Posts tagged: HAWE

KiteGen and Alcoa Updates

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By stekgr, September 21, 2012 3:53 pm

Kite Gen Research has become the third group to express interest regarding the aluminum smelter located in Sardinia run until today by Alcoa.
In Italy we often hear on the news the name of this company, which sadly is associated with the risks of closure and the consequent social demonstrations of its workers.
The area where Alcoa operates is one of the poorest in Italy, where unemployment rate is one of the highest, while the root cause of the problems behind its past and its future are strictly connected with energy prices. The combination of these factors, together with the recent academic studies published by Nature Climate Change (Geophysical Limits to Global Wind Power) inspired KiteGen in proposing an alternative solution to this situation.
On September 10th KiteGen sent an offer to the Italian government and the relative parties involved (Sardinian Regional Government, Alcoa, Minister of Development, Etc): KiteGen proposed the implementation of its “Industrial Program 50 Machines” (currently also under negotiations with other parties) for the production of energy of the Alcoa’s smelter from what it will be the world’s first large scale tropospheric wind farm.

KiteGen received official interest from Alcoa and from the president of the Sardinian Region, Ugo Cappellacci.
On Monday the 17th a delegation from KiteGen headed by its president Massimo Ippolito was hosted by the president of the Region in Cagliari to discuss the contents of the proposal.

KiteGen would like to point out that the meeting has been positive, the Regional authorities present in the meeting together with the academic presence of Dott. Damiano from the Cagliari University, were competent, prepared and opened to the views shared by KiteGen.
The two steps outlined in the documents posted on the 10th of September were discussed and there seemed to be concrete interest from the Sardinian authorities.

KiteGen offers its expertise and its innovation for implementing a short-medium term solution to the Energy issue that Alcoa most of all, but all industries in general have to face sooner or later. KiteGen solution is different from the temporary energy price agreement that might keep the smelter open in the short term. KiteGen wants to provide clean, cheap and abundant renewable energy, the only remedy that could solve this and other difficult situation in Italy, Europe and Globally.
The cost of energy is one of the main reasons why the Sardinian plant has found it difficult to compete and could be sold or closed. A relatively big Kitegen Stem wind farm at regime (200 Stems= 600 MW) could provide continuous power to the smelter at 20 €/MWh, a price lower than the one required by Alcoa to be competitive, 25 €/MWh; lower than the one that Alcoa benefitted from bilateral agreements in the last 15 years of production, roughly 33 €/MWh; and ¼ of the average market value of electricity of 80€/MWh.

Furthermore, if KiteGen will be included in the Alcoa “solution” the smelter might benefit from energy generation through renewable source: this would also contribute in cutting CO2 emissions for the plant and therefore reducing or even save up and trade the allowance assigned by the ETS to the smelter (Emission Trade Scheme) which comes in force from next year.

We hope that the authorities, both Regional and National will soon understand the potential of this source (KiteGen is merely a technology for extraction, the High Altitude Winds are the massive “Oil Fields” above our heads), also because KiteGen would be happier to develop first its technology on the Italian territory and in a social context of real need and only after this important Italian test bench start the commercial and industrial proliferation in other areas.

One of the strengths of the KiteGen proposal is that politicians are now searching for a quick solution, based on energy price subsides needed to keep the smelter on.  Those subsidies, even if allowed by EU, could be granted only for a short time, or in any case they do not represent a long term solution, rather it is just a way to gain time and mitigate the problem until a solution “falls from the sky”.  Whoever the new owners of the plant may be,  they will find it hard to compete without new subsidies, and in a climate of recession the chance for new allowances would be harder.  The KiteGen solution (which literally comes from the sky), could be rapidly deployed during the short term EU allowance that Italian Government is likely to obtain and it will gradually eliminates the need for new energy price agreements, helping securing the future of the Portovesme plant and hundreds of related jobs.

