Posts tagged: High Altitude Winds

Past, Present and Future Tests

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By stekgr, April 2, 2012 12:03 pm

KSU1 Tests

Click For Video Link: 2006 Validation Tests

You can also download the video from here

From Andrea Papini
Edited by Stefano Serra

Many of our followers ask for more details about the tests performed so far, and the ones running right now. First I would like to illustrate the results that were obtained from the first prototype, in order to have a clearer picture about the work we are doing now.

Different test activities necessarily follow each stage of design and development, in particular for an innovative machine like the KiteGen Stem, that represents the most advanced technology in this new sector and a level of details never conceived so far.
Validation tests of the KiteGen technology started in 2005-6, when a first prototype, called Kite Steering Unit 1 (or KSU1) proved that it is possible to transfer the strength of the wind at high altitudes in order to produce energy with a YO-YO cycle (the KSU reached an height of 2500 m a.g.l. with peaks of 60kW)

The Yo-Yo cycle consists of:
An active phase in which the kite gain height unwinding the two cables and operating the motor-alternator and hence producing energy while reaching a maximum altitude.
A passive cycle in which the motor-alternators act as motors and reel the kite to the minimum height of operation, consuming a fraction of less than 1% of the energy produced in the active phase; the cycle then restarts.

The several tests sessions performed with the KSU1 included includes a big amount of so -called “flying hours”. In slightly more technical terms the flying hours have been classified into different types of test flight manoeuvres (modules). For example: “Take off tests”, “Production of electric power”, “Safety in case of wind burst”, “Side-slip manoeuvre” etc.. Tests also included some operations on the ground to change the wing set-up, replace cables, and some other variables of the KSU1.

I would also point out that the tests on the KSU1 were “boolean”, hence focused on succesful repetition and optimization of each manoeuvre. Tests were also performed on the whole “yo-yo cycle” (which is the union of the various operations) however this was not the main object of study because as with every first test a complex system, it is good practice to test the each modules of which is composed, like links in a chain.

The test results have demonstrated the effective productive potential of electric power (great success of the module “manoeuvres for the production of electric power”), which was a result of historic value, that has not penetrated the minds of media, institutions and investors as we expected. However, these tests have also shown that the first small-scale prototype KSU1 was inadequate to perform the full yo-yo cycle, this for two main reasons:

1: The inability to safely handle the kite in case of strong gusts of wind (problems in the module “manoeuvres for safety in case of wind burst”);
2: The inability to dissipate the heat accumulated in the KSU1 pulleys.

At that point, it was necessary to redesign the generator so that would resolve those problems. Since the productive potential had been demonstrated successfully, in order to shorten the time it has been chosen to point directly to an industrial prototype. As outcome of these activities the KiteGen team obtained:

1: A new structure designed with the implementation of “stem” to absorb the gusts mechanically;
2: The FEM designed  "igloo" acting as a big spring in order to limit the 2m diametre bearing peak forces;
3: The diametre, operation and orientation of drums and pulleys have been modified;
4: A cooling system has been integrated;
5: A manipulator has been envisaged at top of the stem, in order to further help take off procedures.

From this work, the world’s first “KiteGen Stem” came into being.

with this new configuration is now possible to test:

1: Module "manoeuvres in safety in case of wind burst" with the aid of the stem;
2: The efficacy of the cooling system (it has been oversized in design phase);
3: The new "forms of automatic take off" (actual testing);
4: Different kite flight paths in order to optimize the production;
5: The active dampening of frames oscillations due the wing dynamic.
Many other tests will be performed to evaluate the efficiency, affordability and endurance of the generator and its different components.

As soon as the boolean tests on the various modules will be finished and validated, we will focus on testing yo-yo cycle in continuous mode in order to validate the predicted power curve and its endurance

Briefly it means that repeated full cycle tests will start when we will have verified that the KiteGen Stem is fully functional. These final tests will be set the ground to start the optimization of productivity and final manufacturability of the system as a whole. All of these steps are performed by the KiteGen Team keeping in mind that “ A chain is not stronger than its weakest link” and we are carefully focusing our limited resources on each single step.

We know there are many out there waiting for us… just a little more patience and especially support.

