Post on 05-Oct-2020
14-Nov-13
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A Comprehensive Course on Energy
Management for FM Professionals
Energy Efficiency in Air-conditioning
Installations
Contents
1. Concepts of energy calculation in Air-conditioning Installations.
2. Applications and Calculation of energy saving on Air Conditioning System
3. COP of chiller, COP of unitary air-conditioner, air distribution system fan
power, duckwork leakage limit, thermal insulation, piping system
frictional loss, energy metering and system control etc.
4. Brief review on respective Building Energy Code from perspective of FM
5. Introduction of latest technologies in energy efficient HVAC system
6. Experience sharing and updates
7. Case studies
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Concepts of energy calculation in Air-
conditioning Installations.
Concepts of energy calculation
Method 1
Annual Cost Saving (kwh) = (Eold – Enew) x top x Energy Tariff Charge
Method 2
Annual Cost Saving (kwh) = (Eold x Percentage of Saving) x top x Energy Tariff
Charge
Simple Payback = ������������
���� ���� ����
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Performance Terms and Definitions
Tons of refrigeration (TR): One ton of refrigeration is the amount of cooling obtained by one ton of ice melting in one day: 3024 kCal/h, 12,000 Btu/h or 3.516 thermal kW.
Net Refrigerating Capacity. A quantity defined as the mass flow rate of the evaporator water multiplied by the difference in enthalpy of water entering and leaving the cooler, expressed in kCal/h, tons of Refrigeration.
kW/ton rating: Commonly referred to as efficiency, but actually power input to compressor motor divided by tons of cooling produced, or kilowatts per ton (kW/ton). Lower kW/ton indicates higher efficiency.
Coefficient of Performance (COP): Chiller efficiency measured in Btu output (cooling) divided by Btu input (electric power).
Energy Efficiency Ratio (EER): Performance of smaller chillers and rooftop units is frequently measured in EER rather than kW/ton. EER is calculated by dividing a chiller's cooling capacity (in Btu/h) by its power input (in watts) at full-load conditions. The higher the EER, the more efficient the unit.
energy efficiency parameters conversion
COP = 0.293 EER EER = 3.413 COP
kW/Ton = 12 / EER EER = 12 / (kW/Ton)
kW/Ton = 3.516 / COP COP = 3.516 / (kW/Ton)
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Applications and Calculation of energy
saving on Air Conditioning System
8
Key Energy Efficiency Requirements
Topic 9 Energy Audit
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9
Energy Utilization Intensity (EUI)
Annual energy and EUI (3 years)
Monthly EUI (recent 12 months)
MJ/m2/annum
Topic 9 Energy Audit
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Energy Consumption Distribution
Topic 9 Energy Audit
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Components of an HAVC system
A typical commercial heating, ventilation and air-conditioning (HVAC) system consists of 5 components:
Airside loop (yellow) Chilled-water loop (blue)
Refrigeration loop (green) Heat-rejection loop (red)
Controls loop (purple)
Topic 9 Energy Audit
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Components of an HAVC system (Airside Loop)
Airside loop:
Cooling coil is used to cool and dehumidify the
supply air before it is delivered to the space
A typical cooling coil includes rows of tubes passing
through sheets of formed fins. A cold fluid, either
water or liquid refrigerant, enters one header at the
end of the coil and then flows through the tubes,
cooling both the tubes and the fins
Air-handling system draws outdoor (fresh) air intake,
transfers the cooling effect to the air and
distributes cooled air in the indoor environment
Topic 9 Energy Audit
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Components of an HAVC system (Airside Loop)
The airside loop responds to changing cooling loads in
the conditioned space by varying wither the temperature
or the quantity of air delivered to the space
A constant-volume system provides a constant quantity
of supply air and varies the supply-air temperature in
response to the changing cooling load in the space
A thermostat compares the temperature in the
conditioned space to a set point. It then modulates
cooling capacity until the space temperature matches the
set point
Topic 9 Energy Audit
Constant supply-air quantity, variable supply-air temperature
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Components of an HAVC system (Airside Loop)
A variable-air-volume (VAV) system varies the quantity of
constant-temperature supply air in response to the
changing load in the space
Each space has a separate VAV terminal unit that varies
the quantity of supply air delivered to that space
A thermostat compares the temperature in the
conditioned space to a set point. It then modulates the
quantity of supply air delivered to the space by changing
the position of the airflow modulation device (a rotating-
blade damper) in the VAV terminal unit.
