Solar race to become the leading energy source by 2040

Investment in solar power will reach $500 billion this year and will exceed for the second year in a row the flow of resources dedicated to all other accumulated electrical technologies, according to the (always conservative) calculations of the International Energy Agency. This growing wave of capital, attracted by the continually decreasing costs and great flexibility of use, will finance the production of 70 billion solar cells, which will power individual homes, energy communities, large industrial plants and power grids, without making noise, without emitting fumes, without burning fuel and without costing anything for decades.

These cells, which currently cover less than 10,000 square kilometres of the earth's surface, generated 1,600 terawatt-hours of energy in 2023, or 6% of the world's electricity. It sounds little, but the revolutionary character of solar power is its growth rate. In 2004 it took one year to install one gigawatt of solar capacity, in 2010 one month, in 2016 one week and in 2023 less than one day. Last year, the world's solar capacity reached 1,419 gigawatts, and for this year, analysts at Bloomberg New Energy Finance predict about 600 gigawatts of new capacity: almost twice as much is installed every day as was installed in a year 20 years ago. At this rate, solar will produce more electricity than nuclear in 2026, wind in 2027, hydro in 2028, gas in 2030 and coal in 2032. The Iea predicts that the sun will become humanity's largest primary energy source - not just electricity - by 2040.

The growth of solar energy does not depend on the climate policies of governments, but on its affordability. In 50 years, the cost of a solar megawatt-hour has fallen by more than a thousand times and this trend continues, regularly beating all forecasts. Today the cost of electricity (Lcoe) for solar and onshore wind is about $40 per megawatt-hour, lower than that of coal, which is the cheapest of the fossil fuels. The only problem is that the vast majority of solar cells and almost all of the purified silicon come from the Chinese industry, which has enough margin to maintain this rate of expansion in the years to come, even with government help. Chinese control over this technology is certainly less problematic than Opec's control over the price of oil, but it remains worrying. Western industry, however, still has time to react, as almost all demand for solar is concentrated in the future.

The raw material for solar cells is easily found: it is quartz sand, a crystalline form of silicon. To purify it, it is heated to 1,900 °C in electric arc furnaces with a certain amount of carbon in the form of coke. The oxygen in the sand reacts with the carbon to release carbon monoxide: what remains is molten 'polysilicon', which is then cooled, crushed and reacted with hydrochloric acid to produce a liquid called trichlorosilane, which is then distilled repeatedly to remove all traces of impurities. The most advanced foundries work at '10 nines', meaning that their polysilicon is 99.99999999 per cent pure.

Until the early 2000s, the only products worth this kind of effort were the wafers from which chips were made. The solar cell industry lived on scraps. But the increase in demand for photovoltaics changed the situation and Asian companies started to invest in foundries dedicated to the photovoltaic industry. Thus Beijing built up its monopoly: in 2023, Chinese companies produced 93% of all the world's polysilicon for solar. Some have expanded vertically and also produce the cells. Others leave the cutting of the ingots into wafers, the polishing and the 'doping' that turns the silicon into a semiconductor to their customers.