1. Thoughtful cooling Engineering student certificate Workshop
Active Cooling Principles

2. TABLE OF CONTENT What is Active Cooling?
Difference between Active and Passive Cooling
Application of Active cooling
Refrigeration Cycle
HVAC System Types
Energy Efficiency in HVAC Systems
Energy Efficiency Approach for Active Cooling
Refrigerants
HVAC Monitoring & Maintenance and Ongoing Efficiency

3. Key Takeaways
Heat transfer processes in conventional refrigeration cycle
Equipments in a conventional HVAC system
Concepts of HVAC Efficiency (EER, COP)
Environmental issues of conventional HVAC: energy intensiveness, Direct and Indirect GHG Emissions, Total Equivalent Warming Impact (TEWI) of f-gas refrigerants
Space, structure and environmental implications for design studio projects

4. WHAT IS ACTIVE COOLING?
Active Cooling refers to cooling of buildings by using energy based mechanical systems.
The trainer should explain that Active cooling focuses on cooling/ conditioning of spaces by use of mechanical energy to achieve desired specific temperature, humidity for specific time periods irrespective of the external environmental conditions.
Whereas Passive design focuses on achieving indoor comfort conditions considering the type of climate, building form, adaptive comfort levels.
Active cooling

5. ACTIVE COOLING - SYSTEM OBJECTIVE
Temperature Regulation - Cooling to perimeter and core spaces.
Moisture Regulation - Humidification or dehumidification as needed.
Fresh Air Provision - Ventilation to occupied spaces.
Improvement of air quality - Healthy, productive, comfortable indoor environment.
Continued Supply - Deliver over time and space.

6. DIFFERENCE BETWEEN PASSIVE AND ACTIVE COOLING
Passive Cooling:
It is a strategy wherein a space is cooled by not using any mechanical device that uses energy. Passive cooling requires less or no electrical energy for cooling.
Passive cooling is a design approach, which is used to achieve indoor comfort by preventing and controling heat ingress within the built space, by least use of energy, either through architectural design, non-energy based cooling strategies or choice of material or all of the above.
ZERO OR LESS ENERGY USAGE
Active Cooling:
Uses energy to generate cooling required to achieve the desired thermal comfort, irrespective of the climate or original condition of the space. It consumes less or more energy for cooling depending on the prevailing indoor conditions.
Should only be used if the cooling possible through evaporation is not sufficient or violates thermal comfort conditions (i.e. in humid regions wherein dry bulb and wet bulb temperatures do not differ greatly)
ENERGY INTENSIVE
Emphasize that instead of considering active cooling as a “must provide”, project must first examine the possibility of passive cooling and should look at active cooling as a supportive system or last resort with a energy savings viewpoint.

7. TYPICAL ELECTRICAL CONSUMPTION PATTERN IN BUILDINGS
Explain HVAC
Typically HVAC systems dominate building energy consumption.
*HVAC – Universal Abbreviation of Heating, Ventilation and Air Conditioning. Active cooling is a part of HVAC

8. APPLICATIONS OF ACTIVE COOLING.
Discuss that depending on size, function, time and frequency if use, desired temperatures and indoor conditionings the choice of active cooling system is done.
Small Scale
Large scale
Specialized
Individual rooms
Homes
Small Commercial Buildings
Large Commercial Buildings
Hospitals
Institutional buildings
Office spaces
Museums
Manufacturing Units (Pharmacy industry, Food manufacturing, Textile industry etc.)
Operation Theatres
Cold Storages
Generally Decentralized systems like Split ACs
Mostly Centralized system.
District cooling etc.
Specialized controlled
systems in terms of Humidity/ temperature/ air velocities/ air filtration levels etc.

9. FUNDAMENTALS OF ACTIVE COOLING
Active cooling is provided by ‘pumping’ heat from the space to be cooled (a heat source, at a low temperature) to the atmosphere (a heat sink, at a higher temperature): heat rejection
Its all about ‘evaporation’. The cycle relies upon ‘evaporation’ of refrigerant and the subsequent ‘passing-the-parcel’ game of heat till ‘rejected’ to the atmosphere
The only way to reject heat once absorbed by the refrigerant is to elevate its temperature (after it has evaporated) to a magnitude much higher than the ambient air temperature into which heat must be rejected.

