Energy Efficiency in Diesel Generator Operation

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Diesel generators are highly consuming equipment in Nepalese industry. This presentation explains how to operate Diesel Gensets efficiently. It was prepared for energy auditor training in Nepal in the context of GIZ/NEEP programme. For further information go to EEC webpage: http://www.eec-fncci.org

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Energy Efficiency in Diesel Generator Operation

  1. 1. FOCUS AREAS FOR ECONOMIC DG SET OPERATION D. PAWAN KUMAR
  2. 2. TYPICAL GRID POWER SCENARIO FEATURES  Frequent power trippings  Low voltage problems  Captive power generation has become a necessity  Power cuts  Low frequency problems
  3. 3. ADVANTAGES  In the context of utility sector short falls, it augurs well in the national perspective to encourage captive generation.  Offsets large capital investment for utility side Capacity addition  T & D loss component literally vanishes  Power quality ensured (V, f)
  4. 4. TYPES OF CAPTIVE POWER OPTIONS AVAILABLE  Purely power generation mode or: • Coal/oil based thermal cogen (boiler-turbine-generators) Fully condensingExtraction condensing Back pressure
  5. 5. TYPES OF CAPTIVE POWER OPTIONS AVAILABLE  Gas based / oil based GT route • Open cycle (GT only) • Closed cycle  Combined cycle • GT, HRSG, ST  DG Sets • Diesel based • Heavy fuel oil based
  6. 6. DG OPTION FROM THE COMMON USER STAND POINT – ATTRACTIVE FEATURES  Low project payback period 2-3 years  Low space requirements (Even a shed will do)  Good conversion efficiency  Easy fuel to handle  Quality of Power ensured (V, f)
  7. 7. AMONGST CAPTIVE GENERATION OPTIONS  Diesel generation attributes are: • Efficiency 43 – 45% • Very compact • Investments lower • Gestation period lowest (1 – 1.75 years) • Low auxiliary power needs
  8. 8. DG OPTION FROM COMMON USERS STAND POINT – ATTRACTIVE FEATURES  Low project implementation period (Less than 1year)  Low space requirements  Good conversion efficiency  Easy fuel to handle  Quality of power ensured (V, f)  Investments lower than utility generation  Waste Heat Recovery possible to reduce operational expenses
  9. 9. DG SYSTEM OPTIONS INCLUDE: Individual user end installations Group of industries generate by funds pooled Companies promoted to set up and to operate power stations Power generated is distributed to participating industries through utility distribution system (wheeling route) Co-operative ventures/centralized generation for economy of scale
  10. 10. IMPACT OF INDUSTRIAL DIESEL POWER GENERATION Effect on foreign exchange reserves, energy security • Oil import bill constitutes good part of export earnings in many developing countries • Real cost of oil is much different from the administered cost • Highest operational efficiency of diesel power generation makes economic sense for industry & has a much larger impact in national economy
  11. 11. IMPACT OF INDUSTRIAL DIESEL POWER GENERATION A good share of DG Set population is old/second hand with low efficiencies & high SFC on account of factors like • Ageing • Inadequacies in maintenance • Low capacity utilisation • Fluctuating load characteristics • Inefficient operational practices • Derating effects • Wrong sizing and selection issues
  12. 12. IMPACT OF INDUSTRIAL DG POWER GENERATION  Regular energy audit and performance monitoring would help to identify appropriate rectification measures retrofits & judicious replacement policies • Parallel operation of captive DG sets • Paralleling captive DG sets with grid  Compared to stand alone operation, parallel operations help to raise the operational economy of DG Sets on account of higher loading, with the options including:
  13. 13. EXPERIENCES INDICATE 5 to 10% FUEL SAVINGS POTENTIAL THROUGH INCORPORATION OF VARIOUS MEASURES
  14. 14. LOADING IMPROVEMENTS  Under loading is the root cause for fuel guzzling in DG Sets  KW readings efficacy often suspect Engine capability (BHP based) limits to be referred to, to assess mechanical loading Alternator capability (kVA based) limits to be referred to, to assess electrical loading Check of exhaust temp, fuel rack setting,charge air pressure, turbocharger rpm helpful to assess engine loading kWh, PF, monitoring helpful, to assess electrical loading  Use of trivector type static energy meters desirable on DG Sets
  15. 15. LOADING IMPROVEMENTS  Parallel operation among DG Sets & with grid can help  Short run operations increase specific fuel consumption Choice of loads on DG Sets & choice of DG Sets is also a key for improvement
  16. 16. ECONOMIC OPERATION OF DG SETS: – AREAS OF CONCERN  Maintenance practices  Operation records inadequacy  Inadequacies and absence of • Inadequacy and absence of records on maintenance. & operation • Instrumentation • Monitoring A MIS template of desirable information follows:
