Many of our readers are eager to receive information about KiteGen, but this post and others that will be published in these early days have the aim to frame the issue in a broader perspective, clarifying the use of technical terms and fixing some basic notions that will help to clarify the purpose and the issues we face in our blog.
Kilo: k 1000 Thousands
Mega M 1000000 Millions
Gig: G 1000000000 Billions
Tera: 1000000000000 T Trillions
So for example. 1 Gigawatt is one billion watts
is measured in Joules (J) and represents the capacity to do work. For example, a vehicle of mass (m) travelling at a speed (v) has an energy (kinetic) of 1/2mv^2. To brake the vehicle up to a stop the brake system will perform a work equal of its kinetic energy (which in this case is dissipated in heat)
is measured in Watts (W) that is Joules/second and represents the rate with which you perform a work, that is, how much energy is consumed by a user in a second. It is commonly used in the measure of Watt-hour (Wh) which indicates an energy, because 1 hour is composed of 3600 seconds and in the product between J / s and 3600(s) the seconds gets simplified. In other words 1 Wh = 3600 J.
Sometimes there is confusion between kW and kWh that is, confusion between power and energy. An example to clarify this: a 2000 W hair-dryer (2 kW=Power) consumes 1000 Wh in half an hour (1 kWh=Energy)
Tropospheric wind technology
It is the innovative methodology to exploit the wind at altitudes not reachable by traditional wind farms that are installed on land and offshore. It is based on the fact that wind energy is significantly more frequent and intense at altitudes a.g.l. (above ground level) higher than the 300 meters, and that this progression of continuous power, without solution of continuity, is function of the wind speed elevated to the cube, until the theoretical technical exploitable height of 9,000 meters, which represents the upper limit of the troposphere.
Technically Exploitable Height
It is the height reachable by wind energy capture devices appropriately dimensioned and controlled, without suffering from decreasing of power output, limitations of flight control and prediction of trajectories. Typically, this natural resource has a specific power of more than 1,000 times those found at 50 meters a.g.l. , after 9000 meters this power declines sharply due to the lower air density.
It is the maximum working altitude limited by considerations of compatibility with the air traffic, or by safety considerations in order to avoid power of the wind so intense as to be unmanageable from the specific machine. The exploitable height may vary from site to site depending on the conditions mentioned above. The first KiteGen generators will exploit winds between 300 and 2000 meters a.g.l.
Wings or Kites
Are the technological devices, light or ultralight, that interact directly with the strength and speed of the wind by transmitting its mechanical power to the ground through special ropes. The flight of the wings or kites is controlled by a special software that interacts with the generator and the parameters given by the sensors mounted on the wing/kite.
It is the set of ground-based systems needed to manage the automatic manoeuvres of the wing or kites, including take off, landing as well as the rapid recovery procedures in case of emergency. At the same time, the generator contains the devices needed for the transformation of kinetic energy coming from the cables into electrical energy using servo-alternators with variable frequency that produce direct current.
Tropospheric wind installation
It is a plant for production of electrical energy by direct conversion of the tropospheric wind’s kinetic energy. The system is mainly composed of wings or kites which transfer the force to the ground, by means of ropes, which enables the rotation of the drums with a speed function of the wind speed. The drums are connected directly to one or more alternators, then, one or more groups of inverters convert the direct current into alternate current ready to be in sent into the grid;
Tropospheric wind farm (Stem Farm)
It is the name of a group of single winged Stem generators distributed on the same territory and connected to each other in terms of flight control and energy output management system. The minimum distance between generators in the same Stem Farm can be as close as 80-150 m from one to another.
It is intended as the 2 phases cycle that characterise the operational time of interaction with the wind. The first (active phase) is the production phase, where the traction of the wing pulls it away from the generator gaining height and generating energy. The second phase (passive phase) is the recovery of the wing, until the minimum operational altitude, that allows the restart of production cycle. The passive phase has an expenditure of energy equal to a fraction of about 1/100 of the energy produced in the active phase.
Tropospheric wind farm on land
It is a plant installed on a terrestrial site which is connected to the network with the distribution lines at medium-voltage.
Tropospheric wind farm at sea
It is a tropospheric wind farm built in waters up to 20 meters deep, requiring platforms fixed from the sea bottom by columns and footings, and that requires a DC connection to an inverter station to the ground.
Tropospheric wind farm in the deep sea
It is a tropospheric wind farm which is implemented in waters beyond 20 meters depth, which is composed by floating buoyancy system with a volume of less than 100 cubic meters. The system is anchored through winches and flexible cables to an appropriate heavy body lying on the seabed. It requires a shared connections for submarine DC or AC that will reach the land.
Carousel Tropospheric wind system
It is the future and ultimate design for a large size plant for production of electrical energy by direct conversion of kinetic energy of the high altitude wind, with rated power not less than 1 GW. It is mainly composed by a set of interacting wings connected to a circular structure with a diameter approximately of 1 or more kilometres. The giant ring acts as rotor and rotates continuously on a vertical axis under the traction of the combined work of the kites.
Carousel Tropospheric wind system Offshore
It is the offshore evolution of the machine described in the previous section, with components suitable for working in sea conditions and fixed at the seabed by support columns.
Carousel Tropospheric wind system Deep Offshore
It is the Deep Offshore evolution of the machine described in the previous section, with components suitable for working in sea conditions and mounted on a floating structure anchored to the seabed by means of special mooring cables connected to a series of anchors lying on the seabed.
Rated power (or nominal, or peak) of a tropospheric wind energy installation
It is the electrical power of the system, determined by the sum of each rated power (or nominal, peak) of each generator of the same installation, or tropospheric wind farm.
Example: Rated Power of a Stem Farm of 10 generators KiteGen Stem 3MW = 30MW
HAWE (High Altitude Wind Energy)
Term used internationally used to identify this emerging field.
AWE (Airborne Wind Energy)
Terms used mainly in North America usually to identify Flygen systems
FlyGen and GroundGen
Are the terms recognized internationally to distinguish the two main approaches to harvest tropospheric wind energy. The two philosophies are distinguished by the position of the generators, either on the ground (like KiteGen and most European HAWE companies) or directly in the sky mounted on the flying object (like Makani Power and most of the north-american concepts). The two systems have different characteristics that will be analysed more in depth in future posts.
Pumping Kite & yoyo
Terms used in the literature to describe the production cycle of GroundGen concepts