Topic 9 Energy Audit
Variable supply-air quantity, constant supply-air temperature
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Components of an HAVC system (Chilled Water Loop)
Chilled water loop:
Why chilled water?
Water is an effective medium for
transfer of thermal energy
Specific heat:
For water = 4.2 kJ/kg/K
For air = 1 kJ/kg/K
Density:
For water = 1000 kg/m3
For air = 1.2 kg/m3
Topic 9 Energy Audit
Water is abundant
Water is chemically stable
Water is nontoxic
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Components of an HAVC system (Chilled Water Loop)
Chilled water flows through the cooling
coil, absorbing heat from the air
Evaporator, is one component of the
refrigeration equipment (chiller), is used
to cool the chilled water back to desired
supply water temperature
Pump is used to move water around the
loop.
This pump needs to have enough power
to move the water through the piping,
the evaporator, the tubes of the coil etc.
installed in the chilled water loop
Topic 9 Energy Audit
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Components of an HAVC system (Chilled Water Loop)
Similar to the airside loop, the chilled-water loop responds to changing cooling
loads by varying either the temperature or the quantity of water delivered to
the cooling coil
The most common method is to vary the quantity of water flowing through
the cooling coil by using a control valve
As the cooling load decreases, the modulating control valve reduces the rate
of chilled water flow through the coil, decreasing its cooling capacity
Topic 9 Energy Audit
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Components of an HAVC system (Refrigeration Loop)
In the chilled water loop, the evaporator
allows heat to transfer from the water to
cold liquid refrigerant
As heat is transferred from the water to the
refrigerant, the liquid refrigerant boils
The resulting refrigerant vapor is further
warmed (superheated) inside the
evaporator before being drawn to the
compressor
The compressor is used to pump the low-
pressure refrigerant vapor from the
evaporator and compress it to a higher
pressure
Topic 9 Energy Audit
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Components of an HAVC system (Refrigeration Loop)
This increase in pressure also raises the temperature of the refrigerant vapor
Common types of compressors includes: reciprocating, scroll, helical-rotary
(screw), and centrifugal
The hot, high pressure refrigerant vapor enters a condenser
Topic 9 Energy Audit
The condenser is a heat exchanger that transfers
heat from the hot refrigerant vapor to air, water, or
some other fluid that is at a colder temperature
As heat is removed from the refrigerant, it condenses
and returns to the liquid phase
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Components of an HAVC system (Refrigeration Loop)
The final step of the refrigeration cycle is for this hot liquid refrigerant to pass
through an expansion device
This device creates a large pressure drop that reduces the pressure, and
correspondingly the temperature, of the refrigerant
Topic 9 Energy Audit
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Components of an HAVC system (Refrigeration Loop)
Topic 9 Energy Audit
1 → 2
Constant-pressure heat absorption
(cooling effect)
2 → 3
State 2 is a saturated vapor;
isentropic (reversible, adiabatic)
compression
3 → 4
Constant-pressure heat rejection;
stage 4 is a saturated liquid
4 → 1
Constant-enthalpy expansion
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Components of an HAVC system (Refrigeration Loop)
Topic 9 Energy Audit
Cooling effect:
=
Isentropic compression:
=
Heat rejection:
=
Throttling,
=
( )1212
hhmq −=•
( )2323
hhmw −=•
( )4334
hhmq −=•
14hh =
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Coefficient of Performance (COP)
Topic 9 Energy Audit
COP = Cooling effect/ Power input
The objective of a refrigeration cycle is to
remove heat (q12) from the refrigerated
space. To accomplish this objective, it
requires a work input (w23)
COP is an index of performance of a
thermodynamic cycle or a thermal system
23
12
hh
hh
−
−=
24
Coefficient of Performance (COP)
Topic 9 Energy Audit
Example:
Consider an ideal refrigeration cycle using R-
134a as the refrigerant. The gage pressure of
the refrigerant in the evaporator is 0.192 MPa.
