This weekend, with the blessing of the temperamental British summer, the world's first solar powered balloon, designed and built in Bristol, will take off in front of thousands of people at the Bristol International Balloon Fiesta.
Standing at 25m tall the design and construction of the balloon has harnessed the expertise of Bristol balloon designers and some surprisingly simple science, as Pamela Parkes reports.
Home of Ballooning
A huge red brick building in Bedminster has for decades been home to Cameron Balloons and is the centre of Bristol's ballooning heritage.
Out of the factory comes balloons of all shapes and sizes which are exported around the world.
However, while they may be experts at constructing some of the world's most outlandish balloons, the company found getting a solar balloon project off the ground frustratingly difficult.
Sales director Nick Purvis said the main problem to overcome was not the technology but strict aviation safety criteria: "The science is relatively simple, but the balloon is an aircraft and has to meet certain design standards."
The company tried to promote the idea of the solar balloon project for nearly a decade but it looked likely never to be realised.
The breakthrough came when Bristol was awarded European Green Capital: "It was a wonderful opportunity," says Purvis.
"We started with a research and design project looking at different materials, different construction techniques and, even though this was done in the winter period, it gave us the information and the numbers to come up with a design."
Creating a giant
Inside the Cameron factory huge rolls of balloon material are methodically lined up next to balloon baskets of all shapes and sizes.
Vast machines hum as the material is cut and printed to almost any specification to create weird and wonderful hot air balloon shapes.
The team of 50 people are used to handling unusual requests but the solar balloon is something special.
Huge panels of solar fabric, specifically developed to soak in the sun's rays and heat up the air inside, have been cut and sewn together to create the balloon envelope, by a number of specialist sewing machinists on the top floor of the factory.
They sit in a semi-circle around a huge pile of fabric, slowly piecing the puzzle together.
Leading the team of machinists is Marilyn and she explains how the balloon will finally come together.
Surprisingly simple science
The balloon will be a hybrid aircraft, partially powered by the sun and partially powered by a conventional propane burner.
Purvis said while this is a world first for ballooning the technology has been around for decades: "If you go back-to-the-basics of solar balloons it works on the principle that it will absorb the suns energy and heat the air inside it.
"A regular hot air balloon runs 60-70 degrees above ambient...because you can only get the solar balloon to heat to 20-25 degrees means you have to do two things. Firstly, the balloon has to be very light and secondly, the balloon has to be very large.
“We have had to source material that will not only have the correct absorption and insulation properties that we need, but which is it strong enough and light enough to meet aviation standards."
A very green project
Without Bristol 2015 there would be no solar balloon, says Purvis. The balloon is designed not only to fly but to inspire a new generation about alternative power resources.
"When the public (at the Bristol International Balloon Fiesta) see a balloon 25m tall and the sun heating that balloon up and floating away I think that will be a very popular message about how strong the energy from the sun is," says Purvis.
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 – is now developing the world's first hybrid solar-powered hot air balloon.
Is this the future?
Ultimately the balloon will be nothing more than a showcase piece says Purvis.
While it is unlikely to change the face of ballooning he thinks it will influence the "choice of colours and fabric and how material absorbs or reflects the heat of the sun".
"The studies we've done will be useful in the long-term. Just like motor-racing in a way influences car designs, this work can influence the design of balloons."
However, the real opportunity comes with what we can learn from the design and development of the balloon says Purvis: "It's a lesson in science, technology and environment."
Photo Credits: Shutterstock and Bristol 2015
