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April 2006

Feature

 

 

Solar Cells take Stellar leap

By Dr Garth Cambray

A solar panel system such as this one will provide power to an average household - but - the average South African household cannot afford it - when new panels based on the invention of Prof Vivian Alberts and his team reach our shores, the 4 times reduction in price will solar energy a viable option for many South African families.

South Africa has always branded itself as 'Sunny South Africa' - so its little shock that the country has emerged as a world leader in inventing and fine tuning solar power generating technology. A research team led by Professor Vivian Alberts of the University of Johannesburg (formerly Rand Afrikaans Universiteit) has developed an advanced photo voltaic system that is providing the final push needed to make solar power an accessible energy option.

The conventional solar panels that we see dotted around on telephone systems, remote aerials and some peoples roofs use silicon based photo voltaic cells. These cells each consist of two layers of silicon crystals doped with a very small number of phosphorous atoms in one layer and boron in the other. The phosphorous doped layer in sunlight will generate a surplus of electrons which will flow, via an external circuit, to the boron doped surface where a shortage of electrons exists. As the electrons go around this circuit they can do work - such as charging a battery or powering the computer I am using right now.

In a perfect world, a silicon based photo voltaic cell can convert roughly 25% of the incipient solar energy it receives into electricity - this is the total section of the solar radiation hitting the cell that can be used - the rest of the solar radiation is either too high or too low intensity to do anything. In reality, only 15% (under optimal conditions) of incipient solar energy is harnessed by the cell.

Silicon based solar cells are relatively expensive, as shown in the related article in this edition on a solar powered house (link) where it could take about 5 years to recoup the costs of the solar panel.

The patent lodged globally by Prof. Vivian Alberts () changes much of this. The heart of the photo voltaic cells consist of special super thin (5 micron) copper-indium(gallium)-diselenide alloy layer which is produced by a step wise reaction involving hyrdogen suphide and argon and a gradually increasing temperature to arrange the components of the copper-indium(gallium)-diselenide alloy in the appropriate conformation. The result is that the thickness of the photo voltaic cells can be reduced from about 350 microns to 5 microns - that is a 70 times reduction in the size of the cell.

The panels based on this alloy will have a working life of about 20 years. In addition to this advantage of the new panels, they will also be considerably less expensive than competing products costing about R7.90 to R8.00 per watt as opposed to R35-R40 per watt.

Production of the panels in South Africa will begin soon, and panels are already being made in Germany.

So if you do the maths on this, assuming you have a household which uses about the same amount for lighting on consumer electronics as the house in this article (link) it will cost you R1000 for a solar panel as opposed to the replacement cost of R4800 for the one used in that solar house. With batteries, invertors and power management systems, that means that the system will pay itself off in about 1 year. For a more energy thirsty system, it would take about 2 to 3 years and after that, a household would be looking at 17 years of just about free energy. Now that's what we call a lucky star shining on you!

From the ScienceinAfrica team, we truly congratulate Prof. Alberts and his team and the University of Johannesburg - great research, great results - when can we buy one?


More information:

 University of Johannesburg 

Related articles:

Novel invention could mean cheaper source of energy from solar power

Fermenting waste fruit to fuel ethanol

Off the grid for 5 years

 

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