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This topic thread could discuss BloombergNEF (BNEF) and its AWE opinions. See also:
====================================================== The commentary below is by Massimo Ippolito. The paper he refers to is a paper for which he has a copy. As yet, I have not found a copy of the paper except that copy sent in email to me. ---------- Forwarded message --------- From: Massimo Ippolito m.ippolito@kitegen.com [kitegen] Date: Tue, Jun 18, 2019 at 8:11 AM Subject: [kitegen] BloombergNEF - KiteGen [[Note:
the first signed notes are machine translated from Italian to English
by a Google translation tool; see original, if in doubt.]] BloombergNEF has issued an information for investors on Airborne Wind in the annex They
give KiteGen a leading role along with Makani and Ampix, for those who
understand the subject knows that both Makani and Ampix have completely
wrong the system architecture, so the document in a sense could be
comforting but the absolute inability to distinguish the technologies
is somewhat disappointing. I replied with the following clarifications but unfortunately they kept the current version. I wonder what the ultimate purpose of BloombergNEF is because if these investors, who are also their customers, read the report in depth, they certainly do not come close to these projects.
I have some issues regarding the content, as follow: page 1 “five to ten years” This great length of time could imply that the research is not complete. That is not the case, since it has been thoroughly tested and specified. A fully-specified design of a special machine typically takes, without constraints, six months to set up production and another six months to rework the design and production of parts or components causing unreliable or out-of-specification results. The main hurdle is setting up the wide and diverse organization dedicated to the project, because in a new technology, each person involved needs to be retrained before again becoming a contributor; experience has taught it takes one full year. So my full and funding-unconstrained estimate is two years. The risk is that such a widespread opinion will delay full commitment at all levels of the chain, becoming a self-fulfilling prophecy. I have been fighting against this notion since 2016, when we completed the design, suffering exactly from the prophecy of IRENA, the EU and other major institutions that only guessed at such a number of years without a reasonable degree of insight. All the smart technologists we have met, after a comprehensive examination of the project, at a certain point, have declared the glaring obviousness of the process and its outcome. This preventive acquisition of a reasonable understanding is missing in most independent evaluations. “costs continue to drop” As an early expert technologist in Photovoltaic (PV) and wind turbines, I have some difficulty in recognizing this statement as true. I.E., the recent Haliade-X 12MW requires a full investment of $400m. With a conservatively computed unit cost of $150m in batch production, excluding the BOS, that equates to $12.5m/MW, when turbines were typically priced around $1m/MW. Adopting the same tools and methodology to evaluate the KiteGen Stem, we obtain $0.2m/MW; an advantage of 62 times, compared to Haliade without accounting for our doubling the Capacity Factor. Another issue occurs in the PV industry when it decided in 2009 to reduce the silicon refining process from solar-grade to upgraded-metallurgical grade, thus reducing the conversion efficiency to 14% of the top industry standard of 21% and halving the life of the cells with a major impact on users’ business plans. This was strictly a deceptive strategy, because the 25-year PV lifespan has already been commonly established for solar-grade silicon, but nobody has thought to recompute the LCOE with this new and obvious handicap. Page 2 “developer claim capacity factors...” As per wind turbine installation, the expected capacity factor is computed in advance, before installation, because it isn't primarily a function of the turbine itself, but a function of the site. Analogously, for HAWT, precise mathematical and reanalysis tools are available and can be adopted by anyone, obtaining the same results. KiteGen early-on spent significant funds to independently validate such tools for HAWES. I.E., we commissioned this work to KAUST. https://www.nature.com/articles/s41598-017-10130-6, or a new document about LIDAR measurement and our reaction. https://www.researchgate.net/publication/332422870_Interactive_Commentary_on_Improving_mid-altitude_mesoscale_wind_speed_forecasts_using_LiDAR-based_observation_nudging_for_Airborne_Wind_Energy_Systems
Page 4 “stationary bases are much more prevalent” As explained in our reaction paper to the ECORYS report, the stationary bases are but a step in the direction of the KiteGen Carousel. The modular nature of the Carousel can accommodate several KiteGen Stems in a ring, the advantage being a further dramatic improvement of the capacity factor, because there is no need to lose wind for aerodynamic activation (no operative/functional reel-out of the lines). “Fly-gen system show promise for higher capacity factors than ground-gen, ...” “Ground-gen Lower weight in the air, may allow for faster flight (linked to higher generation)” These two statements are in contradiction, because in both architectures the flight speed plays a quadratic role in energy production; the fly-gen is necessarily braked by the propellers so it flies at a slower pace, losing most of the power. Page 5 “Tethers add both weight and drag to the system, which can decrease speed and thus electricity generation.” This is claimed by competitors, but isn't true. The tether weight is not significant because of the “figure-eight” path of the wing in airspace. The weight, 50% of the time, is favorable to the flight speed, (when the wing direction is toward the ground). The other 50% of the time could be profitably exploited to