Finalization of test campaign for the Power Generation Apparatus (PGA)

March 2022

After years of development, manufacturing, and testing, the PGA completed the final validation and verification phase. This is a huge milestone in Ampyx Power’s history as it means that one out of the three main apparatuses of the AP3’s facility is ready for operation. Let us dive into the technical details of the PGA.

PGA stands for Power Generation Apparatus. Its main function is to convert the mechanical power generated by the pull that the aircraft exerts on the tether into electrical power. Subsequently, this electrical power is fed to the grid for general consumption.

The mechanical to electrical conversion is done by means of regenerative braking; similar technologies are also applied in electric vehicles. Basically, the PGA “tries to decelerate” the wind-driven motion of the aircraft. Obviously, the braking force is just enough for the aircraft to still follow its intended trajectory in the air.

Since the PGA and aircraft are always connected by the tether, the PGA must follow the latter’s motion in all other phases of the mission. For example, it needs to reel-in tether every cycle for the aircraft to reenter a power generation phase. Conversely, tether must be reeled-out during power generation, launch and climb. The PGA also must contribute to arresting the aircraft during landing.

Our aircraft generates power in a pumping cycle fashion which cannot be directly passed on to the grid. Ideally, the system should output average power based on the available wind. This inevitably calls for some sort of energy buffering capability. That is why the PGA is equipped with electrical storage, based on ultracapacitor technology. By cyclically charging and discharging power to and from the storage, the power being outputted to the grid can be smoothened.

Safety and reliability requirements are no less demanding. AP3’s goal is to demonstrate uninterrupted and autonomous operation, which derived in providing the PGA with many redundant systems such as an additional motor/generators on the winch’s drum, a mechanical brake, and an Uninterruptible Power Supply feeding the control system. Furthermore, the abovementioned electrical storage allows the apparatus to maintain operation in the event of grid loss.

Fulfilling all the requirements has been a challenging effort. The uniqueness of the application combined with the use of commercial-off-the-shelf components leaves the difficult part to the architectural design and integration.

The resulting PGA is composed by a high-speed winch and an electrical drive train, here are some key figures:

  • Tether speed up to 38 of m/s.
  • 9.4kNm of rated torque, being able to peak up to 14kNm.
  • Up to 40 m/s2 of acceleration and deceleration.
  • More than 500kW of installed power.
Render image of the PGA

The PGA’s brain resides on an embedded computer which not only controls all the PGA’s systems but also communicates with the aircraft’s computer. The control software has been developed in-house using a Model-Based Design for seamless integration with the aircraft control algorithms.

Looking back on the PGA’s history, the project kickstarted in 2015. A strategic decision regarding what parts of the project were to be outsourced had to be made. After researching the market, it was decided that Ampyx Power would be responsible for the apparatus’ design, whereas its manufacturing and integration would be carried out by external parties. Additionally, the PGA ought to be composed by commercial-off-the-shelf to facilitate outsourcing, reduce time-to-market, and cut development costs.

For the realization of the project, the PGA was split into two sub-assemblies. The Power Management Module, which would include all the power electronics, and the Winch Mechanism Module. These assemblies would be produced by ELMA BV and Dromec Winches respectively. Examples of the commercial-off-the-shelf products used are ABB’s ACS880 drives, ultracapacitors supplied by Skeleton and Beckhoff’s control system.

After 4 years of development, the PGA manufacturing started in 2019 and became integrated in 2020. Since then, intensive testing and debugging have been performed ultimately leading to the verification campaign which started last December. During verification, the apparatus has been tested to its full envelope, and safety items captured on the FMEA have been validated.

The PGA’s next destination is our high-wind test site in Bangor Erris, Ireland. There it will be integrated with the other two apparatuses: platform and aircraft. Ampyx Power is now one step closer to demonstrate 24/7 and full autonomous operation of their AWES AP3 system.

Learn more about our AP-3 system here.