Photovoltaic solar energy and energy transition

It wasn't until the turn of the century that the first solar cells were produced, the photoelectric effect was explained by A. Einstein in 1905, and it was another fifty years before modern silicon cell technology was born. With the developments associated with the conquest of space, modern photovoltaics was born. The theory, based on quantum physics, was established, and new processes and new thin-film materials were emerging (GaAs, CdTe, amorphous silicon, Cu(In,Ga)_Se2), while yields were constantly increasing, with a creative and innovative ferment that is still growing today, with the discovery of new chemical processes such as organic photovoltaics and perovskite. However, it wasn't until the turn of the century that the dream of generations of scientists and utopians of seeing photovoltaics take root on earth finally came true. Thanks to the impact of proactive public support policies, in Germany and Japan in particular, and to technological progress, the industrial sector was able to establish itself, first in Europe and then in China, consolidating the photovoltaic value chain and initiating the cost reduction associated with the change of scale. High costs, an insurmountable barrier, were finally broken down, to the extent that they have fallen by a factor of 10 in ten years, and now make it possible to generate economically competitive electricity. Such is the progress made that the International Energy Agency calls it the "Sun King". In fact, photovoltaics has become the world's cheapest source of electricity.

At the same time, photovoltaic production capacity is exploding worldwide, with annual installations rising from 300 MW in 2000 to 143 GW in 2020, for a total capacity approaching the symbolic threshold of one Terawatt. In some countries, including Germany, nearly 10% of electricity consumed is photovoltaic, compared with 2.5% in France.

Photovoltaic solar energy has thus entered the big league in terms of its contribution to the energy transition. The abundance of solar resources and their worldwide distribution mean that the potential for development and acceleration is considerable, from local rooftops to large-scale onshore and offshore installations. Numerous forward-looking studies predict that solar energy will make a major contribution to the future energy mix, replacing fossil fuels.

This large-scale development also raises fundamental questions about the economic sustainability of this progress, and its environmental and social impacts. It will only be possible if photovoltaic technology meets these criteria, and if it is socially acceptable, thanks to public support for industrial development, and a commitment to the fight against climate change.

Beyond the technological and scientific aspects, and the in-depth analysis of life cycles (resources, carbon footprint, recycling, etc.), it is also cultural elements, linked to the very perception of mankind's relationship with solar energy and to the necessary confidence, that will determine the success or otherwise of photovoltaic energy. They will further stimulate the research efforts currently underway in laboratories the world over, in connection with the complementary issues of storage, hydrogen production and other "solar fuels", capable of compensating for the - fortunate - intermittency inherent in our star's light.