What is Energy? FEC Services Ltd 2010 Energy management training 2010

Transcription

1 What is Energy? 1

2 Energy and power Power: capacity to supply or use energy What you see quoted on a light bulb, a motor or a generator Watts for a light bulb Kilowatts for a heater Horse power for an engine Standard measurement unit ; Joule/second = Watt (W) 1 J/s = 1W Energy measure of power use over time Litres of oil, units of electricity on the bill Standard measurement unit is the Joule (J) Common units (e.g. kwh) 3600 Joules 2

3 A word about multiplication factors Kilo (k) = 1,000 Mega (M) = 1,000,000 Giga (G) = 1,000,000,000 e.g. 1kW = 1,000W 1kWh = 1,000Wh etc 3

4 Common primary units of energy Kilowatt-hour (kwh) (gas and electricity bills) Megajoule (MJ) (climate control computers solar energy, animal feed) 1 kwh = 3,600,000J or 3.6 MJ 4

5 Common units for energy buying kwh is the main unit for energy utilities Litres of oil Tonnes of coal Therms of gas Useful to convert to kwh using standard tables 5

6 By Weight By Volume 6 Solid fuels kwh / tonne Coke 8,278 Coal (weighted average) 7,444 Liquid fuels kwh / tonne kwh / litre Crude Oil (weighted average) 12, Heavy Fuel oil 11, Medium fuel oil 12, Gas/diesel oil 12, Kerosene 12, Petrol 13, LPG 13, Ethane 14, Gaseous fuels kwh / m3 Natural gas 11.0 Caution: Landfill gas 10.7 Depends on Sewage gas 10.7 calorific value Solid Renewables kwh / tonne Tyres 8,888 Refuse derived waste 5,194 General industrial waste 4,444 Straw 4,166 Hospital waste 3,889 Industrial wood (pallets e.t.c) 3,305 Domestic wood (logs) 2,778 Municipal soild waste 2,639 Poultry litter 2,444

7 Conversions can vary The quality of fuel (calorific value) changes slightly depending on the batch Obvious with wood, coal, etc - but also changes with gas Gas calorific value is published for each Transco region each month and appears on the bill Gas calorific value expressed in MJ/m 3 7

8 Variation in calorific value by region Calorific value Eastern East Midlands North East Northern North Thames North West Scotland South East Southern South West West Midlands Wales North Wales South Region Up to 3.2% difference 8

9 Measuring gas Gas meters don t read energy They measure volume m 3, ft 3 or 100ft 3 (HCF) Need to correct for Temperature changes Pressure changes Correction factor Can be done on standard figures or by using a corrector Calorific value then applied 9

10 Large gas meters Have correctors next to the meter These adjust the volume for temperature and pressure 10

11 Your gas bill.. Shows consumption (or corrected consumption) in ft 3 or m 3 May be a multiplier (e.g. x10, x100) Applies a standard correction factor if you have an uncorrected meter Uses a calorific value to work out kwh 11

12 Gas meter reading 100 ft 3 to m 3 (x 2.83) Multiplier (x10, x100) Gas corrector reading 100 ft 3 to m 3 (x 2.83) Multiplier (x10, x100) Correction factor (for temp/ pressure - from bill) Calorific value (MJ/m 3 ) div by 3.6 = kwh Calorific value (MJ/m 3 ) div by 3.6 = kwh 12

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14 About different oils Buying different oils you must consider Price Energy value Suitability 16

15 Comparing the cost of different fuels Use conversion factors to calculate which fuel is cheapest Units of purchase Cost per unit supply kwh per unit of purchase Cost per kwh Electricity kwh 8p (day) 4p (night) 1 8p 4p Diesel / fuel oil Litre 35p LPG Litre 26p Mains gas Therms 50p p 3.5p 1.8p 17

16 Application efficiency You must also consider how efficiently the fuel is used to meet your needs 100% Boiler loss 25%? Primary pipe Loss 10%? 55%? Application efficiency loss 10%? Distribution system Loss 10%? 18

17 So which fuel is the cheapest? I want to heat water - Should I use 35.6p / litre or 4p / kwh? Electricity 100% efficiency for water heating 4 / 1 = 4p / kwh supplied Oil 35.6p / litre / 10.8 = 3.2p / kwh 55% efficiency for water heating 3.2 / 0.55 = 5.8p / kwh supplied In this case electricity is cheaper 19

18 The efficiency rule Real price = Purchase price Efficiency of use (as a decimal) 20

19 Run a generator or buy electricity? 36p / litre or 8p / kwh? Generator efficiency = 30% Cost for generated electricity Convert litres to kwh = 36p / litre / 10.8 = 3.33p / kwh Apply efficiency factor = 3.33p / 0.3 = 11.1p / kwh Excludes capital & maintenance costs Don t generate buy! 21

20 Remember When choosing fuels.. it is not just the cost of the fuel It is the cost of getting the result you want a tank of hot water? a greenhouse temperature of 20 o C? 22

21 Calculating savings We buy energy not power kwh or units = kw x hours Energy = power x time A 10 kw motor running for 5 hours = 50 kwh 23

22 Calculating savings Saving = [current use new use] x energy cost Example: a light bulb used for 2,000 hrs per year Now:100 W tungsten bulb Future?: 20 W compact fluorescent Saving = [(100x2000) (20x2000)] x (0.08/1000) per year saved Lamp cost is 1 Payback less than 1 month 24

23 Operating time is critical In our example If the operating time was 1 hr / week Saving would reduce to 0.36 year Payback would increase to 3 years 25

24 Don t always blame the biggest equipment 30 kw water transfer pump Used 1 hr / week 30 kw x 1 hour x 52 weeks = 1,560 = W yard light Used 10 hr / day every day year round 0.5 kw x 10 hours x 365 days = 1,825 = The larger piece of equipment used less 26

25 Session summary You buy energy to do a job It is the cost of doing the job that matters All fuels can be compared by converting all cost in p/kwh Consider both fuel cost and efficiency To calculate savings, consider both rating and time ; (old technique use new technique use) x cost of energy 29