Among the 510 successful balloon flights at the 37th Bristol International Balloon Fiesta this weekend, one of them was the world’s first certified hybrid solar-powered hot air balloon. The innovative lightweight and highly insulated balloon was created by Bristol-based Cameron Balloons as part of the Bristol 2015 European Green Capital initiative.
Although the black and silver balloon can be powered solely by solar energy, relying on the black side of the balloon to absorb heat from the sun to make the air inside of the balloon envelope warmer than the ambient temperature and then the silver side of the balloon to prevent that heat from escaping, it is a hybrid balloon as there is a backup set of propane burners on board in case the sun disappears mid-flight!
“It feels extremely fitting that Bristol – the current Green Capital, and the home of ballooning – has developed the world’s first hybrid solar-powered hot air balloon”
We caught up with David Boxall the Design Engineer for Cameron Balloons (who have been making Balloons in Bristol for 43 years!) to find out more about how the balloon works and operates: “Hot air balloons fly because the air inside them is hotter than the air outside. To make the solar balloon we had to minimise the temperature difference between the inside and the outside air, maximise the absorption of solar heat and minimise the heat loss.”
“To minimise the temperature difference we built the balloon from lightweight fabrics and load tapes to minimise its weight. We fitted a lightweight basket and the balloon is around twice the size we would normally use to carry its payload.
“To maximise the absorption of solar heat we made one side of the balloon black. The sun heats the black skin and the air inside the balloon.
Solar-hybrid balloon: The crew celebrate a successful lift off
“To minimise heat loss the shaded side of the balloon is insulated by being made form a double layer of fabric with an air-gap between the layers to provide insulation. The fabric on the shady side is aluminised to minimise heat loss via radiation.
“The reaction to the project has been very positive both from balloonists and the public”
“The balloon is fitted with turning vents to allow the envelope to be rotated to keep the black side facing the sun. The balloon can be controlled by rotating it to vary the amount of the black side facing the sun.” You can see more about how the balloon was made in the video below:
As for how the project came about and people’s reaction to it, David tells us, “The balloon was built as part of the Bristol 2015 European Green Capital initiative. It both promotes Bristol’s role as Green Capital and is an eye-catching and simple demonstration of the power of the sun. The reaction to the project has been very positive both from balloonists and the public. We believe that in particular the insulation technology has potential for wide use within hot-air ballooning.”
Andrew Garrad, Chairman of Bristol 2015 said: “One of the reasons Bristol won the title of European Green Capital is the city’s impressive track record in pioneering new forms of green technology. It feels extremely fitting that Bristol – the current Green Capital, and the home of ballooning – has developed the world’s first hybrid solar-powered hot air balloon. I hope that this project will inspire many more firsts for Bristol.”