Kite Gen asks the government to apply for EU funds of 1.3 billion euros ($1.7 billion) available for innovative projects, to demonstrate the feasibility of the KiteGen Stem technology at the scale required for the Sardinian plant, and hopes the authorities will not lack such a strategic view of the problem, considering also that there are already so many investments in other directions less promising than the one proposed by KiteGen.

In our view the risks are outplayed by the great opportunities of a competitive and fully sustainable technology that only scratches the greatest source of kinetic energy that our planet has. Is it also your view?


Global Warming & Global Power? Wind can power and even cool down the world!

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By stekgr, September 21, 2012 11:22 am

Translated from Massimo Ippolito’s post:

On September 9th NATURE CLIMATE CHANGE Journal published a paper by Ken Caldeira, Kate Marvel, Ben Kravitz containing further confirmation of KiteGen positions and other brand new information of great importance. The following day, as a logical consequence and necessary act, we sent two letters to the Italian government with the proposed solution for ALCOA. Maybe it was an act too confident about the immediate impact of the NCC’s work and the good media coverage obtained by the article[Short video that introduces the study].

We counted on the contents of the scientific paper, full of meaningful information, in order to provide support to the economic arguments regarding the natural source and our technology. We thought that the Italian Minister of Economic Development Corrado Passera would jump up from his chair saying “Here’s the solution!”, instead, so far, all we heard through journalists is a skeptical comment.

Now let’s try to in this article to analyze the work of Caldeira, Marvel and Kravitz maybe step by step in several posts, of course well-reasoned comments from the readers are welcome.

Climate Change and Global Warming/Cooling?

The blog linked here (Italian), written by Physics and Mathematics professor Marco Pagani, identified and highlighted an aspect of the NCC work that turns out to be a novelty, perhaps a safety anchor of great relevance in relation to climate change/global warming. The graph analyzed by Pagani explains how it is possible to extract enough energy to power humanity with negligible changes in atmosphere temperature, while it is even possible to cool down the atmosphere if we could extract roughly 430TW (20 times humanity’s need) from the wind. The essential point is that Caldeira et all, clearly state that we can use as much wind power as we want, with negligible consequences to the climate, and that the only limits to wind energy technology might be relative to their costs and efficiency. While an extensive usage of this source might even be a solution to global warming.

How much can we get from wind?

Beside of climate change discussions, according to scientific publications and substantially confirmed by this latest paper, above Italy flows a total power whose magnitude is around the 100 TW. Let set 1TW as maximum extractable power from Italy, or an arbitrary 1% of what naturally flows, for the pleasure of round numbers and in order to offer a significant metaphor. Saudi Arabia produces 12.5 million barrels of oil per day, 521,000 barrels per hour, the thermal power equivalent of about 1 TW, equivalent to what hypothesized that we can extract from the Italian tropospheric wind while limiting climatic changes. This is great, isn’t it? Check the calculations if you do not believe it, they are fairly easy.

Technically we also have so much solar radiation, but to collect it we need devices deployed on the territory, while for wind power the photovoltaickinetic panel is the atmosphere itself! Already naturally deployed and maintained, KiteGen is only the PTO that collects the energy collected from the atmosphere.

I would like to highlight another graph showing in particular the advantage of tropospheric wind.

KEE vs drag area graph

The blue line is attributable to KiteGen, the red line is attributable to wind turbines. The vertical axis indicates the size of the surface that intercepts the wind, compared with the rate of extraction of kinetic energy on the abscissa.

In order to draw a power of 480TW, each kilometer cube of the entire surface of the planet must have a “classic” wind turbine that catches a wind front of 10000square meters, one hectare, while in the tropospheric wind are sufficient equivalent of 23 square meters for km cube.

The tropospheric wind, however, is not limited to cubic kilometer near the ground, but the study uses ideally the whole atmosphere, and to clarify the calculation of the equivalence of the surface of 23 square meters must be multiplied by the number of stacked cubes, typically 10, corresponding to the entire troposphere.

