31
05/04/2011 1 Tarik al-Shemmeri 1 Building’s Heat Gains
05/04/2011 1 Tarik al-Shemmeri 1
Building’s Heat Gains
05/04/2011 Tarik al-Shemmeri 2
SOURCES OF THERMAL ENERGY TRANSFER FOR BUILDINGS
Generally, there are FOUR heat transfer sources within any building, they are:
Fabric: Heat losses Ventilation: Heat loss Solar: Heat gains Internal: Heat gains
05/04/2011 Tarik al-Shemmeri 3
Solar Heat gains FOR BUILDINGS
Solar heat gain through windows and/or walls provides
a valuable contribution of space heating.
05/04/2011 Tarik al-Shemmeri 4
The solar heat gain through a glazed area is calculated by:
QSolar = Area of window x solar intensity
x Transmissivity.
Solar Heat gains FOR BUILDINGS
05/04/2011 Tarik al-Shemmeri 5
Casual Heat gains FOR BUILDINGS
Casual heat gains inside a building provide a valuable source of heat contribution to space heating. Sources include :
• occupants • lights • equipments
05/04/2011 Tarik al-Shemmeri 6
Casual Heat gains FOR BUILDINGS
05/04/2011 Tarik al-Shemmeri 7
Casual Heat gains FOR BUILDINGS
Type of Heat Source
Typical Heat Emission
Adults:
Sleeping
80W
Seated quietly
120W
Walking slowly
230W
Medium work
265W
Heavy work
570W
05/04/2011 Tarik al-Shemmeri 8
Casual Heat gains FOR BUILDINGS
adult male 100%child ( male, or female) 75female ( adult ) 85old people ( male, or female) 80
05/04/2011 Tarik al-Shemmeri 9
Casual Heat gains FOR BUILDINGS
05/04/2011 Tarik al-Shemmeri 10
Casual Heat gains FOR BUILDINGS
Type of Heat Source FROM LIGHTS
Typical Heat Emission
Fluorescent @ 400 lux
20W/m2 floor area
Tungsten @ 200 lux
40W/m2 floor area
05/04/2011 Tarik al-Shemmeri 11
Casual Heat gains FOR BUILDINGS
05/04/2011 Tarik al-Shemmeri 12
Casual Heat gains FOR BUILDINGS
Typical Heat Emission
Desktop computer
150W
Computer printer
100W
Visual display unit
200W
Photocopier
800W
Hair dryer
800W
Domestic fridge-freezer
150W
Colour TV
100W
Hi-fi unit
100W
Toaster
500W
Oven
2500W
Electric and Electronic Equipment:
05/04/2011 Tarik al-Shemmeri 13
TUTORIAL EXAMPLES
05/04/2011 Tarik al-Shemmeri 14
WORKED EXAMPLE
20m
5m
10m
W W
D
THE building shown has thermal data as indicated in the table; It is used for a 5-a-side game of football, there are 50 forty watts lights, switched on continuously, and a 1.5 kW heater inside the hall. Determine the heating load for this building, when the internal and external temperatures are 20 and zero degrees centigrade.
05/04/2011 Tarik al-Shemmeri 15
Element
U-value W/m2K
Area m2
Temp. Difference (oC)
Heat loss W Door
2
6
Windows
3
12 total
Walls
0.5
Roof
0.45
Floor
0.45
Fabric heat loss = TOTAL ( Doors, Windows, Walls, Roof & Floor) =
Ventilation Heat Loss = 0.335 N V ΔT
Heat gains from occupants
Heat gains from lights
Heat gains from machines
Net heat transfer for the building
WORKED EXAMPLE
05/04/2011 Tarik al-Shemmeri 16
SOLUTION EXAMPLE Element
U-value W/m2K
Area m2
Temp. Difference(oC)
Heat loss W Door
2
6
20
240
Windows
3
12 total
20
720
Walls
0.5
282
20
2820
Roof
0.45
200
20
1800
Floor
0.45
200
0
0
Fabric heat loss = TOTAL ( Doors, Windows, Walls, Roof & Floor) =
-5580 Ventilation Heat Loss = 0.335 N V ΔT =
-6700 Heat gains from occupants = No. of people x energy/person =
+600 Heat gains from lights = No. of lights x wattage =
+2000 Heat gains from machines = No. of machines x output =
+1500 Net heat transfer for the building =
- 8180 W
05/04/2011
What do we need Light for: • Visual clarity and color perception
• Reduced eye strain and fatigue
• Greater learning ability and intelligence
• Enhanced mental awareness, concentration and productivity
05/04/2011
05/04/2011
Light bulbs
as we know them, were invented by Thomas Edison in the late 19th century. They are extremely inefficient systems. Their main goal is to provide light, over 95% of the energy in an incandescent bulb is released as heat. Less than 5% of the electricity going into your light bulb is being turned into light. There is a little bit of room for improvement there.
05/04/2011
Mysore palace, lit up by 27,000 light bulbs - Southern India
05/04/2011
ORDINARY light bulbs are to be banned across the European Union within two years in the fight against climate change. The 490 million citizens of the 27 member states will be expected to switch to energy-efficient bulbs after a summit of EU leaders yesterday told the European Commission to "rapidly submit proposals" to that effect. - Ian Johnston Environmentalists said the change would save the public up to £5.4 billion a year in fuel bills and also about 20 million tonnes of carbon emissions every year.
05/04/2011
2020 VISION on Energy: The key EU targets and objectives: • A minimum 20 per cent EU cut in greenhouse gas emissions by 2020, and a push for a bigger cut of 30 per cent in future. • A target of 20 per cent energy efficiency savings by 2020, requiring homes, offices and streets to switch to energy-saving lighting.
05/04/2011
05/04/2011
05/04/2011
05/04/2011
Tips - Energy Efficiency for Lighting
One Switch off all lights when not needed. Two Label light switches to clearly identify the lights they control. Three clean light fittings regularly. This will increase output and lead to fewer lights being turned on. Four Install modern slimline fluorescent tubes – they will last much longer than ordinary bulbs and use less energy. Five Where double tubes have been fitted check whether one is sufficient. Six Maximise natural lighting by ensuring windows are clean and window ledges are not cluttered. Seven Ensure that your office layout considers the availability of natural and artificial lighting. Eight Consider fitting Presence Detectors
05/04/2011
Tips - Energy Efficiency for Lighting • By switching off lights in rooms which aren’t being used you could cut your lighting costs by as much as 15%
05/04/2011
Tips - Energy Efficiency for Lighting • Make the most of the natural daylight by adjusting blinds and curtains accordingly
05/04/2011
Tips - Energy Efficiency for Lighting • Fit infra-red presence detectors to switch off lights when rooms or desks are unoccupied
05/04/2011
Tips - Energy Efficiency for Lighting Replace all light bulbs with energy efficiency recommended bulbs, which will use around a quarter of the electricity and last up to 12 times longer!
05/04/2011
Tips - Energy Efficiency for Lighting • Clean windows
