Solar power, the poster child for green energy, has a dark past.
For more than a decade, global solar panel manufacturing has used more electricity than the final products have generated. With most of the shortfall coming from burning fossil fuels, solar power may have added to the very problem it was meant to solve.
That situation now looks set to change. According to Michael Dale and Sally Benson of Stanford University, 2012 likely saw the world’s solar photovoltaic (PV) panels become net electricity generators for the first time (Journal of Environmental Science and Technology, doi.org/k5x).
Although individual panels generate more electricity over their lifetimes than they consume, the rapid expansion of the solar power industry since 2000 has meant the short-term energy costs have outweighed the long-term gains.
Now, thanks to improvements in the manufacturing process, the balance has tipped the other way. “The industry is making positive strides,” says Dale.
For the majority of solar panels, the most energy-intensive step is the production of silicon from silica rock, requiring temperatures of over 1600 °C. By reducing the amount of silicon used in each panel, and by minimising the material lost in the manufacturing process, the industry has reduced this energy cost substantially.
Alongside advances in solar panel efficiency, this led to a greater than 50% chance that PV panels made a net electricity contribution in 2012. This figure rises to an almost certainty by 2015, assuming current trends continue.
Yet the technology is still far from clearing its energy debt; just five years ago, the industry used 75% more electricity than it generated. To be considered a success, “PV panels must ultimately pay back all the energy that went into them,” says Dale.
This could happen as early as 2015 – and no later than 2020 – as long as manufacturers continue to cut their energy demands.
However, the researchers warn, should the industry focus on reducing its financial costs, energy reduction may become a secondary concern. Currently the most expensive steps, installation and wiring, account for over a third of the financial cost, but just 13% of energy use.
Despite the potential for setbacks, Dale is optimistic about the future of solar power: “In spite of its fantastically fast growth rates, PV is producing – or just about to start producing – a net energy benefit to society.”