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