  17. 17. kWkW % Lits/kWhLits/kWh DG Set Ref DG Set Capacity Derated DG Set Capacity Fuel Used Avg. % Loading w.r.t. Derated Capacity Specific Fuel Oil Consumption Specific Lube Oil Consumption O C O C Charge Air In / Out Temperature Exhaust Gas Temperature Kg/cm2 rpm Turbocharger Pressure Turbocharger rpm
  18. 18. MAINTENANCE COST RECORDS  Break-up of cost also help in budgeting, maintenance planning  An illustrative DG set Maintenance cost break-up follows:
  19. 19. DG Set Reference : ABC S.No. Failure Type % Total Maintenance Cost 1. Fuel Injection & Supply 9.7 2. V/V, V/V System & Seats 3.6 3. Cooling System & Water Leakage 0.4 4. Controls & Electricals 0.0 5. Governers 0.0 6. Pistons 43 7. Lubrication System 6.2 8. Bearings 17.9 9. Turbocharger 1.3 10. Gears & Drives 0.0 11. Miscellaneous 7.2 100
  20. 20. CONDITION MONITORING RECORDS While OEM Guidelines are often conservative, condition monitoring is a powerful technique for cost control • Typical examples  Lub Oil Tests • Color / visual observations • Kin. Viscosity at 40O C/100O C • Viscosity index • Flash point (O C) • Total base number • Cracking test
  21. 21. Location Orientation Displacement Range (µ) Velocity Range (µ) Turbo Charger Suction Horizontal Vertical Axial 60 – 130 68 – 140 90 – 180 8 – 13 4 – 8.4 7.2 – 16 Turbo Charger Discharge Horizontal Vertical Axial 80 – 130 58 – 150 100 – 190 8 – 8.4 4.6 – 14 7.8 – 16 Alternator Bearing Horizontal Vertical Axial 18 – 40 25 – 50 28 – 60 2 – 4 2.8 – 6.4 3.2 – 14  Such observations can help improve preventive maintenance function and availability of DG Sets  Desirable for bearings, Gears, Turbochargers, Pumps  Illustrative observations on DG Sets in a plant VIBRATION ANALYSIS
  22. 22. DESIRABLE ON-LINE PARAMETERS TO TRACK:  Suction air temperature  Charge air pressure  Charge air temperature (before and after Cooler)  Turbocharger (T.C) RPM  Gas Temperature at cylinder exhaust  Gas temperature, at T.C. In and Out  Fuel rack / rocker arm setting  Alternator V, A, PF, kW, & Hz.  Fuel flow indicator  Ambient air DBT / WBT indicator  Conductivity meter for CW system
  23. 23. TYPICAL FAULTS TO LOOK OUT FOR:  Based on OEM Guidelines & as run observations, diagnosis of faults is called for:  Typical concern areas include: • Choked fuel valves  Record of overhauls • Leaky piston rings • Leaky exhaust valves • After burning • Early firing  Historical data before / after each overhaul helps to • Check efficacy of overhaul carried out • Establishing in-situ parameter limits
  24. 24. WASTE HEAT RECOVERY IN DG SETS  m x 0.25 x (tg – 180) where m, is gas quantity in Kg / Hr ( typically 8 Kg / kWh ) and tg is exhaust gas temperature,180 being the safe exit gas temperature limit, after, heat recovery.  Exhaust temperature 350O C to 500O C  Scope for waste heat recovery  Indicative recovery potential in kCal per hour would be:  Close to 35% of energy exhausted through stack
  25. 25. WASTE HEAT RECOVERY (WHR) IN DG SETS  Set loading, temperature of gases  Refrigeration capacity feasible through vapor absorption system option:  Factors affecting WHR  Hours of continuous operation  Back pressure of set  End use options available for Steam / waste heat  About 100 TR per MW output, based on 500KG waste heat steam /MW and 5KG/TR steam required for a double effect VAR system. Water Lithium Bromide VAR schemes for 8O C chilled water available
  26. 26.  At 60% load, WHR scope is 0.95 x 106 kCal / Hr  5 MW set with turbo charging – an illustration: EXHAUST GAS TEMPERATURE & FLOW vs % LOADING Load % Gas Flow Kg/Sec Temperature O C 60 7.5 325 70 9.08 330 90 10.08 355 100 11.84 370  At 90% load, WHR scope is 1.42 x 106 kCal / Hr
  27. 27. EXHAUST GAS TEMPERATURE & FLOW vs. % LOADING Back pressure limit of 250 – 300 mmWC, sets limit on limiting pressure drop in Waste Heat Recovery system.  Economics vary w.r.t. set loading and base load operation.  Large convective Heat Transfer Area called for  Typically, 0.5 TPH Waste Heat based steam generation scope exists per MW output.
  28. 28. EMERGING AREAS OF INTEREST  Fuel additives / treatment systems for better efficiency  High efficiency turbochargers  Improved Noise control systems  Harmonics filtration  Tri-generation adoption  Suction air cooling schemes for increasing capacity
  29. 29.  Ensure steady load conditions on the DG set, and provide cold, dust free air at intake  Improve air filtration.  Ensure fuel oil storage, handling and preparation as per manufacturers’ guidelines/oil company data.  Calibrate fuel injection pumps frequently.  Ensure compliance with OEM maintenance checklist.  Ensure steady load conditions, avoiding fluctuations, imbalance in phases, harmonic loads.  For base load operation, consider waste heat recovery system steam generation and vapour absorption system adoption where viable.  Consider parallel operation among the DG sets for improved loading .  Provide adequate instrumentation for monitoring performance, and plan for operations and maintenance accordingly.
  30. 30. THANK YOU

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