The Max Planck is scared to fly

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By stekgr, March 22, 2012 9:22 am

Dear readers,
This article is a translation of Massimo Ippolito’s response to a paper published by the Max Planck institute regarding the potential of high altitude winds.

Here is what Massimo had to say regarding this work.

The Max Planck is scared to fly

Tullio De Mauro informs us, from the pages of the “Corriere Della Sera” that 71 percent of the Italian population is below the minimum level required for comprehensively reading a text of medium difficulty[Italian]. From this, unfortunately, we can deduce that the recent study of the Max Planck Institute can be understood, critically evaluated and read between the lines by a homoeopathic percentage of average citizens. Therefore I apologize in advance for my frankness, accompanied by some discomfort that I am obliged to use. As we shall see we are indeed facing a very contestable work, and frankly, what is even more surprising is the willingness to publish it by the Earth System Dynamics and that to forward it by Quale Energia (which has also kindly offered a right of reply).

Those who are used to read scientific publications will definitely be surprised by the very title of the paper, “Jet stream wind power as a renewable energy resource: little power, Big Impacts” that introduces the spirit of the paper, inexplicably aggressive. In the paper itself, each paragraph devoted too much space, without supporting reasoning, at repeating what has been expressed in the title and then reiterated in the conclusions.

From the works of the IPCC, for example, we are all used all to see every prediction made from a model accompanied by a certain degree of uncertainty. However, it is already difficult to establish a good level of scientific seriousness from one particular statement, contained in the papers of the Max Planck, which states that one can extract from the atmosphere exactly 7.5 TW,1 without providing the reader with appropriate error bars, bars that could be available by running the model modifying their assumptions in their area of plausibility.

They estimate only 7.5 TW, but in hindsight, it is still not that little!

Paradoxically, the study by researchers of the Max Planck Institute, while performed by using arguments that we will prove incorrect, it positions itself among hundreds of other wind resource assessments, as the least generous of all. Even if harsh about it, it is basically another confirmation of the validity of KiteGen and high-altitude wind power more widely. This because it confirms that only by the use of high-altitude wind power it can be possible to extract, in a sustainable way, amounts of energy greater than the world’s primary energy needs despite saying it in direct polemic with a more optimistic study by Ken Caldeira and Christina Archer, in which the available power is estimated at 100 times more.2
In fact, quoting from their publication: “
Our estimate for maximum extraction of kinetic energy from Sustainable jet stream is 7.5 TW3. However, despite this pessimistic limit of 7.5 Terawatt, the noble and precious electricity, is far more than that required by the entire basic human needs! Such requirement today stands at 16 TW fossil, therefore thermal, where much less than half of it is transformed into useful energy services. A coal power plant consumes about three times more thermal energy than its electricity output, and a car burns and scatters five times the thermal energy of fuel respect to the mechanical energy that actually reaches the wheels. Almost all of our energy use is affected by these unavoidable proportions of waste. Therefore we can say, without fear of contradiction, that the present human needs, in terms of power, is widely under 6TW (multiplied by the 8760 hours, to obtain the energy need on an annual basis), if already set in the elegant electrical or mechanical form rather than thermal.

Power or energy? That is the question
Now we will get into the job.
Those professionally involved in energy discussions share with me the feeling of having to endure the oppressive, continuous and widespread confusion between the different concepts of power and energy. On page 202 of the paper in question, the entire first paragraph repeatedly and ineffably combines the two concepts. Here an example:
“If we take the present global energy demand of 17 TW of 2010 (EIA, 2010), then this estimate would imply that 1700 TW of wind power can be sustainably extracted from jet streams. However, this estimate is almost twice the value of the total wind power of 900 TW (Lorenz, 1955; Li et al. 2007; Kleidon et al. 2003; Kleidon, 2010) that is associated with all winds within the global atmosphere.”4
The current demand for energy, according to the authors, 17TW, is a Power measure, which is clear (but only to professionals) for whom is willing to understand the average power absorbed by the all services during a planetary year. Yet, this is expressed with a superficiality which is not eligible even for an high school student during an oral exam, let alone a team of researchers, who have also had the opportunity to proofread the work several times before releasing it. Furthermore, stating that the total power of the wind is 900 TW means forcing a physical concept: there is no power in a fluid, if anything, it has energy. At the extreme, you could try to evaluate the energy possessed by the steady atmospheric regime, but that is measured in TWh (terawatt-hours). Those 900 TW, could be the power that the sun transfers to the atmosphere and that is then transformed into kinetic form, or the power that the atmosphere loses into heat by continually interacting with the ground and in the phenomena of friction between the various layers. This should be enough to reconsider that there are many approaches of better quality and certainly of better interest on the theme, like the followings:

Brunt (1939) calculates the total kinetic energy of the atmosphere in 100PWh.

