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NBS-M016 Contemporary Issues in Climate Change and Energy 2010

18. Energy Balance Tables

N.K. Tovey (杜伟贤 ) M.A, PhD, CEng, MICE, CEnv

Н.К.Тови М.А., д-р технических наук

Energy Science Director CRed Project

HSBC Director of Low Carbon Innovation1

Professor Stephen Glaister is wrong (letter, 4 March). There will be plenty of electrical power to recharge the batteries of Boris Johnson's electric cars, without a large use of fossil fuels, at night, which is when electric car batteries are normally recharged.

Relatively little electricity is used at night industrially, domestically or for transport or retail. The bulk of overnight use is met from nuclear, hydro-electric, wind and tidal generation; and generation from these sources will increase in the future.

Sir Reginald E W Harland Bury St Edmunds, Suffolk

7th March 2009

What is wrong with the following letter to the editor?

Sir Reginald Harland is incorrect (letter, 7 March) when he implies that there will be plenty of electricity available overnight without a large use of fossil fuels. The data of electricity generation in the UK in the night hours of midnight to 6am over the last four months show that on average 79 per cent of it came from fossil fuel. This percentage was only slightly less than the daytime use of fossil fuels, at 81.4 per cent.

Indeed, during the past four months, the minimum overnight fossil fuel component (on 22 February) was 69.2 per cent, while on 6 January it reached 86.8 per cent. Thus the major part of overnight electricity is always derived from fossil fuels. Indeed, the situation will get worse in the short term with the closure of our nuclear ageing plant, as despite a significant recent increase in renewable generation from wind etc, this has not kept pace with the loss of low-carbon nuclear capacity.

Dr Keith Tovey CEngReader in Environmental Sciences, University of East AngliaNORWICH

10th March 2009

• Energy balance tables provide information on:

– Overall energy consumption in a country for a given year.

– Details of production and consumption of specific fuels

• Allow overall efficiency of energy use within a country to be ascertained

• Give information on energy losses

• Give information on sector split of energy consumption

• Information from Balance tables is needed as a first stage in an accurate estimate of carbon emission factors in a country

Energy Balance Tables

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Energy Balance Tables

• Best Constructed on a Heat Supplied basis – i.e. potential that fuel has – usually based on calorific value.

• Units vary widely for one source to another

• Many use MTOE – but what is calorific value of oil - many sources (but not all) assume 41.868 GJ/tonne – this is International Standard

• Check what value is actually used.

• Scientifically it is better to use Joules throughout

• For a country use either PJ or EJ, depending on size of country.

• Primary Electricity convention is not always consistent -

• may include hydro and nuclear, but may be specified in thermal equivalent.

• sometimes hydro is included in renewable electricity – sometime as primary electricity

Energy Supply including imports/exports

Energy Conversion

Energy Industry Use

Industrial Demand

Transport Demand

Other Energy Demand

UK Aggregate Energy Balance 2008 - Dukes (2009)PetaJoules ( PJ)

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Simplified Aggregate Energy Balance 2008 - from Table 1.1 Dukes (2009)

• Aggregate Energy Balance Tables• Summarises overall situation for a country

• Specific Fuel Energy Balance Tables• Covers more detailed split of energy and uses for that fuel

PetaJoules (PJ)

A B A* =A+B

C D E F = A*+ C-D-E

G H I J=G+H+I K = F-J

  Coal Manu-factured fuel(1)

Primary oils

Petroleum products

Natural gas(2)

Renewable &

waste(3)

Primary electricity

Electricity Heat Total

UK Production 475.7 - 3,290.0 - 2,917.0 182.6 542.8 - - 7,408.1

Net imports 1,087.3 22.0 544.6 -331.5 1,009.5 39.7 - 35.9 - 2,407.4

Net Energy Available 1,563.0 22.0 3,834.6 -331.5 3,926.5 222.3 542.8 35.9 - 9,815.5

Transfers - -5.3 -146.1 146.3 -0.2 - -44.2 44.2 - -5.3 Net Consumption 1,563.0 16.7 3,688.5 -185.2 3,926.3 222.3 498.6 80.1 - 9,810.2

