Hydrogen could lift drones higher, UAE research shows
Drones are often in the headlines, whether it is because they are involved in controversial military missions or being proposed as delivery vehicles.
Also referred to as unmanned aerial vehicles (UAVs), they vary in size, shape and mode of operation – the military and surveillance aircraft offer a contrast to the small, helicopter-like vehicles seen or heard overhead.
It is these smaller civilian drones that are the subject of a research project at the American University of Sharjah.
As announced by the university, a research exercise run by Prof Mohamed Gadalla, of the mechanical engineering department, has resulted in a multi-propeller drone powered by a hydrogen fuel cell being flown in front of the main university building.
It has been described as the first time such a craft has been flown outside North America. The hydrogen cell system used was bought in, although the group has worked on developing its own.
“Working with a hydrogen fuel cell it can stay in the air two to three hours. For a drone powered by a battery, it can stay only for 25 minutes. It’s designed for longer endurance,” says Prof Gadalla.
“It has an autonomous system, automatic pilot – it can go and come back.”
Chief among the attractions of using hydrogen power – instead of a petroleum derivative – is that the chemical reaction that releases the energy does not produce greenhouse gases – combining hydrogen and oxygen produces nothing more harmful to the environment than water.
“Actually, the water vaporises right away. It’s a very small amount of water,” says Prof Gadalla.
And unlike battery-powered drones, the process does not end with spent batteries that must be disposed of. A small amount of energy from a battery is needed to power the input from the controller. The research in Sharjah is part of wider efforts to look at what applications hydrogen power could be put to. Other applications include using it in cars.
But before its more widespread use can truly offer environmental benefits, difficulties in finding an eco-friendly way to produce the hydrogen will have to be found.
There are two principal methods of generating hydrogen – producing it from natural gas or coal, or generating it from water.
When it comes to producing hydrogen from natural gas or coal, the process typically involves using steam to heat the fossil fuel. This, however, produces carbon dioxide, a greenhouse gas, which negates the environmental benefits of using hydrogen as a fuel. However, researchers are studying other methods to “crack” methane, such as by utilising a “heat bath” of molten tin.
First discussed more than a decade and a half ago, and now the subject of renewed research interest, this method produces waste carbon in the form of soot, which can be scraped off.
The other main method to produce hydrogen involves splitting water into its constituent parts – hydrogen and oxygen – in a process known as electrolysis. If the electricity used to do this has been produced using fossil fuels, the environmental benefits of using hydrogen as fuel are negated. But if instead renewable energy is used to split the water (or, when producing hydrogen from methane, to heat the molten tin bath), the eco benefits are retained.
“That’s the green way. We’re trying to get to cleaner sources of power. That would be by using wind or solar or any other renewable source of power to produce hydrogen by electrolysis,” said Dr Ahmad El Kharouf, who researches fuel cells in the School of Chemical Engineering at the University of Birmingham in the UK.
Even if hydrogen can be produced in an environmentally sustainable way, limits will remain on how widely it can be used in transport. For example, do not expect to see hydrogen-powered passenger aeroplanes replacing the aircraft we are used to travelling on.
Dr El Kharouf, who is from Jordan and has worked on hydrogen-powered UAVs, says the amount of hydrogen that would have to be stored “would be massive”. But he says hydrogen-based systems could be used for smaller power units.
And he is very optimistic about using hydrogen to power cars. Major manufacturers such as Toyota, Honda and Hyundai have made such vehicles available commercially – the Toyota Mirai recently claimed first place in the Monte Carlo e-rally for zero-emissions vehicles – while other brands have research programmes.
Dr El Kharouf suggests there will be an intermediate period when battery-powered electric cars are more popular, before hydrogen technology plays a more prominent role.
Although the range of electric cars has increased, they still take a long time to charge, often many hours, although rapid charging points have reduced this.
“Or it could be in future a combination between the battery-based and hydrogen fuel cell vehicles,” he said.
Whatever the future for cars, the scientists in Sharjah are focused on improving their drone.
While small drones might be designed to carry 2 kilograms or so, Prof Gadalla’s group is attempting to build something much more powerful. Their current aim is to produce a drone that can carry a payload of 20kg.
“We’re designing a winch system – [so that] it can drop the payload in the location that you need,” says Prof Gadalla.
And their ultimate goal is even more ambitious – a drone that can lift 60kg, more than many adults weigh.
“We need a very powerful fuel cell or we integrate many of them,” says Prof Gadalla.
It will take at least a year to develop the more powerful drone, but no doubt many people will be keen to see this upgraded aircraft in action when it takes to the skies.
Published: December 31, 2016 04:00 AM