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Drive for Energy Efficiency
Roger S H Lai23.04.2007
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
Half of the projected increase in emissions comes from new power stations, mainly using coal & mainly located in China &
India
Increase = 14.3 Gt (55%)
0
10
20
30
40
50
1980 1990 2004 2010 2015 2030
Gt o
f CO
2
Coal Oil Gas
Alternative Policy Scenario: Global Savings in Energy-
Related CO2 Emissions
Improved end-use efficiency of electricity & fossil fuels is accounts for two-thirds of avoided emissions in 2030
Alternative Policy Scenario
Reference Scenario
Increased nuclear (10%)Increased renewables (12%)Power sector efficiency & fuel (13%) Electricity end-use efficiency (29%)
Fossil-fuel end-use efficiency (36%)
26
30
34
38
42
2004 2010 2015 2020 2025 2030
Gt o
f CO
2
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 reductionCO2 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 stationsc) 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 achievedCase 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
LightingT5 tubes much more energy efficient“Plug and enhance” devices now availableElectronics ballasts incur less lossUse of reflective luminairesMuch of the existing lighting systems could be retrofittedSuitable de-lamping
Fluorescent Tubes Lighting (1)
Power (lamp only)
Length(mm)
600 900 1200 1500
T8 18W 30W 36W 58W
T5 14W 21W 28W 35W
Fluorescent Tubes Lighting (2)
CoatingHalo-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 ballastsPotential Energy Saving
Take 1200mm system as an example
Standard T8 EMB to T8
EB
Standard T8 EMB to T5
EB
Standard T8 EB to T5 EB
44W to 36WSave 18%
44W to 31WSave 30%
36W to 31WSave 14%
Plug and Enhance (7)PnE not using QEBIt use tri-phosphors T8 tube with shorter than standard length and lamp power together with an additional EMB11% reduction in energy consumption
Use of LED Exit Signs
Conventional Exit Sign
18W 2-year service life
LED Exit Sign 3W 5-year service life Estimated savings: 24,800 kWh/annum
Replacement of Incandescent LampsIncandescent lamps
CFLs
Incandescent lamps
CFL
Lamp wattage (W) 40 9
Total circuital power (W)
1,672 264
Lighting level (lux) 1,300 1,600
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 deviceUse of PROA to reduce scaling on the refrigerant side of the heat exchangerVSD for the air flow control and liquid flowCO2 sensing and controlOperational control: water temperature reset, air temperature reset, air duct static pressure reset
Typical areas for big savings
Thermal integrationPower systemsDesigning friction out of fluid-handling systemsWater/energy integrationSuperefficient and heat-driven refrigerationSuperefficient drivesystemsAdvanced controls
Let’s look at one example: pumping systems (information from Rocky Mountain Institute www.rmi.org)
Why focus on pumping? examplesPumping is the world’s biggest use of motorsMotors use 3/5 of all electricityA big motor running constantly uses its capital cost in electricity every few weeksRMI (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
99% 1%
hydraulic pipe layout
vs.
Then minimize piping friction
EXAMPLE
1%
Boolean pipe layout
optional
99%
New design mentalityNew 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
• 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)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)
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 energyLower capital cost
“Bonus” benefit also captured70 kW lower heat loss from pipes
Additional benefits not countedLess space, weight, and noiseClean layout for easy maintenance accessBut needs little maintenance—more reliableLonger equipment life
Count these and save…~98%?
Fat, short, straight pipes — not skinny, long, crooked pipes! Benefits counted
92% less pumping energyLower capital cost
“Bonus” benefit also captured70 kW lower heat loss from pipes
Additional benefits not countedLess space, weight, and noiseClean layout for easy maintenance accessBut needs little maintenance—more reliableLonger equipment life
Count these and save…~98%?
This case is archetypicalMost technical systems are designed to optimize isolated components for single benefitsDesigning 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 performanceWe 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
to chiller
to chiller
to chiller
return from tower
return from tower
return from tower
• Less space, weight, friction, energy
• Fewer parts, smaller pumps and motors, less installation labor
• Less O&M, higher uptimereturn
from tower
to chiller
return from
tower
…or how about this?
