Solar Energy Day and Night

NextPV is an International Joint Laboratory specialized in researching the photovoltaic field. They are working on special balloons able to catch the rays of the sun from above the clouds, producing clean energy day and night thanks to the help of a fuel cell.

NextPV is a Franco-Japanese company involving several partners, including the University of Tokyo and the National Centre for Scientific Research (CNRS).

The idea is not entirely new. It consists of mounting solar modules on balloons floating about 6 km above sea level, where the rays of the sun are most direct and cloud formations almost totally absent. In this way the researchers estimate that it would be possible to generate an amount of electric energy three times higher than the one obtainable today with panels positioned on the ground. To ensure the production of electricity 24 hours a day NextPV thought of using hydrogen as energy carrier. In practice, a fuel cell takes advantage of the excess energy during the day to split water (contained inside it) into hydrogen and oxygen (electrolysis). The hydrogen is then stored in the flask until after dark, when again it reacts with atmospheric oxygen and it generates water and electricity ready to use thanks to a reverse process (see explanatory image below).

The balloons are still in the photovoltaic concept phase, however the team led by François Guillemoles plans to build the first working prototypes within the next two years. "The main problem with photovoltaic energy is that sunlight can be obscured by clouds, which makes electrical production intermittent and uncertain. But above the cloud cover, the sun shines all day, every day. Anywhere above the planet, there are very few clouds at an altitude of 6 km—and none at all at 20 km. At those heights, the light comes directly from the Sun, as there are no shadows and hardly any diffusion by the atmosphere. As the sky loses its blue color, direct illumination becomes more intense: the concentration of solar energy results in more effective conversion, and hence higher yields". said Jean-François Guillemoles from CNRS.

Source: TreeHugger