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Autonomous aircraft could make wind power less expensive

Wed 11 Apr 2018 by David Foxwell

Autonomous aircraft could make wind power less expensive

Small-scale autonomous aircraft flying from offshore platforms could one day make wind power significantly less expensive, a Dutch company claims.

A study published by the company, Ampyx Power, earlier this month suggests that a new type of offshore wind energy concept might well be feasible and could cost significantly less than conventional offshore windfarms. Itís known as the airborne wind energy system (AWES).

In a report from the Offshore Wind Journal conference earlier this year, I highlighted the potential of airborne offshore wind systems, in particular a concept developed by Kite Power Systems in the UK.

The AWES is similar to Kite Power Systemsí airborne wind energy system which, the British company believes, offers the prospect of a much lower cost of energy than the next generation of conventional horizontal axis wind turbines.

Kite Power Systemsí concept is based on kites tethered to offshore platforms that fly at altitudes of up to 457 m. The kites are attached by tethers to a winch system which drives a generator as they spool out, thus producing electricity for the grid. The company believes the technology has the potential to transform the global onshore and offshore wind generation markets, not least because this kind of offshore wind power could be much less expensive to manufacture and requires less construction and installation materials than conventional wind turbines.

Ampyx Powerís AWES generates electricity from the wind, but unlike the British system it uses a small-scale tethered aircraft flying at an altitude of up to 500 m. The company envisages that it could be deployed in deep water on small, relatively inexpensive anchored floating platforms. The autonomous rigid wing aircraft is tethered to a generator on its offshore foundation. It moves in a regular cross wind figure-of-eight pattern. When the aircraft moves, it pulls the tether which drives the generator. Once the tether is reeled out to a maximum length of approximately 750 m the aircraft automatically descends to a lower altitude causing the tether to reel in. Then it ascends and the process is repeated.

The whole process is automated. The aircraft takes off, flies and lands from the offshore platform. It generates power, lands when necessary, guides itself back to launch position and launches again when the wind picks up, all without the need for human interaction. All this is made possible utilising an array of sensors which provide the autopilot with the information it needs to safely operate.

Ampyx Power has developed several prototypes and started production of a 150 kW prototype, the AP3, in 2017. This prototype is designed to demonstrate safe and autonomous operation of the system. The next prototype, the AP4, will be larger and will be used to demonstrate the systemís power generation capability. In the long-term the Dutch outfit is aiming at a generating capacity of 2 MW.

In the Sea-Air-Farm project, a consortium including Ampyx Power, the Energy Research Centre of the Netherlands, Maritime Research Institute Netherlands and Mocean Offshore studied potential applications of AWES and the feasibility of building an offshore windfarm using it. Their work was funded with a subsidy from the Ministry of Economic Affairs and concluded that an offshore windfarm using large numbers of AWES is feasible and would be competitive with conventional windfarms. As the authors of the report also noted, an offshore windfarm using AWES is especially promising, given the fact that the AWES concept is still at a very early stage of technical and commercial development, and significant further cost reductions can be expected in the future.

You can watch a video of AWES with this link.

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