor
Low starting current of 2A
compared with 500A on a
conventional compressor
The slower the compressors speed,
the greater the efficiency
Provide best part load efficiency
Speed
Energy3
Problems associated with Oil
ASHRAE study (Research Project 361)
Typical lubricated chiller circuits show reductions in
design heat transfer efficiency of 15%-25%, as
lubricant accumulates on heat transfer surfaces,
denatures and blocks normal thermodynamic
transfer processes
72
Typical Integrated Part Load Value
(kW/ton)
 Reciprocating Compressors : 0.9 to 1.2
 Screw Compressors : 0.6 to 0.7
 Turbocor : 0.4
Suitable Application of the new high
speed chiller
Replacement of old conventional chillers
Replacement of old compressors
One example under consideration:
Existing chiller plant power consumption: 1.2kW/TR
Estimated power consumption of chiller plant with
Turbocor compressor: 0.4kW/TR
Estimated energy saving:50,000kWh/year
74
Are the targets realistic?
Conclusion: Target realistic, but we
need to be courageous enough to adopt
new technologies and overcoming
institutional hurdles.
Also new technologies will be developed
to further improve the energy efficiency
in future (say, in the next 20 years),
hence situation remains optimistic
How do we go about it? (1)
Set ourselves a vision and devoted to it.
Senior management to lead and provide
support.
In the past, we might not have a vision. We
may just be trying out and be satisfied with
some minor improvements since we do not
have a vision or target. We may also just rely
on good housekeeping
Now we should think in terms of technology,
think in longer terms, and think about
corporate responsibilities.
How do we go about it? (2)
Know the subject extensively. Have a
thorough understanding.
Be vigilant on development of new energy
efficiency technologies.
Think of how to try them out.
Be serious and meticulous about M&V,
especially in establishing the baselines before
change, and then measurement after change.
How to go about it (3)?
Verify the long term efficacy of the initiative.
Pilot scheme.If there is no contractor supplying
the equipment we want, try to consider
buying the equipment in HK and install them
ourselves.
Find legitimate ways to overcome institutional
barriers.
Institutional barriers that may
hinder changes and innovation
Traditions and established practices and
designs
Market structure and conditions may
not encourage adoption of innovative
products
Habits
We need some courage to adopt
changes
Thank you.