Friday, 9 January 2015

Energy and Power Density

The fundamental reason for the inevitable failure of renewable energy (RE) is the pathetic power and energy densities they give. Let's compare everything on similar scales - in kiloJoule (kJ). kiloJoules per kilogram (kJ/kg) and kiloWatts per square metre (kW/m2). To convert between energy and power, remember that kJ = kW for 1 second. Look how dense Uranium is compared with fossil fuel (methane). How much better methane is than hydro. How pathetic wind is.

Lithium battery1,800
Lead battery170
Hydro (100m dam)1

PS: One joule (J) = work required to produce one watt (W) of power for one second, or one "watt second" (W·s)

Fossil fuels (like methane: 55,500 kJ/kg) are so energy dense and so convenient that we'd have to invent them if they weren't already there. The only way we were ever going to replace them was with something better, something far denser : uranium and thorium.

The consequence of weak power and energy density with an insistance upon RE-only energy must one of:

  1. Power Density Primer, by Vaclav Smil (pdf)
  2. Energy density (wikipedia)
  3. Why Power Density Matters, by Robert Wilson

1 comment:

  1. Your readers may have some interest in energy density calculations relating to a wider range of nuclear fuels; both fission and fusion.

    Energy Content Approximations for Nuclear Fuels
    (assuming complete consumption of the nuclear fuel in each instance) -

    Some Convenient Energy Content Approximations for Nuclear Fuels -
    Fission of Pu-239: 7.23832 x 10^7 MJ/kg
    Fission of U-235: 7.36384 x 10^7 MJ /kg
    Fission of U-233: 7.44752 x 10^7 MJ/kg


    Fusion of proton – Boron-11: 7 x 10^7 MJ/kg
    Fusion of He3-He3: 2.075 x 10^8 MJ/kg
    Fusion of lithium-6 deuteride: 2.67776 x 10^8 MJ /kg
    Fusion of tritium and deuterium (50/50): 3.363936 x 10^8 MJ/kg
    Fusion of pure deuterium: 3.439248 x 10^8 MJ/kg

    (Full E=MC^2 Energy Conversion)
    Total conversion of matter to energy: 8.983048 x 10^10 MJ/kg

    Comment - Of all nuclear reactions (fission or fusion) - D-D fusion of pure Deuterium separated from sea water produces the highest energy yield per kilogram of fuel consumed.
    Deuterium-Deuterium fusion is slightly more complex than D-T fusion which is more commonly and popularly discussed.

    D-D Fusion of Deuterium fuel produces energy through four reactions:

    D + D -> He-3 + n + 3.268 MeV
    D + D -> T + p + 4.03 MeV
    (side chains)
    D + T -> He-4 + n + 17.588 MeV
    He-3 + D -> He-4 + p + 18.34 MeV

    The net effect of these four fusion reactions taken together is:
    6 D -> 2 He-4 + 2p + 2n + 43.243 MeV

    The energy output that results from all four D-D fusion reactions is 3.439248 x 10^8 MJ/kg. The maximum temperature generated by an efficient burn reaches 350 million K.

    Data needed to make the above energy density calculations was taken from the following reference (Carey Sublette) which is believed reliable -