PV Gap

Paul Said:

what is the study of solar cells and windmill produced energy?

We Answered:

What do you want to find out about them?
If you want to know how to build them, you would have to be an engineer,
If you want to know their impact on the economy, you would have to be an economist.
If you want to know how they impact on the environment, you would have to be an ecologist.

Maureen Said:

Energy to create Solar Cells?

We Answered:

It depends a little on what sort of cell and where it is used. The main problem is that the silicon needs to be EXCEEDINGLY pure - and with the exception of the polycrystalline cells, the cells have a very finite life.

Most of the amorphous ones are producing less than half rated power in about 5-7 years and next to useless in about 10-12.

If you plonked any *modern* polycrystalline cell in a country which enjoys HUGE amounts of bright sunshine all year around, then it WILL sooner or later produce more power than it took to make it.

Any other cell (current technology) and certainly in less favourable sunlight conditions will have failed before it reached unity.

One particularly ghastly scan was done in Sri Lanka about four years ago, a very impressive sales pitch was made on the wonders of solar electricity (electricity not available in many parts of SL), the locals were given credit agreements to sign and their panels installed. Even when they were first put in, the output was a fraction of what was promised - spec given for the best polycrystalline panels, delivered was a poor type of amorphous panel. Now 4 years down the line, most panels have reduced their output (such as it was) by over half. Alas there do not have "trading standards" in SL, just money collectors with guns and wooden clubs to encourage you to pay on time. A digression I agree - but I wanted to illustrate the difference between old and new design panels.

The biggest problem is the energy input required to make the silicon pure, the rest of it is *reasonably* ok. We shall ignore the energy requirements to make the glass they are bonded too and the substantial amount of power to produce the aluminium backing.

Solar cells DO have a place (remote power etc etc) but from an environmental point of view, they really have some way to go before they truly benefit the planet.

A far more useful way of extracting power from solar is to use panels to heat hot water, not only for central heating / hot water - BUT if used with reflectors and focused on a single point, VERY high temperature can be attained sufficient to drive steam turbine engines - there are a few commercial plants that do this today. http://americanhistory.si.edu/powering/i… being one case in point.

Hopefully in time, cells will become more efficient, more economical ways of making pure silicon will be found and the use of solar for making electricity directly WILL become more practical from a "green" point of view.