10. FUNDAMENTALS OF ACTIVE COOLING
This ‘artificial’ elevation of temperature (through pressure increase ) is the core function of the ‘compressor’ – the ‘soul’ of the VCR system.
The conventional refrigeration cycle is a Vapor Compression Cycle; it must perform work (i.e. use energy) to be able to force heat to flow against the temperature gradient.
Therein lies the crux of its energy intensive operation (the process does not occur spontaneously; needs assistance)

11. REFRIGERANT PROPERTIES
Low boiling point Low freezing point Low Specific Heat High Latent Heat High Thermal conductivity Non Flammable Non Explosive Non Toxic Non Corrosive Low ODP & GWP Easily availability and storage

12. REFRIGERATION CYCLE Compressor Heat source P = 1 atm T = 7°C
Heat sink
T = 24°C
Latent heat of vaporization
Compressor
evaporator
P = 2 – 3 atm
T = -16°C
P = atm
T = 28°C
INCREASE IN PRESSURE
HENCE
INCREASE IN TEMPERATURE
HEAT PICK UP FROM ROOM/SPACE TO BE COOLED
The property of the refrigerant of having very low boiling and freezing points should be highlighted.
The trainer has to explain the basics of refrigeration cycle including the various state, temperature and pressure of refrigerant at various stage of the cycle.
Refrigeration cycle explanation to begin with heat-absorption from an occupied space at the evaporator which causes refrigerant to ‘evaporate’ or ‘boil’ under low pressure. HVAC engineers follow the perplexing practice of explaining the cycle from the compressor or condensor onwards – which is ineffective as a teaching practice as it is non-intuitive and does not harness ‘experiential’ understanding of cooling – which therefore must be the starting point.
Explain heat transfer across the system as a ‘passing the parcel’ game wherein heat makes its way from the room to the atmosphere where it is thrown into the air via the condensor.
HEAT REJECTION TO EXTERNAL ENVIRONMENT THROUGH AIR OR WATER
PRESSURE REDUCTION TO REDUCE TEMPERATURE
Image source:

13. REFRIGERATION CYCLE
The trainer to explain detailed refrigeration cycle using the schematic shown in the picture.

14. REFRIGERATION CYCLE
The trainer to explain detailed refrigeration cycle using the schematic shown in the picture.
Animations:

15. HVAC Classification Basis 1: by condenser-side cooling medium
Depending on whether the heat collected from the space is rejected to either air or water; HVAC systems are classified as Air Cooled or Water Cooled

16. AIR COOLED SYSTEM Ideal for Decentralized cooling.
The trainer needs to explain that basically there are basically two ways of cooling air in a compression system:
Direct Air cooling by Refrigeration cycle
Indirect Air cooling by a medium like water which is chilled by the refrigeration cycle.
The pros and cons of each type of cooling can be discussed by the trainer.
Ideal for Decentralized cooling.
Efficient cooling for small volumes of air cooling/ conditioning.
Image source:
Image Source:

17. WATER COOLED SYSTEM Ideal for Centralized cooling.
Efficient cooling for large volumes of air cooling/ conditioning.
Large distance Distribution of chilled water easier

18. LIST OF COMPONENTS Compressor Cooling Tower Condenser Coil
Chiller Unit
Explain the role of each component
Expansion Valve
Pump
Evaporative Coil
Diffuser
Return/Exhaust Air
Cooled Air
Fan

19. Central Plant -Chiller Based
HVAC Classification Basis 2: by Physical Confirguration
Air Conditioning
Non-centralized
Window AC
Split AC
Centralized
Packaged AC, VRF
Central Plant -Chiller Based

20. NON-CENTRALIZED Window ac Split ac HOT AIR EXHAUST COOL AIR SUPPLY
Image source:

21. CENTRALIZED AIR CONDITIONING
Centralized AC system
Ductable Split
Air Cooled
Water Cooled
VRF
Chillers
CENTRALIZED AIR CONDITIONING

22. DUCTABLE SPLIT

23. VRV

24. Image source: http://clubchillercontrol.blogspot.in/
CHILLER BASED
Image source:

25. ENERGY EFFICIENCY IN HVAC SYSTEMS
DEPENDS ON –
Choice of system and components
Design of HVAC High-Pressure side (i.e. compressor discharge through condenser to expansion valve inlet), and Low-Pressure side (expansion valve outlet through evaporator to compressor inlet)
Efficiency of Individual Components
Energy efficiency in each component in the HVAC system need to be explained.

26. ENERGY EFFICIENCY IN HVAC SYSTEMS
COP – Coefficient of Performance
- defined as Watts of Cooling / Watts of Electrical Input (dimensionless number)
EER – Energy Efficiency Ratio*
- defined as Btu/hr. of cooling / Watt of Electrical Input (units of [Btu/h]/W)
Note: Bureau of Energy Efficiency’s (BEE) determined ‘EER for ACs’ for the star rating system are in fact COP values (i.e. Watt/Watt)
EXPLAIN

27. ENERGY EFFICIENCY IN HVAC SYSTEMS
IPLV – Integrated Part Load Value
- weighted average cooling efficiency at part-load capacities
ASHRAE Standard 90.1 for IPLV =
IPLV = 1 / (0.01 / A / B / C / D) 
where 
A = kW/ton at 100%
B = kW/ton at 75%
C = kW/ton at 50%
D = kW/ton at 25% 
EXPLAIN

