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Energy Resources

 

Despite the continuing developments of solar, wind and hydro power, over 80% of the World's electricity is still derived from heat sources. This page lists some the main sources of energy which are used for electrical power generation together with the energy content of the source.

For a description of how electrical energy is generated from these sources and the conversion losses involved see the Electrical Energy Overview

 

Calorific Energy Content of Fuels and Chemicals

The energy content of various materials usually, but not always, refers to the calorific or thermal energy which can be extracted from the material, usually by burning it and using the heat in some way to generate electricity.

 

Energy Sources:

Key

Fossil Fuel

Green Energy

Nuclear Fuel

Thermal

ElectroChemical

Kinetic

 

Generation

Process

Fuel

Thermal Energy

(Calorific Content)

kWh/Kg

 

 

 

Thermal

 

 

 

 

 

 

 

 

 

 

 

 

Brown Coal (Lignite)

2.8

Coking (Black) Coal

8.3

Oil

12.5

Natural Gas (North Sea) [1]

10.8

Liquefied Petroleum Gas (LPG) is a mixture of Propane and Butane

13.8

Propane

13.9

Butane

13.7

Kerosene (Paraffin Oil)

13.0

Petrol (Gasoline)

13.0

Diesel

12.9

Bio diesel

10.9

Ethanol

8.3

Methanol

6.4

Dry Wood

4.4

Green Wood

2.5

Agricultural Crop Residues

2.5 - 5.0

Municipal Waste

2.0 - 2.5

Uranium 235

22,800,000

 

Hydrogen [2]

39.4

 

Candy Bar (Mars Bar)

5.55

Sources:
UK National Physical Laboratories (NPL)
UK Department for the Environment and Rural Affairs (DEFRA)
Indian Ministry of Non-conventional Energy Resources (MNER)

[1] Natural gas consists primarily of methane (70 to 90%) but includes significant quantities of ethane (5 to 15%), butane , propane , carbon dioxide , nitrogen , helium and hydrogen sulfide.

[2] Hydrogen is not a primary energy source. It takes 50 kWh of electricity to produce 1 Kg of hydrogen by electrolysis.

 

Electrochemical Energy Content of Chemical Species

Using the calorific energy content of various chemical substances and materials to generate electricity involves three energy conversion processes each of which introduces inefficiencies.

 

Energy Conversion Process

 

Chemical elements however contain intrinsic electrochemical energy potential associated with the energy of the electrons in the outermost electron shell or valence band (explained in the Energy section on the Cell Chemistries page) and this energy is converted directly to useable electric energy in batteries. The table of Electrode Potentials on the same page gives an indication of the relative magnitudes of these energies at the molecular level. The following table shows the magnitude of energy available from these sources when used in practical devices.

 

Generation

Process

Cell Chemistry

Electrical Energy

kWh/Kg

 

Electrochemical

 

Primary Battery (Alkaline)

0.175

Rechargeable Battery (Lead Acid)

0.04

Rechargeable Battery (NicKel Cadmium)

0.05

Rechargeable Battery (Nickel Metal Hydride)

0.08

Rechargeable Battery (Lithium Ion)

0.14

 

 

Energy Content of Naturally Occurring Energy Flows

The ideal renewable energy sources are naturally occurring energy flows. The energy is free, but harvesting it could be very costly. The following table indicates some of the possibilities.

 

Source

Natural Energy Flows Providing 1 kW of Available Power

Wind Turbine

Wind speed 12.5 m/s

Turbine swept area 0.85 m2

Wind speed 4 m/s

Turbine swept area 31.84 m2

Hydro Turbine

Water flow 1 m3/s

Head of water 0.1 metres

Water flow 100 litres/sec

Head of water 1.0 metres

Solar PV

(Electromagnetic

Radiation)

Surface perpendicular to the sun's rays at noon with sun directly overhead

Surface area 1m2

For an hourly average of 1kW taken over a day

Surface area 2.5 m2 to 5 m2 depending on location

Geothermal

(Ocean) Temperature difference 20°C

Water flow rate 10.8 litres/min *

(Hot rocks) Temperature gradient 40°C/km, Area 1 km2, Depth 3.5 km

Water flow rate 0.2 litres/min *

(Aquifers) Temperature gradient 30°C/km, Area 1 km2, Depth 3.0 km

Water flow rate 0.24 litres/min *

     * After Garnish J. D. (1976) - Geothermal Energy (HMSO)

To convert to alternative energy units - see the Conversion Table

 

Utilisation of Energy Resources for Electricity Generation

 

World Electricity Generation by Fuel (Terawatt hours - TWh)

World Electricity Generation by Fuel

Source OECD Factbook 2007

Note that electrical energy consumption has more than tripled from 5,200 to 17,400 TWh in 23 years. (17,400 TWh = 1,496 Mtoe)

Over the same period the share of energy generated by nuclear power has shown the greatest growth with other renewables close behind, but the majority of the world's electrical power is still generated from coal.

 

World Electricity Generation by Fuel (Percentage)

World Electricity Generation 1971World Electricity Generation 2004

Source OECD Factbook 2007

 

Fuel used for electricity generation in the UK

Fuels used for energy generation

 

Electricity generated from renewable resources

 

 

Electricity Generating Costs per kWh for Different Fuels

 

Electrical Energy Costs

Source Canadian Energy Research Institute 2006

Costs are 2003 values and include amortisation of capital costs, operations and maintenance, and fuel costs. (CAD $1.00 = USD $0.92)

Decommissioning is not included.

In the case of intermittent sources such as solar and wind the costs of maintaining and using standby capacity must be added.

 

Summary of All Energy Sources and Uses for All Applications in the USA (Not Just for Electricity Generation)

See Conversion Table to convert Quads to other units.

Energy Use inthe USA

 

See also Energy Efficiency and Energy from Coal?

 

Return to Electrical Energy Overview

 

 

 

 

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