Technology

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At higher altitudes there is sufficient wind to power the world’s growing energy demand, but we need the right technology to harvest this enormous potential.

Ampyx Power is developing an Airborne Wind Energy System (AWES) with a tethered aircraft that converts wind at higher altitudes into electricity. The objective of our Airborne Wind Energy System is to capture the vast wind resource at higher altitudes with much less material than used in conventional wind turbines. We replace concrete and steel with state-of-the-art technology. Watch this video to see how it works.

"Our vision? To create innovative, elegant technology to harvest untapped energy sources for a sustainable future."

Richard RuiterkampFounder and CEO Ampyx Power

HOW DOES IT WORK?

Our automatic aircraft is tethered to a generator on the ground. It moves in a regular cross wind pattern at an altitude from 200 m up to 450 m. When the aircraft moves, it pulls the tether which drives the generator. Once the tether is reeled out to a predefined tether length of about 750 m, the aircraft automatically returns towards a lower altitude causing the tether to reel in. Then it ascends and repeats the process.

The aircraft lands and takes off automatically from a platform, by utilizing an array of sensors which provide the autopilot with critical information to perform the task safely.

Ampyx Power has specific in-house aircraft knowledge and expertise in constructing automatic aircraft.  For instance, in terms of the algorithms the automatic pilot is equipped with.  Many code lines in the software ensure that the aircraft can fly completely automatically while responding to changes indicated by numerous sensors. Adjustments can be made within milliseconds, allowing the aircraft to continuously fly in its pattern.

PROTOTYPE AP3 AND COMMERCIAL SYSTEM AP4

After three generations of prototypes (AP0-AP2) we started the production of prototype AP3 in 2017. This prototype is designed to demonstrate the safety and autonomous operation of our system. With AP4, our commercial product, the emphasis will be on power generation. With this system we will work towards a capacity of 2-4 MW with the aim to replace conventional turbines with comparable capacity that have been built since the beginning of this century and are now at the end of their lifetime.

Wing in production with a span of 12 meters

AP3

In order to demonstrate safety and autonomy of AP3 we work towards 24/7 automatic operation without human intervention. The full cycle will be automated: launch, power generation, landing, repositioning and relaunch. Including a safe automated response to any off-nominal condition, such as a sudden drop in wind or a failure of one of the systems. We will develop gradually the software and control algorithms to be certified. AP3 will safely land if the tether breaks or if an actuator of a control surface gets stuck. The automatic landing has to be spot-on: it will touch down within meters from the target. In this way we can afford to have a very small landing platform. We will fly AP3 in Ireland, on the site that we will develop with E-ON. There we will build up AP3 flight hours to prove the avionics. We should eventually be able to fly the AP3 at night and in extreme weather for days in a row. We aim to fly sufficient hours to gain meaningful experience on operations and maintenance aspects.

Two fuselages instead of one – the drone with two fuselages is a patented concept. It is being controlled on the tether much like a conventional aircraft using control surfaces. The two fuselages have several advantages; they provide enough space to house the electric systems, sensors, landing gear and propulsion systems; the double fuselage provides the necessary clearance for the tether during maneuvers as the tether is attached midwing, in the center of gravity; and, the propulsion needed for climb after launch can be divided over both fuselages, although the two propellers are only needed for tethered climb -the drone can return to base in any condition using only one propeller. The propulsion is not active during power generation or during normal landing.

In contrast to a conventional aircraft that needs to be able to carry people or freight, our wing is optimized for power output. The high lift design generates an immense lift equal to twelve times the mass of the aircraft (4200 kg force) needed to generate a large tether tension. The wing has a carbon spar and the wing skin is made of fiber-glass. The wing can sustain significant impact damage, even puncture, without losing its overall integrity (think e.g. of impact of heavy hail or of a small bird) because of a very strong spar. The structure is designed for infinite lifetime, it is designed to sustain fatigue loading even following superficial damage.

The horizontal tail is set between the fuselages and is an all-moving tail. This maximizes the control authority and secures sufficient pitch control during landing (nose down/nose up direction), even if the wind would suddenly drop.

The landing gear consists of four retractable legs with shock dampers. It is designed to enable landing on either the platform or on a test field.

Control of the aircraft is fully automatic in all weather conditions and even in case of failure. Many code lines in the software ensure that the aircraft can fly completely automatically while responding to changes indicated by numerous sensors. Adjustments can be made within milliseconds, allowing the aircraft to continuously fly in its pattern. The autopilot makes use of a triple-redundant on-board computer developed to the most stringent aviation standard. Each computer is connected to a separate set of sensors and has an aviation grade real-time operating system with dual partitions each running an independently developed code. The main control code takes care of nominal behavior and deals with detection and recovery of any single system failure. A back-up landing algorithm runs continuously in parallel to take over should the main code for some reason falter. The drone computers communicate with the platform. The winch dynamics are demanded by the drone and the launch and land system is controlled by independent control loops that are synchronized with the drone dynamics. This architecture makes it possible to achieve a safety and reliability level approaching that of commercial aviation.

The tether remains attached to the drone in all normal operations and most contingencies. The tether is made of Dyneema DM20, a creep resistant version. The bottom part that is cycled onto and off the generator wears down the most. It is replaced once a year. The top part wears little. It is thinner to reduce drag and is replaced once every 5 years. It is coated for minimal wear and features a noise-reducing strake.

The tether is wrapped around a composite drum that rotates when tension is applied by the aircraft. The winch contains a spooling mechanism that takes care of orderly spooling the tether on and off the drum. The motor / generator combination is responsible for the efficient conversion of tether tension into electrical power during the reel-out phase and for the efficient reel-in of the tether during the retraction phase. During the reel-in phase, the aircraft glides towards the generator. Reel-in is performed at only 1% of the operational tension. The generator is designed to minimize inertia and to limit the size to what is strictly required. The generator converts the current and inserts it into the grid.

 

A power storage solution smoothens the output during reel-out and guarantees that no power needs to be drawn from the grid for reel-in. If the wind exceeds a critical value, a power capping algorithm is activated between the drone and the winch that reduces the pull on the cable to keep the power generated within limits of the back-end electronics.

The launch is identical to a conventional glider winch launch. The aircraft is launched by a catapult into the wind and also lands into the wind. Therefore, the platform needs to be able to rotate with the wind direction. For the landing Ampyx Power has designed a completely new approach. With this patented approach, the platform only needs to be about 20 m long. The drone will be gliding down almost horizontally for landing, but does not aim to land onto the platform. It will fly over it. Just before the drone overflies the platform edge, the winch is slowed down. The winch retrieves the tether at the same time, keeping it taut, and the winch pull is used to help control the drone speed. This creates a slack in the tether between winch and drone. As the drone flies on, the tether gets taut again. The drone passes over a pulley that can slide over a rail but only as it compresses a damper system. In this way, the kinetic energy of the drone is dissipated and the drone drops vertically onto the platform. The landing gear absorbs the impact. After landing the winch is used to pull the aircraft back into its launching position using guide rails in the landing deck to re-position it for next launch, automatically, without human intervention. The drone is expected to land only once every few days.

Where can our systems be deployed?

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