28. ENERGY EFFICIENCY IN HVAC SYSTEMS, COP
Window AC
2.7 to 3.2
Split AC (up to 3 TR)
2.7 to 3.5
Ductable Split – Air Cooled
VRV – Air Cooled
3.2 to 4.5
VRV – Water Cooled
3.8 to 5.5
Centrifugal Air Cooled Chiller
2.9 to 3.0
Centrifugal Water Cooled Chiller
5.8 to 6.3
Screw Chiller Air Cooled
Screw Chiller Water Cooled
4.7 to 6.5

29. ENERGY EFFICIENCY IN HVAC SYSTEMS
Water-cooled systems > efficient than air-cooled systems
ability of water to absorb and discharge heat per unit volume much greater than air
specific heat of water ~ 4x air, mass density of water ~ 800x air
thermal conductivity of water ~ 24x air
Variable Frequency Drives for Compressors, Fans and Pumps to reduce energy consumption during part load operations.
Appropriate Compressor selection based on cooling load profile:
for fixed loads ~ centrifugal compressor's
variable loads (part load performance required) ~ screw and scroll compressors

30. ENERGY EFFICIENCY IN HVAC SYSTEMS
operating temperatures of Evaporator and Condenser
higher operating temperatures = higher COP
COP ~ 3.2 for 70C Evaporator/120C Condenser system
COP ~ 4.2 for 150C Evaporator/200C Condenser system
optimal AHU duct design
reduced duct length
reduced refrigerant piping bends and length
reduced sensible and latent heat load
thermostat setting: ~ 8 to 15 % energy savings per 0C rise in set-point temperature

31. HVAC ENERGY EFFICIENCY HEIRARCHY
Natural Ventilation feasible?
Mechanical Ventilation feasible?
Mixed-Mode Ventilation feasible?
Heating and Cooling (without humidity control) feasible?
Opt for Air Conditioning with Humidity Control NO
Increasing Energy CONSUMPTION
& GHG EMISSIONS

32. ENVIRONMENTAL ISSUES WITH CONVENTIONAL HVAC SYSTEMS
Refrigerants used are largely f-gases with high GWPs
Energy intensive since they ‘pump’ heat (rather than ‘draining’ heat)
Inefficient since they use air as a heat-transfer medium through AHUs

33. ENVIRONMENTAL ISSUES WITH CONVENTIONAL HVAC SYSTEMS
Compressors can only operate on electricity; largely fossil derived with low thermal efficiency (~30 %) and substantial transmission losses (~30 %)
4.76 kWh fuel used
1.42 kWh generated
1 kWh available

34. ENVIRONMENTAL ISSUES WITH CONVENTIONAL HVAC SYSTEMS
Require air-tight envelopes which impair indoor air quality unless fresh-air permitted, which increases energy consumption
Buildings with these systems often have inoperable windows; prevent operation as a mixed-mode building
Introduce cooled and de-humidified air at significant distances from occupants, hence unnecessarily low operating temperatures

35. GHG emissions OF AC SYSTEMS

36. LIFE CYCLE GHG EMISSIONS OF COOLING TECHNOLOGIES

37. LIFE CYCLE GHG EMISSIONS OF COOLING TECHNOLOGIES
Scope 1 Emissions (Ref. Fugitive Emissions)
Scope 2 Emissions
( Electricity Emissions)
Scope 3 Emissions
( AT&C Loss Emissions)
Total Life Cycle GHG Emissions

38. CASE A Library Building 84 TR Direct-Expansion Chiller System
EER of System = 2.93
R22 Refrigerant
3,000 hours/year use
Energy Cost = INR/kWh
Energy Penalty (above contract demand) = INR 300 / kVA / month
Capital Cost = INR Lakh
Building Dimensions:
Length: 131 feet
Width: 82 feet
Height: 10 feet 6 inch per floor
5 Floors

39. CASE A
Step 1: Derive power consumption for 84 TR system cooling output
84 TR = 84 TR x kW / TR = kW cooling
EER = 2.93 = kW output / X kW input
X = kW / 2.93 = kW input (electrical)
Step 2: Determine annual energy consumption for calculated system kW
• kW x 3,000 hours/year = 302,486 kWh/year
Step 3: Calculate annual GHG emissions for energy consumption
Scope 2 Emissions (Indirect Electricity Emissions) = 302,486 kWh/year x
0.96 kg CO2e/kWh (Avg. India Grid Electricity Emission Factor) = MT CO2e/year
Scope 3 Emissions (AT&C Loss Emissions) = 302,486 kWh/year x 0.29 kg CO2e/kWh (Avg. India Grid AT&C Losses Emission Factor) = 87.7 MT CO2e/ year