So a wing brushes 230 square meters in altitude would be equivalent to a wind turbine that works against a wind surface of a hectare.

We said “wing brushing a surface”, but how big must the wing be?

A simplified method is to divide the area to be swept with the same aerodynamic efficiency of a wing with efficiency 10 so that we will have an area of ​​23 square meters equivalent to a 2.5 MW classic wind turbine typically “brushing” one hectare of wind.

The practical and technological interest is to obtain the desired power in an ideal compromise between workload and surface, which is why we chose the KiteGen Stem flying below 2000 meters with wings up to 150 meters of surface.

The fluidity of data and KiteGen performance, which depend heavily on configuration decisions: the wing, the altitude and the wind speed; are obviously one of the things that annoy people used to precise specifications, these people instead of enjoying the freedom of modulation and opportunities they tend to be cautious over the whole project, probably the view also of some government consultant.

In fact, in this latest media coverage, as I said, the only comment we heard from the Ministry that should support us (Innovation & Economic Development) was a very general kind of skeptical comment on KiteGen technology. Personally, it seems that politicians are no longer able to think independently without the lobbies that hound them constantly. Those sectors who has not created a lobby is excluded from all reasoning and opportunities, even if it is for the benefit of the country and the community.

But if it would be clear to everyone that we have the equivalent of a Saudi Arabia within the national territory, would we still be asking questions at the level of bankers, executives, politicians, ministers regarding the particular system of drilling to extract that energy and how to achieve it?

No! please, is complex, just trust all the patents “Granted”, the awards and the 12 proposals in response to calls for national and regional technological innovation, awarded funding but unfortunately still without coverage. Instead put us in a condition where we can keep working and we will solve all of your doubts.

High Altitude Wind Energy from David North’s (NASA) point of view

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By stekgr, July 18, 2012 12:54 pm

Image credit The system developed at Langley flies a kite in a figure-8 pattern to power a generator on the ground

Originally written by Andrea Papini and Eugenio Saraceno

As our readers already know, one of the most titled teams that recently joined the at high altitude wind energy sector is that of NASA, which at the Langley Research Center in Virginia is developing its own project. According to David North, engineer of the team, in an article reported by

“most tower turbines are about 80 to 100 meters (roughly 300 feet) high, which is pathetically down in the boundary layer of Earth. The boundary layer is where friction from Earth’s surface keeps the wind relatively slow and turbulent. The sweet spot for wind energy starts around 2000 feet up (600m). To use wind at that altitude to generate electricity, you’d have to build a turbine tower taller than the Empire State Building. Or you can fly a kite.”

Read more at: ”
Or the older article about the early stage of the NASA research

The Langley Research Center is the only one, so far, who has also left also the sensors on ground. This choice derives from extreme simplification of the flight control, possible due to awareness of not having to create a commercial product yet. In essence the kite is “observed” by a special camera which communicates to a control system based on a shape recognition technology, similar to those adopted by some recent video games with which they can interact by means of the movements of the body (eg MS Kinetics).

We can say that lately, as well as KiteGen, other groups have reported being able to run the automatic control of the kite:

SkySails Marine


NASA Langley (in March).

TuDelft (In June)

( plus at least 5 other groups who are still working on that)

However, only KiteGen and SkySails are now able to perform take-off and landing automatically.

We are pleased to note that some of the concepts on which KiteGen is been insisting for years, are now being repeated by NASA:

- Flying the kite only reduces the weight (and therefore the cost) of the generator;

- Flying only the tip of the existing wind turbines, which are the parts of the blades that produce 90% of the total energy.

- The power depends on the cube of speed, and therefore it is better to have more efficient kites/wings (contrary to what is being developed by SkySails so far).

Related post ( March 2012)


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By stekgr, June 20, 2012 4:03 pm

Originally written by Massimo Ippolito

An insightful analysis, as always, by Domenico Coiante argues about renewable energy issues and the need for daily and seasonal storage.

