Harvesting solar, 6km in the air

We all know the benefits of solar power: It's clean and it's cheap.

The problem with renewables is that we are never guaranteed a constant supply of sunshine, wind or wave power. By their very nature, these clean sources of energy fluctuate in intensity and abundance.

But, for solar power at least, could bypassing clouds hold the key to our clean energy future?

NextPV is a French-Japanese collaboration which focuses on photovoltaic cells, with photovoltaics being a way of directly converting light into electricity.

For NextPV – which is an International Joint Laboratory between France's National Center for Scientific Research (CNRS) and the University of Tokyo – the idea of harnessing solar energy by placing solar panels on balloons and sending them above the clouds is gaining traction.

"Balloons high in the air can harvest much more energy – five times more – in a very predictable way. This is also a solution available everywhere on the planet," Jean-Francois Guillemoles, senior researcher at the CNRS and visiting professor at the University of Tokyo, told CNBC via email.

"As a secondary benefit, being made of a lightweight structure, we believe they can be made using less resources, can be installed easily and have a low environmental impact overall," Guillemoles added.

Guillemoles said that there could be potential for "synergies with energy storage, in the form of hydrogen, for instance," that could enable a round the clock supply of clean energy.

The potential of solar is huge. According to the International Energy Agency, by 2050 the sun could well be the world's biggest source of electricity.

"From a few meters high to stratospheric heights, the concept is versatile," Guillemoles went on to add.

"At this stage we are focusing on tethered balloons just above clouds – that is around 6 kilometers (in) altitude – which we think is the most promising approach," he said.

According to the project, the solar balloon would be able to produce electricity during the day, with a battery continuing to generate electricity at night.

Looking forward, Guillemoles was positive on the potential of the concept, although several challenges do remain.

"I believe this may be seen rather soon," he said. "A lot of technology is already available, and what is not could be developed."

Guillemoles said that thorough economic studies would need to be made in order to see how the idea could be made in a cost effective way. It would also have to be made compatible with current regulations. "This is especially an issue with the usage of hydrogen," he said.

For Sasja Beslik, head of responsible investments at Nordea Asset Management, ideas such as the one being looked at by Guillemoles and his colleagues are promising. "I think the potential is fantastic… it will also be financially attractive," Beslik told CNBC via email.

Describing solar as a "great investment opportunity," Beslik went on to add that, "Solar and nuclear – as a transit solution – will be the focus for… insightful investors in the next five to ten years. Solar in particular will attract a lot of assets from the 'old/fossil' energy mix."

Innovation is equally important for the Solar Energy Industries Association (SEIA). "While we have not put a lot of time into advocating for or researching solar balloons, innovation is at the core of what has led to skyrocketing growth in the solar sector," Dan Whitten, the SEIA's VP of Communications, told CNBC via email.

"Solar balloons are the kind of technology that generations from now could lead to solar energy being the electricity source of choice around the world," Whitten added. "The vast potential of the sun for energy is undeniable, and early investments in research and development are critical."

Commenting on the wider potential of solar, Whitten was also positive. "Solar can be deployed cost-effectively and quickly and creates more jobs per megawatt than any other technology," he said. "From our perspective, with smart policies in place, the potential for solar is virtually limitless."