Presentation on theme: "ENERGY CONSERVATION STRATEGIES FOR HVAC SYSTEMS"— Presentation transcript:
1 ENERGY CONSERVATION STRATEGIES FOR HVAC SYSTEMS V.P. Gupta, Principal Chief Engineer (Electrical)Bharat Sanchar Nigam LimitedTamilnadu Electrical Zone(An ISO 9001:2000 Unit)
2 INTRODUCTIONFor Telecom Buildings, Exchange Equipment is compact but more powerful, fragile and very sensitive to high temperature.It is necessary to provide high reliable AC SystemsHVAC Systems consume 50-60% of total power – Thus huge potential for Energy SavingInnovative strategies can be applied to reduce Energy Bills
3 INNOVATIVE STRATEGIES Building Orientation/Architectural FeaturesEstablishing Baseline Performance IndicesHigh Sensible Air-Conditioning SystemPackage AC Units :-7 TR2x1.5 TR & 2x2 TRAutomation & BMSVariable Voltage Variable Frequency Drives
4 INNOVATIVE STRATEGIES Heat Recovery Wheel /Desiccant CoolingSystem for Fresh AirPanel CoolingVapour Absorption MachinesRoof Top ChillersFree Cooling or Cooling by Total Air Displacement
5 Building Orientation/ Architectural Features Points to be considered:OrientationDouble Glass PanelsInsulation on RoofNo Leakage from Windows/Doors/Ceiling/Return AirLong side should be having minimum heat gain.Minimum heat gain from NORTHEASTSOUTH &WEST
6 Building 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.
7 Establishing Baseline Performance Indices Points to be consideredSpace 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 EndTons / Sq. MeterKW / TonKWH / DayKWH / Year
9 High Sensible Air Conditioning System Specially designed AC Package Units to handle a high sensible heat factor of 0.95Liberal Evoporation and Condensor Coil AreaHigher Saturation TemperatureHigher CFMAir-Cooled Condensers with two/variable Speed MotorsCondenser 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 heatingSaving of precious electrical energy. Constant airflow maintained even during dehumidification
11 High Sensible Air Conditioning System 2x1.5TR Recently Approved for Ph. V TendersHighly Energy Efficient unit with Build-in Timers, Microprocessor Controllers to Switch from Active UnitsStand-by Units and backDesigned for continuous 24 X 7 Operations
12 ENERGY CONSUMPTION RECORD / SAVING COMPARISON Model/ TypeKWh in12 HrKWh Savings in 12 HrAnnual KWh savingsAnnual savingsin Rs.1.5TRSAC20.5NA1.5TR Hi-Sensi14.85.7416120,805
13 PAYBACK CALCULATION Cost of 2x1.5TR Hi-Sensible Rs.100000 Cost of 1.5TR SACRs.60000Incremental initial cost of Hi-S AC (A)Rs.40000Pay back period of Hi-S AC on (A)1.9 YearsTotal savings after the payback period over operating life of Hi-Sensi ACRs
14 ASSUMPTIONS & TEST PARAMETERS Con. Amb. Temp. maintained (ODU)35°CShelter (IDU) Temp. (DB)25°CShelter (IDU) Temp. (WB)Running Hr for Energy Consumption12 HrsAverage unit cost (KWh)Rs.5/-Life span of SAC unit6 YrsLife span of Hi-Sensi AC unit9 YrsEst. Cost of 1.5TR SAC (i/c Taxes)Rs.30000Est. Cost of 2x1.5TR Hi-Sensi unit(i/c Taxes & w/o controllers)Rs
15 HIGH 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.
16 ENERGY 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/HrPower input in Watts
17 Capacity : 1.5 TR Split AC Unit MakeCooling Cap in Kcal/HrPower Consmp in WattsEERPurison18802.71Videocon20002.68National Aircon18402.57Gujral18602.52Hitachi18002.51LG2.45Universel Comfrt2.14
18 Automation and BMSEnsures Optimum Operation of all machines by avoiding energy wastage due to overcooling / overheatingCO2 Sensors to control ventilation in response to varying people load – by controlling damper operationProgrammed Start/Stop of AC M/s, Ventilation System, Chiller, etc.Run-time equalisation & auto adjustment of set points
19 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 or 51.2%Reduction in mechanical wear and tear as motors run at low speed. Results in additional saving in maintenance cost.
20 Pressure (P) œ Square of speed (N2) 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.
23 Heat Recovery Wheel/ Desiccant Cooling Induction of fresh air into building is necessary to reduce “Sick Building Syndrome”ASHRAE specifies 20 cfm of outdoor air per person.Creates additional load on A/C systemDesiccant 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 rpmSensible 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 Universal Rules of Total Energy Wheels Heat Recovery Wheel / Desiccant CoolingUniversal Rules of Total Energy Wheels1. Heating/Cooling Energy (e.g. 80%) Is Always Returned To Where It Came FromHeat InCooling Energy OutHeat OutCooling Energy In2. Moisture and Dry Air (e.g. 80%) Is Always Returned To Where It Came FromMoisture InDry Air OutMoisture OutDry Air In
28 Panel CoolingThe 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 CoolingPanel 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 toHigh cost of secondary energy. Easy avail. of gasNoiseless, No Moving Part, Low Cost of Mtce.Uncertainty in view of CFC phase-out
31 Vapour Absorption Machines - Principle of Operation
32 Roof Top ChillersCostly 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 airWhen the temperature is in between 11 to 16 °C, a of mixture of return air and ambient air can give the required inside conditionsIn 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 Free Cooling or Cooling by Total Air Displacement AMBIENTDAMPERCOOLING COIL>20°CD2 OPEN, D1 PARTIALYOPEN FOR REQUIRED FRESH AIRON11-16°CD1 AND D2 PARTIALLYOPENOFF16-20°CD1 OPEN D2 CLOSEFRESHAIRPLENUMD1DAMPERS D2RETURN FILTER COOLING FAN COND. AIR COIL SPACEPLENUMEXHAUST RETURN AIRTOATMOSPHERE
37 ConclusionThe 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.