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Fundamentals of Airborne Wind Energy Systems
Antonello Cherubini
PERCRO Robotics Laboratory,
Via alamanni 13b, Ghezzano, Pisa
December 2017
Universidad Carlos III de Madrid
15 December, 2017 Antonello Cherubini 2
About me
Antonello Cherubini ( www.antonellocherubini.com )
5 years experience in Wind DronesMechanical engineer
Work Experience in AWE
• 2013-2017 PhD in wind drones at Sant’Anna Pisa, the finest technical university in Italy
• 2012-2013 Mechanical engineer at Kitegen Research, Italian airborne wind energy company
Publications in AWE
• A. Cherubini, G. Moretti, M. Fontana, “Sistema aereo di captazione eolica d’alta quota per generatoreeolico”, patent application
• ‘Airborne Wind Energy Systems: A review of the technologies’, 2015First google result after wikipedia typing ‘airborne wind energy’
• ‘Simplified model of offshore airborne wind energy converters’, 2015
• ‘Dynamic modeling of floating offshore airborne wind energy converters’, 2016, accepted
• ‘Puleggia perfezionata per verricello ad alta efficienza’, patent application ITTO20130365, 2013
Program• Energy and Renewable Energies, the current scenario
• Introduction to Airborne Wind Energy (AWE)
• Basic power rating of Airborne Wind Energy Systems (AWES)
• AWES classifications and examples
• Tether sag shape and angle of attack control
• Power curve of AWES
• Betz limit does not exist in AWES
• Iterative solvers for AWES
• Momentum conservation in fly-gen AWES
Energy and Renewables Where are we?
15 December, 2017 Antonello Cherubini 5
Energy is vital
• Everything is energy: food, houses, medical drugs, clothes
• Italy produces between 50 and 60% of its own wheat*,to move it we need energy
• Countries who do not have access to abundant energy are third world countries
* Source: http://www.ilfattoquotidiano.it/2016/07/11/produzione-grano-agricoltori-contro-industriali-si-accollino-perdite-stop-
ai-prezzi-da-discount-a-causa-dellimport/2891657/
Examples:
15 December, 2017 Antonello Cherubini 6
31% production of inorganic fertilizers
19% production/use of machinery
16% transport of food
13% irrigations (pumps etc.)
8% stock farming (feeding excluded)
5% drying
5% production of pesticides
3% other consumptions
FOSSIL FUELS
91%
SUN 9%
Embodied energy
Sources: graphical representation by Marcello Corongiu, data from:
D.JC. MACKAY, Without the hot air, Cambridge University, 2000
D. COOLEY E. GOODLIFFE – J. MACDIARMIK - Embodied energy of food, Exeter University, 1998
15 December, 2017 Antonello Cherubini 7
Effects of energy availability: +250% productivity in agriculture
Graphical representation by Marcello Corongiu
15 December, 2017 Antonello Cherubini 8
Effects of energy availability: urbanization
Graphical representation by Marcello Corongiu
15 December, 2017 Antonello Cherubini 9
Effects of energy availability: transport
Graphical representation by Marcello Corongiu
15 December, 2017 Antonello Cherubini 10
Effects of energy availability: welfare (late 19th century)
Graphical representation by Marcello Corongiu
Health
care
Free
time
Pensions
Social
mobility
15 December, 2017 Antonello Cherubini 11
Effects of energy availability: population growth
Picture from Wikipedia https://en.wikipedia.org/wiki/World_population#/media/File:Population_curve.svg
15 December, 2017 Antonello Cherubini 12
The largest market in the world
9 of the top 12 companies with the largest revenue are in the energy market.
Energy is a multi trillion dollar market
Graphical representation by Daidalos Capital. Data source Fortune 500.
Avg. per-capita consumption, Italy 2014*
Non electrical Electrical
15 December, 2017 Antonello Cherubini 13
Primary energy vs electrical energy
Primary Energy: includes all energy
consumptions (e.g. petrol, gas, electricity..)