In the condenser, the gage pressure of the
refrigerant is 1.217 MPa. Estimate the
coefficient of performance of the air-
conditioning system
Solution:
Absolute pressure
= Gage pressure + atmospheric pressure
p1 = p2 = 0.192 + 0.101 = 0.293 MPa
p3 = p4 = 1.217 + 0.101 = 1.318 MPa
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Coefficient of Performance (COP)
Topic 9 Energy Audit
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Coefficient of Performance (COP)
Topic 9 Energy Audit
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Coefficient of Performance (COP)
Topic 9 Energy Audit
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Components of an HAVC system (Heat Rejection Loop)
In the refrigeration loop, the condenser
transfer heat from the hot refrigerant to
air, water, or some other fluid.
In a water-cooled condenser, water
flows through the tubes while the hot
refrigerant vapor enters the shell space
surrounding the tubes,
Heat is transferred from the refrigerant
to the water, warming the water
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Components of an HAVC system (Heat Rejection Loop)
A heat exchanger is required to cool the
water that returns from the condenser
back to the desired temperature (29.4 oC) before it is pumped back to the
condenser
When a water-cooled condenser is used,
this heat exchanger is typically either a
cooling tower
Topic 9 Energy Audit
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Components of an HAVC system (Control Loop)
Each of the previous four loops contains several components
Each component must be controlled in a particular way to ensure proper
operation
Many building operators want to monitor the system, receive alarms and
diagnostics at a central location, and integrate the HVAC system with other
systems in the building. These are some of the ructions provided by a
Building Automation System or Building Management System
Topic 9 Energy Audit
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Energy Management Opportunity (EMO)
During the audit, the air-cooled chillers are found to be operated for over 20
years. Would chiller replacement help in reducing the energy consumption?
What is the COP stated in the manual?
Any record of electricity consumption?
Any record of chilled water supply and return temperature?
Any record of the chilled water / refrigerant pressure?
How frequent of those record?
Topic 9 Energy Audit
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Energy Management Opportunity (EMO)
What is the COP stated in the manual?
The rated COP is usually the for a specific condition:
Specify loading
Specify chilled supply temperature
Specify outdoor temperature
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Energy Management Opportunity (EMO)
Topic 9 Energy Audit
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Energy Management Opportunity (EMO)
Any record of electricity consumption?
For example:
Annual electricity consumption for the aged chiller = 273,480 kWh
If the COP of the aged chiller = 2
Cooling load = kWh = 546,960 kWh
COP of the new chiller = 3
Annual electricity consumption after chiller replacement =
=182,320 kWh
About 33% energy saving per year, that is 91,160 kWh
Topic 9 Energy Audit
InputPower
Load Cooling COP =
480,2732×
3960,546 ÷
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Energy Management Opportunity (EMO)
Where can I get the COP of the existing chiller?
Method 1:
By recording the refrigerant pressure of the evaporator ad the condenser
By knowing the type of refrigerant
Refer to the pressure – enthalpy diagram
Topic 9 Energy Audit
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Energy Management Opportunity (EMO)
Method 2:
Measure the chilled water flow rate
Measure the supply and return chilled water temperature
Cooling load =
m = mass flow rate of the chilled water
C = specific heat capacity
= temperature difference between supply and return chilled water
Measure the power consumption or current
Topic 9 Energy Audit
TmC∆
InputPower
Load Cooling COP =
T∆
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Energy Management Opportunity (EMO)
.
Topic 9 Energy Audit
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Energy Management Opportunity (EMO)
Any record of electricity consumption?
Yes, but I do not have the electricity consumption of chiller
Topic 9 Energy Audit
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Energy Management Opportunity (EMO)
Make reasonable assumption:
For example: 60% electricity consumption is due to chiller installation
Topic 9 Energy Audit
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Energy Management Opportunity (EMO)
Monthly cooling load:
Topic 9 Energy Audit
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Energy Management Opportunity (EMO)
Monthly energy saving:
Topic 9 Energy Audit
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Energy Management Opportunity (EMO)
Cost saving:
Topic 9 Energy Audit
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Energy Management Opportunity (EMO)
What is the payback for this chiller replacement?