40. CASE A
Step 4: Determine Non-Energy (Fugitive) Emissions from Refrigerant Use Life- Cycle
Step 1: Methodology for determining total emissions from refrigerant leakage from refrigerators and air conditioners Guidelines: REFRIGERATION AND AIR CONDITIONING, Volume 3: Industrial Processes and Product Use, Chapter 7: Emissions of Fluorinated Substitutes for Ozone Depleting Substances, 2006 IPCC Guidelines for National Greenhouse Gas Inventories Etotal ,t = Econtainers,t + ECharge,t + Elifetime,t + Eend −of −life,t EMISSIONS FROM MANAGEMENT OF CONTAINERS Econtainers, t = RMt • c / 100 Where: Econtainers, t = emissions from all HFC containers in year t, kg RMt = HFC market for new equipment and servicing of all refrigeration application in year t, kg c = emission factor of HFC container management of the current refrigerant market, percent

41. CASE A EMISSIONS WHEN CHARGING NEW EQUIPMENT
Echarge, t = Mt • k / 100 Where:
Echarge, t = emissions during system manufacture/assembly in year t, kg
Mt = amount of HFC charged into new equipment in year t (per sub-application), kg
k = emission factor of assembly losses of the HFC charged into new equipment (per sub-application), percent
EMISSIONS DURING EQUIPMENT LIFETIME
Elifetime, t = Bt • x / 100 Where:
Elifetime, t = amount of HFC emitted during system operation in year t, kg
Bt = amount of HFC banked in existing systems in year t (per sub-application), kg
x = annual emission rate (i.e., emission factor) of HFC of each sub-application bank during operation, accounting for average annual leakage and average annual emissions during servicing, percent
EMISSIONS AT SYSTEM END-OF-LIFE
Eend-of-life, t = Mt-d • P/100 • (1-nrec,d/100) Where:
Eend-of-life, t = amount of HFC emitted at system disposal in year t, kg
Mt-d = amount of HFC initially charged into new systems installed in year (t-d), kg
p = residual charge of HFC in equipment being disposed of expressed in percentage of full charge, percent
ηrec,d = recovery efficiency at disposal, which is the ratio of recovered HFC referred to the HFC contained in the system, percent

42. CASE A
IPCC/TEAP IPCC/TEAP Special Report: Safeguarding the Ozone Layer and the Global Climate System. Intergovernmental Panel on Climate Change
SCENARIO
DISTRIBUTION PHASE
HFC- USE PHASE
END-OF-LIFE PHASE
FROM HANDLING CONTAINERS
OPERATIONAL LEAKAGES
LEAKAGES FROM INITIAL CHARGING
REMAINING CHARGE FOR SERVICING
LEAKAGES FROM SERVICING RECHARGE
REMAINING CHARGE AT END-OF-LIFE
RECOVERY EFF.
[% OF MARKET]
[% OF INITIAL CHARGE / YEAR]
[% OF INITIAL CHARGE]
[% OF INITIAL CHARGE]
[% OF SERVICING RECHARGE]
[% OF REMAINING CHARGE]
BUSINESS-AS-USUAL SCENARIO
10% 1%
60% 2%
80%
INTERMEDIATE LEAKAGE SCENARIO 5%
65%
85%
BEST-PRACTICES SCENARIO
0.20% NA
0.40%
90%

43. CASE A System Type Refrigerant Type GHG EF Units
Calculated Refrigerant (Fugitive) Life-Cycle Emission Factors for Developing Countries (India) with Minimal Leakage Mitigation Efforts
System Type
Refrigerant Type
GHG EF
Units
Ductable AC Conventional)
Avg. High GWP Refrigerant Mix
149.76
kg CO2e/kW cooling/year
Ductable AC (Conventional)
HFC-32
16.32
R-290
0.08

44. CASE A
Step 4: Determine Non-Energy (Fugitive) Emissions from Refrigerant Use Life-Cycle
Scope 1 Emissions (Refrigerant Leakage) = kg CO2e/kW cooling/ year x kW cooling = 44.2 MT CO2e/year
Step 5: Determine Annual Operating (Energy) Cost
Energy Use Cost = 302,486 kWh/year x INR/kWh = INR Lakh/ year
Energy Penalty Cost:
Electrical Load = kW
Power Factor = 0.9
Apparent Power = 100.8/0.9 = 112 kVA
Penalty Cost = 300 INR/kVA/month x 112 kVA x 12 months/year = INR Lakh/year

45. Annual Emissions and Cost Summary
CASE A
Annual Emissions and Cost Summary
Parameter
Value
Units
Scope 1 Emissions
44.2
MT CO2e/year
Scope 2 Emissions
290.4
Scope 3 Emissions
87.7
TOTAL GHG Emissions
422.3
Capital Cost
16.20
INR Lakh/Year
Annual Operating Cost
44.11