It seems a good opportunity to introduce and clarify the opportunities offered in this area by the largest source of concentrated energy on the planet, the tropospheric wind.

The graph shown here comes from the methodology section of the “atlas of the winds of high altitude” of Cristina Archer and Ken Caldeira. It is a sophisticated representation which expresses a competitive or collaborative comparison between the possible accumulation of traditional systems, and the ‘opportunities to exploit the naturally stored energy in the geostrophic wind. Furthermore, it introduces “a trick” to get an annual availability of 99.9%, or 8751 hours a year guaranteed, far higher than any traditional source and nuclear power plants.

My suggestion is to devote sufficient time to decipher the original document, because the implications are of extreme importance. On this graph I added the indications referred to an example of KiteGen 3MW to make it easier to understand the logic. Note that the KiteGen Stem machines that fit in the example should be equipped with wings of 150 square meters with an equivalent aerodynamic efficiency of over 20.

The winds that envelop the planet can be seen as a huge “flywheel” of energy storage. The atmosphere has a total mass of 5 million billion tons, 5 * 10 ^ 18 kg, that flow with an average speed as to bring the total of 100,000 terawatt-hours of energy accumulated. To provide a comparison, this figure corresponds to the energy needs of the current activities of humans for over a year, but with the advantage that this massive accumulation is permanently restored by the photothermal solar dynamics.

While the photovoltaic panels must be deployed on the territory in order to minutely collect the energy supplied by the sun, KiteGen instead, is the PTO of this wide ” photovoltaic photomechanical panel” already naturally established and maintained by the atmosphere itself. This panel has collected energy in the kinetic form, which is a noble form, and it is therefore available for an efficient electrical conversion.

In a specific place, the example is referred to the New York area, the KiteGen generator can reach and pick up energy from this flow, with the probability of finding it powerful enough to produce power at rated power for 68% of the time, an equivalent already amazing of about 6000 hours per year. However, there is a limitation that does not depend on the flow of the wind fading but simply by the fact that it changes cyclically and erratically latitude.

So what is the idea that the diagram shows to push the tropospheric wind up to a 95% availability or even to a 99.9%? Simple enough, you need two generators located throughout the area at a distance sufficient to have at least one hit by the wind flow. The two generators are to be considered as a single system that will double the need for 68% of the time, but that will give a guarantee of delivery of the nominal value of one (of course this will cost twice as much).

In the chart, a comparison is made with equivalent and hypothetical electric storage systems, to achieve the same result of the two generators spaced.

If we assume a cost of electrochemical accumulation of 1 € / Wh, a point I have shown in the figure (b) it suggests 34.5 MWh. From this we get 34.5 million euro only for the storage batteries necessary for carrying out the service and bring availability to a 95%, cost in the order of magnitude of more than 10 times compared to the brilliant idea of having a spatial distribution of tropospheric generators.

What do we get from these reflections?:

1) The intermittent supply that plagues conventional wind and solar can be successfully overcome with the tropospheric wind; attributing the exclusive of the baseload on thermal plants is no longer correct.

2) The economic balance of this double facility can easily sustain the redundant generators as it can count on 68% + 68% + 32% of hours of availability, which would correspond to 11560 hours / year equivalent.

3) In case of advanced deployment and sufficient spatial distribution of KiteGen Stem farms, or KiteGen Carousel, these reflections will lose their special value, since the effect of redundancy is achieved inherently.

4) The redundancy would lead to have an excess of potential output, but the KiteGen are easily and quickly adjustable by means of a central coordination, providing a precise adaptation to the demand curve.

5) The excess energy due the redundant operative systems could be contractually provided at discounted rate to interruptible customers

6) The graph refers to the New York area, but the orographic influence that slow the winds fades as we go at higher altitudes, making it a good example for most of the globe.

The Success of the recent Open Day (Sunday 13th of May)

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By stekgr, May 22, 2012 11:21 am

Last Sunday (13th of May) KiteGen hosted an Open Day for followers, and actual or future investors.