Simple payback =
Total annual saving = Electricity cost x Annual electricity consumption
Assume the electricity cost = $1 per kWh
Assume the cost of chiller replacement = $400,000
Simple payback = = 4.4 years
Topic 9 Energy Audit
Saving AnnualTotal
Investment Total
$91,160
$400,000
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Pump
In a pumping station, it may be
advantageous to install two or more
pumps together – either in series or
parallel
Pumps connected in series cause an
increase in pressure but no increase in
discharge
If two identical pumps are connected
in series, output pressure will
approximately double that afforded by
one pump while discharge remains
unchanged
Topic 9 Energy Audit
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Pump
Pumps connected in parallel cause an increase in discharge but no increase in pressure
If two identical pumps are connected in parallel and are discharging to the atmosphere, discharge will approximately double that afforded by one pump while pressure remains unchanged
Topic 9 Energy Audit
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Pump
System pressure loss vs. flow rate
Cv
is a cumulative effect of fluid
friction, valves, fittings and other
flow resisting devices (e.g. heat
exchangers)
Topic 9 Energy Audit
pCV v ∆=•
rateflow system =•
V
constant system =vC
system in drop pressure=∆p
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Pump
Topic 9 Energy Audit
Pump Curve and System Curve
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Pump
Topic 9 Energy Audit
Parallel-pump operation
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Pump
Topic 9 Energy Audit
Power of circulating water:
pVpm
Pw ∆=∆
=•
•
ρ
waterof rateflow mass =•
m
waterof rateflow volumetric=•
V
increase pressure =∆p
waterof density =ρ
input Power
power Water efficiency Pump =
50
Energy Management Opportunity (EMO)
Replacement of Pump
In case of a chiller plant using an oversized pump, the chilled water flow rate
will exceed the design condition. The chilled water flow rate can be lowered by
using a partially closed valve.
A possible EMO is to replace the existing oversized pump with a pump that has
an appropriate lower rating.
Topic 9 Energy Audit
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Energy Management Opportunity (EMO)
Reset the temperature in air-conditioned zone
The Electrical & Mechanical Services Department (EMSD) of HKSAR
recommends setting the indoor air temperature to 25.5 oC for an air-
conditioned zone to save energy. If the indoor air temperature is raised, heat
gain of the building from the ambient environment will decrease.
The amount of heat gain Q can be estimated by:
i = type of construction material (concrete wall, glass window, roof etc.)
A = area of building envelop
K = thermal conductance
Text_surf = temperature of the exterior surface
Tin = indoor air temperature
Topic 9 Energy Audit
( )∑ −=i
insurfextii TTKAQ_
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Energy Management Opportunity (EMO)
Given measurement for the existing HVAC operation:
Indoor air temperature, Tin = 21 oC
Total cooling load, Q1 = 350 kW
Electric power consumption, P1 = 100 kW
COP1 = Q1/ P1 = 350/100 = 3.5
Building envelop area = 6,600 m2
Average thermal conductance, K = 1 W/m2K
Building exterior surface temperature, Text_surf = 32 oC
If indoor air temperature is raised to 25.5 oC, chilled water temperature can be
raised and the COP becomes, COP2 = 3.8
Estimate the energy saving by raising the indoor air temperature to 25.5 oC
Topic 9 Energy Audit
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Energy Management Opportunity (EMO)
Cooling load due to heat gain through the envelop for the existing operation,
Qe1 = AK(Text_surf – Tin) = 6,600 x 1 x (32 – 21) = 72.6 kW
Cooling load due to heat gain through the envelop after indoor air temperature
is raised to 25.5 oC,
Qe2 = AK(Text_surf – Tin) = 6,600 x 1 x (32 – 25.5) = 42.9 kW
Total cooling load after temperature adjustment,
Q2 = 350 – (72.6 – 42.9) = 320.3 kW
Electrical power consumption after temperature adjustment,
P2 = Q2/ COP2 = 320.3/ 3.8 = 84.3 kW
Energy saving = P1 – P2 = 100 – 84.3 = 15.7 kW (or 15.7%)
Topic 9 Energy Audit
VAV Box Minimum Airflow Reset
