2.basics of energy and its various forms

8/8/2019 2.Basics of Energy and Its Various Forms

1/25

Basics of Energy and itsvarious forms


2/25

Syllabus

Basics of Energy and its various forms:

Electricity basics - DC & AC currents, Electricity tariff,

Load management and maximum demand control, Power

factor. Thermal Basics -Fuels, Thermal energy contents offuel, Temperature & Pressure, Heat capacity, sensible and

latent heat, evaporation, condensation, steam, moist air and

humidity & heat transfer, units and conversion.


3/25

Various forms of energy

Potential energy Chemical

Nuclear

Mechanical stored energy

Gravitational

Kinetic Radiant Thermal

Motion Sound

Electrical


4/25

Oil burns to generate heat -->

Heat boils water -->

Water turns to steam -->

Steam pressure turns a turbine -->

Turbine turns an electric generator -->

Generator produces electricity -->

Electricity powers light bulbs -->

Light bulbs give off light and heat


5/25

High and Low grade energy

High grade energy is concentrated

Energy Examples are Light energy, chemical

energy, electricity

Low grade energy rapidly dissipates(molecules are more randomly

distributed) Example: heat energy


6/25

Direct current and Alternating current

Direct current: Non-varying unidirectionalcurrent

Current produced by batteries

Alternating Current: Reverses in regular

recurring intervals with alternate +ve and vevalues at specified number of times per second

In 50 cycle AC, current reverses direction 100 times

a second (twice in one cycle


7/25

Current, Voltage, Resistance & Frequency

Current or Ampere is rate of flow of electricity current which produces a specified force between two

parallel wires, which are 1 metre apart in vacuum

Voltage is measure of electric potential orelectromotive force A potential of one volt appears across a resistance of one

ohm when a current of one ampere flows through thatresistance.

Resistance = Volts / Current and denoted asOhms

Frequency is cycles at which alternating currentchanges Unit is Hertz which is number of cycles per second


8/25

KVA, KVAR, KW & PF KVA = Kilovolts (KV) x Amperes(A)

Also called as as Apparent power

Measures the electrical load of system

Single phase = V x A/1000

Three phase = 1.732 x V x A /1000

KVAR is reactive power i.e. portion of apparent

power that does no work KW is real power or work producing part of power

Single phase = V x A x PF/1000

Three phase = 1.732 x V x A x PF /1000 KWH is energy consumed by 1000 Watts in 1 hour

Power Factor (PF) is ratio of real power to apparentpower PF = KW/KVA or KW/(KW2 + KVAR2)


9/25

Electrical Tariff

Billing demand is highest KVA recordedduring 1-demand interval(30 minutes) in onemonth-measured by digital tri-vector meter

Maximum demand is maximum KVA or KWover one billing cycle

Contract demand is amount of electric power(KVA or KW) demanded by consumer frompower utility


10/25

Connected Load, Demand factorand Load factor

Connected Load is name plate readings(in KVA or KW) of all equipment in aindustry

Demand factor = maximum demand/connected load

Load factor = average load/ maximumload


11/25

Time of Day (TOD)

Utilities prefer flat demand curve

Encourage users to draw power duringoff-peak hours (i.e. Night time) Utilities have TOD offer or incentives or

disincentives Separate energy meters to record peak

and off-peak power consumption

Opportunity for user as off-peak powertariff is usually lower


12/25

TOD charges for different time zone for one electric utility

A-Zone:

22 hrs to

6 hrs

B-Zone:

6 hrs to 9

hrs & 12

hrs to 18

hrs

C-Zone:

9 hrs to

12 hrs

D-Zone:

18 hrs to

22 hrs

205

280330

370

0

50

100

150

200

250

300

350

400

Paise

TOD charges for different time zones for one of the Indian electric

utility


13/25

Example:

3 phase power measurement

A 3-phase AC induction motor (20 kW capacity) is usedfor pumping operation. Electrical parameter such as

current, volt and power factor were measured with power analyzer. Find energy consumption of motor inone hour? (line volts. = 440 V, line current = 25 amps

and PF = 0.90).Power = 3 x V x I x Cos

Measured energy consumption =

3 x 0.440 x 25 x 0.90 x 1 = 17.15 kWh


14/25

Example

Motor loading calculationIn nameplate details of motor, kW or HP indicates the outputof the motor

at full load .The other parameters such as volt, amps, pf are the input

condition of motor at full load

A 10 kW motor has the name plate details as 415 V, 18.2 amps and 0.9

PF. Actual input measurement shows 415 V, 12 amps and 0.7 PF

which was measured with power analyzer during motor running.. What

is motor loading?

Rated output at full load = 10 kW

Rated input at full load = 1.732 x 0.415 x 18.2 x 0.9 = 11.8 kW

The rated efficiency of motor at full load = 10/11.8 = 85%

Measured (Actual) input power = 1.732x 0.415 x 12x 0.7 = 6.0 kW

Motor loading = Measured KW/Rated KW = 6.0/11.8 x 100 = 51.2%


15/25

Thermal Energy Basics

Temperature is denoted in Fahrenheit (F) to Celsius(C)

Calorie is unit of heat: 1 kilocalorie can raise 1000 kgof water by 1oC

Specific heat is amount of heat required to raise 1 kg

of water by 1oC Heat quantity = mass x specific heat x rise in

temperature

Latent heat of fusion is amount of heat applied tosolid to change its state to liquid