limit excess power by climbing inside the spot wind window, introducing the concept of potential energy accumulation, endo-phanic and exo-phanic paths in the airspace (direction of the lemniscate evolution). Also, tether drag is a non-issue. Tether drag doesn’t affect the wing speed or the system AE of Kitegen. The reasons are easily understood: During the tests, we pushed a wing at 2400m and 65m/s, observing no tether drag issues. This demonstrates KiteGen’s justification to reject the overly simplistic analysis based on some “system drag” idea that combines line and wing, appearing for the first time in the Loyd patent, the validity of which is limited to the domain of tethered aircraft (A) equipped with tails that drive and force their pitch. Thanks to in-depth research and simulation, it has been established that the drag of the line is irrelevant to wing speed and energy production. It is, instead, simply a geometric dynamic, conceptually affecting the path in airspace only of (B). Tether drag only limits the crosswind motion distance that can be achieved in one stroke, before the wing has to change direction. This is a feature that can be successfully exploited by the controls in order to extend the wind power spot. Issues related to transverse wave propagation on the line The wing is typically set to fly at 80 m/s. When the wing changes direction, a new displacement transverse wave acts upon the line, while the axial wave is running at 270 m/s. Such a transverse wave is slow, due the air mass added to the line’s linear density, taking several seconds to affect the entire line. Thus, the wing has the freedom to fly for a few hundred meters before line-bending changes its optimal angle toward the wind. The models adopted in literature expose an excessively tight time boundary, or even a “snapshot”, to track such behavior. Line drag is applied axially to the wing, the same effect that gravity has on gliders, that obviously never slows the aircraft. The force vector representing the drag of the lines binding the wing is only manifested axially, thus thrusting the wing as with gliders (above case, picture B). As Gustav Eiffel taught us, when the Reynold number of the segment of the line near the wing reaches an elevated value, a new effect called “drag crisis” takes place, greatly reducing it. The tether drag issue is speculation based on a fixed cylinder in a flow experimental setup, with a measured coefficient ranging between 1.2 and 1.5. The lines are light in specific weight, which means they are locally free to oscillate and rotate on the axis, dynamically losing air pressure accumulation. Thus, they cannot be compared to a typical fixed cylinder in a flow. Larger scales lessen the significance of the issue; this due to the line section and Reynolds surface ratio of the line section being the squared function of the diametre; the drag surface being linear, it is an advantage that grows dramatically with increasing scale. KiteGen’s scientific committee published an article trying to explain the limits and errors of the proposed models in the literature review; unfortunately, there being no skilled audience. Furthermore, in order to gain more flight freedom, KiteGen patented lines that were appropriately tapered in order to reduce the drag coefficient to 0.03, instead of the classic 1.2 of a cylinder immersed in a fluid, that the lines are immersed in as well. This patent applies to the domain of possible and potential future enhanced optimization of the technology. To repeat, as this is an extremely important concept, because the production of energy depends on the square of the flight speed. The line drag is not added to that of the wing, which remains free to fly at the speed of its glide factor or aerodynamic efficiency. This topic may require a lot of insight to be fully understood. Page 6 “The idea is to avoid the inconsistency of ground-gen by flying the wings out of phase so that one is generating while the other is in recovery.” KPS is a very recent initiative and was looking for a little IP niche in which to work, circumventing KiteGen's IP, instead of collaborating under a licensing agreement. The KPS niche is to operate two kites together with a mechanical axis at the level of the lines’ reeling drums. This approach is highly impractical because the climbing kite needs a different reel-out speed and line tension, compared to the reel-in requirement of the kite in the recovery phase. This feature is currently state-of-the-art and is patented by KiteGen and is obtained with a farm interaction. Two (or better, three) separate KiteGen Stems can logically act in counter-phase (remote and parametric electrical axis) in order to provide a continuous supply of energy at farm level, not machine level, hence respecting also the distance requirements between machines and flying wings and their cones of optimum operational pertinence. A greater number of units in a wind farm lower the possible discontinuity of supply, cancelling the idea of a lower capacity factor. Currently, KPS, following my public criticisms, recognized the superior effectiveness of the electrical axis, changing the focus of their development. But the technological history was established, and KPS lost its claimed uniqueness. We find it quite surprising that these little reasonings do not develop in an autonomous manner into everyone's mind, but that is why it is necessary to explain and reiterate them, creating an almost embarrassing situation in the face of obvious facts. Page 7 “Airborne wind does operate at higher heights than conventional wind, it is not high enough to obtain a radically better generation profile and is not as disruptive as it may appear based on power output alone.” This is another false notion circulating in scientific literature. We have observed that, due to the absolute originality and novelty of this concept, there is a lack of qualified peer review, and blatant errors have been propagated and transferred, undisturbed, from one poorly informed