• VAV box manufacturer specify minimum airflow for each VAV
box
• Actual acceptable minimum set point usually lower than that
of this minimum value
• Minimum shall reset to fit actual minimum flow requirement
• CO2 concentration level monitoring system shall be installed
to supplement the flow control system
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VAV Box Minimum Airflow ResetExisting annual electrical energy consumption for AHUs
= 7,200,00MJ
= 2,000,000kWh
Existing annual electrical energy consumption for chillers
= 10,800,000MJ
= 3,000,000kWh
Total cooling air flow reduced percentage
= percentage of VAV boxes x reduced airflow percentage
= 30% x 20%
= 6% of total cooling airflow
Fan energy saving percentage for AHUs
= 1- (1-6%)3
~ 15%
Annual energy saving
= AHU fan energy saving + cooling energy saving
= AHU annual energy consumption x energy saving percentage x time percentage + chiller energy x saving percentage x time percentage
= 2,000,000kWh x 15% x 20% + 3,000,000kWh x 6% x 20%
= 96,000Wh
Annual cost saving
= Annual energy saving x Electricity unit charge
= 96,000kWh x HK$0.97 / kWh
= HK$ 93,120
Heat Pump
• Heat sources : air, chilled water return
• Output temperature : max 60oC
• COP : ~3 with output temperature at 45oC
• Need hot water storage tanks
• Potential uses : central domestic hot water, HP dehumidification,
pool heating
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Heat Pump
Heating capacity : 150kW – 2000kW
COP : > 5 (temperature rise 40oC)
Temperature of
water source
: 7 to 40oC
Max. output temp. : ~ 60oC
Heat Source : Condensing water
Potential uses : • Hot Water / Dehumidification
• Customers with simultaneous high air-
conditioning & hot water demand, e.g. Hotels,
Hospitals, etc
Heat Pump
COP : > 3.5
Refrigerant : Carbon Dioxide (CO2)
Max. output temp. : ~ 85oC
Heat Source : Condensing water / Geothermal heat /
Waste heat generated from
manufacturing process
Application : Hot water supply / Dehumidification /
Industrial process drying
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COP of chiller, COP of unitary air-conditioner,
air distribution system fan power, duckwork
leakage limit, thermal insulation, piping system
frictional loss, energy metering and system
control etc
Air-conditioning System Load Design
Conditions
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Air Leakage Limit of Ductwork
Minimum Insulation Thickness for
Chilled Water Pipework
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Minimum Insulation Thickness for Refrigerant Pipework
(Suction)
Minimum Insulation Thickness for Ductwork and
AHU Casing
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65
Minimum Coefficient of Performance for Chiller
Topic 9 Energy Audit
Air Cooled Chiller
Water Cooled Chiller
Brief review on respective Building
Energy Code from perspective of FM
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Building Energy Efficiency Ordinance
Building Energy Efficiency Ordinance (BEEO) (Cap. 610)
http://www.legislation.gov.hk/blis_pdf.nsf/6799165D2FEE3FA94825755E003
3E532/4F82C8740A5D73DA482577ED005330F2?OpenDocument&bt=0
3 December 2010 Gazetted
21 March 2011 Subsidiary regulations in operation
21 September 2012 Full Operation
Subsidiary regulations: Registered Energy Assessors (REA)
Codes of Practice: Energy Audit Code (EAC)
Building Energy Code (BEC)
Topic 9 Energy Audit
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Building Energy Efficiency Ordinance
Building Energy Code (BEC)
Commercial building
Industrial building: common area
Residential building: common area
Composite building: common area, portion not for residential or industrial
use
For example:
Hotel and guest house Municipal services
Educational building Medical and health
Community building Government building
Railway station Airport passenger building
Topic 9 Energy Audit
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Building Energy Efficiency Ordinance
Energy Audit Code (EAC)
Commercial building
Composite building (commercial portion)
BEEO does not govern:
Small building
Building with main electrical switch with approved load ≤ 100 A
Historical building
BS installations, with specific operational and technical natures such as fire
protection, lift safety, industrial undertaking etc.
