If you live in Abu Dhabi, Muscat or Ahmedabad, you might have seen a weird bird flying above you. Wider than a Boeing 747 but weighing only 1% of its weight, Solar Impulse is a 4-engine solar-powered plane on its way to fly around the globe. It has absolutely no other fuel than solar energy.
Flying only thanks to solar energy would have seemed impossible a few years ago. We now have the demonstration that investing in alternative energy sources and innovative technologies pays off and allows us to step beyond the limits. And the technology used does not come from a special top-secret multi-billion dollar futuristic program: it is everyday technology that anyone can acquire and easily use.
With its 17000+ solar cells and 4 lithium-ion batteries to mitigate the intermittence and fly at night, it proves that solar can power energy-consuming activities for days and nights without a problem. Imagine how much fossil fuel we could save if every single house was solar-powered like Solar Impulse…
However, since the plane can only hold one person on-board, it needs to stop now and then for the pilot to rest and get food and water supplies.
Whilst it could theoretically fly forever above the clouds if it was an unmanned vehicle (using the sun during the day and its batteries at night) and if it didn’t get caught in a jet stream, the need to fly below the clouds to land make it dependant on ground-level weather conditions: rain, wind and….. solar irradiance!
Indeed, Solar Impulse 2 will need accurate solar irradiance forecasting to be able to fly without running out of batteries. This is one of the reasons why the plane will take so long to circumnavigate the globe: for long journeys that can take up to 5 days non-stop (from China to Hawaii for example), the team will need to make sure there will be enough sun to climb up and down.
The solar impulse multidisciplinary team will not use ground cameras, but will rely on reports from national weather services issued from satellite images and models for long-term forecasts.
Yet another domain of application of solar irradiance forecasting!