Sam Shead
Reporter
This week saw the first successful intercontinental solar-powered manned flight with Swiss pilot Bertrand Piccard flying the €90m Solar Impulse HB-SIA straight into the record books. But if you scan the skies for a second you’ll soon find that some solar powered planes are flying that extra bit further.
Solar Impulse’s carbon fibre-bodied aircraft flew a distance of 830km while travelling from the Spanish capital of Madrid to the Moroccan capital of Rabat, with the flight path taking in the 39km Gibraltar Strait. The power generated by the 12,000 individual cells on the upper surface of the aircraft’s gigantic 208ft wingspan was just about enough to power the plane’s motors, which in turn charge the 400kg lithium polymer batteries that account for a quarter of the aircraft’s overall mass.
The Solar Impulse team now have their eyes set on a round the world solar flight next year. However, with an average flying speed of 70kmh (44mph), Solar Impulse poses no immediate threat to commercial passenger jets, which fly at more than 10 times the speed. A flight from Madrid to Rabat can be completed in just over an hour.
Furthermore, while this manned solar flight is certainly a landmark; the distance it achieved, or is looking to achieve, is dwarfed when one looks at solar powered unmanned aerial vehicles (UAVs).
The UK-built QinetiQ Zephyr solar powered UAV managed to linger in the air for 336 hours and 22 minutes (or the equivalent of two weeks), albeit just above a US military base in Arizona. Charlotte Pichon from Solar Impulse’s press department told The Engineer: ‘Of course 336 hours is very impressive, but QinetiQ’s UAV is an unmanned aircraft, while Solar Impulse is piloted by a human for 19 hours. It’s not only a technological challenge, but a human one.’
Looking ahead, the Defence Advanced Research Projects Agency (DARPA) have designed their future solar powered ‘Vulture’ UAV so that it can stay in the air for a staggering five years above areas that need to be kept under constant surveillance.
There is clearly a need for green aircraft technology, but solar power may not necessarily be the way to go.
AeroVironment’s carbon neutral Global Observer UAV – an endurance aircraft said to be capable of flying 3-4 times further than any other fixed wing aircraft – uses hydrogen to power four highly efficient electric motors. A fact sheet on AeroVironment’s website states: ‘From the Stratosphere, the GO will act like a mobile, 12-mile high tower, covering an area of 600 miles in diameter.’ The Global Observer is capable of flying for 5-7 days at a time, at heights well above conventional aircraft, which fly at altitudes up to 65,000ft.
While the aforementioned UAV spy planes may not be quite as evangelical as Solar Impulse – which simply wants to demonstrate that progress is possible using clean forms of energy – they are certainly picking up a few extra air miles. But why? Well the reality is that people have their needs and these needs all add extra weight to an aircraft. Build in a toilet, a kitchen, some storage and window or two, and you’re soon racking up those all-important kilograms that solar powered vehicles can’t afford to accommodate.
If Solar Impulse are successful in their round the world attempt then aerospace engineers must then continue to look at improving the power output of renewable energy sources. Current solutions are just about capable of lifting the equivalent of a small car off a runway. As a result, I don’t think we’re in any immediate danger of the four jet engines on 747s being replaced with the four batteries on the Solar Impulse. However, I can certainly see renewables working for sligtly more lethargic UAVs.
90 million Euros to prove what? That solar and human payloads are a non-starter?
Nice budget for a fun but ultimately pointless adventure.
Well done Solar Impulse. Range 835km’s lifting ability 400kilos. It is difficult to see a future transport solution here. However, it is all about batteries. With all the current development in place we have to be very close to a break through in more power for less bulk. I am increasingly concerned about the rush to build electric driven cars as a step change in battery performance and size will make a lot of models obsolete and we could be faced with an additional environmental problem of disposing of the old cars.
Come on guys, it’s a pretty impressive first step. These criticisms are like looking at the very first motor cars and saying “4mph? its difficult to see a future transportation solution here”… when clearly things have moved on a bit since then. Battery tech will improve. Consider the potential… (pun intended)
All Solar PV technologies suffer from the same problem: a lack of efficiency. Significant improvements are going to be required (around 100% to 200% above current ‘best of’) for this to become a mainstream power source. Battery technology also needs a step-change in capacity vs. weight.