Energy Conversion                    

Inputs -1488.5 - -3688.5 - -1430.1 -148.1 -498.6 - - -

Outputs   69.9   3624.4       1343.8 53.6 -

Net energy balance - - - - - - - - - -2162.0

Energy Industry Use 0.2 35.6 - 200.0 249.1 - - 95.6 3.0 583.4

Transmission losses - 9.9 - - 49.1 - - 98.7 0.0 157.7

Delivered Energy Available 74.4 41.1 - 3239.2 2198.0 74.2 - 1229.6 50.6 6907.1

Balance Check 74.4 41.1 - 3239.2 2198.0 74.2 - 1229.6 50.6 6907.1

Energy Demand                    

INDUSTRY 52.2 31.1 - 266.3 477.0 14.1 - 408.8 32.4 1281.8

TRANSPORT - - - 2397.7 - 34.4 - 30.4 - 2462.4

OTHER 22.1 10.0 - 186.5 1687.6 25.7 - 790.5 18.3 2740.7Final Consumption (Energy only) 74.4 41.1 - 2850.5 2164.6 74.2 - 1229.6 50.6 6485.0

Non-Energy use - - - 388.7 33.3 -0.1 - -0.1 0.0 422.1

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Simplified Energy Balance Tables

  CoalManufactured

fuel(1)Primary

oilsPetroleum products

Natural gas

UK Production 475.7 - 3,290.0 - 2,917.0 Net imports 1,087.3 22.0 544.6 -331.5 1,009.5 Net Energy Available 1,563.0 22.0 3,834.6 -331.5 3,926.5 Transfers - -5.3 -146.1 146.3 -0.2 Net Consumption 1,563.0 16.7 3,688.5 -185.2 3,926.3

 

Renewable & waste(3)

Primary electricity Electricity Heat

Total

UK Production 182.6 542.8 - - 7,408.1

Net imports 39.7 - 35.9 - 2,407.4

Net Energy Available 222.3 542.8 35.9 - 9,815.5 Transfers - -44.2 44.2 - -5.3

Net Consumption 222.3498.6 i.e. nuclear 80.1 - 9,810.2

ABA*

• Transfers represent transfers between columns – e.g. Primary electricity is generally large scale renewables and nuclear, but the non-nuclear component is transferred as it is not involved in the energy conversion process in next section.

• i.e 498.6 PJ is attributed to gross nuclear generation (i.e. before conversion), and 44.2 is transferred as renewables.

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• -ve quantities indicate inputs to conversion, +ve indicates outputs.

• 1488.5 PJ of coal was used as input to conversion processes of which 1252.3 PJ (see box in full table) went to electricity production.

• 3688.5 PJ of crude oil produced 3624.4 PJ of Petroleum products.

  CoalManufactured

fuel(1)Primary

oilsPetroleum products

Natural gas(2)

Net Consumption 1,563.0 16.7 3,688.5 -185.2 3,926.3

Energy Conversion          

inputs -1488.5 - -3688.5 - -1430.1

outputs   69.9   3624.4  

 Renewable & waste(3)

Primary electricity Electricity Heat

Total

Net Consumption 222.3 498.6 80.1 - 9,810.2

Energy Conversion          

inputs -148.1 -498.6 - - -

outputs     1343.8 53.6 -

net energy balance - - - - -2162.0

Simplified Energy Balance Tables: Energy Conversion

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CoalManufactured

fuel Primary oilsPetroleum

productsNatural

gasTransformation [Energy Conversion] -1,488.5 69.9 -3,688.5 3,624.4 -1,430.1

Electricity generation -1,252.3 -35.9 - -41.4 -1,346.7 Heat generation -11.9 -2.2 - -2.5 -83.4 Petroleum refineries - - -3,688.5 3,677.4 - Coke manufacture -179.2 170.1 - - - Blast furnaces -35.7 -71.9 - -9.1 - Patent Fuels -9.3 9.8 - - -

