Intro
Wednesday 15 February 2023 20:00
ENERGY CONCEPTS
Primary Energy • Energy as it occurs in the earth
• Coal/crude oil/natural gas/uranium
Secondary Energy • Useful energy form
• Based on converting from primary energy
• Electricity/petroleum products/processed natural gas/processed fossil fuels
Tertiary Energy • End-use energy services
• Direct heat/process heat/motive force/illumination
1st Law of Thermodynamics
Energy is neither created nor destroyed
Its transformed from one form to another
2nd Law of Thermodynamics
Unavoidable transformation of some energy into unusable forms
Hight grade energy - dissipated as low grade heat
Energy conversion from primary to tertiary
• No energy loss in conversion process
• Unavoidable loss of useful energy
Energy Use in Commercial Building Sector
1) Naturally ventilated cellular
- Simple building
- Often (not always) small
- Sometimes in converted residential accommodation
- Size: 100!! -3000!!
- Domestic approach:
□ individual windows
□ Lower illuminance levels
□ Local light switches
□ Heating controls
- Help to match operation with needs of occupants
- Tends to reduce electricity consumption
- Tend to be few common facilities
- Catering: odd sink, refrigerator, kettle
2) Naturally ventilated open-plan
- Largely open-plan but some cellular offices & special areas
- Size: 500!! - 4000 !!
- Purpose built
- Sometimes converted in industrial space
□ Higher illuminance levels than domestic
□ Higher power densities
□ Higher hours of use
□ More office equipment, vending machines, etc
□ More routine use of equipment
- Lights & shared equipment tend to be switched in larger groups &stay on for longer
because its more difficult to match supply to demand
3) Air-conditioned standard
- Largely purpose-built
- Often speculatively developed
- Size: 2000!! - 8000!!
- Similar in occupancy & planning to 2) ,
- but usually with a deeper floor plan
- Tinted/shaded windows to reduce daylight further
- Can often be more intensively used
- Benchmarks are based on variable air volume(VAV) air-con with air-cooled water chillers
- Other systems often have similar overall consumption but a diff composition of end use
4) Air-conditioned prestige
- National/regional head office/tech or admin centre
- Size: 4000!! -20,000!!
- Purpose-built/refurbished to high standards
- Plant running hours are larger to suit diverse occupancy
- Catering:
□ Kitchens
□ Air-con rooms for mainframe computers & communications equipment
□ Extensive storage
□ Parking
□ Leisure facilities
Commercial Buildings - Energy Cost Indices
Annual kWh/#" of treated floor area (TFA):
1kWh = 1kW for 1 hr
1000J/s x 3600s = 3.6 x $%# J
ENERGY LOSSES/GAINS
Sensible Gains/Losses Inc/dec of temp of a space
• Solar gain
• Transmission (fabric) gain/loss
- Walls, windows, roof, floor
• Air infiltration/exfiltration
• Internal gains
- People, equipment, processes
Latent Gains/Losses Inc/dec of moisture content of a space
• Ventilation
• Air infiltration/exfiltration
• Internal
- People, equipment, processes
SPACE LOAD
Components of heating & cooling loads
Sensible load Any process that results in a temp change within a space
Latent load Any process that results in a moisture content change within a space
Wednesday 15 February 2023 20:00
ENERGY CONCEPTS
Primary Energy • Energy as it occurs in the earth
• Coal/crude oil/natural gas/uranium
Secondary Energy • Useful energy form
• Based on converting from primary energy
• Electricity/petroleum products/processed natural gas/processed fossil fuels
Tertiary Energy • End-use energy services
• Direct heat/process heat/motive force/illumination
1st Law of Thermodynamics
Energy is neither created nor destroyed
Its transformed from one form to another
2nd Law of Thermodynamics
Unavoidable transformation of some energy into unusable forms
Hight grade energy - dissipated as low grade heat
Energy conversion from primary to tertiary
• No energy loss in conversion process
• Unavoidable loss of useful energy
Energy Use in Commercial Building Sector
1) Naturally ventilated cellular
- Simple building
- Often (not always) small
- Sometimes in converted residential accommodation
- Size: 100!! -3000!!
- Domestic approach:
□ individual windows
□ Lower illuminance levels
□ Local light switches
□ Heating controls
- Help to match operation with needs of occupants
- Tends to reduce electricity consumption
- Tend to be few common facilities
- Catering: odd sink, refrigerator, kettle
2) Naturally ventilated open-plan
- Largely open-plan but some cellular offices & special areas
- Size: 500!! - 4000 !!
- Purpose built
- Sometimes converted in industrial space
□ Higher illuminance levels than domestic
□ Higher power densities
□ Higher hours of use
□ More office equipment, vending machines, etc
□ More routine use of equipment
- Lights & shared equipment tend to be switched in larger groups &stay on for longer
because its more difficult to match supply to demand
3) Air-conditioned standard
- Largely purpose-built
- Often speculatively developed
- Size: 2000!! - 8000!!
- Similar in occupancy & planning to 2) ,
- but usually with a deeper floor plan
- Tinted/shaded windows to reduce daylight further
- Can often be more intensively used
- Benchmarks are based on variable air volume(VAV) air-con with air-cooled water chillers
- Other systems often have similar overall consumption but a diff composition of end use
4) Air-conditioned prestige
- National/regional head office/tech or admin centre
- Size: 4000!! -20,000!!
- Purpose-built/refurbished to high standards
- Plant running hours are larger to suit diverse occupancy
- Catering:
□ Kitchens
□ Air-con rooms for mainframe computers & communications equipment
□ Extensive storage
□ Parking
□ Leisure facilities
Commercial Buildings - Energy Cost Indices
Annual kWh/#" of treated floor area (TFA):
1kWh = 1kW for 1 hr
1000J/s x 3600s = 3.6 x $%# J
ENERGY LOSSES/GAINS
Sensible Gains/Losses Inc/dec of temp of a space
• Solar gain
• Transmission (fabric) gain/loss
- Walls, windows, roof, floor
• Air infiltration/exfiltration
• Internal gains
- People, equipment, processes
Latent Gains/Losses Inc/dec of moisture content of a space
• Ventilation
• Air infiltration/exfiltration
• Internal
- People, equipment, processes
SPACE LOAD
Components of heating & cooling loads
Sensible load Any process that results in a temp change within a space
Latent load Any process that results in a moisture content change within a space