Building that will cease to fall within 12 months
Topic 9 Energy Audit
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Building Energy Efficiency Ordinance
For existing building:
OA (occupation approval) on or after 1 Jan 1988 (<24 years)
� 1 year from 21 Sept 2012
OA after 31 Dec 1977 but before 1 Jan 1988 (25 – 35 years)
� 2 years from 21 Sept 2012
OA after 31 Dec 1969 but before 1 Jan 1978 (35 – 43 years)
� 3 years from 21 Sept 2012
OA on or before 31 Dec 1969 (>43 years)
� 4 years from 21 Sept 2012
For newly constructed building:
� 10 years after issue of Cert of Compliance Registration
Topic 9 Energy Audit
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Building Energy Audit
Responsibility of building owner:
Engage REA to carry out energy audit according to prescribed time frame
Obtain from REA the Energy Audit Form and energy audit report
Exhibit Energy Audit Form at building main entrance
Energy audit totally independent from BEC compliance – not a checking for
BEC compliance
Implementation of Energy Management Opportunity (EMO) not mandatory
Topic 9 Energy Audit
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Building Energy Audit
Energy Audit Form
http://www.beeo.emsd.gov.hk/en/mi
bec_forms.html
Name of building
Address of building
Registered Energy Assessor (REA)
Commencement and completion
dates of energy audit
Energy Utilization Index
(MJ/m2/annum)
Valid for 10 years from the date of
completion of energy audit
Topic 9 Energy Audit
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Building Services Installations
BS installations required by Ordinance to comply with BEC?
For newly constructed building:
YES
For existing building:
Only for major retrofitting works completed on or after 21 Sept 2012
Major retrofitting works:
Addition/ replacement of BS installation:
- a total floor area covered by the works under the same series of work
within 12 months ≥ 500 m2
Addition/ replacement of a main component:
A complete electrical at rating ≥ 400 A
A chiller or a unitary air-conditioner at rating ≥ 350 kW capacity
Topic 9 Energy Audit
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Penalties
Fines at various levels from HK$2,000 to HK$1,000,000 to be imposed for
offences, e.g. (not exhaustive):
Reference: Section 22
Building owner failing to cause an energy audit to be carried out within the
time frame: Level 5 (Max. Penalty: HK$50,000)
REA failing to send a copy of Energy Audit Form and energy audit report to the
Director, within 30 days of issue: Level 3 (Max. Penalty: HK$10,000)
Topic 9 Energy Audit
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Registered Energy Assessor (REA)
Registered Professional Engineer (RPE) under Engineers Registration
Ordinance – electrical, mechanical, building services or environmental
discipline
� at least 2 years practical experience
� has the knowledge for the performance of the duties and functions under
the BEEO
Corporate member of HKIE in electrical , mechanical, building services or
environmental discipline or equivalent qualification
� at least 3 years practical experience
� has the knowledge for the performance of the duties and functions under
the BEEO
Topic 9 Energy Audit
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Registered Energy Assessor (REA)
Newly constructed buildings:
�Certify BS installations comply with BEC for developers to apply for
Certificate of Compliance Registration (CORC)
�Certify BS installations comply with BEC for owners to apply for COCR
renewal
�Issue Form of Compliance (FOC) for major retrofitting works
Existing building:
� Issue the FOC for major retrofitting works
Topic 9 Energy Audit
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Registered Energy Assessor (REA)
Central BS installations in commercial buildings/ composite building
�Conduct energy audit
�Issue Energy Audit Form
�Prepare and issue Energy Audit Report
Topic 9 Energy Audit
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Energy Audit Code
Objective
Systematic review: Energy consuming equipment/ system
Information for decision making – accounting for
environmental and economic benefits
Key steps
1. Collection of information of the building
2. Review of energy consuming equipment/ systems
3. Identification of Energy Management Opportunity (EMO)
4. Cost benefit analysis of EMO
5. Recommendations
6. Compiling energy audit report/ Energy Audit Form
Topic 9 Energy Audit
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Energy Audit Code
1. Collection of Building Information
�Energy consuming equipment inventories, brochures, manuals, drawings
�Building’s internal floor areas
�Energy consumption data past 36 months (or since operation)
�Building’s O&M programmes
�Operation records hours, temperature, flow, pressure vs. settings
�Past audit/ EMO
Topic 9 Energy Audit
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Energy Audit Code
2. Review of Energy consuming Equipment
Compile records based on findings
Calculate power and energy consumptions
� Utilization pattern: operation hours, occupant density etc
� Indicative parameters, absolute and changes – temperature, flow rate etc.