Gustavson (1979) estimated the average total dissipation in 3600TW, (further supporting the data from Brunt)
Gustavson (1979) 1200TW dissipation within the boundary layer with the orography of the territory and the energy transfer to the seas,
Lorenz (1967) 1270TW, Skinner (1986) 350TW, Peixoto and Oort (1992) 768TW, Sorensen (1979 and 2004) 1200TW, Keith et al.(2004) 522TW, Lu et al. at., (2009) 340TW, Wang and Prinn (2010) 860TW.
The differences between the results described above are motivated by analysis that are partitioned and on ordered flows, purely horizontal and potentially exploitable, but basically all the authors are in relative agreement on the orders of magnitude.

Gustavson (1979) believes that 130 TW can be exploited – 10% of what is dissipated naturally – with an explicit attention to the climate by the author, which in my opinion remains the most credible person who has understood and said everything that there was to understand and say. Another great work is Sorensen’s, which overlaps almost perfectly with that of Gustavson.

Going back to the confusion between power and energy on the paper by L.M. Miller, F. Gans and A. Kleidon, the reader has to be very lenient and approximate to accept these formulations:
“Archer and Caldeira (2009) estimated the potential of jet stream wind power as “… roughly100 times the global energy demand.” If we take the present global energy demand of 17TW of 2010 (EIA, 2010), then this estimate would imply that 1700TW of wind power can be sustainably extracted from jet streams. However, this estimate is almost twice the value of the total wind power of 900TW (Lorenz, 1955; Li et al. 2007; Kleidon et al. 2003; Kleidon, 2010) that is associated with all the winds within the global atmosphere.

Here we resolve this contradiction between the energy that can maximally extracted from the jet stream […], in terms of differences in velocity and dissipation rates, the limit on how much kinetic energy can maximally be extracted, […], atmospheric energetics. The contradiction originates from the erroneous assumption that the high wind speeds of the jet streams result from a strong power source. It is well known in meteorology that jet streams reflect quasi-geostrophic flow, that is, the high wind speeds result from the near absence of friction and not from a strong power source.“ 5

1) There is an artificious accusation towards Archer and Caldeira to say that 1700 TW are sustainable, while the real meaning of their statement was that by having a potential of 100 times the global demand, the extraction is particularly abundant also from a single geolocation, and that for now, we can let go undisturbed what we do not collect. In addition, the estimate of Archer and Caldeira does not only refer to the jet streams.

2) A certain TOTAL WIND POWER is mentioned, associated with all the winds of the atmosphere, and it does not give an average power, or at least mediated by TW per year, which is a serious error.
3) It indicates a maximum energy that can be extracted, which has no meaning except with through a shifted interpretation of energy, being it power.
4) It indicates the maximum kinetic energy that can be extracted, which would have meaning only if there would have been added, even just lexically, a time base.
5) Moreover, the absence of friction is false. In fact we know that in the atmosphere are lost globally 7W per square meter, of which 2.5 W m is the portion eventually available for the wind technologies (not to be confused with the average 700W per square meter, available locally, as the summation of collection in the large cardioids upwind the generators).

The intent of the authors, that forcibly put together different concepts, even at the risk of seeming superficial, it is unclear, and certainly not very scientific. Thinking carefully about it, it all give credits to the suspicion of wanting to attack at all costs the concept of high-altitude wind.

However, in reality no one with a glimpse of wisdom has ever thought to exploit directly the Jet Stream

The Jet Stream feeds disproportionate images and dreams. For this reason, often, when it comes to wind energy, there is a sort of intellectual itch to dissertate on the subject.