Latent heat of vapourisation is amount of heatapplied to liquid to change its state to vapour


16/25

Thermal Energy Basics:

Superheat is heating of vapour to a temperaturehigher than its boiling point at existing pressure

Moisture content in air is humidity Actual weight of water vapour mixed in 1 kg of dry air

Humidity factor is kg of water vapour per kg of dry air

Relative humidity is degree of saturation of air at any drybulb temperature ( given as % of actual water content of airdivided by moisture content of air at exiting temperature

RH = Percentage (%) at temperature (oC

Dew point is temperature at which condensation ofwater vapour from the air begins as the temperatureof the air-water vapour mixture falls


17/25

Thermal energy basics

Dry bulb Temperature is an indication of the sensibleheat content of air-water vapour mixtures

Wet bulb Temperature is a measure of total heatcontent or enthalpy. It is the temperatureapproached by the dry bulb and the dew point assaturation occurs

Specific gravity is density of fuel relative to water Viscosity is measure of internal resistance to flow

Calorific value is measure of heat content in organic

matter Gross or high calorific value and Net or low calorific value

d


18/25

Units and Conversion

1 MW 1,000 kW

1 kW 1,000 Watts

1 kWh 3,412 Btu

1 kWh 1.340 Hp hours

1,000 Btu 0.293 kWh

1 Therm 100,000 Btu (British Thermal Units)1 Million Btu 293.1 Kilowatt hours

100,000 Btu 1 Therm

1 Watt 3.412 Btu per hour

1 Horsepower 746 Watts or 0.746 Kilo Watts1 Horsepower hr. 2,545 Btu

1 kJ 0.239005 Kilocalories

1 Calorie 4.184 Joules

1 kcal/Kg 1.8 Btus/lb.

1 Million Btu 252 Mega calories1 Btu 252 Calories

1 Btu 1,055 Joules

1 Btu/lb. 2.3260000 kJ/kg

1 Btu/lb. 0.5559 Kilocalories/kg


19/25

Units of energy

1 Joule (J) = 0.2390057 calorie (cal) = 9.47817210-4 Britishthermal unit (Btu)

1 cal = 4.184 J = 3.96566710

-3

Btu 1 Btu = 1055.056 J = 252.1644 cal = 2.93071110-4 kilowatt-hour (kWh)

1 kWh = 3.6 Megajoule (MJ) = 0.8604207 Mcal = 3412.142 Btu

Power (Energy Rate) Equivalents

1 kilowatt (kW) 1 kilo joule /second (kJ/s)

1 kilowatt (kW) 3413 BTU/hour (Btu/hr.)1 horsepower (hp) 746 watts (0.746 kW)

1 Ton of refrigeration 12000 Btu/hr.


20/25

Units for Pressure

Gauge pressure is defined relative to atmosphericpressure

Absolute pressure = Gauge pressure + Atmosphericpressure

Units of measure of pressure:Metric (SI) : kilopascals (kPa)

Imperial : pounds per square inch (psi)

1 pascal (Pa) = 1 Newton/m2 (N/m2 )

1 physical atmosphere (atm) = 101325 Pa = 760 mm of mercury

(mm Hg) = 14.69 lb-force/in2 (psi)

1 technical atmosphere (ata) = 1 kilogram-force/cm2 (kg/cm2 )=9.806650104 Pa


21/25

Fuel to KWH Conversions

Natural gas

LPG (propane)

Coal

CokeGas oil

Light fuel oil

Medium fuel oilHeavy fuel oil

M3 x 10.6

Ft3 x 0.3

therms x 29.3

m3 x 25

kg x 8.05

kg x 10.0litres x 12.5

litres x 12.9

litres x 13.1litres x 13.3

kWh

kWh

kWh

kWh

kWh

kWhkWh

kWh

kWhkWh


22/25

Energy Conversions

To: TJ Gcal Mtoe MBtu GWh

From: Multiply by: . . . .TJ 1 238.82.388 x 10-5 947.8 0.2778

Gcal 4.1868 x 10-3 1 10-7 3.968 1.163 x 10-3

Mtoe 4.1868 x 104 107 1 3.968 x 107 11630

MBtu 1.0551 x 10-3 0.252 2.52 x 10-8 1 2.931 x 10-4

GWh 3.6 860 8.6 x 10-5 3412 1


23/25

Mass conversions

To: kg t lt st lb

From: multiply by: . . ..

kilogram (kg) 1 0.001 9.84 x 10-4 1.102 x 10-32.2046

tonne (t) 1000 1 0.984 1.1023

2204.6

long ton (lt) 1016 1.016 1 1.1202240.0

short ton (st) 907.2 0.9072 0.893 1 2000.0

pound (lb) 0.454 4.54 x 10-44.46 x 10-4 5.0 x 10-41


24/25

Volume conversions

To: gal U.S. gal U.K. bbl ft3 lm3

From: multiply by: . . . .

.

U.S. gallon (gal) 1 0.8327 0.02381 0.1337 3.7850.0038

U.K. gallon (gal) 1.201 1 0.02859 0.1605 4.5460.0045

Barrel (bbl) 42.0 34.97 1 5.615 159.00.159

Cubic foot (ft3

) 7.48 6.229 0.1781 1 28.30.0283

Litre (l) 0.2642 0.220 0.0063 0.0353 10.001

Cubic metre (m3) 264.2 220.0 6.289 35.31471000.0 1


25/25

End

2.basics of energy and its various forms

Documents