DG SetsManish Jangid

Introduction

Diesel Generator is a combo of diesel engine with an electric generator to produce electrical energy.

Why do we require one?• A load which requires 24x7 energy needs a backup in case

of grid failure like mobile towers.• The availability of renewable solar energy varies over the

year. Cannot rely completely on solar energy.• A hybrid system consisting of DG sets, grid,batteries and

renewable energy resource is more cost efficient compared to other alternatives.

Power Button

Control Panel Display

Radiator Exhaust

Air inlet

Fuel input and electrical

outputAcoustic enclosureBase frame

Control Panel

Alternator

Exhaust system

Radiator Diesel Engine

Engine• Can use various fuels like diesel, gasoline, propane (in

liquefied or gaseous form), or natural gas or dual feed.• The size of the engine is directly proportional to the

maximum power output the generator can supply.• Four stroke, multi cylinder engine is used.• Must maintain a constant speed to ensure constant

frequency of output voltage.

Sump

GovernorAs the load increases, speed will decrease. To

maintain constant speed, increases the fuel supply.Flywheel

It provides an inertial mass to overcome the cyclic irregularity of combustion process. Prevents stalling of engine and easy starting.Turbocharger

Pressurizes air for mixing with fuel. Increases fuel efficiency.

AC alternator

• Part of DG that produces electrical output, is coupled to diesel engine.• Consists of rotor(rotating part) ,stator (stationary part) and

exciter

Stator• Contains windings which generate output voltage• Is connected to automatic voltage controller which ensures

stable voltage outputRotor• coupled to diesel engine• It’s winding carry DC current which provide rotating

magnetic field for voltage generation

Exciter• Generates DC current for rotor

• Can be small alternator connected to diesel engine or a coil

AVR Senses the voltage output from alternator’s stator and compares to the reference. If it is different, it adjusts the current going into rotor by changing excitation

• Alternator is rated in KVA or in KW at 0.8 pf• Overload is allowed (10%) for a limited time only• Speed of rotation needs to be kept fixed for constant

frequency operation (50 Hz). Cummins generally has 1500 rpm• Power output depends on temperature, humidity and

altitude and has to be checked accordingly.

Control Panel

• Displays various parameters like voltage, current, frequency, fuel level, oil pressure, temperature of coolant, etc.• Control panels can be combined with an Automatic Transfer

Switch (ATS) to maintain the continuity of electrical power. The ATS detects an outage of power when your local grid fails and signals control panel to start the generator• Contains built-in-shutdown in case of any abnormality like

overload, over/under speed, overheating.

Cooling and exhaust systemVarious components get heated up.Air cooled or liquid cooledA coolant level indicator is present

Lubrication SystemA generator has moving parts in its engine.

Lubricated by oil stored in a pump

Fuel system Fuel tank and pipes

Ventilation and overflow pipe connected to fuel tankFuel pumpFuel filterAir filter

Battery and battery chargerFor auto-start of diesel engineCharged by alternator

Circuit breakers

Frame assembly

• Structural base support• The frame also allows for the DG to be earthed

safely• Damps vibrations and noise• Protects against weather

Generator Characteristics

Fuel Consumption per KWh vs % load

Generator Configurations

Series Configuration

Engine AC Gen

SetBattery Charger

Renewable

Resource

Controller

Battery Inverter Load

r

Switched Configuration

Engine AC Gen

Set

Battery Charger

Renewable

Resource

Controller

Battery Inverter

Load

r

Transfer Switch

r

r

Engine AC Gen Set

Renewable

Resource

Controller

Battery

Inverter Load

Parallel Configuration

Integration of Diesel-PV

Step 1- Load assessment Done using a data logger or manual load assessment.Daily Load profile over 24 hoursTotal energy consumption per dayMaximum demandSurge load (like TV, motors require high starting current)Some DG vendors do load assessment for you

Step 2-Choose DGVendors do that for you as well

Step 3-Choose PV arrayChoose array size to minimize budget constraints like annual

expenditure and net operating costcalculate the energy produced for the day.

Step 4- Choose batteriesThe number of hours you want batteries to power loadBased on it select capacity of batteriesChoose charger

Step 5- Choose InverterBased on battery bank and operating voltages

Example

Load assessment Form

Load Profile

Generators are generally oversized to meet any future demands

Choose a PVSuppose average load demand is 3 KW (including batteries)

Total consumption of energy per day is = 24*3KWh=72 KWhPV size is = 5 KW (assume)PV energy produced per day = 5*6*0.8=24 KWhRest supplied by DG

Choose batteriesSuppose batteries are 600Ah @48 VEnergy used from batteries = 600*48*0.5=14.4 KWhFor the load current required= 3000/48*0.9= 70 AmpTime for which batteries will power=600*0.5/70= 4.5 hoursIf charging cycle is twice, 9 hours without DG.

Choose inverterBased on battery voltage, load operating voltage, peak power

demand, surge demand etc.

Issues and challenges

• Only suitable for moderately large loads.

• Space conflict and costly. High CAPEX.

• Complexity of analysis- load profile, economic analysis etc. There is no single proposed best solution. Most are just optimized given available data.

• Surplus energy produced should be fed back to the grid

• Need to come up with better batteries.