Offshore Kites Ready to Transform Wind Technology

Kite Power Systems

Published Jun 25, 2017 3:35 AM by The Maritime Executive

Kite Power Systems of  Scotland has secured a £2million ($2.5 million) equity investment from the Scottish Investment Bank for its offshore wind generation kite.

The investment follows an investment by E.ON, Schlumberger and Shell Technology Ventures, who announced a combined £5million ($6.4 million) investment in the company in December 2016.

Kite Power Systems’ power system features two kites which fly up to an altitude of 1,500 feet. Both kites are attached by tethers to a winch system that generates electricity as it spools out. By achieving flight speeds of up to 100mph (45m/s) in 20mph (9m/s) winds, the kite’s tether tension causes the line to rapidly spool out from a drum, which turns a generator producing electricity.

The technology has the potential to transform the global offshore wind generation market, as it is cheaper to manufacture and requires less construction and installation materials than conventional wind turbines, says the company. It can reduce the capex of conventional offshore turbines by as much as 50 percent, because its patented power system doesn’t require large quantities of steel or specialist installation vessels. 

Kite Power Systems has been flight testing its current 40kW system there over the past few weeks and has secured planning consent to deploy the new 500kW power system, following delivery of the completed model during August 2017. This will lead to a planned onshore demonstration array of multiple 500kW systems within the next few years, elsewhere in Scotland. Thereafter, Kite Power Systems will develop a 3MW onshore system at the test facility and then deploy a similar sized power system in offshore waters.

Lower capital and operational costs means that kite power generation would not need government subsidies and could be deployed in U.K. and Irish waters (and other areas of the North Sea) and in waters up to and potentially deeper than 40 meters (130 feet) found offshore of countries such as Portugal, Japan and the U.S. 

How it Works

Phase 1

The wing is flown in a circular looping path akin to the tip of a wind turbine blade. By achieving high flight speeds, over 100mph in a 20mph wind, strong aerodynamic lifting forces are developed by the wing and exerted against the tether. This tether tension causes line to be rapidly spooled out from a drum which is connected to a generator. In this way the 100-200-meter line is drawn from the reel.

Phase 2

The wing must be retracted to its start position consuming the minimum amount of energy. The pitch of the wing is actively changed to minimize aerodynamic force, and the kite exits the loop to be held static in an overhead position to be glided back towards the starting point. Line tension can easily be reduced by a factor of 10 or more, such that a net energy gain is achieved over the generation/retraction reciprocating cycle.

Two kites fly in the same airspace such that whilst one is generating power the other is being retracted; energy production is therefore constant and the alternator kept rotating near optimal speed.