Indeed, the wind speed at that altitude is 90 knots average, an equivalent of about 16 kW per square meter, with frequent peaks of over 100 kW per square meter. A single hypothetical fan of only 20 cm in diameter, immersed in the jet stream, could actually provide plenty of energy for a house all year round, both day and night.

However, a machine that is submerged in the middle of the Jet Stream, at 9000 meters above sea level, is difficult even to imagine. Only technologically immature fantasies can speculate as to whether or not is possible to exploit that mighty and unmanageable stream. The high altitudes technologies, in all of its forms, are focusing to the residual flow, which propagates from the jet stream and drops to lower altitudes. Flow that is destined to dissipate its energy into heat while breaking between the tops of mountains, forests and the orography of the area. Do we have to think that the drafters of the paper in question did not know this? That they criticised a technology while ignoring even the simple basics of it? Personally, this is at the same time a legitimate and very disturbing doubt.

And again, the work of Christina Archer and Ken Caldeira, which is cited in the study as supporting the hypothesis, does not focus at all on the possibility of exploitation of the jet stream. The atlas of high-altitude winds that they published takes into account all the latitudes and longitudes at various heights, is therefore unacceptable to attribute their focus exclusively on the jet stream.

The magic inherent in the machines that aim at exploiting the tropospheric wind is precisely the possibility of adjusting the working height in order to find always a breeze, not too strong nor too weak, with the primary goal of competing with the stability and constancy of the thermal power plants, which convert the energy providentially stored by our planet in fossil sources for millions of years.

The high-altitude wind power has also the advantage of finding this energy concentrated in the stationary atmospheric regime, which can be accessed from virtually any place on Earth’s surface, without the need to deploy hundreds of thousands of installations in the territories. What is good about having this huge source of energy accumulated in the jet stream, it cannot certainly be the immature and pointless intention of extracting thousands of TW; but it is instead the awareness that we can seize the advantages of a machine that can draw from the energy losses of this tank to satisfy the operating specifications of a technology and its relative power output.

The Betz limit

On page 206 the Betz law and its limit of 59.3% in mentioned. The mathematical formulations of Betz actually describe the methodology needed to curb the flow of the wind in order to extract energy. They allow us to understand that the wind flow does not have to be fully exploited because it has to flow through the machine without losing all its speed and the energy possessed. A necessary condition to obtain the best result.
However, the Betz’s laws are valuable for wind turbines, which exploit a relatively small wind front limited by the size of the rotating blades, so the wind keeps the residual energy that is not converted by the machine. In the case of high altitude technologies (ground generator), those laws lose much of their importance as the wind front exploitable is dozens of times more than that of wind turbine blades and that the wind speed is reduced only slightly.

The authors of the paper forced the so-called Betz’s law, with the intent to assert that the discovered maximum kinetic power of 7.5 TW is, due to the Betz’s law (59.3%), reduced in 4.5 TW of electric power. This is not true, because if the kinetic power would actually be limited to 7.5 TW, the machines should process wind for 12 TW preserving a flow of 4.5 TW, this absolving the specific that only 7.5 TW Kinetic are subtracted.

Mathematical models

It is often said that science and scientists are divided in deciphering various topics, such as it happens for models that describe the climate chaos and its anthropogenic responsibility.

Many politicians do not want to hear about models anymore, probably because they have seen demonstrations of opposing views supported by their relative opposing models. Well, it is a real shame because the essence of a statesmen ad policymakers should be to predict the future with sufficient time to react properly.

I think I have focused quite clearly on the main factor common to cognitive and communication failures on many subjects of a certain complexity. These are about different perceptions and interpretations regarding both dynamic and retroactive phenomena. I can even say that there is a clear line of demarcation between those who study, perceives and is conscious of the various phenomena with their set of dynamic and retroactivities, and who perceives the science and its phenomena with static representations or simple trend projections, as it happens with the mainstream economists or demographers. Unfortunately, it is possible to manufacture the so-called “predictive models” with both mentalities, but with very different qualitative results.

