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INFORMATION SHEET 12
SOURCES OF ENERGY
As described in Information Sheet 3 you can choose between energy basedtargets or CO2based targets. One of the advantages of CO2 based targetsis that it gives you additional flexibility. This is because different fuels havedifferent carbon contents and by switching to one with a lower carboncontent you will contribute towards a CO2 based target without changing theenergy intensity of your process.
For example, by simply substituting electrical heating with gas you wouldreduce carbon dioxide emissions by around 50% per unit of energy used.Similarly, conversion from heavy fuel oil to gas reduces CO2emissions by
about 25% per unit of energy. Another example is replacing electricalpower from the grid with electricity sourced from renewables. Renewablepower could either be provided through the grid or via local generation. Inthis case using renewables would provide two benefits: a) a 100% reductionin CO2 emissions in proportion to the amount of renewable energy used,and b) a reduction in the amount of Levy paid, again in proportion to theamount of renewable energy used.
Calculating CO2Emissions
When any fuel is burnt, energy is produced and carbon dioxide (CO 2) andother chemicals, mostly water, are produced. The ratio of energy produced
to CO2 differs according to the type of fuel used. Table 5.1 shows thecarbon emission factor of different fuels, expressed as kg Carbon/kWh.
Table 5.1 Carbon Intensity of Different Fuels
Type of fuel kgC/kWh primary
Electricity (from grid) 0.0453
Natural Gas 0.0518
Gas Oil / Diesel Oil 0.0680
Heavy Fuel Oil 0.0709
Coal 0.0817
Liquid Petroleum Gas 0.0627
New Renewables 0
It may be seen for example that the carbon emissions per unit of energyfrom burning natural gas are much less than those from the high carbon-content fuels such as coal and oil.
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Electricity is generated from a range of fuels including nuclear, gas, oil and coal. The figurefor grid electricity in Table 5.1 reflects the current mix of fuel sources used in UK electricitygeneration. The carbon figure stated is per kWh of primary energy for electricity primary
energy is 2.6 times the delivered energy. Some power is generated from new renewablesources such as wind or landfill gas. New renewables have a zero CO2emission.
To calculate the carbon dioxide emissions associated with your energy use, simply multiplyyour primary energy use by fuel type by the appropriate factor from Table 5.1. If youmeasure your energy used by weight or volume rather than directly in energy terms, thenyou should first convert your fuel use to energy units using the conversion factors shown inTable 5.2.
Table 5.2 Fuel Conversion Factors
Fuel Usual
Units
Conversion Factor Conversion Factor
units
Natural gas 00 ft3 Depends on local conditions. See bill.
Electricity kWh 1.00 kWh/kWh
Gas Oil litres 10.6 kWh/litre
Light Fuel Oil litres 11.2 kWh/litre
Medium Fuel Oil litres 11.3 kWh/litre
Heavy Fuel Oil litres 11.4 kWh/litre
Propane kg 13.89 kWh/kg
Butane kg 13.69 kWh/kg
Dry steam coal tonnes 8,500 kWh/tonne
Anthracite tonnes 8,236 kWh/tonne
Coke tonnes 7,750 kWh/tonne
Nitrogen hcum kWh/hcum
Carbon dioxide hcum kWh/hcum
Steam kg Depends on conditions. Check with supplier.
Hot water kg Depends on conditions. Check with supplier.Condensate kg Depends on conditions.
The following table of unit conversions may be useful.
To convert Operation Constant
From To
ft3 m3 multiply by 0.02832
therms kWh multiply by 29.31
MJ kWh divide by 3.6
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Example: Lovely Lollies Ltd annually uses 1 million litres of heavy fuel oil in its boiler
house. What are the annual carbon emissions associated with this oil use? By howmuch would the emissions be reduced by converting the boiler house to natural gasfiring?
Step 1. Refer to Table 5.2. The calorific value of heavy fuel oil is 11.4 kWh/litre.Therefore the energy used in Lovely Lollies boiler house is given by:
1,000,000 litres x 11.4 kWh/litre = 11,400,000 kWh.
Step 2. Table 5.1 shows that 0.0709 kg of carbon are emitted per kWh of energyderived from heavy fuel oil. The annual carbon emissions associated with this energyuse is:
11,400,000 kWh x 0.0709 kg/kWh = 808,260 kg of carbon.
Step 3. Refer again to Table 5.1. The carbon emissions per kWh of energy fromnatural gas burning are 0.0518 kg/kWh. Hence if the same amount of energy were tobe derived from natural gas rather than heavy fuel oil, the carbon emissions would be:
11,400,000 kWh x 0.0518 kg/kWh = 590,520 kg of carbon.
Step 4. The emissions saving is (808 590) or 218 tonnes. This is 26.9% of currentemissions from combustion of boiler fuel.
Note that this calculation assumes unchanged combustion efficiency, which might notbe the case in practice.
Renewable Energy
Energy derived from new renewable sources are defined, for the purposes of the ClimateChange Levy and energy reporting to have zero carbon dioxide emissions. Newrenewable sources are listed below:
Wind Energy Geothermal hot dry rocks
Hydro power up to 10 MW Geothermal aquifers
Tidal power Municipal and industrial wastes
Wave energy Landfill gas
Photovoltaics Agricultural and forestry wastes
Photoconversion Energy crops
Renewable electricity is available from many electricity supply companies and can be bought
in the same way as conventional electricity.