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Highest Wind LLC response to FAA docket 2011-1279 regarding
Airborne Wind Energy Systems (AWES).
Dimitri Cherny Founder, CEO Highest Wind LLC
February 3rd, 2012
General comments on all AWES from Highest Wind LLC.
1. All American AWE system developers are years away from
commercialization. We are all currently in the development and test
phase and will likely remain here for the next three or four years
before any of us have systems ready for purchase.
2. Unlike other aircraft, development of AWE systems requires
frequent, and eventually continuous flight testing, day and night in
all weather conditions for weeks and months on end. Longevity,
survivability, and extremely low maintenance requirements are the keys
to the commercial feasibility of AWE systems. Only by keeping AWE
systems in the air for months at a stretch will any developer be able
to determine whether their system is ready for commercialization. We
are all essentially designing flying vehicles that must be as reliable
as wind turbines – more reliable than the best existing passenger
aircraft.
3. Testing of AWE systems must occur at all the altitudes at which
they will eventually be allowed to fly commercially. Testing at lower
altitudes will enable us to confirm flying vehicle designs but not
entire system designs enough to confirm commercial feasibility.
4. Cost-effective testing of these designs will require a minimum of
restrictions on marking and lighting. Early test systems will all be
considerably smaller than final commercially viable systems, meaning
the additional weight, drag and electrical generation requirements
imposed by lighting and marking devices on small test systems will
adversely impact testing and development.
5. Final commercially viable systems will generally be larger, better
able to handle the additional weight, drag and electrical generation
requirements of lighting and marking devices.
6. Many AWE systems in development utilize “cross-wind motion”, flying
nearly perpendicular to the wind at high speeds. Such motion across
the wind induces high levels of drag in the tether, a problem many
developers are struggling to overcome. The addition of flags or lights
on the tether would increase tether drag even further, compounding
this problem to the point that many otherwise successful AWE designs
might become completely infeasible.
7. As a group, we AWE developers believe we can find a number of
private land-owners around the country willing to host our flight
testing. These private lands would each have hundreds of acres of
uninhabited land adequate in size to contain our “flight cylinders”,
in windy and remote areas already located in Class-G airspace and
experiencing virtually zero aircraft traffic below 3,000 AGL.
1. Diagram of AWES "Flight Cylinder" and size of footprint depending
on flight angle.
8. If the FAA can designate a specific number of no-fly zones up to
2,000 feet AGL above these private lands, our testing and development
could continue unhindered.
9. In a few years, as AWE developers approach final designs ready for
commercialization and have a better understanding of how the
additional burdens of weight, drag and on-board electrical generation
requirements will impact their systems, further clarification of the
marking and lighting requirements should be made.
10. What we are suggesting is a two-phase approach to the regulation
of AWES. During the testing phase for the next few years, limit us to
specific testing areas we find free of other aviation but reduce our
burden of marking and lighting to an absolute minimum and allow us to
fly in these areas up to 2,000’AGL. After our systems have reached
commercial viability and we have a better understanding or what our
systems can handle, let us all re-visit the issues of marking and
lighting, location and permitting.
Responses to the questions posed by
the FAA regarding AWES.
•General information on a developer’s specific AWES design concept and
plans for operation.
o What type(s) of mechanical devices
are you employing to keep the system aloft?
Highest Wind has arrived at an autogyro design which we believe will
eventually stay aloft in wind speeds as low as eight mph and as high
as eighty mph. Our AWES is of the “ground-gen” type employing a
relatively lightweight flying vehicle (the “glider”) which ascends,
pulling the tether, which spins a generator in the “Energy Trailer” on
the ground. At the end of each ascent, the glider quickly descends
while the tether is reeled in. At some minimum altitude the descent
stops and the ascent cycle starts over again. Ascent/descent cycles
will complete every minute or less, possibly ranging from 500’AGL up
to 2,000’AGL depending on which altitudes have wind speeds of more
than 20mph. On the eventual commercially viable system, each ascent of
the glider will pull the tether with more than a ton of force at a
speed of no less than 20mph producing as much as 100kW of power during
the ascent. Continuous energy output of the system will be some
percent of that maximum – TBD – based on duty cycles, overall system
efficiencies, and wind speeds aloft. We have found a continuous energy
output of 30kWs to be the sweet-spot for our target market of US
farmers.
o What are the physical dimensions
of the device(s) with relation to the above?