* Source: statistiche Terna 2014 http://download.terna.it/terna/0000/0607/85.PDF
** Source: statistiche Ministero Sviluppo Economico 2014:
http://dgsaie.mise.gov.it/dgerm/downloads/situazione_energetica_nazionale_2014_v4_con_allegati.pdf
Electrical
580 W
(16%)
(non electrical)
3020 W
(84%)
Electrical energy: it is a fraction of primary
energy
Primary
3600 W
15 December, 2017 Antonello Cherubini 14
Sources of energy (primary)
Sources of primary energy in Italy 2015*
Natural Gas OilCoal and solid fuels Electricity from other renewablesHeat from renewables Electricity from solar and wind
Natural gas
720 TWh
Oil
688 TWh
Electricity from renewables
(excluding solar and wind) 69 TWh
Heat from renewables
123.2 TWh
Coal and solid fuels
168.5 TWh
Solar 1.2 % (22,9 TWh)
Wind 0.8% (14,9 TWh)
* Fonte: statistiche Ministero Sviluppo Economico 2015:
http://dgsaie.mise.gov.it/dgerm/downloads/situazione_energetica_nazionale_2015.pdf
15 December, 2017 Antonello Cherubini 15
The problem with NON renewables
1. They won’t last
2. Global warming
“..even if by a magic wand we could stop all emissions overnight, the average temperature of Earth would continue to rise or stay at current levels for several hundred years.” [1,2]
[1] Solomon S, Plattner G K, Knutti R, Friedlingstein P. Irreversible climate change due to carbon dioxide emissions.
Proceeding of the National Academy of Sciences 2009; 106(6): 1704–9.
[2] Tingzhen Ming, Renaudde Richter, WeiLiu, Sylvain Caillol, Fighting global warming by climate engineering: Is the Earth
radiation management and the solar radiation management any option for fighting climate change?, Renewable and
Sustainable Energy Reviews, 31 (2014) 792–834
* Pictures from: NASA http://www.giss.nasa.gov/research/news/20150116/ , http://climate.nasa.gov/evidence/
15 December, 2017 Antonello Cherubini 16
The problem with NON renewables
Picture from: https://oilandgasleaks.wordpress.com/2011/12/03/the-gulf-of-mexico-is-dying/
28000 abandoned wells in the Gulf of Mexico
15 December, 2017 Antonello Cherubini 17
The problem with renewables
1. Expensive*
(example 300 €/MWh photovoltaic, roughly 4 times higher than coal or gas)
2. Intermittent
(We can’t fully manage renewables, they just happen to be there when they want)
* Hydro power is the only exception, no surprise that it is historically well exploited
15 December, 2017 Antonello Cherubini 18
Grid balancing
* Source: Terna daily data, 3 sept 2016 https://www.terna.it/it-it/sistemaelettrico/dispacciamento/datiesercizio/datigiornalieri.aspx
Today we do not store energy, it costs too much.
This is a sample daily electricity demand/offer, Italian grid, 2016 (forecasts in green, real data in red)
15 December, 2017 Antonello Cherubini 19
Sad truth
When you here something like “grid parity has been reached by renewable energy project x in location y”, be happy but remember that:
- renewables are usually given priority over fossil fuels
- electricity is only 16% of the energy problem
15 December, 2017 Antonello Cherubini 20
So what?
• Assume (desperately hope) that some geniuses (or wise politicians) create a cheap and high-density storage solution (Public investments in supercapacitors? Synthetic fuels?)
• Assume (desperately hope) that some geniuses (or wise politicians) bring down the cost of renewables (Airborne Wind Energy? Stabilized Perovskites solar panels?)