The work of L. M. Miller, F. Gans and A. Kleidon reveals little knowledge of systems’ dynamics. In fact, while claiming to have used a mathematical finite element model, they have applied forcibly and everywhere a series of fluidic brakes as emulation of high-altitude wind machines. A colossal mistake, taking into account that the wind machines must necessarily have a geolocation, and also this aspect has been completely ignored by them.

If the powerful streams of high-altitude winds are so mobile and in near absence of friction, any eventual obstacle would be largely bypassed, creating unprecedented dynamic scenarios, but still possible to model with more rigorous approaches.

Here I reproduce an image to show that, while writing, above England, France, Italy and Greece, there was a wind of roughly 200 kph. As you can see these flows accelerate, slow down and change direction, involving huge masses of air at great speeds and great accelerations. Situation that in a few hours have completely different configurations and a large exchange and dissipation of energy.

It is enough to think about the energy conveyed by the winds as the foehn, frequent in Piedmont, which while it spreads billions of tons of snow on the Alps, is able to raise the temperature of an entire region to summer levels in midwinter.

To give a quantitative indication resulting from the image, above Italy there was a wind power of 200 TW, approximately 15 times the global primary demand. I this case I can properly speak of ‘power’ because I have defined an area (the wind front on the Italian peninsula) and a reference time (the time to which the image refers). The study of these atmospheric dynamics symbolically recreates the difficulties cited above. Yet there are those who think they can put down a handful of equations, in direct conflict with the model, and expects to obtain meaningful results.

Anyway, assuming a limit of exploitation of a few TW represents now a more than comfortable, wide and I would say shareable objective, until we can confirm with more rigorous models, that the more we use tropospheric winds the more tropospheric wind will be available. Basically, maybe, it is a resource that regenerates and grows automatically.

The absorption of kinetic energy by wind turbines, in fact, lowers the temperature of up to several hundredths of a degree in the cardioid downwind of the atmosphere. And the thermal differential, together with the vapour content, is the great engine of the winds.

Most of the exploitation of the resource, for geographical and demographic reasons, will focus on the Ferrel cells of atmospheric circulation, which represent a colossal energy short circuit between the Hadley cells and the Polar cells. Subtract energy to these cells can mean that the surrounding dynamics of the atmospheric circulation will come back in full.

Where are the institutions?
After this essential critical work of the Max Planck Institute, finally we can share the elements to state that, without sounding exaggerated, only from Italy, with its transversal position to the large pseudo-geostrophic flows, we could easily extract 1 TW of power continuously, or more than 8000 TWh of electricity annually. Which, prosaically turned into money, they would amount to a net production of purely endogenous wealth estimated at 800 billion euro each year….!!! Amounts enough to embarrass all the unfair financial manoeuvres that we are imposed to by our governments.

A few dozen of large wind machines or KiteGen farms, distributed from North to South, they would do all work without worries of intermittency, at perhaps not even a tenth of the cost that we would have had from nuclear power.

The fact of writing and demonstrating credible technological design procedures has given us the promise (but only that one) of public funds for a total of 78 million euro. We participated in calls for research and innovation, and the relative commissions have always been enthusiastic about the project, so much that many technical and strategic observers have felt compelled to personally congratulate with me. I remember Zorzoli, Clini, Silvestrini, Degli Espinosa, Pistorio… Then, regularly, the funds were frozen and the leaders sacked, or the procedures went in the hands of lunar bureaucrats. Degli Espinosa and in particular Pistorio at the time of “Industria2015″ had convinced themselves wisely, that at least one KiteGen, produced on an industrial scale, was absolutely a “must see”.
Consuming copious amounts of energy from renewable sources is the credible and unique primary motor for the economy of the future, but it seems that a feeling of powerlessness and nihilism are reigning and that who could give us a hand prefers to see the collapse that we are facing.


1L. M. Miller, F. Gans and A. Kleido. “Jet stream wind power as a renewable energy resource: little power, big impacts”, Earth System Dynamic, 2011, 2, 201-212. p.206. accessed on the 17th of January 2012

2Pdf available at

3Miller et all. “Jet stream wind power as a renewable energy resource: little power, big impacts” p. 211.

