This document discusses options for economic operation of diesel generator sets for captive power generation. It outlines the typical advantages of captive generation such as ensuring power quality and offsetting transmission and distribution losses. It then describes different captive power options available, highlighting that diesel generator sets are attractive due to their low implementation period, efficiency, and investments compared to other options. The document also discusses measures to improve the economic operation of diesel generator sets such as improving loading, parallel operations, maintenance practices, and harnessing waste heat recovery potential.

1. FOCUS AREAS
FOR
ECONOMIC DG SET OPERATION
D. PAWAN KUMAR

2. TYPICAL GRID POWER SCENARIO FEATURES
 Frequent power trippings
 Power cuts
 Low voltage problems
 Low frequency problems
 Captive power generation has become a necessity

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. TYPES OF CAPTIVE POWER OPTIONS AVAILABLE
 Purely power generation mode or:
• Coal/oil based thermal cogen (boiler-turbine-generators)
Fully
condensingcondensing
Extraction
Back pressure

5. TYPES OF CAPTIVE POWER OPTIONS AVAILABLE
 Gas based / oil based GT route
 Combined cycle
• Open cycle (GT only)
• Closed cycle
• GT, HRSG, ST
 DG Sets
• Diesel based
• Heavy fuel oil based

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. 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. 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. DG SYSTEM OPTIONS INCLUDE:
Individual user end installations
Co-operative ventures/centralized generation
for economy of scale
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)

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. 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. IMPACT OF INDUSTRIAL DG POWER GENERATION
 Regular energy audit and performance monitoring would
help to identify appropriate rectification measures
retrofits & judicious replacement policies
 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:
• Parallel operation of captive DG sets
• Paralleling captive DG sets with grid

13. EXPERIENCES INDICATE 5 to 10%
FUEL SAVINGS POTENTIAL THROUGH
INCORPORATION OF VARIOUS
MEASURES

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. 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. ECONOMIC OPERATION OF DG SETS:
– AREAS OF CONCERN
 Maintenance practices
• Inadequacy and absence of records on maintenance. &
operation
 Operation records inadequacy
 Inadequacies and absence of
• Instrumentation
• Monitoring
A MIS template of desirable information follows:

17. DG Set Ref
kW kW
DG Set Capacity
Derated DG Set Capacity
Fuel Used
% Avg. % Loading w.r.t. Derated Capacity
Lits/kWh Lits/kWh Specific Fuel Oil Consumption
Specific Lube Oil Consumption
O
C Charge Air In / Out Temperature
O
C Exhaust Gas Temperature
Kg/cm2 rpm
Turbocharger Pressure
Turbocharger rpm

18. MAINTENANCE COST RECORDS
 Break-up of cost also help in budgeting, maintenance planning
 An illustrative DG set Maintenance cost break-up follows:

19. DG Set Reference : ABC
% Total Maintenance
S.No. Failure Type 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. 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 40OC/100OC
• Viscosity index
• Flash point (OC)
• Total base number
• Cracking test

21. VIBRATION ANALYSIS
 Desirable for bearings, Gears, Turbochargers, Pumps
 Illustrative observations on DG Sets in a plant
Displacement Velocity
Location Orientation Range (µ) Range (µ)
Turbo Horizontal 60 – 130 8 – 13
Charger Vertical 68 – 140 4 – 8.4
Suction Axial 90 – 180 7.2 – 16
Turbo Horizontal 80 – 130 8 – 8.4
Charger Vertical 58 – 150 4.6 – 14
Discharge Axial 100 – 190 7.8 – 16
Alternator Horizontal 18 – 40 2–4
Bearing Vertical 25 – 50 2.8 – 6.4
Axial 28 – 60 3.2 – 14
 Such observations can help improve preventive maintenance function
and availability of DG Sets

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. 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
• Leaky piston rings
• Leaky exhaust valves
• After burning
• Early firing
 Record of overhauls
 Historical data before / after each overhaul helps to
• Check efficacy of overhaul carried out
• Establishing in-situ parameter limits

24. WASTE HEAT RECOVERY IN DG SETS
 Close to 35% of energy exhausted through stack
 Exhaust temperature 350OC to 500OC
 Scope for waste heat recovery
 Indicative recovery potential in kCal per hour would be:
 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.

25. WASTE HEAT RECOVERY (WHR) IN DG SETS
 Factors affecting WHR
 Set loading, temperature of gases
 Hours of continuous operation
 Back pressure of set
 End use options available for Steam / waste heat
 Refrigeration capacity feasible through vapor absorption system option:
 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 8OC chilled water available

26. EXHAUST GAS TEMPERATURE & FLOW vs %
LOADING
 5 MW set with turbo charging – an illustration:
Gas Flow Temperature
Load % Kg/Sec O
C
60 7.5 325
70 9.08 330
90 10.08 355
100 11.84 370
 At 60% load, WHR scope is 0.95 x 106 kCal / Hr
 At 90% load, WHR scope is 1.42 x 106 kCal / Hr

27. EXHAUST GAS TEMPERATURE & FLOW vs.
% LOADING
 Economics vary w.r.t. set loading and base load operation.
Back pressure limit of 250 – 300 mmWC, sets
limit on limiting pressure drop in Waste Heat
Recovery system.
 Large convective Heat Transfer Area called for
 Typically, 0.5 TPH Waste Heat based steam
generation scope exists per MW output.

28. EMERGING AREAS OF INTEREST
 Suction air cooling schemes for increasing capacity
 Fuel additives / treatment systems for better efficiency
 High efficiency turbochargers
 Improved Noise control
systems
 Harmonics filtration
 Tri-generation adoption

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. THANK YOU