OR
• Get ready for the worst times of modern history since WW2
15 December, 2017 Antonello Cherubini 21
Some good news
• Global PV industry is now a net energy provider (it produces more energy than it consumes) and by 2020 it will likely have completed its energy payback time [1]
[1] M. Dale, S. M. Benson, “Energy Balance of the Global Photovoltaic (PV) Industry - Is the PV Industry a Net Electricity Producer?” Environ. Sci. Technol., 2013, 47 (7), pp 3482–3489
15 December, 2017 Antonello Cherubini 22
Some good news
• Laboratory efficiency of solar cells keeps growing [1]
[1] Data: Solar Cell Efficiency Tables (Versions 1-50), Progress in Photovoltaics: Research and Applications, 1993-2017. Graph: Fraunhofer ISE 2017 https://www.ise.fraunhofer.de/content/dam/ise/de/documents/publications/studies/Photovoltaics-Report.pdf
15 December, 2017 Antonello Cherubini 23
Some good news
• Some offshore wind farms in Northern Europe reached grid parity with prices as low as 50€/MWh [1]
(typical LCOE for offshore wind is around 130€/MWh)
[1] McKinsey Report 2017 https://www.mckinsey.com/business-functions/sustainability-and-resource-productivity/our-insights/winds-of-change-why-offshore-wind-might-be-the-next-big-thing
15 December, 2017 Antonello Cherubini 24
So what?
OK!!! Let’s be optimistic! Someone will create the
technological system to make us all happy, what next?
15 December, 2017 Antonello Cherubini 25
We need 16TW, from where do we take them?
Elaborated from: S.M. Benson - F.M. Orr, Sustainability and energy conversions, MRS Bulletin, Apr 2008, Marcello Corongiu
15 December, 2017 Antonello Cherubini 26
Physical limitations: how much solar surface do we need?
* Assuming total solar irradiance
of 1500 kWh/m2/year and total
efficiency of 10%. Each square is
45 km wide
To satisfy electricity
demand
(34 m^2 per capita)*
To satisfy non electrical
primary consumption
(211 m^2 per capita)*
Each of us needs 245 m^2 (approx, slightly pessimistic)
15 December, 2017 Antonello Cherubini 27
How much solar surface do we need?
Each of us needs 245 m^2 (approx.)
Countryside example: Marta (my hometown) needs to cover 2.5% of its surface
(3440 people in 33 km^2)
Big city example: Milan would need to be 83% bigger and be 100% covered by panels
(1 360 000 people in 181 km^2)
15 December, 2017 Antonello Cherubini 28
Physical limitations: how many wind mills do we need?
We need a wind turbine each 55 people (approx.)
Italy needs 1 090 000 wind turbines*
* Assuming all wind turbines are
2MW size and operate at 10%
total efficiency
15 December, 2017 Antonello Cherubini 29
How much solar surface do we need?
Countryside example: Marta (my hometown) needs 62 windmills
(3440 people in 33 km^2)
Big city example: Milan would need 24500 windmills
(1 360 000 people in 181 km^2)
We need a wind turbine each 55 people (approx.)
15 December, 2017 Antonello Cherubini 30
Offshore would be nice but it’s even more expensive
Will it happen?
High altitude wind energy
15 December, 2017 Antonello Cherubini 32
Wind Power Density
𝑊𝑃𝐷 =1
2𝜌 𝑉3
[ W/ m 2]
15 December, 2017 Antonello Cherubini 33
High altitude winds, way more power, everywhere
15 December, 2017 Antonello Cherubini 34
High altitude winds, way more power, everywhere
15 December, 2017 Antonello Cherubini 35
High altitude winds, way more power, everywhere
15 December, 2017 Antonello Cherubini 36
High altitude winds, everywhere
Picture from: Cristina L. Archer; Ken Caldeira. Global Assessment of High-Altitude Wind Power. Energies, v 2, n 2, p 307-319, June 2009. See
also Atlas of high altitude wind power http://homes.esat.kuleuven.be/~highwind/wp-content/uploads/2011/07/atlas_of_airborne_wind_energy.pdf
Green regions at
10,000 m feature
more than
5kW/m^2 for
more than
50% of the time
15 December, 2017 Antonello Cherubini 37
High altitude winds, way more power, everywhere
Picture from: Antonello Cherubini, “Advances in Airborne Wind Energy and Wind Drones”, PhD Thesis, Sant’Anna University of
Pisa, 2017
15 December, 2017 Antonello Cherubini 38
High altitude winds, higher availability
Pictures from: Ragusa Salvatore Marco. Valutazioni energetiche dell'eolico d'alta quota: Kitegen. Politecnico di Torino, Bachelor
Thesis, 2007.
