ENERGY CONSERVATION STRATEGIES FOR HVAC SYSTEMS

1. ENERGY CONSERVATION STRATEGIES FOR HVAC SYSTEMS V.P. Gupta, Principal Chief Engineer (Electrical) Bharat Sanchar Nigam Limited Tamilnadu Electrical Zone (An ISO 9001:2000 Unit)

2. For Telecom Buildings, Exchange Equipment is compact but more powerful, fragile and very sensitive to high temperature. It is necessary to provide high reliable AC Systems HVAC Systems consume 50-60% of total power – Thus huge potential for Energy Saving Innovative strategies can be applied to reduce Energy Bills INTRODUCTION

3. Building Orientation/Architectural Features Establishing Baseline Performance Indices High Sensible Air-Conditioning System Package AC Units :- 7 TR 2x1.5 TR & 2x2 TR Automation & BMS Variable Voltage Variable Frequency Drives INNOVATIVE STRATEGIES

4. Heat Recovery Wheel /Desiccant Cooling System for Fresh Air Panel Cooling Vapour Absorption Machines Roof Top Chillers Free Cooling or Cooling by Total Air Displacement INNOVATIVE STRATEGIES

5. Points to be considered: Orientation Double Glass Panels Insulation on Roof No Leakage from Windows/Doors/Ceiling/Return Air Long side should be having minimum heat gain. Minimum heat gain from NORTH EAST SOUTH & WEST Building Orientation/ Architectural Features

6. Plant Room and AHU locations should be such that ducting/ piping are minimum. Sufficient Fresh Air Intake to avoid “Sick Building Syndrome” Sun Shades over glass area with proper inclination to avoid direct sunrays. Partitions and closure of air grills of unutilized conditioned space. Building Orientation/ Architectural Features

7. Establishing Baseline Performance Indices Points to be considered • Space Temperature (23-26°C) - Task & Non-Task, Eqpt. Room etc. (against earlier 20-26°C) • Space Humidity 30-70% (against earlier 40-60%) • Usage Time Schedule - Working Hours, Holidays etc. • P.F. target 0.95, rationalise contract demand and A/C space.

8. Establishing Baseline Performance Indices • Total tons at worst conditions - At Machine End - At User End • Tons / Sq. Meter • KW / Ton • KWH / Day • KWH / Year

9. High Sensible Air Conditioning System • Specially designed AC Package Units to handle a high sensible heat factor of 0.95 • Liberal Evoporation and Condensor Coil Area • Higher Saturation Temperature • Higher CFM • Air-Cooled Condensers with two/variable Speed Motors • Condenser fan motor stops completely when compressor is stopped

10. High Sensible Air Conditioning System 7 TR • Package AC provided with dehumidification mechanism by reducing effective coil area to 2/3rd whenever dehumidification is required. • Control system enables a solenoid valve to cut off 1/3 of cooling coil providing a lower evaporating temperature and dehumidification without any heating • Saving of precious electrical energy. Constant airflow maintained even during dehumidification

11. High Sensible Air Conditioning System 2x1.5TR • Recently Approved for Ph. V Tenders • Highly Energy Efficient unit with Build-in Timers, Microprocessor Controllers to Switch from Active Units • Stand-by Units and back • Designed for continuous 24 X 7 Operations

12. ENERGY CONSUMPTION RECORD / SAVING COMPARISON

13. PAYBACK CALCULATION

14. ASSUMPTIONS & TEST PARAMETERS

15. Comfort type Split AC is designed at 35°C Hi Sensible AC is designed at 43°C. Energy saving at temperatures higher than 35°C will be even greater on using Hi Sensible AC unit. HIGH SENSIBLE AC UNITS

16. EER is the Ratio between Cooling Capacity of AC Unit in Kcal/Hr and Power input to AC Unit in Watts EER = Output in Kcal/Hr Power input in Watts ENERGY EFFICIENCY OF SPLIT AC UNITS

17. Capacity : 1.5 TR Split AC Unit

18. Ensures Optimum Operation of all machines by avoiding energy wastage due to overcooling / overheating CO2 Sensors to control ventilation in response to varying people load – by controlling damper operation Programmed Start/Stop of AC M/s, Ventilation System, Chiller, etc. Run-time equalisation & auto adjustment of set points Automation and BMS

19. Step less variation of Fans, Pumps and compressor speed in tune with load reqmts can be achieved with VV-VF Drives. Power Consumption in Pumps/Blowers is proportional to Cube of Speed, eg. At 80% speed, power consumption is cube of 0.8 or 0.512 or 51.2% Reduction in mechanical wear and tear as motors run at low speed. Results in additional saving in maintenance cost. VARIABLE SPEED DRIVES (VV-VF)

20. Variable Speed Drives (VV-VF) The power consmp proportionality can be explained from Affinity law governing fluid flow: Flow (F) œ Speed (N) Pressure (P) œ Square of speed (N2) Power (E) œ F x P or N3

21. Variable Speed Drives (VV-VF) • VVVF system basically consists of a input rectifier and an inverter connected through a controller. • V/f ratio is kept constant throughout the operating range of the motor to maintain torque. • Performance depends on location and accuracy of sensors providing load demand feedback.

