Electrosolar : Photovoltaic Energy

Relevant statistics:

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)
    density of carbon     = 2266        kg/m3
    earth area            = 5.101e14  m2
    land area             = 1.49e14 m2

    mass of atmosphere    = 5.27e18 kgs
    population            = 6000e6
    co2molefraction      = 360/1e6 {fraction by volume of CO2 currently in the atmosphere}
    secs per year         = 60*60*24*365.25
    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
    depth of atmospheric carbon if it was solid graphite on the ground    = 0.7mm
    land area per person    = square of 160 metres side
    current atmospheric carbon per person  = 130 metric tons


    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).

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

This IS increasing EXPONENTIALLY with a typical three year doubling period
Initial Cost of PV plant in pounds ~= PV Production capability in watts peak per 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.
It is estimated that 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.
In the UK we have a rather pathetic 100 Homes PV project

 Existing technologies for Photovoltaics:

Crystalline Si    12% to 24% efficient  

- Payback time 2 to 10 years.   25year lifetime.

Gallium Arsenide - Hold record for highest ever efficiency of 34%

- Expensive to produce, poisonous materials.

Amorphous Thin film Silicon

Cadmium Telluride

CopperIndiumSelenide

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 - Prof Richard Friend (Cambridge)

- Currently only 1% efficient
- Current research is a biproduct of the discovery of light emitting polymers

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

- Tuneable band gap




This is page 2
Click here for page 1 : The future of photovoltaic energy
Click here for page 3 : List of relevant websites
Click here for page 4 : How you can help
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