15 December, 2017 Antonello Cherubini 39
Please be elegant
Picture from a company website, company not stated on purpose
Do not use average
Use percentile instead
15 December, 2017 Antonello Cherubini 40
Low altitude winds, smooth?
Picture from: Antonello Cherubini, based on http://blog.ucsusa.org/john-rogers/climbing-on-top-of-a-wind-turbine
Did you know that large scale conventional wind turbines capture a wind stream that flows in different directions?
Up to 60 degrees angular difference from the top to the bottom
15 December, 2017 Antonello Cherubini 41
High altitude winds, smooth?
Picture from: antonellocherubini.com AWE Blog
Where is AWE?
15 December, 2017 Antonello Cherubini 43
Some investors in wind drones
Graphical representation by Daidalos Capital.
15 December, 2017 Antonello Cherubini 44
Where is AWE?
Picture from: http://www.starnetllc.net/valley-of-death/
AWESales
start
15 December, 2017 Antonello Cherubini 45
Technology development
Pictures from: Delabole wind farm, UK http://130.226.56.150/site_background_information.php?site_code=delaboleAirborne Wind Energy book 2013, U. Ahrens, M. Diehl, R. Schmehl Eds. Damon vander Lind, «Analysis and Flight Test Validation of High Performance Airborne Wind Turbines» Chapter 28
Wind farm 4 MW 10 turbine VESTAS WD34 400 kW
Makani 20 kW prototype, 2013
15 December, 2017 Antonello Cherubini 46
Wind drones vs wind turbines: lower size, lower cost
Wind drone (left) vs a conventional
wind turbine (right) with the same
power output.
Impression from Ampyx Power
15 December, 2017 Antonello Cherubini 47
Where is AWE?
Picture from: Antonello Cherubini, “Advances in Airborne Wind Energy and Wind Drones”, PhD Thesis, Sant’Anna University of
Pisa, 2017
15 December, 2017 Antonello Cherubini 48
Where is AWE?
Picture from: Antonello Cherubini, “Advances in Airborne Wind Energy and Wind Drones”, PhD Thesis, Sant’Anna University of
Pisa, 2017
15 December, 2017 Antonello Cherubini 49
Where is AWE?
Picture from: Prof. Roland Schmehl
How does it work?
15 December, 2017 Antonello Cherubini 51
Crosswind flight
Example: Leading Edge Inflatable (LEI) kite
Picture in public domain.
Wind window (wind going inward)
15 December, 2017 Antonello Cherubini 52
Crosswind flight
15 December, 2017 Antonello Cherubini 53
Ground-gen vs fly-gen
Picture from: Antonello Cherubini, Andrea Papini, Rocco Vertechy, Marco Fontana, “Airborne Wind Energy Systems,
a review of the technologies”, Renewable and sustainable energy reviews, 2015 51, 1461-1476
Example of Ground-Gen (a) and Fly-Gen (b) AWESs.
Picture from: Ampyx Power website, 2015. http://www.ampyxpower.com/our-technology/technology-concept/
15 December, 2017 Antonello Cherubini 54
Ground-gen pumping cycle
Modified version of picture by R. Paelinck from: Moritz Diehl “Airborne Wind Energy: Basic Concepts and Physical
Foundations”, “Airborne Wind Energy” book, 2013.
15 December, 2017 Antonello Cherubini 55
Single wind drone - fly-gen
Fly-gen continuous operation
15 December, 2017 Antonello Cherubini 56
Single wind drone - flygen
Video from: Makani Power Website.