Our eventual market-ready system will have a rotor diameter of less
than 50 feet with a small body suspended beneath it no taller than 20
feet. We still have a few years of development and testing before
final dimensions will be available. During those years our testing
will be done on systems no smaller than about a ten foot diameter
weighing about thirty pounds.
o What kind of materials will
comprise this device?
At this point we are unsure if our system will use rotor blades made
of aluminum or some sort of composite material. The internal
structures of the body will be primarily composed of aluminum with
some sort of plastic aero-shell around the body. For the next couple
of years of testing our rotors will continue to be made of wood.
o What are the operational
dimensions (requirement for airspace) for the system?
Our system will fly no lower than about a 30 degree angle above the
horizon. At an elevation of 2,000 feet (our maximum preferred
altitude), depending on wind direction, our flying vehicle could be
anywhere (downwind) within a virtual flight cylinder (see diagram
above) with a radius of 3500 feet (contained within a square space of
1,125 acres). At an elevation of only 1,200 feet (our minimum
preferred), the flight cylinder reduces in size to be contained within
a 405 acre square. We anticipate that further testing will determine
that our angle above the horizon will be considerably higher than 30
degrees, further reducing the ground-space requirement.
o Is there a requirement to
operation more than one device in the air?
Each of our systems will operate independently and will most likely
eventually be purchased in quantities of one by our target buyers in
the US - farmers.
o What are your long-term plans for
this system?
We intend to bring this system to commercialization and sell it in the
US, primarily to farmers in rural areas within Class G airspace.
•Marking and lighting.
o Can you comply with marking and
lighting requirements?
If the marking and lighting requirements to be complied with are those
described in FAA Advisory Circular 70/7460 – 1K, Chapter 11 “Moored
Balloons and Kites”, the answer is “no”. Those marking
requirements are overly burdensome and the lighting requirements would
make our system commercially and technically infeasible. See details
below.
o Can you identify any impacts to
your system when complying with current guidance for marking and
lighting standards?
The current requirement for anti-collision lighting the same as for
towers (L-864 and L-865) will require the development of new lights
meeting those standards which have half the weight, size and energy
requirements of those available today. However, that seems like it
could be possible within the next few years.
The requirement for the same lights on the tether at 350 foot
intervals would make our system commercially infeasible given the
current or future technologies for those lights. We have no easy way
to provide power to those lights along the tether and would face
extreme difficulties with any system to attach or detach those lights
as the tether is reeled in and out. Similarly, the current requirement
for flags every fifty feet on the tether would be very difficult to
achieve.
o What are your plans or how is your
system designed to make the system conspicuous to the flying public?
We are planning to sell our system for use only where there is no
flying public. My pilot training stressed remaining above 3,000 AGL at
all times other than for landings and take-offs. Having toured
agricultural areas in more than forty states, I know virtually zero
aircraft other than the occasional crop duster fly below 2,000 AGL in
class-G airspace more than five miles from any airport. That said, we
plan to provide adequate anti-collision light on the flying vehicle to
make it conspicuous to pilots in all weather conditions.
•Safety to other airspace users and
persons and property on the ground.
o What safety mechanisms or devices
have you designed into the system to ensure all aspects of aviation
safety?
At this point, only anti-collision lights and an on-board alarm
(described below) have been considered for aviation safety. Should the
worst-case situation of a tether-break occur, as with any tethered
flying vehicle, our vehicle will be unstable in un-tethered flight,
settling quickly to the ground.
o What safety mechanisms or devices
have you designed into the system to minimize or mitigate hazards to
persons or property on the ground?
We intend to sell our system only to farmers and other single large
land-holders with primarily uninhabited agricultural land large enough
to contain the entire flight cylinder footprint. That said, in a
worst-case situation of a flying vehicle crash, an on-board alarm will
sound whenever the vehicle descends below some pre-designated
altitude. However, long before an imminent crash, the system is
designed to reel the flying vehicle in at a speed adequate to keep it
aloft and under control to pull it to a safe landing upon its landing
platform.
•Minimized impacts to NAS
facilities.
o What are your plans or how is your
system designed to reduce a large radar cross-section and become less
conspicuous to surveillance systems?
Our eventual flying vehicle ready for commercialization will utilize a
rotor no larger than that of a BlackHawk helicopter with a body below
the rotor less than one quarter the size of the BlackHawk.
o What are your plans or how is your
system designed to reduce impacts to any communication or navigation
systems supporting the NAS?
We anticipate no impacts to communication or navigation systems from a
vehicle no larger than a BlackHawk helicopter.
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