Conventional wind turbines just scratch the surface in a few favorable locations on what is an enormous energy field. They cannot reach upper altitude winds, and conventional designs now are close to dimensional limits. For instance, there is difficultly positioning hubs at over 100 m up, towers grows exponentially heavier and more unstable that previous designs, and above all, they are more expensive with height. Now consider that the flight-prohibited area over a nuclear power plant can easily contain 1 GW of wind power, equal to the power the plant generates. You’re getting the picture.
To reach altitude wind and exploit its greater kinetic energy, the Kite Gen project starts from a change of perspective: no heavy designs like current wind turbines, but instead, light and dynamic structures. To extract energy from an altitude of 800 to 1,000 m, this design from an Italian team suggests power kites, semi-rigid automatically piloted high efficiency air foils. All the heavy machinery for power generation remains on the ground. Two cables connect each kites to a winch that controls its direction and angle to the wind while the winch sits on a large-diameter carrousel.
The Kite Gen concept is comparable to a wind turbine in that the blade tips are the most efficient part of a rotor, say designers, because they reach highest speeds. The generator is then conveniently located on the ground. The resulting structure is much lighter and cheaper than a conventional design would be for equivalent output. Moreover, a kite’s operating height can be adjusted to wind conditions.
The winch, a kite steering Unit (KSU) pilots a power kite or an array of power kites over a predefined flight path. A video at kitegen.com shows some detail. The power kite is maneuvered by unrolling and recovering the two lines to each kite, each on a motor driven winch.
Each Kite Gen power plant is composed by several steering units pulled by power kites along a circular track at ground level. Control software also receives data from on-board avionic sensors to pilot the power kites, control their flight patterns, and maximize energy production.
Conventional wind turbines must be spaced to avoid shading one another which would decrease the total yield. A wind farm can require more than 40 km². In contrast, a Kite Gen power plant and a safe area around it would use about 5 km². Energy production takes place in a distributed manner by several generators thus avoiding unmanageable sizes to electrical equipment.
The modular approach makes possible to build powerful Kite Gen plants. For example, a 100 MW Kite Gen power plant, not much larger than the illustrated example, would have a ground level diameter of about 1 km and deliver an estimated energy at a cost of less than €0.03/kWh. At this writing, a 1,000 MW plant is under study. The exponential growth of the total wind power that can be harnessed is the main reason behind larger Kite Gen power plants.
Designers say the scalability of the Kite Gen power plants comes without significant structural and cost constraints because of the design’s modularity. For example, it would allow adding winches and kites to produce energy from a larger diameter.
In scaling up plant dimensions, one technology that researchers plan to explore is the conversion of mechanical energy into electrical energy through linear-magnetic motors run in a reversible fashion.
The theoretical boundaries of such configuration appears to be a ring of about 25-km diameter, which would be the stator on which rotates a magnetically levitated Kite Gen. The tethered high power kites in such a size would fly at up to 10 km in a controlled formation, generating more than 60 GW.
Filed Under: Turbines