Great idea of PV-balloon farms with a potential of 1MW each. A clean and sustainable solar energy harvesting solution.
How to capture the sun as long as possible with solar panels? By installing on tethered balloons to large hydrogen which would be situated several kilometers above sea level, above the clouds. Additional advantage: they generate their own lifting gas to store electricity and redistribute overnight. Explanations.
Photovoltaics is an intermittent source of electricity: the utilization rate of solar cells is only 15% and it varies, depending on weather conditions and seasons. Jean-François Guillemoles, research director at the CNRS and Director of the Franco-Japanese laboratory NextPV details the existing solutions: “For it is better utilization, storage is an important new technology with cells high. yield higher than 30%, can be installed in the modules, but they are not ready commercially. to capture the sun longer, you can also place the cells on trackers or make concentrated solar. but the best is place above the clouds. ” Quite simply.
The idea is similar to Zephyr project, but much larger. The specialist reveals extraordinary figures: not only the light intensity is higher in altitude (+ 20%) since the rarefied atmosphere less diffuse rays and there are no shadows, but also the capacity factor is multiplied by three to reach 50%. “At 5,000 or 6,000 meters, everything becomes more profitable. And the resource is distributed in a roughly equal to the Earth’s surface,” he says. The solution is to design and implement captive balloons 30 meters in diameter, partially covered with photovoltaic sensors to mimic a giant eyeball. “A ball correspond to a plant of 1 MW and would have a storage equivalent to one week of production”, says Jean-François Guillemoles. For this is the elegance of this idea: the ball would fill himself hydrogen – gas lighter than air will keep it aloft – by performing electrolysis of an onboard water reserve.
Specifically, during the day, the electricity produced by solar radiation will be channeled to the ground via the cable retention. Part of this current will also be used to recharge the fuel cell which decomposes water (H2O) into hydrogen (H2) and oxygen (O2). Hydrogen stored in the envelope of the balloon, then used at night to continue to generate electricity through fuel cells that recombine the two components in water. Several projects are currently being studied, including Stratobus Thales, the Loon Google or Havoc NASA. The laboratory director NextPV admits: “The captive balloons are technically feasible but they are not cheap.” Progress must be made in the production of polymer materials, lightweight, durable, low energy content, while remaining easy to industrialize. Another difficulty, regulatory one: hydrogen remains prohibited in balloons and replaced by helium – yet heavier and more scarce – since the 1930s and the Hindenburg disaster.
However, the promise of higher yields, abundant and predictable resource, extremely small footprint, and an early and reversible deployment could convince the authorities and industry to explore this track. The Franco-Japanese team is now working on the completion of a first demonstrator. Only problem: the presence of floating photovoltaic farms in the air lead to a staggering increase in airline pilots testimonials affirming – in good faith – have seen something strange in the sky …