**Solar constant:**

"The solar energy reaching the periphery of the earth's atmosphere is considered to be constant for all practical purposes, and is known as the *solar constant*. Because of the difficulty in achieving accurate measurements, the exact value of the solar constant is not known with certainty but is believed to be between 1,353 and 1,395 W/m^{2} (approximately 1.4 kW/m^{2}, or 2.0 cal/cm^{2}/min). The solar constant value is estimated on the basis of the solar radiation received on a unit area exposed perpendicularly to the rays of the sun at an average distance between the sun and the earth."

[http://almashriq.hiof.no/lebanon/600/610/614/solar-water/unesco/21-23.html]

**Radius of the Earth:**

The value of 6371 km used here is the Volumic Radius, ie the value giving a fairly exact value for the Earth's volume by the usual formula for a true sphere. Because the Earth is actually an oblate spheroid, other radii have been calculated.

[http://en.wikipedia.org/wiki/Earth_radius]

**Calculations:**

Taking the solar constant to be 1.4 kW/m2, and the Earth's radius to be 6371 km, the cross-sectional area of the Earth is pi*r^2, ie 3.142*((6371*10^3)^2)=1.2753E14 sq m.

With the Earth at its average distance from the Sun, total energy received (ignoring atmosphere etc) is 1.2753E14 times 1.4 = 1.785E14 kW. This is equal to 178,500,000 GW (gigawatts). (For a world population of ca 6 billion, solar energy per person= ca 30,000 kW.)

1 year=365.25*24 hr =8766 hr. Total solar energy received/yr = 8766*1.785E14 kW-hrs = 1.564731 * 10^{18 }KW-hrs = 5.6330316 * 10^{24} joules.

1 kilowatt hour = 3 600 000 joules = 3.6E6 joules. 1 kilowatt = 1.0 x 10^{-6} gigawatts

The whole-world total at end is calculated from the China figure using the factor "China now consumes 13.6 per cent of the world's total energy." from [http://www.bp.com/genericarticle.do?categoryId=2012968&contentId=7006684].

Country | *Population | **Energy | §Consumption | Power Draw |

Consumption | per head | per head, kW | ||

Australia | 20155 | 119 | 5.9 | 8.083 |

Bangladesh | 141822 | 17 | 0.12 | 0.1644 |

Brazil | 186405 | 188 | 1.01 | 1.3837 |

Canada | 32268 | 308 | 9.53 | 13.0561 |

China | 1315840 | 1386 | 1.05 | 1.4385 |

Hong Kong | 7041 | 24 | 3.38 | 4.6306 |

Egypt | 74033 | 54 | 0.73 | 1.0001 |

France | 60496 | 263 | 4.35 | 5.9595 |

Germany | 82689 | 330 | 4.01 | 5.4937 |

Iceland | 295 | 3 | 8.81 | 12.0697 |

India | 1103370 | 376 | 0.34 | 0.4658 |

Indonesia | 222781 | 110 | 0.49 | 0.6713 |

Iran | 69515 | 156 | 2.24 | 3.0688 |

Italy | 58093 | 184 | 3.16 | 4.3292 |

Japan | 128085 | 515 | 4.02 | 5.5074 |

Kazakhstan | 14875 | 53 | 2.56 | 3.5072 |

Kuwait | 2687 | 23 | 8.37 | 11.4669 |

Mexico | 107029 | 145 | 1.36 | 1.8632 |

Netherlands | 16299 | 95 | 5.85 | 8.0145 |

Norway | 4620 | 39 | 8.44 | 11.5628 |

USA | 298213 | 2332 | 7.82 | 10.7134 |

Whole World | 6000000 | 10000 | 1.67 | 2.2879 |

**(million tonnes oil equivalent)

§ (tonnes oil equivalent)

(End)

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