Photovoltaic cells—those black squares an array of which comprises a solar panel—are getting more efficient, and gradually less expensive, all the time, thanks to ever-better designs which all them to focus the gathered sunlight on a more and more concentrated point. The size of the cells is decreasing as their efficiency rises, meaning that each cell becomes cheaper to produce and at once more productive. As far as the aforementioned cost, the price of producing solar-generated energy per watt hour has come down to $4.00 at the time of this writing. Just 17 years ago, it was nearly double that cost. Read the rest of this entry »