Energy Conversion

Renewable & waste

Primary electricity Electricity Heat

Total

Transformation [Energy Conversion] -148.1 -498.6 1343.8 53.6 -2,162.0

Electricity generation -148.1 -498.6 1,343.8 - -1,979.3 Heat generation - - - 53.6 -46.4 Petroleum refineries - - - - -11.1 Coke manufacture - - - - -9.1 Blast furnaces - - - - -116.7 Patent Fuels

- - - - 0.5 1252.3 PJ of coal went into electricity generation as did 35.9 PJ of coke, 41.4 PJ of oil, 1346.7 PJ of natural gas. 148.1 PJ of waste/biomass and 498.6PJ of nuclear equivalent.

In total 1343.8PJ were generated from thermal plants

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Energy Conversion

In 2008, 1252.3 PJ of coal went into electricity generation as did 35.9 PJ of coke, 41.4 PJ of oil, 1346.7 PJ of natural gas. 148.1 PJ of waste/biomass and 498.6PJ of nuclear equivalent.

Total Input = 3323.1 PJ with 1343.8PJ generated.

Thus the overall thermodynamic efficiency of generation

= 1343.8 / 3323.1 = 40.4%

In the balance table 498.6PJ was nuclear input,

actual amount of nuclear electricity generated = 498.6 * 0.404 = 201.6PJ

Electricity use on stations = 58.7PJ (from full table)

Overall station efficiency of fossil fuel plant allowing for station use

= (1343.8 – 58.7 ) / 3323.1 = 38.67%

Transmission Losses = 98.7PJ or 98.7/(1343.8-58.7) = 7.68%

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• The supply of electricity is 1388.4 from thermal plants• The total losses associated with the electricity industry = 58.7 + 98.7 + 4.6 = 162.1 • So first order Primary Energy Ratio for electricity = 3323.1/(1343.8 – 162.1) = 2.81

assumes that the PER for coal, oil and gas is 1.0• Similar first order analysis gives a PER of 1.11 for oil.

• Using an iterative approach second order estimates are obtained as follows.

• However, what about fuel extracted overseas. This second order analysis assumes that the PERs in those countries are same as UK.

Energy Conversion

Fuel Primary Energy Ratio

Coal 1.0227

Oil 1.1292

Gas 1.062

Electricity 2.911

Pumped Storage

A more accurate estimate of emission factor in electricity generation• Emission factor in electricity generation depends on:• Carbon emission factor of burning fuel• Efficiency of power station• Transmission losses• Example Japan

  Coal Japan in 2007 

Gas derived from Coal processes

 

Other Bituminous Coal 

Coke Oven Gas

Blast Furnace Gas

Basic Oxygen Steel

Furnace Gas

Unit kilotonnes TJ TJ TJ TJTotal Transformation 101305 2969006 79643 224498 27639Electricity Plants 94324 2764410 79643 224498 27639CHP Plants 0 0 0 0 0Heat Plants 24 703 0 0 0

1 tonne coal has a calorific value of 29.3076 GJ

Data from IEA data base for Coal for Japan

A more accurate estimate of emission factor in electricity generation  Coal Japan in 2007 

Gas derived from Coal processes

 

Other Bituminous Coal 

Coke Oven Gas

Blast Furnace Gas

Basic Oxygen Steel

Furnace Gas

Unit kilotonnes TJ TJ TJ TJTotal Transformation 101305 2969006 79643 224498 27639Electricity Plants 94324 2764410 79643 224498 27639CHP Plants 0 0 0 0 0Heat Plants 24 703 0 0 0

Total coal based products consumed in power stations = 3096190 TJ

Total Electricity generated 310796 GWH = 118866 TJ

Efficiency of coal fired generation = 118866/3096190 = 36.14%

Transmission Losses 4.50% so overall efficiency = 36.14 * 0.955 = 34.51%

If carbon factor for direct combustion is ~ 310 g/kWh

Carbon factor for coal generation = 310/0.3451 = 898 g/kWh

If efficiency ~ 30% then carbon factor would have been 1033 g/kWh

Figures in Red from IEA data base for Electricity (Japan)