ENERGY CONSERVATION STRATEGIES FOR HVAC SYSTEMS V.P. Gupta, Principal Chief Engineer (Electrical) Bharat Sanchar Nigam Limited Tamilnadu Electrical Zone.

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


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


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


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


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.


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.


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


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


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


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


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


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


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


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.


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


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


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


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.


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)


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)


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)


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)


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


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


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



UNIVERSAL HEAT RECOVERY ENERGY WHEEL



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.


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.


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


Vapour Absorption Machines - Principle of Operation


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


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


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


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.


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



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


ThankYou

ENERGY CONSERVATION STRATEGIES FOR HVAC SYSTEMS V.P. Gupta, Principal Chief Engineer (Electrical) Bharat Sanchar Nigam Limited Tamilnadu Electrical Zone.

Documents

electrical wing

tr slide

unit slide

tn package ac

ac space

watts slide

precious electrical

tn automation