http://www.google.com/makani/solution/
Constant
cable length
15 December, 2017 Antonello Cherubini 57
Ground-gen vs Fly-gen
Ground-gen Fly-gen
Simpler, easier testing and development
More complex, slowerdevelopment
Duty cycle efficiency Continuous operations
Gravity affects power output and cut-in
Gravity affects mainly cut-in
Takeoff: needs motors or other features
Takeoff ok, built-in
15 December, 2017 Antonello Cherubini 58
Math time
Theoretical optimal power output, Loyd 1980
Hypotheses:
- Steady state flight
- E > 10
- Power zone flight
WPDAerodynamic
parameters
Wing area
15 December, 2017 Antonello Cherubini 59
Basic power rating
• Start from Loyd’s model
• Add cable drag
• Add elevation angle cosine
Picture from: Antonello Cherubini, Andrea Papini, Rocco Vertechy, Marco Fontana, Airborne Wind Energy Systems, a review of
the technologies, 2015
State of the art
15 December, 2017 Antonello Cherubini 61
AWES Taxonomy (1)
Picture updated from: Antonello Cherubini, Andrea Papini, Rocco Vertechy, Marco Fontana, “Airborne Wind Energy
Systems, a review of the technologies”, Renewable and sustainable energy reviews, 2015 51, 1461-1476
Pictures from: Companies’ websites and web
15 December, 2017 Antonello Cherubini 62
AWES Taxonomy (2) - drones
Makani Power
Fly-gen drone
Kitemill
Ground-gen with
takeoff motors
Skypull
Biplane
TwingTech
Ground-gen with
takeoff motors
Sant’Anna Pisa
Multi drone
system
Ampyx Power
tethered glider
Pictures from: Companies’ websites
15 December, 2017 Antonello Cherubini 63
AWES Taxonomy (2) - kites
Kitegen
2 lines
semirigid kite
NTS Energy
4 line kite on rail
Kitenergy
2 lines kite
Skysails power
1 line kite with
control pod
Skysails marine
1 line kite
with control pod
Swiss Kite
Power
3 lines kite
TU Delft
Soft kite with
control pod
15 December, 2017 Antonello Cherubini 64
AWES
Pictures from: Antonello Cherubini, Andrea Papini, Rocco Vertechy, Marco Fontana, “Airborne Wind Energy Systems,
a review of the technologies”, Renewable and sustainable energy reviews, 2015 51, 1461-1476
Ground-gen drone with takeoff motors
15 December, 2017 Antonello Cherubini 65
Sailplane
Pictures from: Antonello Cherubini, Andrea Papini, Rocco Vertechy, Marco Fontana, “Airborne Wind Energy Systems,
a review of the technologies”, Renewable and sustainable energy reviews, 2015 51, 1461-1476
Ground-gen drone with takeoff motors
15 December, 2017 Antonello Cherubini 66
Ampyx Power
Picture from: AWEC 2017, Freiburg, book of abstracts
• Ground-gen
• Sailplane as kite
• Onboard control and batteries
15 December, 2017 Antonello Cherubini 67
Ampyx Power – winch takeoff and autonomous crosswind
Video from: https://www.youtube.com/watch?v=oP8t4zHFxD0&t=2099s Ampyx Power 50 minutes fully automatic flight
15 December, 2017 Antonello Cherubini 68
Ampyx Power – landing without tether
Video from: https://www.youtube.com/watch?v=oP8t4zHFxD0&t=2099s Ampyx Power 50 minutes fully automatic flight
15 December, 2017 Antonello Cherubini 69
Ampyx Power
Picture from: AWEC 2017, Freiburg, book of abstracts
15 December, 2017 Antonello Cherubini 70
Scalability of onboard batteries
• As size grows, batteries become THE payload
Storage material Energy type Specific energy(MJ/kg)
Deuterium-Helium-3 (in Fusion reactor)
Nuclear fusion 384,000,000[2]
Uranium (in breeder) Nuclear fission 80,620,000[3]
Hydrogen (compressed at 700 bar)
Chemical 142
Methane or natural gas Chemical 55.5
Diesel Chemical 48
Gasoline (petrol) Chemical 46.4
Table from Wikipedia https://en.wikipedia.org/wiki/Energy_density