Summary of improved piping and ductwork
Reduce bends to minimize obstructions to flowUse 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 BATCXBATCX as the trial site for “big pipe small pump’conceptBATCX was commissioned in 19992 x 330kW sea water-cooled ammonia chiller1/F sea water pump room pumping cooling water to 4/F chiller plant room
BATCX – Sea Water Flow Schematic Diagram
Proposed Modification
Existing ConfigurationWate
r Path
No. of fittings
12 x 90o
2 x branches2 x 45o
22 x branches2 x 45o
32 x 90o
2 x branches2 x 45o
Proposed Design
Water
Path
No. of fittings
12 x 90o
1 x branch
22 x 90o
2 x branches
3 2 x branches
Proposed Modification - 1/F Pump Roomsome bends eliminated
Before After
Proposed Modification - 4/F Chiller Plant with one section of pipe
enlarged
Before
After
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
The impeller should be trimmed down as to reduce the flow back to the point before the pipe work modification
Impeller Trimming (2)
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 (3)
The impeller was trimmed down from 228.6mm to 221.6mm (7mm) in diameterImprovement recorded ~8%
Impeller Trimming (4)
12.High Efficiency MotorP erformance Curve
72.0%
74.0%
76.0%
78.0%
80.0%
82.0%
84.0%
86.0%
88.0%
90.0%
50% Load 75% Load Full load
Loading
Effici
ency
Existing Motor High Efficiency Motor
EFFI of ECMEMP
Power Consumption of Sea Water Pump #2 at Different Stages
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
Before Pipe Work ModificationAfter Pipe Work ModificationAfter Impeller Trimming After Installation of HighEfficiency Motor
Pow
er
Consu
mpti
on (
kW
)
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 systemGovernment conducted a study in 1999, water-cooled a/c much more efficient than air-cooled a/cLaunched the pilot scheme for using fresh water cooling towers for water-cooled a/c systemsSome installed systems have achieved good results
Development
Year 2000 2001 2002 2003 2004 2005
Pilot Scheme Designated Areas
6 11 28 45 57 71
Non-domestic Gross Floor Areas (m2)
9 M 16 M 28 M 40 M 52M 70 M
Coverage of Territorial Non-domestic Gross Floor Areas
12% 18% 30% 41% 53% 70%
Private Sector Participation
November 2005 figures46 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 kWAnnual energy saving: 35,120,000 kWh/yrAnnual emission reduction:
CO2 24,584 tonnes/yrNOX 63 tonnes/yrSO2 49 tonnes/yrParticulate 3 tonnes/yr
Benefits of Pilot Cases
1. Lower heat rejection system energy cost for replacing air-cooled 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
Shell and Tube Condenser
Tube Cleaners Collector and Injector
Tube cleaner Trap
To drain
Condensing Water
Injection pressure (from pump, air compressor, or dynamic pressure of condensing water)
PLC Controller
Tube cleaners
Common Configuration of Ball Type Automatic Tube Cleaning System
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 pressureconstant pressure
Area of Concern:Unnecessary high duct static pressure occurs in partial load condition and results in energy wastage
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
Operating points with and without RSP control
Required fan pressure reduced without change of flow rate
RSP VAV A/C Controls
Relationship Between Supply Air Pressure and Fan Speed
Relationship between supply air pressure and fanspeed
76.85 91.74 128.52
174.22
224.00
254.33
0.0050.00
100.00150.00200.00250.00300.00
20 25 30 35 40 45 50Frequency (Hz)
Pre
ssu
re (
Pa)
Pressure (Pa)
Relationship Between Fan Power Consumption and Fan SpeedRelationship between fan power consumption
and fan speed
10.22
8.72
6.34
4.423.152.16
0.002.004.006.008.00
10.0012.00
20 25 30 35 40 45 50Frequency (Hz)
Po
wer
Co
nsu
mp
tio
n(k
W)
Power Consumption (kW)
Comparison of Hourly Average Static Pressures Between RSP and CSP Modes
Average Static Pressure under RSP and CSP
225
196
159
114132
73
250
179
161
166
144
157 145 151
169181
251
242244
255
248 249 252
256 253
234
0
50
100
150
200
250
300
07:30 08:30 09:30 10:30 11:30 12:30 13:30 14:30 15:30 16:30 17:30 18:30 19:30Time
Su
pp
ly a
ir p
ress
ure
(P
a)
Average static pressure under RSP Average static pressure under CSP
Comparison on Daily Performance with same Cooling-degree Hour
CSP mode RSP mode
Averaged outdoor temperature (deg.C)
27.6 27.4
Operating Schedule 0730 – 1900hrs. 0730 – 1900hrs.
No. of Daily Cooling-degree Hours (CDH)
147.65 145.60
Total kWHr 90.86 66.65
kWhr/CDH 0.62 0.46
Saving 25.8%
Preliminary Findings on Energy Performance
CSP mode RSP mode
No. of sampling days 25 7
Total No. of Cooling-degree 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.
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
Theory
Condenser
F
TT
F
T F
T F
T F
T F
T F
T F
VFD
VFD
VFDVFD
VFD
VFD
JohnsonControlDDC
Hartman Loop
Optimum Energy
Controller
Existing CCMS
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
Energy Saving
High Efficiency Centrifugal Compressor System
69
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
Inverter Speed Control
Synchronous
Brushless DC
Motor
Motor and
Bearing Control
Inlet Guide Vanes
2-stage Centrifugal Compressor
Pressure and Temperature
Sensors
Components of the 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
Variable speed nature of the high efficiency centrifugal compressor
72
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
Problems associated with Oil
Typical Integrated Part Load Value (kW/ton)
Reciprocating Compressors : 0.9 to 1.2
Screw Compressors : 0.6 to 0.7
Turbocor : 0.4
74
Suitable Application of the new high speed chiller
Replacement of old conventional chillers
Replacement of old compressorsOne 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
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 housekeepingNow 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
innovationTraditions and established practices and designsMarket structure and conditions may not encourage adoption of innovative products HabitsWe need some courage to adopt changes
Thank you.
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