Can the world's energy be 100% renewable?

A sustainable world powered entirely by renewable energy sources is viable, according to a new study from scientists in Germany.

Over the past 60 years, atmospheric concentrations of carbon dioxide have risen from about 315 ppm (parts per million) to around 410 ppm. This means that today, 410 particles out of every 1 million air particles in Earth’s atmosphere are carbon dioxide, or 0.041%. The presence of excess carbon dioxide in the atmosphere warms the Earth, and is linked to climate change. In fact, the average global temperature has risen by 0.8ºC since 1880.

One of the biggest contributors of carbon dioxide emissions is the burning of fossil fuels, much of it to power vehicles and heat homes. A possible solution to lowering carbon dioxide emissions would be to replace fossil fuels with renewable energy sources, like solar or wind power. Whether it is possible, though, for 100% of the World’s energy to come from such sources is a subject of fierce debate.

In an earlier analysis¹, researchers at the University of Adelaide, Australia, led by Benjamin Heard, looked at a series of 100% renewable energy scenarios to assess their feasibility. Although, as Heard points out, “we looked only at whether the proposed systems were physically capable of working, we didn’t explore whether they could be delivered within the social, political, and economical constraints of society."

The findings of the Australian study were that a "100% renewable electricity supply would, at the very least, demand a reinvention of the entire electricity supply-and-demand system to enable renewable supplies to approach the reliability of current systems." In a nutshell, with today's technology, an entirely renewable energy supply is not on the cards.

Currently, renewable sources account for only about 25% of the world's energy consumption, which is also set to rise by 28% by the year 2040. That means renewable energy production would have to increase by over 80% in the next 22 years to keep pace with the world's projected rising energy demand. But is this realistic on a global scale? Certainly some countries and regions have already reached 100% renewable energy, but they tend to be small and are often special cases.

One well-known 100% renewable energy model is the country of Iceland. Iceland runs primarily on geothermal and hydropower. But Heard and his team point out that Iceland’s energy model cannot be applied to other countries due to its “unique endowment of shallow geothermal aquifers, abundant hydropower, and a population of only 0.3 million people.” But does this mean that 100% renewable energy is possible only for countries with an abundance of natural resources?

Now a team at Karlsruhe Institute of Technology, in Germany, lead by Tom Brown, has revisited the Australian study and are more upbeat about the prognosis². “You can fill the gaps when the sun isn’t shining and the wind isn’t blowing with hydroelectricity,” explains Brown. "Or [for example] there is a power line between the Netherlands and Great Britain, so when the wind isn’t blowing in Great Britain you can import [the energy] from Holland and vice versa. And finally, there’s storage. You can store energy when there’s lots of wind and solar, and can feed it back into the grid when there isn’t so much [wind and solar]."

According to the German team, "100% renewable energy scenarios proposed in the literature are not just feasible, but also viable." And rather than a reinvention of the electricity supply-and-demand system, "only a directed evolution of the current system is required to guarantee affordability, reliability and sustainability."

One thing experts can definitely agree on is the urgency of this issue. “People need to know how urgent this is. Now is the time for action," explains Brown. And according to  Heard, “We’ve spent 30 years talking about global warming, and we’ve been misunderstanding the scale of this problem. We need a massive reset on our approach if we want to make the next 30 years different."