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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)
22/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
INTRODUCTIONINTRODUCTION
• 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
33/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
INNOVATIVE STRATEGIESINNOVATIVE STRATEGIES• 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
44/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
INNOVATIVE STRATEGIESINNOVATIVE STRATEGIES
• 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
55/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
Building Orientation/ Architectural FeaturesBuilding Orientation/ Architectural Features
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
EASTSOUTH &WEST
66/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
Building Orientation/ Architectural FeaturesBuilding Orientation/ Architectural Features
• 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.
77/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
Establishing Baseline Performance IndicesEstablishing 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.
88/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
Total tons at worst conditions - At Machine End- At User End
Tons / Sq. Meter
KW / Ton
KWH / Day
KWH / Year
Establishing Baseline Performance IndicesEstablishing Baseline Performance Indices
99/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
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
1010/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
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
High Sensible Air Conditioning System 7 TRHigh Sensible Air Conditioning System 7 TR
1111/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
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
High Sensible Air Conditioning System 2x1.5TRHigh Sensible Air Conditioning System 2x1.5TR
1212/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
ENERGY CONSUMPTIONENERGY CONSUMPTION RECORD / SAVING COMPARISON RECORD / SAVING COMPARISON
ENERGY CONSUMPTIONENERGY CONSUMPTION RECORD / SAVING COMPARISON RECORD / SAVING COMPARISON
Model/ Type
KWh in
12 Hr
KWh Savings in
12 Hr
Annual KWh
savings
Annual savings
in Rs.
1.5TR
SAC
20.5 NA NA NA
1.5TR Hi-
Sensi
14.8 5.7 4161 20,805
1313/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
PAYBACK CALCULATIONPAYBACK CALCULATIONPAYBACK CALCULATIONPAYBACK CALCULATION
Cost of 2x1.5TR Hi-Sensible Rs.100000
Cost of 1.5TR SAC Rs.60000
Incremental initial cost of Hi-S AC (A) Rs.40000
Pay back period of Hi-S AC on (A) 1.9 Years
Total savings after the payback period over operating life of Hi-Sensi AC
Rs. 147716
1414/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
ASSUMPTIONS & TEST PARAMETERSASSUMPTIONS & TEST PARAMETERS
Con. Amb. Temp. maintained (ODU) 35°C
Shelter (IDU) Temp. maintained @ (DB) 25°C
Shelter (IDU) Temp. maintained @ (WB) 25°C
Running Hr for Energy Consumption 12 Hrs
Average unit cost (KWh) Rs.5/-
Life span of SAC unit 6 Yrs
Life span of Hi-Sensi AC unit 9 Yrs
Est. Cost of 1.5TR SAC (i/c Taxes) Rs.30000
Est. Cost of 2x1.5TR Hi-Sensi unit
(i/c Taxes & w/o controllers)
Rs.100000
1515/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
HIGH SENSIBLE AC UNITSHIGH SENSIBLE AC UNITS
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.
1616/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
ENERGY EFFICIENCY OF SPLIT AC UNITSENERGY EFFICIENCY OF SPLIT AC UNITS
• EER is the Ratio between Cooling Capacity of AC Unit in Kcal/Hr and Power input to AC Unit in WattsEER = Output in Kcal/Hr
Power input in Watts
1717/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
Capacity : 1.5 TR Split AC UnitCapacity : 1.5 TR Split AC UnitMake Cooling
Cap in Kcal/Hr
Power Consmp in Watts
EER
Purison 5096.90 1880 2.71
Videocon 5366.45 2000 2.68
National Aircon 4737.00 1840 2.57
Gujral 4681.94 1860 2.52
Hitachi 4531.70 1800 2.51
LG 4774.00 1948.50 2.45
Universel Comfrt 4798.00 2000 2.14
1818/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
Automation and BMSAutomation and BMS 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
1919/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
VARIABLE SPEED DRIVES (VV-VF)VARIABLE SPEED DRIVES (VV-VF)
• 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.
2020/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
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
Variable Speed Drives (VV-VF)Variable Speed Drives (VV-VF)
2121/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
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.
Variable Speed Drives (VV-VF) Variable Speed Drives (VV-VF)
2222/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
3 Ph Supply DC REACTOR
CAPACITOR
MOTOR
RECTIFIER SECTION
INVERTER M
L O A D
MAIN
CONTROLLER
Variable Speed Drives (VV-VF)Variable Speed Drives (VV-VF)
2323/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
Heat Recovery Wheel/ Desiccant CoolingHeat 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)
2424/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
Heat Recovery Wheel / Desiccant CoolingHeat 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
2525/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
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.
Heat Recovery Wheel / Desiccant Cooling Heat Recovery Wheel / Desiccant Cooling
2626/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
1. Heating/Cooling Energy (e.g. 80%) Is Always Returned To Where It Came From
Heat In
Heat Out
Cooling Energy Out
Cooling Energy In
Moisture In
Moisture Out
Dry Air Out
Dry Air In
2. Moisture and Dry Air (e.g. 80%) Is Always Returned To Where It Came From
Universal Rules of Total Energy Wheels
Heat Recovery Wheel / Desiccant CoolingHeat Recovery Wheel / Desiccant Cooling
2727/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
UNIVERSAL HEAT RECOVERY ENERGY WHEEL
Heat Recovery Wheel / Desiccant CoolingHeat Recovery Wheel / Desiccant Cooling
2828/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
Panel CoolingPanel 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.
2929/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
Panel CoolingPanel 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.
3030/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
Vapour Absorption MachinesVapour 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 toHigh cost of secondary energy. Easy avail. of gas Noiseless, No Moving Part, Low Cost of Mtce.Uncertainty in view of CFC phase-out
3131/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
Vapour Absorption Machines - Principle of Operation
3232/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
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
Roof Top Chillers
3333/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
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.
Roof Top Chillers
3434/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
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
Free Cooling or Cooling by Total Air Displacement
3535/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
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.
Free Cooling or Cooling by Total Air Displacement
FRESHAIR
PLENUM
D1DAMPERS D2
RETURN FILTER COOLING FAN COND.
AIR COIL SPACE
PLENUM
EXHAUST RETURN AIR TO
ATMOSPHERE
AMBIENT DAMPER COOLING COIL
>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
Free Cooling or Cooling by Total Air Displacement
3737/34/34Electrical Wing, BSNL, TNElectrical Wing, BSNL, TN
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.
Conclusion