We’ve all flown kites for the sheer pleasure of watching them soaring in the blue skies. But what if a kite could actually be used as an energy source? Could generating renewable energy be as simple as just flying a kite?
Apparently yes. But not with just any old kite: an experimental energy one.
Makani Technologies is a California-based company that was founded in 2006 by Saul Griffith and Don Montague, a former World Cup windsurfer. Google’s parent company Alphabet had invested in it and then acquired it in 2013. Alphabet announced in February this year that its collaboration with Makani has come to an end. Makani still hopes to continue with Shell, who has been investing in the company to bring energy to offshore environments.
Today, Makani’s latest prototype energy kite uses clean energy to generate power for up to 300 homes.
We know the world needs to turn to more sustainable energy sources as it is one of the most pressing global issues today. The vision of tapping into wind power is not new: earliest evidence of the use of sailboats goes back 8,000 years and windmills were used in Hellenistic Greece.
However, the first wind turbine to produce electricity was built by Scottish Professor James Blyth in 1887. His holiday cottage in Marykirk was the first house to be powered by wind-generated electricity in that year.
Today, a 2-megawatt commercial wind turbine is built with glass fibre or carbon fibre blades, costs approximately $3-4 million and has a lifespan of 20-25 years.
Also, disposing of decommissioned fibreglass turbine blades in an environmentally-friendly way is challenging. More energy is required to break down the composite material.
So, while wind is a clean and readily available source of renewable energy with unlimited potential how can we better utilize it?
Harnessing airborne wind energy rather than ‘regular’ wind energy has been explored. Industrial wind turbines exploiting regular wind energy are fixed in position and between 90-120 metres in height.
Makani’s airborne wind turbine is lighter, cheaper to produce and to transport. It has the potential to tap wind energy from altitudes with stronger and more consistent winds where terrestrial wind turbines cannot reach.
As we go higher, wind speed increases. There is less turbulence caused by friction and interaction with the earth’s surface, so it gets smoother and more steady. These high strength winds can generate higher amounts of energy.
Makani’s carbon fibre energy kite has the wingspan of a small jet plane. It generates electricity by sending power down a cable tethered to the ground. Propellers on its wing act like rotors which lift the kite off the ground station.
Once the kite reaches an ideal height of 1,000 feet (304.8M), it loops in a circular path like a regular kite does without consuming any energy. Instead, the rotating propellers drive a generator which produces energy from wind. When its work is done, a flight computer guides it back to the ground station.
The latest Makani prototype has a wingspan of 26m and generates 600 kilowatts (kW) of electricity.
In 2019, the latest prototype Makani kite which generates up to 600kW of electricity made the first offshore flight off the coast of Norway but crash-landed in the sea. Despite this, they successfully proved the technology’s ability to launch and generate power.
Even without Google, Makani still hopes to make wind energy more affordable and accessible. To show their commitment to further innovation, they have made their research and experience available, including code repositories, technical videos and a simulation tool.
They have also made a non-assertion pledge for the free use of Makani’s worldwide patent portfolio. You can follow their journey in the documentary Pulling Power from the Sky: The Story of Makani.
Makani uses a rigid wing design. Other contenders are vying in the airborne energy market to create a commercially viable product. Most are using an inflatable (soft-wing) kite design that resembles those used in kitesurfing. This design uses a yo-yo motion to power a generator on the ground as its wing inflates and collapses in flight.
SkySails and Kitepower are two such companies pushing this simpler soft-wing design. In fact, SkySails’s wind-powered auxiliary generator for vessels saves 50 per cent in fuel consumption and emissions.
SkySails has managed to secure long-term financing and is pushing ahead. The Skysails system operates between 200-800m. Their mobile units generate between 200-500kW. The unit can be anchored offshore up to a depth of 700m. It could be an interesting application in the shipping industry. They claim the wind-powered auxiliary generator can make up 5-10 per cent of the total fuel cost of a merchant ship.
Kitepower’s system is just 100kW — significantly less than Makani’s, but ideal for replacing diesel generators.
Airborne wind advocates are counting on substantially reducing costs by minimising materials needed as compared to traditional wind turbines. They have the added advantage of accessing areas where traditional turbines cannot operate.
The ease of transport and deployment means they can be used in hurricane-prone regions, offshore platforms, military installations, or during outages due to storms and natural disasters.
According to the World Bioenergy Association Report 2019, wind power makes up less than one per cent of global renewable energy consumption. With some good headwind, perhaps we can take this up a few notches.