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