Solar PV (photovoltaic) cells generate electricity directly from sunlight. They've been around for decades, though over time have become less expensive and more efficient, with production accelerating quickly in the past few years.
Many experts believe PV is still too expensive to warrant substantial government investment as a means of reducing CO2 emissions, especially in cloudy regions. In Manchester, Jeremy Leggett of Solacentury argued the opposite, making the case for a massive roll-out of PV on domestic and commercial roofs as well as in solar "farms". According to Leggett, few energy sources offer such good long-term investment opportunities – a case in point being the PV cells produced in the 1960s that are still working at 80% capacity, having paid for themselves many times over.
Many solar advocates believe that given appropriate incentives – such as generous "feed-in tariffs" that offer payments to householders for each unit of solar electricity exported to the grid – photovoltaic power could become as inexpensive as conventional generation within a few years. Furthermore, PV can help reduce electricity demand, according to Leggett: when people install solar panels on their roofs, they tend to become more energy-aware and reduce the amount of power they consume.