22. Variable Speed Drives (VV-VF) 3 Ph Supply DC REACTOR L RECTIFIER M O INVERTER CAPACITOR SECTION A D MOTOR MAIN CONTROLLER

23. Heat Recovery Wheel/ Desiccant Cooling • Induction of fresh air into building is necessary to reduce “Sick Building Syndrome” • ASHRAE 62-99 specifies 20 cfm of outdoor air per person. • Creates additional load on A/C system • Desiccant cooling helps in reducing the additional load due to fresh air (applicable for areas with 80-90% humidity throughout year)

24. Heat Recovery Wheel / Desiccant Cooling • The wheel is positioned typically in the duct system so that return air is drawn through its one half and outdoor air is drawn through its other half in a counter flow pattern. • The wheel is rotated at 2 to 20 rpm • Sensible heat is transferred as the metallic substrate picks up and store heat from the hot air steam and gives it up to the cold one. • Latent heat is transferred as the desiccant on the wheel absorbs moisture from the higher humidity air stream and releases the same into the air stream that has a lower humidity ratio

25. Heat Recovery Wheel / Desiccant Cooling • Capable of recovering 80% of heating or cooling energy exhausted from building and reduces energy cost of fresh air. • Enthalpy wheel is usually 4” to 10” deep packed with a heat transfer medium i.e. numerous small air passages or flutes parallel to direction of air flow. This honeycomb matrix is produced by interleaving flat and corrugated layers of a high conductivity material usually aluminium surfaced with a desiccant.

26. Heat Recovery Wheel / Desiccant Cooling Universal Rules of Total Energy Wheels 1. Heating/Cooling Energy (e.g. 80%) Is Always Returned To Where It Came From Heat In Cooling Energy Out Heat Out Cooling Energy In 2. Moisture and Dry Air (e.g. 80%) Is Always Returned To Where It Came From Moisture In Dry Air Out Moisture Out Dry Air In

27. Heat Recovery Wheel / Desiccant Cooling UNIVERSAL HEAT RECOVERY ENERGY WHEEL

28. Panel Cooling • The telecom equipment heat load is only 40% and another 60% heat load is due to the surrounding space/ room. Due to shrinkage of equipment size, improvement in technology , the exchanges are not required to be manned. • Substantial energy saving is possible by mounting small panel coolers instead of window/ split AC units only for cooling the switching equipment and not the entire room.

29. Panel Cooling • Panel cooler - a mini AC unit delivering a fractional TR,directly clamped to eqpmt panel with a close loop air cycle so as to cool the space within the equipment. • Power consumption - only 2.7 KW against earlier 6 KW with 3 number window AC units. • On experimental basis a Pilot Project has been carried out in Hyderabad. • Requires further studies. Vendors to come forward for optimum solution.

30. Vapour Absorption Machines • VAM uses primary energy in the form of heat viz. Steam, CNG, HSD, Kerosene and superior Kerosene. (Whereas VCM uses secondary energy in the form of electricity.) • VAM uses Lithium Bromide as absorbent and water as refrigerant. • Becoming popular due to • High cost of secondary energy. Easy avail. of gas • Noiseless, No Moving Part, Low Cost of Mtce. • Uncertainty in view of CFC phase-out

31. Vapour Absorption Machines - Principle of Operation

32. Roof Top Chillers • Costly built up space inside the building can be saved used as they can be mounted on the roof. • All components like Compressor, Compressor Motor, Evaporator, Chiller and Air Cooled Condenser along with the micro-processor based control panel forms part of the roof top chiller and are highly compact. • A considerable saving of energy as the refrigerant pipes become very small

33. Roof Top Chillers • Factory made and designed with best of components. • All the protecting device and safeties are factory fitted and thus, ensure high level of reliability. • The microprocessor based panels monitor the set points precisely and thereby, save energy. • Designed with energy efficient scroll or screw compressors.

34. Free Cooling or Cooling by Total Air Displacement • Whenever ambient dry bulb temperature is in between 16 to 20 °C, cooling of inside space can be achieved by total displacement of inside air with the fresh air • When the temperature is in between 11 to 16 °C, a of mixture of return air and ambient air can give the required inside conditions • In both cases, the ambient air needs to be 100% filtered

35. Free Cooling or Cooling by Total Air Displacement • Dampers in both the cases to be operated with suitable sensors for free cooling. • Mechanical Refrigeration is needed only when the ambient temperature is more than 20°C. • Free cooling assures power saving of about 80%, we require power only for the operation of fans for exhaust and circulation of air. • Manufacturers have to come forward to fine tune Filters, Sensors and Control of Dampers.

36. AMBIENT DAMPER COOLING COIL Free Cooling or Cooling by Total Air Displacement >20°C D2 OPEN, D1 PARTIALY OPEN FOR REQUIRED FRESH AIR ON 11-16°C D1 AND D2 PARTIALLY OPEN OFF 16-20°C D1 OPEN D2 CLOSE OFF FRESH AIR PLENUM D1 DAMPERSD2 RETURNFILTER COOLING FAN COND.AIR COIL SPACE PLENUM EXHAUST RETURN AIR TO ATMOSPHERE

37. Conclusion The above strategies can be suitably applied for optimization of airconditioning system and energy savings. Manufacturers/Vendors to come forward for providing optimum solution with Panel Cooling and Free Cooling Strategies.

38. Thank You