Miller et all. Jet stream wind power as a renewable energy resource: little power, big impacts”. p. 202

5 Miller et all. Jet stream wind power as a renewable energy resource: little power, big impacts”. p.201-202

Taking-Off, Flying and Landing in Safety

By stekgr, March 13, 2012 10:52 am

Click for Video

You can also download the video from here

Taking-Off, Flying and Landing in Safety.

After many technological developments related to: the automatic take-off procedures, the controlled movement of the stem, the sensors installed and interlinked, radio bridges between the kite and land and many many other “hidden” aspects of KiteGen (each one essential as links in a chain), we are now proud to show the most visible achievement reached so far.

We are sure that this post is exactly what everyone was waiting to read from our blog. Testing activities on our prototype have started a few weeks ago and numerous technical achievements were collected. In one test in particular, Wednesday 15th of February, a successful take-off occurred with just 1.5 m/s of wind speed at ground (video link).

The KiteGen Stem has followed the procedures for the take-off through the “Swing” of the stem, allowing the kite to gain height thanks to the apparent wind generated by this movement (therefore, in this instance, without need of artificial wind as mentioned in the documentation). Once above the generator the kite gained more height finding stronger winds and completely unrolling the cables mounted on the drums for this test (300 m).

We know that the European average wind is around 3 m/s; with this exceptional result the KiteGen demonstrates that it has the freedom to take-off at any time, without aids for at least 5000 hours per year.

The test program will continue and evolve, in order to consolidate the results and check the behaviour of the generator during continuous flight; with the realistic ambition to get as close as possible to the 8760 hours per year of flight. (Although not always reaching full rated power during generation, the theoretical limit for this is just below 6000 hours, still 2-3 times the one of traditional wind farms).

The other obvious result that can be extrapolated from this post is that at least the beta version of the control software is ready. There is still a lot of work for the KiteGen team, however, we reached an important milestone in the estimated time, which suggests that the road is downhill from here.

Ropes completely unrolled (300m)

The KiteGen Stem buried in Snow

The research prototype KSU1 (also called mobilgen) already flew, and produced energy back in September 2006 (video link). This first experiment has allowed us to implement a long list of necessary features and upgrades to add on the industrial machine now under tests. Thus defining an appropriate technology architecture that would allow automatic take-off, manage the excesses of the wind bursts and reduce the wearing of mechanical parts, cables and kites. These specifications were designed and implemented and now are under constant test thanks to the completion of the world first KiteGen Stem.

In a nutshell these were the activities that, for those who follow the KiteGen project since the beginning, kept the KiteGen Team busy, while some impatience led some to criticise the project with statements such as “KiteGen is stopped because it does not fly.” The flight is certainly the most visible achievement but definitely not the only one reached by this company. Further updates will prove the immense work done and facts will convince the more sceptic.

From here the team will carry on as it always had, hopefully with more support, towards the ultimate goal:

Industrialize the first large scale machines that can exploit the huge potential of High Altitude Winds.

Keep up the good work.
Have a good flight KiteGen!

NASA Langley Research Center and KiteGen

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By stekgr, March 4, 2012 6:33 pm

Click For Video

In this video posted on youtube recently by NASAinnovation a familiar image appears.

Originally written by Massimo Ippolito and Andrea Papini

Mark Moore and David North of the Nasa Langley Research Center show how they are exploring the different solutions to take advantage of the tropospheric wind.

David North announced that wants to experiment the configuration with a single rope and the actuators controls directly on-board the wing.

Although the carousel system, and in some ways also the Stem, are independent from the ropes number, we would like to take the opportunity to explain the reasons of KiteGen on opting for the two ropes system and the on ground actuators.

1) Security of the double rope system

A double rope system has an extremely higher security factor than a single cable system plus the further advantage to permit a faster rewinding phase in critical wind conditions.

Furthermore in a double rope system the two motor-alternators and the drums share the load forces transmitted by the ropes, hence the double system has to support half of the forces and the components are easier to handle and to find on the market.

2) The opportunity given by the double rope system to implement the side-slip manoeuvre for the rewinding stage, using the bimodal flight of the wing

By using a single rope the recovery phase has to be done by changing the angle of the wing, guiding the wing at the border of the wind window, strategies already tested by KiteGen back in 2006.

