Focus areas in economic operation of DG sets
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Transcript of Focus areas in economic operation of DG sets
FOCUS AREAS
FOR
ECONOMIC DG SET OPERATION
D. PAWAN KUMAR
TYPICAL GRID POWER SCENARIO FEATURES
Frequent power trippings
Low voltage problems
Captive power generation has become a necessity
Power cuts
Low frequency problems
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)
TYPES OF CAPTIVE POWER OPTIONS AVAILABLE
Purely power generation mode or:
• Coal/oil based thermal cogen (boiler-turbine-generators)
Fully condensingExtraction condensing
Back pressure
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
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)
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
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
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 participatingindustries through utility distribution system (wheeling route)
Co-operative ventures/centralized generation for economy of scale
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
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
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:
EXPERIENCES INDICATE 5 to 10%
FUEL SAVINGS POTENTIAL THROUGH
INCORPORATION OF VARIOUS
MEASURES
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 loadingAlternator capability (kVA based) limits to be referred to, to assess electrical loadingCheck 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
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
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:
kWkW
%
Lits/kW
hL
its/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
OC
OC
Charge Air In / Out Temperature
Exhaust Gas Temperature
Kg/cm
2rpm
Turbocharger Pressure
Turbocharger rpm
MAINTENANCE COST RECORDS
Break-up of cost also help in budgeting, maintenance planning
An illustrative DG set Maintenance cost break-up follows:
DG Set Reference : ABC
S.No. Failure Type% Total Maintenance
Cost
1. Fuel Injection & Supply 9.72. V/V, V/V System & Seats 3.63. Cooling System & Water Leakage 0.44. Controls & Electricals 0.05. Governers 0.06. Pistons 437. Lubrication System 6.28. Bearings 17.99. Turbocharger 1.310. Gears & Drives 0.011. Miscellaneous 7.2
100
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
Location OrientationDisplacement
Range ()Velocity
Range ()
Turbo Charger Suction
HorizontalVerticalAxial
60 – 13068 – 14090 – 180
8 – 13 4 – 8.47.2 – 16
Turbo Charger Discharge
HorizontalVerticalAxial
80 – 130 58 – 150 100 – 190
8 – 8.44.6 – 147.8 – 16
Alternator Bearing
HorizontalVerticalAxial
18 – 40 25 – 50 28 – 60
2 – 42.8 – 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
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
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
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 350OC to 500OC
Scope for waste heat recovery
Indicative recovery potential in kCal per hour would be:
Close to 35% of energy exhausted through stack
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 8OC chilled water available
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
TemperatureOC
60 7.5 32570 9.08 33090 10.08 355100 11.84 370
At 90% load, WHR scope is 1.42 x 106 kCal / Hr
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.
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
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.
THANK YOU