Aeerstatica Energy Airships - Tethered aerostat wind

generator

Peter Lobner, 19 June 2023

1. Introduction

Aeerstatica Energy Airships was founded in 2020 in Ravensburg,

Germany, by brothers
Johannes and David
Gerber after developing for
many years their concept for a tethered aerostat wind generator. The
firm’s website is here: https://www.aeerstatica.de

Aeerstatica’s tethered aerostat wind generator is designed to be

deployed at an altitude of about 300 m (984 ft) above ground level,
where stronger prevailing winds offer more energy for harvesting than
at ground level (Aeerstatica estimates up to eight times more energy).
This gives an airborne generator a potential performance advantage
over wind generators built on the ground.

From the perspectives of land use and environmental impact,

Aeerstatica’s tethered aerostat wind generator requires very little land
development and construction at a deployment site, where an
anchored mooring / winch system and other ground support
equipment will be located. In comparison, conventional wind turbines
require road access for heavy vehicles transporting material for
massive foundations and then assembling the large wind turbine
generator components on site. Both types of wind turbine generators
require similar electrical connectivity to a nearby electric power grid.

Four tethered aerostat wind generators deployed in a rural setting.

Source: Aeerstatica Energy Airships

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 Aeerstatica’s tethered aerostat wind generators face into the wind when
deployed, with the bow and stern rotors rotating in opposite directions.
Source, both graphics: Aeerstatica Energy Airships

I am grateful to Aeerstatica for their thoughtful input for article.

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2. Tethered aerostat wind generator patent

The basic design and operational characteristics of the Aeerstatica

airborne wind generator are presented in German patent
DE102020120769B3, which was granted in September 2021, and
World Intellectual Property Organization (WIPO) document
WO2022/028802A1, which was published on 10 February 2022.

Legend: The airborne tethered wind generator (1) is comprised of a buoyant body (2) with a
suitable outer skin to retain the lifting gas (3). The shape of the buoyant body is established by a
rigid helical structure (4, 5, 6) terminating at hubs (9, 10) at the bow and stern, which support and
house the bearings for rotors (7, 8). The rotors rotate perpendicular to the longitudinal axis, in
opposite directions, and mechanically drive one or more generators to produce electricity that is
delivered to an anchored ground station via an electrical cable attached to the tether (11).

General arrangement of Aeerstatica’s tethered aerostat wind generator.

Source: DE102020120769B3

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The patent notes, “…the buoyant body can have a cigar shape or
have the characteristic shape of airships. This shape offers the
advantage that the buoyancy body can align itself more defined in the
air flow. A corresponding streamline shape can ensure advantageous
aerodynamics so that the rotors are illuminated by the air flow as
effectively as possible.” In Aeerstatica’s 2022 concept artwork, the
airborne wind generator is shown with conventional cruciform tail fins,
which are not addressed in the patent. The addition of the tail fins
provides a stronger turning moment to help keep the streamlined
buoyant body pointing into a fluctuating air stream.

The exterior shape of the buoyant body is established by a rigid

helical exoskeleton installed over transverse ribs. The helical
exoskeleton is comprised of at least two helical substructures that are
wound in opposite directions. This design feature enables the rigid
hull to better absorb the torque loads transmitted into the hull by the
large rotors that are rotating in opposite directions at each end of the
hull.

The lifting gas is stored in several lifting gas cells within the buoyant
body. The patent notes, “…this has the advantage that there is still a
buoyancy force if, for example, one of the lifting gas cells leaks and
gas escapes from it.”

Patent DE102020120769B3 does not address deployment and

recovery of the airborne wind generator.

3. Concept of operation

Lifting gas

Aeerstatica plans to operate their unmanned tethered aerostat wind

generators initially with helium lifting gas. However, as a long term
goal, Aeerstatica envisions using hydrogen as the lifting gas for their
large production aerostat wind generators, taking advantage of the
greater lift and the lower costs of hydrogen, particularly as hydrogen
becomes more widely available for use in transportation systems.
The unmanned nature of the tethered aerostat should help alleviate
most safety concerns about the use of hydrogen.

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The lifting gas cells in Aeerstatica’s rigid aerostat are at atmospheric
pressure. This will result in a lower lifting gas leak rate than a
conventional, non-rigid aerostat that operates at a slight
superpressure, and typically requires regular additions of lifting gas to
make up for leakage. Aeerstatica is evaluating options for
replenishing lifting gas when needed, but without hauling the aerostat
down to a mooring on the ground.

Safety systems to contain an aerostat that slipped its mooring will be

provided. This will include an emergency lifting gas vent system.

Deployment to, and retrieval from, a remote site

Aeerstatica is developing means for deploying an aerostat to a new

site, connecting to installed ground systems, and commencing
operation as a power generator.

One option being considered is to tow the aerostat to the remote site
with a helicopter or drone, lower a tether and connect to the anchored
ground station, and then disconnect from the tow vehicle. During the
tow, the aerostat’s buoyancy would be reduced to near neutrally
buoyancy, as opposed to its highly buoyant state while operating as a
power generator.

Applying this process in reverse, an aerostat could be removed from

one site and delivered to another site (i.e., for reassignment, for
maintenance that can’t be performed onsite, or for decommissioning).

