Electrosolar : Photovoltaic Energy

Relevant statistics (2008):

HomepageThe futureCO2 in the airStatisticsWhat is PVLinksCO2 removalCO2 removal - 2Contribute

 

You don't need a university degree or a computer model to establish the rate of increase of our pollution of the atmosphere with carbon, or to quantify the astounding potential for solar power. It can all be worked out by simple arithmetic from known facts. Below is a list of relevant values which should enable anyone to repeat my calculations.

 

    weight fraction of carbon in carbon dioxide  = 12/(12+32) = 27.2%
    earth surface area                                               = 5.101e14  m2
    land area                                                               = 1.49e14 m2
    mass of atmosphere                                           = 5.27e18 kgs
    population                                                           = 6700e6
    co2molefraction           = 380/1e6 {fraction by volume in the atmosphere} = 0.038%
    seconds per year         = 60*60*24*365.25                ~ 31,500,000
    energy per kg of carbon                                                  = 33 Mega joules
    110 gms of carbon produces 1KWH (=3.6 Mega joules) when burnt
    atmospheric carbon per square metre of land              = 3.5 kg
    atmospheric carbon per square metre of the planet    = 1.0 kg

   density of carbon (as graphite)                       = 2266        kg/m3
    land area per person                                                        = square of 150 metres side
    current atmospheric carbon per person                       = 130 metric tons

  Map showing average solar power Per capita atmospheric carbon
   ·    solar power flux in space = 1350 watts/sqm
 
·
   mean solar flux on earth = 50-350 watts/sqm  {130 in UK}   (average night/day/winter/summer)
 

    THE PROBLEM
    Average energy equivalent power used per person       = 1.2 KiloWatts
    Carbon added to the atmosphere per person per year   = 1.1 metric tons

    THE SOLUTION
 
   Available solar power per person (land and sea)                       = 13.8 Mega watts
    Solar power per person using 15% eff cells and 1% land area   = 6 KiloWatts

 

To download a very simple, well commented Delphi pascal program (updated 10/1/2000) including all sourcecode to re-calculate the above statistics from first principles, click here (~94kb .zip).

 Atmospheric carbon facts and figures:

· Depth of atmospheric carbon if it was solid graphite on the ground    = 0.7mm

· Amount of carbon in 1 cubic metre of air = 0.203 gms

 

Photovoltaic facts and figures:

· Generation capacity of world PV production in 1997  was  130    Mega watts.

· Generation capacity of world PV production in 2007  was  3,500 Mega watts.

· Generation capacity is increasing EXPONENTIALLY with a typical three year doubling period

· Initial Cost of PV plant in pounds ~= PV Production capability in watts peak / year.

· Depending on your global position, the mean energy production of a PV array is typically between 10 and 30% (averaged          night and day, summer and winter) of its quoted peak power

· Between 2010 and 2020 most office buildings in the UK will be PV clad

· In the USA there is a ‘Million Solar Homes’ project.

· The EEC is  setting out a ½ Million PV systems target.

· Germany leads Europe in installed PV systems

 

 Existing technologies for Photovoltaics:

· Crystalline Si            -12% to 24% efficient.       Payback time 2 to 10 years.   25year lifetime.

· Gallium Arsenide    - Previous record for highest efficiency of 34% - Expensive to produce, poisonous materials.

· Amorphous Thin film SiliconStability problems.   ~8%    Thin film - easier manufacture.

· Cadmium Telluride. - Triple junction cells hold current world record efficiency of 40%

· CopperIndiumSelenide (CIS)                    ~ 15% efficient.   Thin film - easier manufacture.

· Copper Indium Gallium Selenide (CIGS) - ~20% efficient.   Thin film - easier manufacture.

· Dye sensitised nanocrystalline Titanium Dioxide {DSNCPV)

- Invented by Brian O'Regan in Professor Michael Gratzel's team Switzerland.

- These are the first 'organic' solar cells

- They use a complex organic dye as a photoelectric converter

- Currently only 9-11% efficient in the laboratory.

· Conductive polymer solid state cells  ~2% efficient Prof Richard Friend (Cambridge)

- Current research is a bi-product of the discovery of light emitting polymers

· Gallium Indium Nitride alloys - Promising material for PV, currently used for ultra bright LEDs

- Tuneable band gap