We can't afford to delay the switch over to renewable energy sources, and while there's much debate about how to achieve this, more and more research along with growing real-world evidence suggest that it's absolutely a viable, practical option.

Now, a new study from an international team of researchers will hopefully help settle this for good.

The study shows that the majority of electricity demand in many industrialized nations can be met by some combination of wind and solar power sources, as long as extra efforts are made to install energy storage facilities to cover times of intermittent production.

By analyzing the energy use of 42 major countries across 39 years (from 1980 to 2018), the researchers were able to model how increases in wind and solar energy power production could potentially meet the demands of nations from Afghanistan to Zimbabwe.

"Wind and solar could meet more than 80 percent of demand in many places without crazy amounts of storage or excess generating capacity, which is the critical point," says Earth system scientist Steven Davis from the University of California, Irvine (UCI).

"But depending on the country, there may be many multi-day periods throughout the year when some demand will need to be met by energy storage and other non-fossil energy sources in a zero-carbon future."

Even without any energy storage, renewable systems could meet the needs of the countries in the study for 72-91 percent of the time, with wind power leading the way, the study shows. Add in 12 hours of energy storage across the board, and that goes up to 83-94 percent of the time, with solar taking over as the dominant energy source.

This is assuming countries were committed to producing enough wind and solar energy to meet the demands of their population – this study is concerned mainly with the dependability and reliability of renewables rather than the amount of power they're able to produce.

Of course, the electricity demands of a population fluctuate over time just like the availability of sunlight and wind. The modeling revealed that larger, lower-latitude countries would find switching to sustainable power easier, because they would be able to rely on solar for a greater part of the year.

Smaller countries at higher latitudes, such as Germany, for example, would find themselves going back to backup sources of energy more often, according to the researchers. However, long-term storage and the pooling of sources (solar from Spain and wind from Denmark, for example), could minimize these issues.

"Historic data show that countries that are farther from the equator can occasionally experience periods called 'dark doldrums' during which there is very limited solar and wind power availability," says Earth system scientist Dan Tong from Tsinghua University in China.

"One recent occurrence of this phenomenon in Germany lasted for two weeks, forcing Germans to resort to dispatchable generation, which in many cases is provided by fossil fuel-burning plants."

In the case of the United States, to give another example, the study showed that wind and solar could account for around 85 percent of total electricity demand. Overbuilding capacity, adding storage methods like batteries, and connecting to other countries on the North American continent would push that number up further.

Each country will need to approach this differently, depending on its location, its needs and its available resources, the researchers say. There are also a few assumptions made in this study to take account of, including perfect electricity transmission with no wasted energy, and annual generation equal to annual demand.

However, these models give us a blueprint as to how we can work towards a sustainable, net-zero emissions energy system across the globe – the point is that it can be done, and in many places worldwide, it's already happening.

"Around the world, there are some definite geophysical constraints on our ability to produce net-zero carbon electricity," says Davis.

"It comes down to the difference between the difficult and the impossible. It will be hard to completely eliminate fossil fuels from our power generation mix, but we can achieve that goal when technologies, economics and socio-political will are aligned."

The research has been published in Nature Communications.