Ground station

Like other large tethered aerostat systems, Aeerstatica’s tethered

aerostat wind generator is connected to ground via an anchored
ground station that performs a variety of functions, including:

• The ground station is the interface between the aerostat wind

generator and a local substation that connects to the electric
power grid.
• The winch on the ground station can adjust the length of the
tether, and thereby optimize the aerostat’s operating altitude
based on wind conditions.

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 • In normal operation, the tether will operate with a relatively high
tension because the aerostat will be trimmed for high aerostatic
buoyancy and the large diameter rotors create significant
aerodynamic drag. These forces are countered by the tension
in the tether.
• The ground station has real-time monitoring and control
systems for aerostat lifting gas, air and electric power systems.

In-service inspections and maintenance

Aeerstatica is evaluating several alternatives for performing periodic

maintenance and inspections aboard a deployed aerostat. Onsite
servicing options include crew delivery via a cable car that climbs the
mooring cable to the aerostat, or a helicopter shuttle that lands the
crew on the deployed aerostat. Alternatively, the aerostat could be
disconnected from its ground station and transferred by air to a
remote servicing point.

Contingency landing

The aerostat, tether and ground station will be designed to enable the
aerostat to ride out high winds aloft, and thereby avoid ground-level
buffeting while moored during a storm. If needed, the winch system
at the ground station will be able to haul in the aerostat for an
automated contingency landing at the deployment site. In classical
rigid airship fashion, a mooring mast would be used. To accomplish
this, the rotors would have to be moved in position to allow clearance
for landing (i.e., so as not to “pin” the airship into the ground with a
downward pointing rotor blade). Space considerations on the ground
for emergency landing will establish distances between ground
stations.

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4. The Aeerstatica industrial team

Aeerstatica’s tethered aerostat wind generator is a scalable design

that has the potential for widespread on-shore deployment, including
areas where large, modern terrestrial wind turbine generators can’t
be installed (i.e., due to limited transportation access, sensitive
environmental area, etc.).

In a 21 March 2022 press release, the firm announced: “Aeerstatica,

Ballonbau Wörner, FormTL and PTS have joined into a strategic
partnership to build a prototype of a new, highly economic and
efficient wind power generation system. The companies aim to make
available renewable energy cheaply and around the clock, to help
keep the environment safe and healthy and to reduce the
dependency on fossil fuels.” The team members have the following
roles in the strategic partnership:

• Aeerstatica UG (Haftungsbeschränkt) is aiming to support the

energy transitions through building and operating aerial power
generation.
• Ballonbau Wörner GmbH from Augsburg is an innovator for
technical textiles in Aeronautics in the design and manufacture
of gas cells and envelopes for aerostats. Their website is here:
https://www.ballonbau.de
• FormTL ingenieure für tragwerk und leichtbau Gmbh, of
Radolfzell near lake Constance, have experience with
simulation for loads and structural design. Their website is here:
https://www.form-tl.de
• PTS Maschinenbau GmbH of Dillingen on the Danube has
extensive lightweight structure experience. Their website is
here: https://www.ptsmaschinenbau.de

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5. Development schedule

Aeerstatica has demonstrated the basic mechanical and electrical

operating principles of their tethered aerostat wind generator with a
sub-scale, non-buoyant model.

Subscale proof-of-principle demonstrator. Source: Screenshot from

Aeerstatica Energy Airships video (2 March 2023).

The first flight of a buoyant prototype tethered aerostat wind

generator originally was planned for summer 2022 at the
Innovationspark in Augsburg, Germany. That date has slipped into
2023.

The flying prototype has an important role in validating the design and
expected performance of the tethered aerostat wind generator and
helping to establish operating and maintenance practices to ensure
high availability and long operating life.

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6. For more information

• “Strategic Partnership to build a prototype,” Aeerstatica, 21

March 2022: https://www.aeerstatica.de/20220321_PMv3.pdf
• Dr. Katja Reisswig, “Airship to Use High Winds to Generate
Wind Electricity,” technewable, 24 May 2022:
o Original article in German:
https://technewable.com/luftschiff-zur-erzeugung-von-
windstrom/
o Article translated to English: https://lynceans.org/wp-
content/uploads/2022/12/a6625e6bc9f4e7fc34b71588d00
3b61f.pdf

Patents

• DE102020120769B3, “Device for using wind energy,”

Inventors: David Gerber & Johannes Gerber, Filed 6 August
2020, Granted 23 September 2021, Assigned to Aeerstatica Ug
Haftungsbeschraenkt:
https://patents.google.com/patent/DE102020120769B3/en
• WO2022/028802A1, “Device for using wind energy,” Filed 7
July 2021, Published 10 February 2022:
https://patents.google.com/patent/WO2022028802A1/en

Other Modern Airships articles

• Modern Airships - Part 1: https://lynceans.org/all-

posts/modern-airships-part-1/
• Modern Airships - Part 2: https://lynceans.org/all-
posts/modern-airships-part-2/
o AirbineTM
o Altaeros - BAT
o LTA Windpower - PowerShip
o Magenn - MARS
• Modern Airships - Part 3: https://lynceans.org/all-
posts/modern-airships-part-3/

Modern Airships 9