The event had 2 primary goals:

1) Show the state of the art of the technology, and perform a quick demonstration.

2) Launch officially the new financial initiative that collects small and medium investors that want to help the KiteGen’s development; SOTER srl

Those who attended the Open Day had the pleasure to see the KiteGen Stem in operation after a detailed presentation about Energy issues in general a quick history of the KiteGen “evolution” until present day.

The importance of the Open Day lies in the possibility of showing live feeds of the state of the art, that at this stage is dedicated to flight-tests, single components tests, single modules tests, etc.. The weather condition of the the day have also helped appreciating the high level of automation that has been achieved so far, in particular reference to the Stem movements. In fact, in the following video you can appreciate a “semi-automatic” take off procedure.

Click For Video Link

Click for Video Link

All the movements of the Stem and (those of the Manipulator) that you have seen in the video were completely automatic. What was manual was the control of the drums ( as the on-board electronics were not mounted). The movement of the Stem are based on the forces acquired by the sensors mounted on it, which reacts and follow in real time the forces transmitted by the wing. During the next trials the wing will be equipped with the on-board electronics (which contains numerous particular sensors) which measure the position and velocity and transmit it to the computer that will control the trajectory, and the consequent actions of the ropes according to the main targets of safety procedures, yo-yo cycle and optimization of energy production.

There is still work to do to make fully automatic flight, but the excellent work done so far on the software to manage the stem movements realized by Massimo Ippolito, Paolo Marchetti and Angelo Conte allows us to be confident on the future successes.

As you can guess the next step will be to accomplish these tasks and increase the power extracted from the wind in order to maximise the performances of the kite.

The Open Day was also dedicated to presenting the activities of Soter srl, company that holds an important share of KiteGen Research and that is exclusively dedicated to support the KiteGen project. KiteGen Research (through SOTER) is in fact now open to new investors that believe like we do, that KiteGen will be a winning technology for the exploitation of the high altitude winds, the new energy sector that will be key to the necessary transition towards a renewable source of energy in economical competition with fossil fuels sources.

Other Open Days will be organized very soon (24th of June)
Contact us for more information.


You can download the video from here

The Attendants of the Open Day together with the KiteGen Team

The Manipulator

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By stekgr, May 7, 2012 10:30 am

Click For Video Link

Here a short explanation of one of the key components of the KiteGen Stem: The Manipulator

The “manipulator”, so nicknamed because its movements resemble the movement of a human wrist that controls the orientation and position of the kite from the top of the STEM. The distance between the two long antennas vary depending on the needs of the control software and its main function is to assist the take-off and landing manoeuvres.

In standby position, (with the kite hanging from the stem like a hammock) without the manipulator the kite tends to twist on itself and therefore blocking the take off manoeuvres, while keeping the antennas open it is easier to keep the kite open and aligned for the take-off. Taking off with the manipulator helps the air to be channelled in the kite and then closes with extreme speed. Once the kite is in the air the two antennas are closed and aligned to the Stem axis and its presence becomes imperceptible.

Each of the antennas is made in Kevlar/carbon and it is sensorised on 2-axis for the pull of the rope that passes through them. The system is capable to feel the forces in play and react in accordance to these inputs, so that in a situation with open antennas where the kite has just been launched, the pull of the ropes transmit a signal to the motors of the manipulator which react and closes automatically.
The two motors at the base of the stem manage the operating levers of the antennas through a long “push-pull” bowden system (similar to the mechanical principle of a bicycle’s brake). During the landing phase the system again spread apart the antennas facilitating the stability of the kite in its descent.

Lastly the sensitivity of the two antennas helps the whole system in terms of force control and positioning, similarly like the last portion of a fishing rod.

The manipulator, now in its fifth version, is a working reality of the concept idealized by M.Ippolito and reproduced in the model presented in various occasions

You can also download the video from here

KiteGen Model realized in 2008

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.

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

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