Such system cannot avoid the lift production by the wing, that causes air resistance which in turn slows the duty cycle and affects the efficiency of the energy production cycle. In addition to that, this system requires a greater expenditure of energy by the motor and drum, which is highly undesirable in an energy production cycle.

Using a double rope system KiteGen demonstrated that by putting the wing in “flag” position, its lift coefficient drops immediately and it is possible to recover the wing in less time and with less energy consumption.

3) The velocity of response from the actuators to the wing.

It is possible to demonstrate that controlling a wing at long distance is possible without having relevant delays. The force transmission goes at the sound velocity along the rope made of “Dyneema® SK75, having E = 107 GPa , ρ = 0.97 kg/dm3 it results in 10.502 m/s”, that is about 30 times the sound velocity in the air.

This delay (0.1 s every 1000 meters of rope) is small enough to be negligible and to null any advantage in a wing with actuators on board.

4) Ropes aerodynamic resistance

The double rope system has a higher drag resistance compared to the single rope system. Such difference is calculated by multiplying the square root of 2 times the drag of one rope. However, thanks to a KiteGen patent the drag resistance of the ropes can be easily and substantially reduced.

5) Ropes twisting

The twist counter is managed by the control system and it is working really well. Even though the control responds promptly even with up to 10 twists, the control can quickly switch from 8 shaped trajectories to ellipses, hence restoring the right flying position.

6) Wing direction control forces

The possibility in the using of control actuators systems on board is strictly related with the dimension of the forces involved.

Small applications for testing and production system in the range of kW can use control actuators systems on board, having limited weight and limited energy consumption.

However, if we consider higher power (MW range), the control systems assume higher weights, higher mechanical forces and stronger auxiliary energy consumption. Using on board control system implies that the actuators are connected to the ground through an electric wire inserted in the ropes, therefore increasing their complexity, weight, costs, drag issues and atmospheric risks.
Further considerations have to be applied at the integration of the control system on the wing, in order to avoid dragging issues and intrinsic inertia transmitted to the wing movement that this solution will generate.

The KiteGen system, by keeping the actuators on ground, has the advantage to avoid all of these issues.


By stekgr, March 4, 2012 4:53 pm

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.

Some definitions:
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.

Exploitable Height
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.

Production cycle
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

The Birth of KiteBlog

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By stekgr, March 1, 2012 1:12 am

Power Kites

Dear friends,
With the present post we are proud to announce the birth of a new “interactive channel” through which it will be possible to follow the latest news about KiteGen and other related topics. In fact the idea behind KiteBlog is to host not only technical articles about KiteGen technology but also contributions related to energy issues in general, status of natural resources, demography and economic systems. We hope to satisfy the curiosity of everyone interested in our technology, stimulating discussion and comments about the exploitation of the immense field of wind energy at high altitudes, where KiteGen represents the most advanced technology. Furthermore, KiteBlog will be used as primary channel to promote the exploitation of high altitude winds as the ultimate solution that our planet have left in order to avoid the worsening of the interaction between the financial crisis and the lack of resources. A situation where the increasing costs of Energy are gradually dragging the global economic system away from the level of “well-being” resulted from the abundant exploitation of fossil fuels in the last century.

A world that wants to: maintain some degree of economical growth; safeguard the welfare system that it created; improve standard of living of the growing countries; guarantee the right of self-determination for a world population that is constantly increasing; and that wants to do so while preserving the fragile equilibrium of our nature, needs a new source of cheap and clean energy, a radical change of perspective that we believe can be achieved only through exploitation of High Altitude Winds. KiteGen is merely a mean towards this noble end.

All of this may seem vague and far-fetched for now, but stay tuned, because over the next posts, and technology updates, we will prove our thesis.
Each posts will have one or more
categories in order to easily follow the topics of interest.
Here are some of the categories that you will find… Enjoy your reading.

News: Updates on events or milestones achieved

KiteGen: short articles that will satisfy the curiosity about many aspects of the KiteGen technology and its applications.

KiteGen in Depth: detailed articles on technical issues concerning the KiteGen technology and many related topics:

High Altitude Winds: Articles related to wind data, energy potential and comparison with other forms of energy

Energy: Articles related to energy issues, EROEI, resources, history of energy etc…

Vision: Posts related to future energy scenarios

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