� Control mechanism
� AC systems and components: chillers, AHUs, AC water pumps etc.
� Luminaires
� Lifts and escalators
� Other BS equipment/ system: plumbing and drainage pumps
� Electrical circuit
� Power quality
Topic 9 Energy Audit
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Energy Audit Code
2. Review of Energy consuming Equipment
� Types, capacity rating, rating conditions
� Metering in-situ/ external
� Measurement at representative instants and time
� Other characteristics affecting energy consumption (e.g. ext shading,
glazing shading coefficient etc.)
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Energy Audit Code
3. Identification of Energy Management Opportunity (EMO)
Reference to codes, guidelines and practices of established international/ local
standards
� Energy performances vs. operation conditions
� Identify deviations from efficient operation
� Comparison with original design
� Applicable operating conditions and system configurations
� Behaviors of responsible persons affecting energy consumption
Lighting W/m2 AHU/ Fan system fan power W/L/s
Pump W/L/s EUI – MJ/m2/annum
Chiller/ heat pump kwh/yr
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Energy Audit Code
4. Cost Benefit Analysis of EMO
Category I – Housing keeping measures
� Involving housekeeping measures which are improvements with practically
no cost investment and no disruption to building operation
Example: Turning off A/C or lights when not in use, revising A/C temperature
set-points, etc.
Category II – Low cost measures
� Involving changes in operation measures with relatively low cost investment
Example: Installing timers to turn off equipment, replacing T8 fluorescent
tubes with T5 fluorescent tubes, etc.
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Energy Audit Code
4. Cost Benefit Analysis of EMO
Category III – Higher cost measures
� Involving relatively high capital cost investment to attain efficient use of
energy
Example: Adding variable speed drives, installing power factor correction
equipment, replacing chillers, etc.
5. Recommendations
Need of further studies
Topic 9 Energy Audit
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Energy Audit Code6. Energy audit report
a) Executive Summary
b) Energy audit scope
c) Building characteristics
d) General description of equipment/ systems audited
e) Energy consumption and performance evaluation
f) Air-conditioning systems/ equipment information – chiller/ air-conditioner capacity & type, system type (CAV, VAV etc)
g) Lighting installations total lighting power
h) Analysis of historical energy consumption
i) Indication of energy supply to units from central BS installations
j) Findings from information review and site inspections
k) Evaluations of potential EMO
l) Referencing to past energy audit (if any)
m) EMO - recommendations
Topic 9 Energy Audit
86
Energy Audit Code
6. Energy audit report
Building characteristics
Internal floor area of building Internal floor area of common area
Number of floors Occupant density
Hours of operation Days of operation
Chiller/ unitary air-conditioner
Type, capacity and quantity
Total lighting power
Topic 9 Energy Audit
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87
Energy Audit Code
6. Energy audit report
Energy consumption analysis
Annual energy and EUI (3 years) Monthly EUI (recent 12 months)
Energy supply to unit (e.g.. Chilled water supply)
Breakdown into air-conditioning, lighting, lift and escalator, others (recent 12
months)
Energy management opportunities
Categorized
Topic 9 Energy Audit
Introduction of latest technologies in
energy efficient HVAC system
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Chiller selection
COP AnalysisOil Free centrifugal chiller(150RT)Normal screw chiller25% 50% 75% 100%
024681012
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Chiller selection
• COP, IPLV, Initial cost, life cycle cost
• Variable speed and dual compressor control deliver significant energy benefits, when applied to a wide range of building types and climates.
• Oil-free design eliminates oil fouling of flooded heat exchangers, which sustains energy efficiency over the life of the system.
• Oil-free, magnetic bearing design has lower annual maintenance and no periodic bearing inspections. Vibration monitoring is built- in to the compressor as standard.
• Every project is unique, and Life Cycle Costing is a valuable tool that can be used to look at the particular chiller options available
Chiller Plant Demand Flow Technology
• Manages chiller plant chilled & condenser water demand flow with specialized control algorithms.