However, before we are too critical, bear in mind the enormous amount of development that has gone into Internal Combustion and Jet Turbine technologies! (They were pretty basic when they were first developed.)
Like Trevor Best, I am a bit concerned about the headlong rush to be ‘seen to be green’ by motor manufacturers. At present, we might be best sticking to hybrid systems – even if only until charging facilities are more widely available.
The real development is Solar Ship , check it in http://solarship.com/
they have load capacity with low cost and high factibility
Let’s be clear about a few things. Batteries have been around for a a very long time indeed, and, after well over a century, they’re still too heavy. In fact, apart from some form of combustion being involved, there is still no lightweight way to store energy.
Photovoltaics are well over fifty years old, and we’re still doing very expensive ‘demonstration’ projects, that have only managed to demonstrate how far we are away from making photovoltaics useful in vehicles. How long have solar cars been racing across Australia now? They still can’t carry a meaningful payload and need a desert environment to do anything.
That’s not to say that renewables have no place in transportation. Static plant, using any one of a wide variety of renewables, can produce hydrogen at acceptable capital cost. Then we put the hydrogen in the vehicle. Oops- that would be ‘Global Observer’ then – carbon-neutral (depending on where the power to produce the hydrogen comes from) and with the potential to carry significant payloads. As for cars, hydrogen fuel cells are already here, such a shame we still can’t fill up with hydrogen at the local filling station.
Hydrogen fuel cells are by far the most promising way to put renewable energy into vehicles.
I still come back to the cost… 90 million Euros !! Did it that aeroplane project really cost that much?
We need to focus on development before using up all of the heavy metals on primitive and inefficient batteries.
This is an inspirational and headline grabbing example of what can be done with co-operation and determination by Industry and Engineering expertise.
Like all developing technologies there will be several ways to combine and use Solar Power with other proven systems to provide an economic reliable and a sustainable alternative to what we have now.
I recall an article some years back highlighting Airships as the way forward for low energy air transport of Cargo & telecommunications platforms. If you remove the need to lift all of the mass by aerodynamics or aerodynamics alone then Solar & Heat generated power over the large surface area of an aerodynamic airship could be used to propel tons of cargo & people around the world.
The first manned flight was very modest, barely lifted of the ground.
Look where we are now. Beginnings are about proving a point, not breaking records that were made with established technology. The amount of €90m that was spent on the Impulse will have spin-offs for industry; I think it is well spend. We always look back years later to the humble beginnings of a technology.
@carolyne all the starting big projects cost high but as we start improving they start being cheap,,,
just you need to start and keep working on,,
if its about hydrofuel it can work as a backup for the solar energy like if there are clouds we can use hydro fuel if there in shiny sky we can use solar energy,,,
and for the safer & green planet we need to work on all the possiblities,,
Firstly, well done indeed to the team that achieved this. But I do have to say to all the people who are talking about ‘a great first step’ – it’s not a first step. It’s its the first time all these components have been put together to do this particular job. The batteries are not new, carbon fibre isn’t new, p.v. panels are OLD. We need the chemists and physicists to come up with something new, not 1% changes in performance. Maybe that 90m Euro would have been better spent on that endeavour?
OK, PV and batteries aren’t that efficient, but neither are internal combustion engines or the round trip efficiency of producing hydrogen. fuel cells don’t last forever due to the membranes. I presume the lots of the money was spent on research rather than just on the plane.
Look at how much better the solar car teams are doing in the Austrailan Solar Car Race after a 25 years of competition, the average speeds are much higher. You have to focus on the whole package rather than just certain aspects of the vehicles
rob…. Do the math…. Current PV cells are about 30% efficient which would mean that a hatchback 10 ft long and 4 ft wide, provides c. 40 sq ft for power generation. Approx 4 sq metres, which will deliver about 1.5hp.
Sorry, but Solar cars are not going to be a practical family vehicle, ever.