Roadblock for solar PV?

Checkmate! Checkmate! Checkmate!

In what could be viewed as one unending chess match between nature and Man, the latter keeps coming up with new solutions to challenges, only to be trapped in yet another new challenge.Just when green alternatives to energy are being taken up seriously, hidden problems associated with these, spring up.

Take solar energy. Just when news comes in of large scale solar plants being commissioned, research has thrown up a twist.Emissions of a greenhouse gas that has 17,000 times the planet-warming capacity of carbon dioxide are at least four times higher than had been previously estimated. Nitrogen trifluoride (NF3) is used mainly by the semiconductor industry to clean the chambers in which silicon chips are made. The industry had in the past estimated that most of the gas was expended during the cleaning process and only about 2 percent escaped into the air. But the first-ever measurements of nitrogen trifluoride levels in the atmosphere, published recently in the journal Geophysical Research Letters show that emissions could be as high as 16 percent.

Making integrated circuits involves depositing layers of materials such as semiconductors and metals on a silicon wafer. These materials also stick to chamber walls. So after each layer is deposited, nitrogen fluoride is pumped into the chamber and is split to release highly reactive fluorine atoms that clean the walls.

A less harmful (for the climate) method is to produce fluorine at the site, but calls for more costs by way of health safety (as fluorine is corrosive and can damage teeth and bones.)

As flat panel LCD television takes off, as also thin film solar cells, there is hurry in production which implies that safeguards may not be adequate. The hitherto unregulated gas will have to be monitored better, says the study.

Perhaps its time to look at new materials for solar cells, besides silica, like dye-sensitised cells. Made with a new type of ruthenium-based dye that helps boost the light-harvesting ability, the new cells showed efficiencies as high as 10 percent, a record for this type of solar cell. Most silicon-based solar cells have so-called efficiencies of around 12 percent. Manufacture of silicon is anyway costly.

Is solar thermal the best bet?