• These algorithms require the conversion of constant speed for all pumps and fans adopted in chller plant to variable speed through the installation of Variable Frequency Drives (VFDs).
• The VFDs allow the Demand Flow algorithms to maintain optimal differential system pressure, reduce excessive pumping energy, reduce equipment runtime and increase system deliverable cooling capacity to end users with require thermal comfort
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Energy Management System
• ISO 50001 is a framework that helps companies manage their energy systems
and plan better to save energy and to reduce pollution as well as costs
• Benefit
1. Resolves energy efficiency problems
2. Improves energy usage of energy-consuming assets
3. Estimates environmental impact of greenhouse gases;
4. Improves energy management and communication;
5. Provides best practices for energy efficiency;
6. Prioritizes new energy-saving technology;
7. Improves energy efficiency of supply chains; and
8. Details greenhouse gas reduction plans
• An Energy Management System (EnMS) is a systematic process for continually
improving energy performance.
Energy Management System
• Assess current state (energy audit)—identify all energy management
opportunities (baseline)
• Use energy audit recommendations to prioritize, plan and allocate
resources
• Create plan to engage organization and drive energy awareness (energy
culture)
• Sub-metering system to identify energy wastage and trigger optimal plant
operation model
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Case Study
Energy Management Opportunity (EMO)
Average electricity unit charge = HK$0.97/kWh
The total annual energy consumption of air conditioners installed = 300,000kWh
Air conditioners could be replaced with energy efficient air conditioners = 80%
Saving percentage by adopting Grade 1 energy label air conditioners = 15%
Annual energy saving
= The total annual energy consumption of air conditioners with a cooling capacity 7.5kW or below x saving percentage
= 300,000kWh x 80% x 15%
= 36,000kWh
Annual cost saving
= Annual energy saving x Average electricity unit charge
= 36,000Wh x HK$0.97/kWh
= HK$34,920
Payback Period
Estimated capital cost
= (HK$ 126,500 ~ HK$ 235,000) / (23 sets)
Payback period
= Estimated capital cost / Annual cost saving
= (HK$ 126,500 ~ HK$ 235,000) / HK$34,920
= 3.6~6.7 years
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Energy Management Opportunity (EMO)
Chiller efficiency could be improved by 3% when applying BMS control for chiller start &stop sequence
Average electricity unit charge = HK$0.97/kWh
Total energy consumption of chiller =3,000,000kW
Annual energy saving
= energy consumption of chillers x saving percentage
= 3,000,000kW x 0.5%
= 15,000kWh
Annual cost saving
= Annual energy saving x Average electricity unit charge
= 15,000kWh x HK$0.97/kWh
= HK$14,550
Payback Period
Unit rate for calibration of flow meter
= (HK$ 10,000 ~ HK$ 20,000) / unit (including installation cost) x 6 flow meters
= HK$ 60,000 ~ HK$ 120,000
Payback Period
= (HK$ 60,000 ~ HK$ 120,000) / HK$ 14,550
= 4.1 ~ 8.2 years
Energy Management Opportunity (EMO)
Damaged thermal insulation area = 10m2
Temperature difference between cold surface to ambient = 22oC
Thermal conductivity improved by proper thermal insulation = 30W/m2oC
Total cooling energy saved = Damaged thermal insulation area (m2) x Temperature difference between cold surface to ambient (oC) x
Thermal conductivity improved
=10m2 x 10oC x 30W/m2oC
=3,000W
Annual energy saving
= (Total cooling energy saved / COP of air-cooled chiller) x Annual operating hours of chilled water system
= (3,000W/ 5.2) x 8,760 hours
= 5,053.8kWh
Annual cost saving
= Annual electrical energy to be saved / electricity unit charge
= 5,053.8kWh/ year x HK$ 0.97 / kWh
= HK$ 4,902.2
Payback period
Unit rate for pipe work rectification
= (HK$ 25,000 ~ HK$ 35,000) / unit (including installation cost)
Payback Period
= (HK$ 25,000 ~ HK$ 35,000) / HK$4,902.2
= 5.0 ~ 7.1years