Energy from High Altitude Balloons
Have you ever watched high clouds scudding across the sky, and maybe wondered, “Where they are going and where do they come from”?
And have you noticed how they seem to flow past at speed, even when there is no more than a slight breeze on the ground?
And have you ever fought against the wind on a windy day – or
One might think the wind is never ending – and you would be right – but there are problems in harnessing it
There is an enormous amount of energy in the high-altitude wind – second only to the radiation from the sun. So, is the effort worth the while?
The Problem with Wind Turbines
Wind turbines have been getting bigger!
Turbines have increased in height and size.
The amount of power produced also increased. The 1995 version could produce 750 kW and by 2015 the giant ground-based turbines were producing 6,000 kW.
But this came with a cost. More concrete and more steel was needed in their construction. They became increasingly expensive to make, repair and maintain. And this applies to land-based turbines as well as the off-shore wind farms. The Vesta turbine contains 417 tonnes of metal in the tower and nacelle and 902 tonnes of concrete in the foundation!
In fact, how near are we to the maximum size for efficiency?
A second problem is the intermittent nature of the energy supply from wind farms.
Wind turbines have a limited range of effective use. They need a certain amount of wind to turn the rotors. Too much and they shut down or can even be destroyed. The approximate range for wind turbine use is wind speeds between 3.5 to 25 m/s. But they mostly don’t work better at wind speed higher than around 14 m/s and by the 25 m/s they have to be shut down.
Limited Areas on Earth are Suitable
And a third problem is that areas of the earth where the winds are suitable at heights of between 0 to 120 metres(393 feet) are limited.
Map credit to https://globalwindatlas.info
The Higher you Go the Stronger the Winds
One of the reasons the wind turbines have grown is because the wind at ground level is weaker and less persistent than at a height.
Now, if you look at the map you can see that over much of the planet, wind speeds at ground level are not sufficient to turn the rotors. (The blue areas). But go up to 240 metres (787 feet) and the situation changes. At this height, most of the inhabited planet has enough wind for efficient energy entrapment.
Added to this is the fact that the power available from wind increases as the cube of the velocity. So, if you double the speed of the wind you get about 8 times the power. Treble it and you get 27 times the available power. And at 2,000 m (6,560 feet) the winds are about three times as fast, on average, than at ground level.
The jet stream at 10,000 m is not yet an available option.
Companies are focussing in harnessing the winds between 500 m and 2,000 m. (1,600 – 6,560 feet). At this level, the wind is far more reliable, so intermittency is much reduced, and the wind speeds are within the most useful range.
Methods of Harnessing the Higher-Level Wind Power
Two main methods are currently in use – balloons and kites. Both need tethering and cables to transmit the energy. Battery storage options are being considered, but the weight makes this difficult. There are several methods including balloons, kites towed by gliders or aircraft, airfoils, drogues and more. Three of the main concepts are:
a.) Lighter than air constructions – balloons (The Altaeros bat)
b.) Kites with attached rotors and generators – the faster they fly the more energy they produce (the Makani kite)
c.) Flying kites attached to ground-based rotors and generators (the Kite-Gen stem)
In this article, I will be concentrating more on the balloon option.
The Altaeros Concept – the Bat
Image reproduced with kind permission Altaeros
Altaeros is an American based company. Their concept sounds simple – a helium balloon which lifts a rotor into the sky at altitudes of 2,000 feet (600 m). There are several tough tethers to the ground, one of which transmits the energy produced to a ground station, which is mobile. They call this “the Bat”.
Because the winds are faster at this altitude and have between 5-8 times the power, the Bat can produce over twice the energy as a ground-based turbine with a similar rating.
As you can see, the aerodynamic design is unusual. There is a novel control system as well as state of the art materials.
The shell is inflated with helium and it channels the wind through a light-weight turbine. The shell provides lift, buoyancy and is self-stabilising.
As an extra benefit. The Altaeros balloon can adjust its height to get the best airflow. It is also is very safe.
Altaeros has a mission: to increase affordable, state-of-the-art power generation to rural communities around the world.
Wind Power from Balloons in Europe
A Portuguese company, Omnidea, is testing a high-altitude balloon near Lisbon. This is designed to fly at two kilometres where wind speeds are eight times stronger. This is a large helium-filled balloon that looks a bit like the old balloon ships. An Electric motor spins it. This stabilises it and produces a physical phenomenon known as the Magnus effect. This increases the lift force considerably.
The balloon has a cable attached, and this rotates a drum on the ground connected to the generator. It can remain airborne for a long time, and the spinning stops when it reaches the required altitude. Then it has to be pulled back to earth. But as the spinning has stopped this uses a lot less energy than the ascent produced.
Various innovations are envisaged: stacking balloons, propellers and more.
Special uses of balloons for providing power
Places like Alaska, where there is a good wind flow, and where communities can be quite isolated, are suitable for balloon wind power. And in addition, industries might be remote or, if there should be a power cut, balloons could provide emergency energy. They are also ideal for disaster relief.
Oil and gas industries, agriculture, as well as military bases, could all benefit from a relatively cheap, portable source of non-polluting energy.
In addition, balloons could serve a dual purpose in telecommunications, as well as observation. This is because the Altaeros balloon can stay high for long periods of time, producing energy from its rotor.
Portable balloons also have advantages in changing location when the need arises. And a balloon can be deflated and packed up quite small to make the transport easier and cheaper. Standard shipping containers can be used.
At present remote areas tend to rely on diesel generators. But diesel fuel is expensive. In addition, the generators are expensive to maintain. So, balloon generated energy could provide cheaper and more reliable power to remote areas. And it doesn’t take long to install a balloon!
Possible Disadvantages Associated with Balloons
The risks with the actual balloon are very small. There is little bird life at this altitude, although they might collide with the tethers, which make up a very small area.
There may be a slight risk to aviation, but we should be capable of sorting out air traffic problems at what is a low altitude for cruising aeroplanes. Typically, commercial aircraft fly between 33,000 feet to 42,000 feet. (that is about 7 miles high). Jet aircraft fly higher at around 41,000 feet, above all the commercial air traffic. And even light aircraft tend to fly at around 10,000 feet.
This is still an area in the fairly early stages of development – so considerable resources need to be spent to make it globally viable. But with some expenditure now the potential for cheap, safe and consistent energy is enormous.
Advantages of high-altitude balloons for generating power
1). They utilise a power source in high altitude winds that is stronger and more constant than wind nearer the ground. Therefore, intermittent power surges and breaks are far less likely. And more power can be obtained.
2). They are relatively cheap to produce – unlike the ground or sea-based wind turbines.
3). Balloons are light and portable, they can be deflated.
4). Non-polluting and constantly renewable energy source.
5). Versatile – especially suitable for isolated communities or workplaces.
7. Easily brought into action in emergencies
8. Little maintenance required.
9. Safe and environmentally friendly.
So, when you watch the high clouds scudding across the sky, you can see they are demonstrating the enormous amount of energy in high-altitude wind.
High altitude balloons for generating electricity are still in the early stages of development. But the massive ground-based wind turbines probably can’t be made much more efficient or cheaper to produce.
The potential for harnessing the power of the wind at this higher level, where the winds are constant and strong, makes this a very exciting field. There is a huge potential for extracting energy. It is there for the taking. And the versatility and manoeuvrability of the balloons, make this a very attractive renewable-energy option.
One might think the wind is never ending – and you would be right – we just need to have the long-term vision to make it possible on a global scale. Quite a challenge!