15 December, 2017 Antonello Cherubini 71
Scalability of onboard batteries
• As size grows, batteries become THE payload
Storage material Energy type Specific energy(MJ/kg)
Gasoline (petrol) Chemical 46.4
Coal, bituminous Chemical 24-35
Methanol fuel (M100) Chemical 19.7
Carbohydrates Chemical 17
Lithium metal battery Electrochemical 1.8
Lithium-ion battery Electrochemical 0.36[7]–0.875[8]
Flywheel Mechanical .36 – .5
Alkaline battery Electrochemical 0.5[9]
Lead-acid battery Electrochemical 0.17
Supercapacitor (EDLC)Electrical (electrostatic)
0.01-0.036[10][11][12][13][14][15]
Table from Wikipedia https://en.wikipedia.org/wiki/Energy_density
15 December, 2017 Antonello Cherubini 72
Scalability of onboard batteries
• Modern batteries have a density 50-100 times lower than
petrol
• As size grows, batteries become THE payload
• For example a commercial plane powered by batteries would
have a flight range of approx. 500km [1] instead of 6000km
[1] http://finanza.lastampa.it/News/2017/04/19/laereo-di-linea-di-wright-electric-e-un-sogno-ma-davvero-lontano-nel-
tempo/MTc5XzIwMTctMDQtMTlfVExC
15 December, 2017 Antonello Cherubini 73
Scalability of onboard batteries
15 December, 2017 Antonello Cherubini 74
Platform takeoff (with propeller)
Video courtesy of Pasquale Adobbato, Pisa, 2017
15 December, 2017 Antonello Cherubini 75
Platform takeoff (with propeller and tether)
Picture from: Prof. Lorenzo Fagiano, AWEC 2017, Freiburg, book of abstracts
15 December, 2017 Antonello Cherubini 76
Video from: Prof. Lorenzo Fagiano, https://www.youtube.com/watch?v=UPiTiHPXciE
Platform takeoff (with propeller and tether)
15 December, 2017 Antonello Cherubini 77
LEI kites
Pictures from: Antonello Cherubini, Andrea Papini, Rocco Vertechy, Marco Fontana, “Airborne Wind Energy Systems,
a review of the technologies”, Renewable and sustainable energy reviews, 2015 51, 1461-1476
Ground-gen drone with takeoff motors
15 December, 2017 Antonello Cherubini 78
TU Delft 20 kW
Pictures from: Uwe Fechner, Roland Schmehl “Model-Based Efficiency Analysis of Wind Power
Conversion by a Pumping Kite Power System”; Rolf van der Vlugt, Johannes Peschel, Roland Schmehl “Design and
Experimental Characterization of a Pumping Kite Power System”, “Airborne Wind Energy” book, 2013.
20 kW peak power output
4 kW average electrical output
• Ground-gen
• LEI kite
• 1 line and Airborne control
pod
15 December, 2017 Antonello Cherubini 79
TU Delft 20 kW
Picture from: Uwe Fechner, Roland Schmehl “Efficiency Analysis of Wind Power Conversion by a Pumping Kite
Power System”; “Airborne Wind Energy” book, Chapter 14, 2013
Efficiencies of the TU Delft demonstrator, simulated at different wind speeds
Product of the first two
Time spent to reel in
Motor and generator
Can be increased
to 50 or 60%
Negative reel in energy
15 December, 2017 Antonello Cherubini 80
TU Delft 100 kW
Picture from: AWEC 2017, Freiburg, book of abstracts
15 December, 2017 Antonello Cherubini 81
Kite Power Systems
Picture from: AWEC 2017, Freiburg, book of abstracts
• Ground-gen
• Ram air kite
• Airborne control pod
• 5 M£ recent investment
• Little information available
15 December, 2017 Antonello Cherubini 82
Other kite systems
Pictures from: Lorenzo Fagiano, Trevor Marksx “Design of a small-scale prototype for research in airborne wind
energy” 2013
Lorenzo Fagiano at UC Santa Barbara
4 consecutive hours of autonomous figure-8 flight
• 3 lines kite
• No control pod
• 2 Angular sensors
• Similar to UC3M
student’s project
15 December, 2017 Antonello Cherubini 83
Ram air kites
