TORONTO -- Most of the electricity demand in advanced, industrialized nations can be met with a combination of wind and solar power, according to a recent study, but contingency measures may be necessary in order to fully satisfy requirements.

, published in the peer-reviewed journal Nature Communications, confronted the question of dependability of electricity systems that rely on intermittent resources. It found the most reliable renewable systems were heavily based on wind and could meet electricity requirements in the countries studied 72 to 91 per cent of the time. By mixing in 12 hours of stored energy, the figure increased to 83 to 94 per cent.

Despite the positive numbers, the researchers caution that even in a system that exceeds 90 per cent of a country's needs, hundreds of hours of unmet demand may occur annually.

"Wind and solar could meet more than 80 per cent of demand in many places without crazy amounts of storage or excess generating capacity, which is the critical point," Steve Davis, study co-author and University of California, Irvine, professor of Earth system science, said in a . "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."

The team of researchers analyzed 39 years of data from 42 countries to determine if solar and wind energy sources could sustain their needs.

They found that large countries closer to the equator could more easily convert to sustainable power resources due to the amount of solar energy available throughout the year. Higher-latitude countries, however, must lean more heavily into wind power.

"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," Dan Tong, lead author and assistant professor of Earth system science at Tsinghua University.

The researchers also found land mass to be a factor in terms of reliability. Countries with the largest land areas, such as Canada, had the most reliable solar and wind systems.

Smaller countries in regions like Europe, however, do not have the same luxury. The researchers say cooperation between nations in terms pooling and sharing energy may help relieve potential problems.

"Europe provides a good example,鈥� Tong said. 鈥淎 lot of consistency and reliability could be provided by a system that includes solar resources from Spain, Italy and Greece with bountiful wind available in the Netherlands, Denmark and the Baltic region.鈥�

To meet more demand for electricity, countries could engage in increased capacity overbuilding, the addition of batteries and additional storage methods.

鈥淎round the world, there are some definite geophysical constraints on our ability to produce net-zero carbon electricity,鈥� Davis said. 鈥淚t 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 sociopolitical will are aligned.鈥�

Currently, two-thirds of Canada鈥檚 electricity comes from renewable resources, according to the . About 59.6 per cent of the total is produced via hydroelectricity, while 5.1 per cent comes from wind and 0.6 per cent comes from solar energy.

Canada also exports about eight per cent of the electricity it generates to the U.S.