The first problem is that the cells convert only 10-15% of the radiation from the sun into energy. The second is that the photovoltaic (PV) material used is a form of silicon that has to be made under high-vacuum conditions and heated in special kilns to 1,400ªC. That makes photovoltaic solar cells horrendously expensive.
Consider the small model home set up in Raleigh by the North Carolina Solar Centre. Its 3.6-kilowatt PV system generates about half of the house's electricity needs. But at $9 per watt, the system would cost a homeowner around $32,000 to install.
How to bring such costs down to a more manageable few thousand dollars? One answer that is attracting attention is to use carbon [base "]nanorods[per thou], superstrong cylinders of carbon atoms that are 75,000 times thinner than a human hair. If a group at the Lawrence Berkeley National Laboratory in California achieves its ambitions, carbon-based solar cells could cost as little as a tenth of the price of today's silicon-based versions.
