Energy Efficiency Opportunities in Buildings
• Building Operation• Building Envelope• HVAC Systems• HVAC Distribution Systems• Water Heating Systems• Lighting Systems• Power Systems• Energy Management Control Systems• Heat Recovery Systems
When the building is not occupied, the building systems should be turned off
or their operation reduced to a minimum.
Building Operation
Energy is saved when the heat exchange between the building and the outside environment is reduced and/or solar and internal heat gains are controlled.
•Insulation•Infiltration control•Roof color•Solar gains
•Window shading•Landscaping•Window quality•Set points
Building Envelope
Building Envelope
• Insulation
1) Cushion,2) Beam rafter,3) Roofmate* PS thermal resistance board4) Water proofing membrane5) Tilling battens6) Counter battens7) Face wood8) Roof cover (roof tiles, schingle)
Source:http://www.bulak.net/dow_roofmate_ps_Eng.asp
Insulation:Multilayer Plane Walls
totalRTT
Q 2,1, ∞∞ −=
AhAkL
AkL
Ah
RRRRR convwallwallconvtotal
22
2
1
1
1
2,2,1,1,
11 +++=
+++=
Building Envelope
U-value = 1/Rtotal
Such that:
)( 2,1, ∞∞ −××= TTAUQ
Windows:Multi-glazing Windows
Building Envelope
)( 2,1, ∞∞ −××= TTAUQ
( )4 4rad s surrQ A T Tεσ= −
Radiation heat transfer:
Heat losses through windows:
Example: Heat loss through a single pane windowGlass area: A = 0.8m × 1.5m = 1.2 m2
k = 0.78 W/m-oC.o
,1 2 o 21
1 1 0.08333 C/W(10W/m . C)(1.2m )i convR R
h A= = = =
oo 2
0.008m 0.00855 C/W(0.78W/m. C)(1.2m )glass
LRk
= = =
o,2 2 o 2
2
1 1 0.02083 C/W(40W/m . C)(1.2m )o convR R
h A= = = =
,1 ,2o
0.08333 0.00855 0.02083 0.1127 C/W
total conv glass convR R R R= + + = + +=
o,1 ,2
o
[20 ( 10)] C 266W0.1127 C/Wtotal
T TQ
R∞ ∞− − −
= = =
,1 1 o1 1 ,1
,1
2.2 Cconvconv
T TQ T T QR
R∞
∞
−= → = − = − Formation of fog or frost on the
surface
Building Envelope
Example: Heat loss through a double pane windowo
,11
1 0.08333 C/Wi convR Rh A
= = =
o11 3
1
0.00427 C/WglassLR R R
k A= = = =
o22
2
0.3205 C/WairLR R
k A= = =
o,2
2
1 0.02083 C/Wo convR Rh A
= = =o
,1 ,1 ,2 ,2 0.4332 C/Wtotal conv glass air glass convR R R R R R= + + + + =o
,1 ,2o
[20 ( 10)] C 69.2W0.4332 C/Wtotal
T TQ
R∞ ∞− − −
= = =
which is 1/4th of the previous result.Inner surface temperature of the window:
o1 1 ,1 14.2 CconvT T QR∞= − = no fogging
Building Envelope
• Equipment efficiency• Ventilation requirements• Distribution system• Controls• Hours of operation• Building envelope
HVAC Systems
Water heating energy is conserved by reducing load requirements, reducing distribution losses, and improving the
efficiency of the water heating systems.
•Flow Restrictors•Tank and Pipe Insulation•Supply Temperatures
•Leaks and Drips•Seasonal Operation•Equipment Efficiency
Water Heating Systems
• Proper lighting levels• Higher lamp efficiency• Reduced operating hours• Daylighting• Lighting maintenance
Lighting Systems
• Power Factor Correction(High efficiency motors, ballasts, correction devices)
• Improving Efficiency(Transformers, motor sizing, efficiency, and VSD)
• Demand Control• Cogeneration
Power Systems
100 MWhFuel
Cogeneration40 % Electrical efficiency50 % Thermal efficiency
40 MWhPower
50 MWhHeat
Energy Management Control Systems
• Minimize occupant control.• Operate equipment only when needed.• Eliminate or minimize simultaneous
heating and cooling.• Supply heating and cooling according to
needs.• Supply heating and cooling from most
efficient source.
Heat recovery opportunities exist where there is a need to reject heat from a
constant supply of high energy fluid such as air, water, or refrigerant.
•Boiler Stack & Blowdown•Exhaust Air•Laundry Air & Water•Refrigeration & Process Loads
Heat Recovery Systems
Heat Recovery SystemsExhaust air heat recovery systems
Recuperator: A recuperator is a special purpose counter-flow heat exchanger used to recover waste heat from exhaust gases. In
many types of processes, combustion is used to generate heat, and the recuperator serves to recuperate, or reclaim this heat, in
order to reuse or recycle it. (Source: http://en.wikipedia.org)
Flue type recuperator Radiation type recuperator
(Source: www.koreathermal.co.kr)
Heat Recovery Systems
Office Building Energy Use
Energy Use in Office Buildings Range (%) Norm (%)
Space Heating 45-65 50
Air Conditioning 20-30 25
Lighting 15-25 20
Special Functions (elevators/escalator, general power, security lights, domestic hot water, refrigeration, cooking)
5-10 5
Hotel Energy Use
Energy Use in Hotels/Motels Range (%) Norm (%)
Space Heating 45-70 60
Lighting 5-15 11
Air Conditioning 3-15 10
Refrigeration 0-10 4
Special Functions (laundry, kitchen, restaurant, swimming pool, elevators, security lighting, hot water)
5-20 15
Retail Store Energy Use
Energy Use in Retail Stores Range (%) Norm (%)
Lighting 40-75 60
HVAC 20-50 30
Special Functions (elevators/escalator, general power, security lights, domestic hot water, refrigeration, cooking)
5-20 10
Hospital Energy Use
Energy Use in Hospitals Range (%) Norm (%)
Environmental Control 40-65 58
Lighting 10-20 15
Laundry 8-15 12
Food Service 5-10 7
Special Functions 5-15 8
Supermarket Energy Use
Energy Use in Supermarkets Range (%) Norm (%)
Refrigeration 40-50 45
Lighting 17-24 20
Fans & Anti-Sweat Devices 10-15 12
HVAC 8-14 12
Special Functions 8-12 10
School Energy Use
Energy Use in Schools Range (%) Norm (%)
HVAC 45-80 65
Lighting 10-20 15
Food Service 5-10 7
Hot Water 2-5 3
Special Functions 0-20 10
Restaurant Energy Use
Energy Use in Restaurants Table Fast food
HVAC 32 36
Lighting 8 26
Food Preparation 45 27
Refrigeration 2 6
Sanitation 12 1
Other 1 4
Apartment Building Energy Use
Energy Use in Apartment Buildings
Range (%) Norm (%)
Environmental Control 50-80 70
Lighting/Plug Load 10-20 15
Hot Water 2-8 5
Special Functions (laundry, swimming pool, elevators, security lighting)
5-15 10