We are very proud to live in Bristol today, as we have seen the worlds first solar hot air balloon take off! It has a back up propane burner. But mainly the heat from the beautiful Bristol sunshine heats up the air inside. It was designed with black material to absorb more hear, and the other half is silver to trap the heat in. It is controlled by closing vents which can help it guide to avoiding the sunshine.
Please check out the video below, to see the solar powered balloon!