The bright future of solar energy

The sun’s rays are the source of all the Earth’s renewable energy. This manna from heaven supplies the equivalent of one barrel (159 liters) of oil per square meter per year – at least in sunny regions, like Switzerland’s canton of Valais – at no cost.

What’s more, our capacity for turning solar energy into electrical power is on the rise. That’s partly because engineers are constantly making improvements to boost the yields of photovoltaic (PV) cells, and partly (or even mostly) because both supply and demand for these units are booming. Nearly 375 GW of solar-panel capacity was installed globally in 2023. That’s four times more than in 2019 and 20 times more than in 2010. It’s a lot, but still not enough.

Christophe Ballif, the head of the EPFL School of Engineering's Laboratory of Photovoltaics and Thin-Film Electronics (PV Lab) in Neuchâtel, puts these figures in perspective: “By 2050, we’ll need to replace 80% of the fossil fuels we currently use with clean energy. It’s a huge challenge. If we continue at the same pace as in 2023, when 375 GW of solar capacity and 110 GW of wind capacity were installed, then it’ll take around 120 years to get there. But our goal is to accomplish the energy transition in 30 years – a more reasonable time frame in light of the climate crisis. That means we’ll need to increase annual solar capacity installation by a factor of nearly four, to 1,500 GW.” Yet he thinks this is possible: “China has invested between $60 billion and $80 billion over the past three years in new manufacturing capabilities for everything from polysilicon to complete solar units. By next year at the latest, it should have the required production capacity. But this Herculean effort on the supply side is actually coming a little too soon. We’re clearly in a situation of overcapacity.”

A combination of solar and wind

Solar power will make up a sharply growing share of the world’s energy mix, which is good news. In Switzerland, the government has introduced targets for transitioning to solar and other kinds of renewable energy by 2050. The goal is to have renewables supply 45 TWh, or more than half of the country’s total power demand based on current levels. Experts agree that the most effective way to reach this target is to combine solar with other forms of clean energy: hydropower, of course, but ideally also a sizable amount of wind power.

To be employed with power grids, both solar and wind power need to be coupled with one or more storage systems such as batteries, dams and synthesis gas. For batteries in particular (including EV batteries), China is once again the world’s manufacturing powerhouse. Here too, the country has made massive investments in new facilities. “China is flooding the market and overproducing to the point where prices are collapsing, for both batteries and solar units,” says Ballif. “That’s good for consumers and the energy transition in general, but it will create a form of dependency that we don’t want. Governments in other regions, including in Europe, need to build and expand their manufacturing capacity in order to make the market more resilient.”

Neuchâtel: A hub of yield-boosting technology

That said, it’s not easy to invest in capacity when you’re up against that kind of competition. But it is possible to find ways of doing things better, or differently. Engineers at Ballif’s lab and at the Centre Suisse d’Électronique et de Microtechnique (CSEM) in Neuchâtel, where Ballif also heads a research group, have developed methods for considerably increasing the yields of PV cells. Some of their technology is being implemented in China’s new factories. For instance, the engineers designed “tandem” cells consisting of a perovskite layer deposited on a silicon cell. These devices set a new world record for power conversion efficiency and broke through the symbolic 30% yield barrier.

A number of solar-energy startups have popped up in and around Neuchâtel, building on the research conducted by researchers there. Some of those companies are developing systems for integrating PV cells into a building’s architecture through panels and tiles with customizable colors (these firms include Freesuns, Solaxess and SwissINSO), while others are creating systems specifically for farming applications (Insolight and Voltiris). “It’s true that these startups operate in niche markets,” says Ballif. “But as far as Switzerland is concerned, their technology can go a long way towards meeting the government’s targets.” They’re also proof that Swiss businesses aren’t about to throw in the towel. Just look at Thun-based 3S, which recently built a new 200 MW/year production line for solar panels that can be integrated into buildings, and Meyer Burger, which now has a total production capacity of 1 GW/year at sites in Europe. Both these companies leverage technology developed in association with CSEM and EPFL.

Forecasts by the Swiss Federal Office of Energy indicate that solar power will be a key component of the country’s energy mix in 2050 (see infographic). “The potential for solar is definitely there,” Ballif explains. “PV cells can be integrated into buildings’ architecture, placed on top of supermarkets and their parking lots, for example, and installed on mountains, where models with bifacial panels – which can also capture the sunlight that reflects off snow – are particularly effective during the winter. Switzerland’s total installed capacity was 1.5 GW in 2023, which can generate 1.5 TWh of solar power per year. This renewable energy should reach 10% of our energy mix in 2024. So it’s on track to make a major contribution to the government’s goal of having 45 TWh of power come from renewables.”

Reshaping geopolitics

Looking at the bigger picture, the pressure that Chinese manufacturers are putting on the prices of PV and wind components, batteries and electrolyzers could substantially alter the geopolitical playing field. “At these prices, operators could build plants in Africa’s deserts and generate power at less than 1.3 cents per kWh. That’s five to ten times cheaper than the cost at newly built nuclear plants. This would make it more economical to produce clean hydrogen by water electrolysis than to produce grey hydrogen from natural gas,” says Ballif. “Another option could be to turn the hydrogen into ammonia, initially for use in crop fertilizer and later for transporting energy to Europe.”

If renewable energy gets that cheap, many governments and businesses could be tempted to ramp up their support for the energy transition, simply because it makes financial sense. That would be a blow to oil-exporting nations like Russia and Saudia Arabia. “China may be saving the planet – but that will create other challenges!” says Ballif.