To most people in Britain, kites are probably things of a childhood pastime – perhaps conjuring up memories of hours spent on less-than-tropical beaches. Yet, the very same principles which underpin kite flying are now being touted as a serious and exciting means to generate renewable electricity.
As with other forms of electricity generation, kites capture energy and use it to rotate a turbine. Each kite has a steel tether which is attached to a turbine, and as a kite harnesses wind energy, it ascends up into the sky. This in turn spins the turbine, which generates electricity. Kites often operate in tandem, with one rising and the other falling at the same time, which ensures energy generation is more constant. In addition, some kites will have rotor blades attached to them which generate electricity, too, in the same way that traditional windmills do.
A technology with the wind in its sails
Given that they both harness the wind as their source of power, kites are often compared to conventional wind turbines when assessing their potential to be a viable method of producing electricity. However, as beneficial for the environment as wind turbines are and have been for the UK, it would appear that kites could offer several potential advantages.
To start with, consider that the strength of the wind – and hence energy generation potential – steadily increases with altitude, with high-altitude winds having twice the velocity of ground-level winds. Moreover, not only do winds blow more forcefully at higher elevations, they do so more predictably, too. Combined, these two facts mean that kites can exploit a stronger and more reliable stream of energy to convert into electricity, relative to turbines on the ground or out at sea.
Another compelling argument in favour of kite generated energy is cost. We know that renewables like solar and wind turbines have, especially recently, seen their costs fall dramatically due to improved economies of scale and technological learning. Yet companies who are in the kite energy sector believe their blossoming technology has the potential to be even cheaper.
Kites use fewer materials in production, are cheaper to build and set up, are easier to maintain once running, and have the potential to last longer. If as a result of stronger and more predictable winds they produce more energy too, then they effectively become all the more inexpensive because of the crucial cost per megawatt hour of energy produced equation by which all generating technologies are judged. Indeed, one kite energy company believes it could install a 100 megawatt capacity wind farm and begin delivering electricity significantly less expensively than £44.50 per megawatt hour.
As with any new technology, however, kite energy generation must be able to transfer its promising potential on paper into the real world. Cost estimates such as the one cited above are certainly eye-catching, but need to be backed up by hard evidence gathered through doing. At the moment, regulatory uncertainty abounds, and investors would want to be sure that any money they put into the hitherto commercially untested technology is not too much of a gamble.
That kites use fewer materials relative to wind turbines also has important environmental consequences. Often made from carbon-fibre, kites do away with literally thousands of tonnes of infrastructure associated with conventional wind turbines – the massive blades and tower, plus the concrete foundations, for instance – thus meaning that they require fewer resources to fabricate, and hence contain less embodied energy. Indeed, the steel and concrete used to build wind farms are some of the most energy and water intensive production materials around – although it must be said that they and other renewables like solar are still much less carbon intensive, relative to conventional fossil fuelled power stations.
Another key selling point for kite generated energy is that kites can be deployed in a wider variety of locations, often where other forms of generation could not be. Conventional wind turbines are limited as to where they can be placed because they must be able to reliably tap into ground windspeeds of at least five meters per second. Consequently, this rules out much of the land across the world. However, higher altitude wind speeds are considerably more constant – regardless of the location 500 or so meters below, where the kites would be anchored. In addition, because of their nature, kites could operate in locations where it is unviable to erect conventional wind turbines because of complex terrain, for instance.
Interestingly, one location where kite energy wind farms could be constructed is on the offshore pilings on which current wind turbines – soon due to be decommissioned – stand. As modern wind turbines are now much larger, the existing pilings have effectively been rendered redundant, and thus replacement ones would have to be (relatively more energy and resource intensively) built, should newly proposed wind farm projects get the go ahead.
Despite impressive credentials, kite energy is not without its drawbacks. From a safety perspective, some have expressed concern about what happens should a kite’s tether snap. Furthermore, others have pointed out the natural susceptibility to lighting strikes which kites will have, flying so high up in the sky. This could not only damage the kite itself, but more importantly knock out the small but vital computers in the kite which control it.
Yet perhaps the greatest challenge with which kites could possibly be faced will be securing regulatory permissions to ascend to such high altitudes. It is not hard to imagine authorities expressing hesitation over agreeing to a series of kites being deployed anywhere close to residential areas, or airspace in the proximity of flightpaths, for instance.
The almost inevitable opposition from the small but vocal minority who already campaign against wind turbines on visual grounds could be a final stumbling block for kite generated electricity. Indeed, it is foreseeable that kites could engender even more opposition than conventional turbines – for whilst some claim that kites in full flight will be virtually invisible, even an ardent believer in renewable energy may not relish the idea of a network of cables extending hundreds, even thousands, of feet up into the sky.
Conventional wind turbines have undoubtedly helped the UK in reducing carbon emissions and decelerating climate change through the way in which they have provided a clean alternative to dirty, fossil fuelled power stations. In the years since their inception, the turbines have become more efficient, and the blades that power them ever bigger. Despite this, it is not unreasonable to look at the developing sector of kite technology and think that the future of renewable energy generation might lie a little higher above our heads than first imagined.
Eamonn Ives is a Researcher at Bright Blue