publication to another, with no-one critically re-analyzing their stratified assumptions. The Betz limit can meaningfully be applied to kites, since the area a kite moves in is generally very large, and the kite will only remove a small fraction of the wind energy passing through that area. Well before becoming aware of high altitude, or tropospheric, winds stronger and more constant than biosphere winds, KiteGen profitably addressed undisturbed wind flow exploitation at low Betz efficiency, that has since been revealed as a viable resource valued at at least three times the power that can be harnessed by a wind turbine under the same conditions. This feature alone was enough to establish the superiority of the concept and our strong commitment to develop it. This enabling feature is currently neither understood nor addressed in any current literature, despite its obviousness: The less we brake the wind,the more the resulting speed is higher. The power available is a cubic function of the wind speed. I.E., since a wind turbine only exploits a fixed window of wind, it needs to optimize the energy harnessed, looking for a compromise between braking effectiveness and residual wind speed. “The drag on the tether (which scales linearly with length)”
This statement is also a farfetched notion. It is not true that drag scales linearly, certainly not for KiteGen. We have a saturation effect that the line loses any additional geometrical effect of dynamic bending over about 3-400m of length. It is even sub-linear for Makani and Ampix architectures, because the line radial displacement of the line during extended flight follows a fourth-order function, exposing a hyperbolic cone of operation, so remarkably different line speeds. Page 9 “Visual impact and noise emission” The flying wing is a dot in the sky, virtually invisible and, in the event of clouds, it disappears. The flight is always subsonic. The noise decay is a quadratic function, almost impossible to hear any noise coming from the wing at 1000m. “complicated to operate near populated areas” Here we know that this is a perspective mismatching, I.E., a 100MW farm needs only a few square km, or about 40 acres, including the safety zone containing the generators and the extended projection of lines and flying wings to the ground. The onshore farm is compatible with forestry and/or agricultural activities. The land purchasing cost for exclusive/primary use is about $120,000, while the tropospheric wind farm produces $20m./year of gross revenue. A matured machine installation can certainly afford the land for exclusive use. Pag 10 “Shorter project lifetimes, cost levelized over less time” This statement is unjustified. The KiteGen stem is composed of two main sections: the flying section, composed of wing and lines, and the ground-gen, that is a giga-robot, including the arms, the alternators, the pulleys and the servo drive electronics. The ground-gen is machinery that needs ordinary routine maintenance with a typical lifetime of 60 years, similar to hydroelectric power plants. The flying section has a shorter life; the endurance tests we performed suggest about one year, but there is only about 800 kg of material involved, to be considered a consumable, like the grease for the bearings. To make a comparison, we need 200 kg of natural uranium or 4000 tons of coal to produce the same energy equal to KiteGen’s 800kg flying consumables (lines and wings). “Higher cost of advanced materials” The same, it is a very small quantity of material. “Longer and more complex permitting process” This isn't a concern for the project, because suitable installation sites are widely available, including flight restrictions already in place. The demonstration of the incredible wealth provided by cheap energy and the solution to several epochal problems will globally pave the way to further installation sites. Page 11 KiteGen didn’t adopt a soft wing. Instead, it is alone in the scenario, based on a semi-rigid wing, certainly not Enerkite or EWIND that are flat wings, hence totally rigid in order to maintain the shape under traction. Page 12 “The M600 is a 600 kW rigid wing model with a 26 meter wingspan.” We do not feel comfortable giving power indications without providing the wind speed or the specific power density. M600 requires 4kW/m2 for nominal power instead the KiteGen Stem 0.5kW/m2 Pag 15 “This so-called ‘valley of death’ is a critical period for technology startups.” This sentence certainly conjures up a fascinating image, but it does not correspond to the reality of a highly innovative and very high-potential development process, since those who lead it are already aware of the necessary work and difficulties. So, you have to proceed to milestones, which for KiteGen was to start demonstrating that the concept exists and produces energy and has been totally successful. Precisely, this experimental success has been so significant that it has triggered hundreds of initiatives around the world which have largely become informal competitors, but now, due to their delay, seriously lag behind in the deep understanding of the subject. The next milestone was to choose the dimensional size of the generator and conduct all the theoretical and technological research to substantiate the product and its feasibility at the required scale, and this process was also successful and accumulated value, mainly in IP and know-how. In the end, the detailed design of the machine started with the creation and validation of the components, putting enough hay in the farmstead to have an accumulated, safe, demonstrable and spendable value. Now it is the turn of batch production to start on a precise and reliable industrial plan, which can be accepted by, and shared with, suitable and interested partners. So, if there was a “valley of death” it was certainly confined to the first milestones. Now it's a simple matter of good engineering practices, good relationship and good industrial agreements.
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