Makani: Turning Wind-Turbines into Kites?!
This is the brief story of how a couple of windsurfers decided to generate wind energy using kites!
Kites.
Yes, the same ones you’ve unsuccessfully tried to mount at the beach when you were 10.
But also the ones that the Chinese used in the military to lift men up 1000 years ago.
So it’s no secret these things have power. A lot of it.
It wasn’t before 1970 when Miles Loyd wrote a seminal paper describing how using a plane on the end of a kite could generate and harness tons of energy. His main takeaway was that a free-flying plane could generate significantly more energy than a fixed, motionless one (like a wind turbine).
However, everyone ignored him.
This is the part when I introduce you to the Makani team, originally comprised of the 3 co-founders; Corwin Hardham, Don Montague and, Saul Griffith. They started off as wind-surfers when, on a boring afternoon, they realized how powerful wind energy really is.
“Wind energy could power the world up to 100 times over, yet only 5% of energy around the world actually comes from the wind.”
Take that in for one second.
We have the ability to power the world over one hundred times over, yet we don’t.
A bit about the problem at hand
According to the World Bank, 91% of the world’s population lives under exposure to polluted air, mostly due to fossil fuel emissions.
We have come to the point where we need to generate 10 Trillion Watts of new and clean energy to off-put the fossil fuels outputted.
Clearly, we have to fix our energy and climate crisis at hand.
Where does Makani come into play?
Using a combination of eagerness to keep the world running accompanied by Miles Loyd’s discoveries, Makani set out to tackle one of the world’s biggest problems: Generating sustainable energy.
About Makani
Known as the company that “pulls power from the sky”, Makani (Hawaiian word for “The Wind”, a 17-year-old start-up funded by Google’s X projects, essentially dedicated themselves to using kites in order to harness wind energy.
The project draws on the concept of wind turbines but without the expensive cost and heavy steel towers that turbines necessitate.
The kites are made up of rigid gliders (with power systems mounted onto them) that are tethered down to grounding stations.
As the gliders fly around in loops, guided by an autonomous flight computer system, the power systems collect the energy and send it down the engineered tether to the ground station where it’s captured.
You could think of their system a bit like an elevator, the elevator follows a simple motion and the tether holds it to the pulley while the grounder of the system gets pushed on with a bunch of energy.
Now you may be thinking to yourself, “There’s no way we have never harnessed energy from kites if it seems so simple.”
But even Eli Patten (Mechanical Engineer of the kite’s tether) discloses:
“We have over 100 years of history in aviation — when the Wright Brothers first started to fly, until now, we’ve been able to do so much more things in aviation. We have jets and propellers and airplanes with wings of all sorts of configurations on planes, and we’ve been to the moon, but we have never in that whole time tried to develop this type of aeronautics or aerodynamics that happen in this type of kited flight.”
And, it only took them 13 years — a record amount of time for a piece of technology that could potentially power all of the United States.
Before we appreciate all of Makani’s successes, let’s deep dive into how Makani Tech works.
Let’s break it down even further
This is the diagram sketch I will go off of to explain how the rigid aerodynamic wing works in 4 parts:
Part 1: Generating Energy
Going off of Loyd’s principle that objects in motion experience more airflow than stationary ones, the rotors placed on the front of the kite receive this powerful airflow and begin spinning to generate electricity.
Part 2: How much gravity is acting on it?
Makani’s kite model can withstand 7–15 Gs.
Gs refer to how much gravitational force is acting on the wing. Since 1 g = 9.81 m/s² (the amount of gravity exerted on you and me right now), and when the velocity of an object increases faster than gravity can change it, our g value will be greater than one, 7 Gs = 68.67 m/s² and 15 Gs = 147.15 m/s².
Therefore, the glider must accelerate until at least 69.67 m/s² of gravitational force is acting on it to collect an efficient amount of energy.
Part 3: How the sensors work?
The piloting system (funded by ARPA-E) works by extracting data from the glider’s GPS along with its other sensors to help the smart software steer the kite in the correct formation.
Part 4: Basics of the navigation
The aforementioned onboard computers run custom flight controller software that guides the kite’s trajectory. This is especially useful during turbulent weather and in ensuring a safe ground landing. The computer even takes into account which aerodynamic trajectory the glider must take, it guides the kite in loops based on the path optimizing for maximum power generation.
For details about how Makani came up with their kite design, read this 5-minute article written by Fort Felker, CEO of Makani.
And for more general information regarding all things Makani, check out this Moonshot Factory article detailing the project.
Overview of kite’s trajectory
- Kite readying for launch
2. Downwind position while rotors begin taking small amounts of energy as thrust
3. Crosswind flight while flight controller begins mapping out looping sequence to get the most power generation
4. Rotors take in large amounts of energy from the wind and begin sending it to the ground station
Makani Today
Now, unfortunately, Makani was shut down by Alphabet Google just last year (February 2020). This was allegedly due to Astro Teller (Captain of X’s moonshots) believing that the “road to commercialization is longer and riskier than hoped”.
Read more here.
Whatever the future of Makani holds, the kite company was overall able to generate 600 kilowatts of wind electricity, enough to power 300 homes in addition to inspiring thousands to pursue their ambitions.
As Fort Felker said: “To achieve a clean energy future we need to be open to exploring a diverse array of new renewable energy technologies, and that means pushing bold new ideas as far as possible, sometimes without a clear roadmap. I am proud of our team’s dedication to expanding access to renewable energy, and I believe that Makani’s journey is an example of the level of commitment, calculated risk-taking, and hard work that are the right building blocks for creating technical solutions to climate change.”
Some resources to dive deeper:
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