Solar power is nothing new. Since prehistoric times, ancient civilisations have used glass and reflective metals to concentrate the sun's rays, usually to light torches or fires. Even the silicon-based photovoltaic cell, the basis for modern solar panels, has more than 50 years of history behind it. The technology emerged in 1954 from the US laboratories of Bell Telephone and found its first successful commercial application in space, powering communications satellites. There, the high cost and low efficiency of early solar panels was no obstacle, as there was no competing technology capable of powering an orbiting satellite for years at a stretch.
Now the same technology is in demand as a potential solution to the planet's energy woes, but bringing it down to Earth poses problems; sunlight may be free, but solar energy is not. On the ground, low costs and high efficiency are paramount concerns. Without plentiful supplies of inexpensive energy, the Earth cannot continue to support its current population, but while the biosphere may be choking on emissions from high-carbon, non-renewable fuels, the trouble is that for most people these remain the only affordable energy options.
The crux of the challenge therefore boils down to trimming construction, installation and operating costs for solar power systems while boosting their output. Much progress has already been made but manufacturers need further improvements to achieve "grid parity", the price point at which solar power can compete, unsubsidised, with other types of power generation. The good news is that such parity is now achievable, according to industry experts. No scientific or technical breakthroughs are needed, just further incremental engineering improvements in materials and manufacturing processes.
"We're getting close to a world where solar energy can really compete, so there are some tremendous opportunities," says Reyad Fezzani, the chief executive officer of BP Solar, a unit of the British oil group that has been developing and marketing photovoltaic solar systems for 37 years. Mr Fezzani, who is looking forward to the business making a bigger contribution to the company's total energy portfolio, is convinced BP Solar is right to stick with traditional silicon-based photovoltaics, rather than seeking bigger efficiency gains from systems that use more expensive materials: "The biggest cost-reduction opportunities in solar today remain in the silicon-based systems and in manufacturing," he maintains.
Jos van der Hyden, the vice president of business development at First Solar, a US thin-film solar panel manufacturer, sees the modular nature of photovoltaic power systems as a key advantage that will open up expansion opportunities. The company has installed everything from 30KW rooftop solar systems to a 53MW array at a German power station. It also has a memorandum of understanding with the Chinese government to develop a 2,000MW system.
"The challenges from our point of view are mainly in construction and scaling," he says. "It's a matter of local implementation. It's the fact that you have to find local construction companies, train people and arrange technology transfer." First Solar has also staked out a technology niche, using semiconductor systems that are less susceptible to temperature fluctuations and function well in diffuse light, providing efficiency advantages in both hot and cloudy climates.
Andreas Gombert, the chief technical officer of Concentrix Solar, a German company developing concentrating photovoltaics systems, sees improving the durability of components and materials as a challenge. "The big problem is that solar cells have to survive very difficult climates," he says. With continued improvement, however, the technology should achieve grid parity in at least some parts of the world within a decade, he predicts. "The most important point," he believes, "is that the world's energy problems can only be solved with solar power."