Pictures from: Antonello Cherubini, Andrea Papini, Rocco Vertechy, Marco Fontana, “Airborne Wind Energy Systems,
a review of the technologies”, Renewable and sustainable energy reviews, 2015 51, 1461-1476
Ground-gen drone with takeoff motors
15 December, 2017 Antonello Cherubini 84
Skysails
Picture from: Skysails
http://www.skysails.info/english/media/
150 m2
• Ground-gen
• Ram air kite
• Airborne control pod
15 December, 2017 Antonello Cherubini 85
Skysails
Video from: Skysails: MS "BBC SkySails"
http://www.skysails.info/english/media/footage/
15 December, 2017 Antonello Cherubini 86
Skysails
Picture from: AWEC 2017, Freiburg, book of abstracts
15 December, 2017 Antonello Cherubini 87
Skysails power
Pictures from:
AWEC 2017, Freiburg, book of abstracts
http://www.skysails.info
• Ground-gen
• Ram air kite
• Airborne control pod (500W typical power consumption)
15 December, 2017 Antonello Cherubini 88
Cable shape - math time
15 December, 2017 Antonello Cherubini 89
Cable shape – polynomial curvature
Picture from: http://www.kitepowersystems.com/markets/onshore-kite-power/
15 December, 2017 Antonello Cherubini 90
Cable shape – polynomial curvature
Picture from: Makani Website
15 December, 2017 Antonello Cherubini 91
Cable shape – math time
15 December, 2017 Antonello Cherubini 92
Angle of attack control - math time
15 December, 2017 Antonello Cherubini 93
Why a control pod
• Makani’s example of angle of attack time history [1]
[1] Airborne Wind Energy book 2013, U. Ahrens, M. Diehl, R. Schmehl Eds. Damon vander Lind, «Analysis and
Flight Test Validation of High Performance Airborne Wind Turbines» Chapter 28
[2] Airborne Wind Energy book 2013, U. Ahrens, M. Diehl, R. Schmehl Eds. Richard Ruiterkamp and Soren
Sieberling, «Description and Preliminary Test Results of a Six Degrees of Freedom RigidWing Pumping
System» Chapter 26
• Ampyx’s example of angle of attack time history [2]
+ 1°
+ 3°
15 December, 2017 Antonello Cherubini 94
Plane with fabric wing (?)
• Why a fabric-wing plane doesn’t exist?
• Or doesn’t it?
Video from https://www.youtube.com/watch?v=ZEss6sWw6EY
15 December, 2017 Antonello Cherubini 95
Swept rigid wing
Pictures from: Antonello Cherubini, Andrea Papini, Rocco Vertechy, Marco Fontana, “Airborne Wind Energy Systems,
a review of the technologies”, Renewable and sustainable energy reviews, 2015 51, 1461-1476
Ground-gen drone with takeoff motors
15 December, 2017 Antonello Cherubini 96
Swept rigid wing
Picture from: AWEC 2017, Freiburg, https://www.tudelft.nl/en/2017/lr/awec-conference-tailwind-for-airborne-wind-energy/
Enerkite
15 December, 2017 Antonello Cherubini 97
Rotary takeoff system
Picture from: Enerkite https://www.youtube.com/watch?v=6cb9Pxf9Xro
Enerkite
15 December, 2017 Antonello Cherubini 98
Semirigid kite
Pictures from: Antonello Cherubini, Andrea Papini, Rocco Vertechy, Marco Fontana, “Airborne Wind Energy Systems,
a review of the technologies”, Renewable and sustainable energy reviews, 2015 51, 1461-1476
Ground-gen drone with takeoff motors
15 December, 2017 Antonello Cherubini 99
Semirigid kite
Picture from: http://kitegen.com/2014/08/29/la-prima-power-wing/
15 December, 2017 Antonello Cherubini 100
Semirigid kite
Picture from: Kitegen on indiegogo
15 December, 2017 Antonello Cherubini 101
Ground-gen drone with takeoff motors
Pictures from: Antonello Cherubini, Andrea Papini, Rocco Vertechy, Marco Fontana, “Airborne Wind Energy Systems,
a review of the technologies”, Renewable and sustainable energy reviews, 2015 51, 1461-1476
Ground-gen drone with takeoff motors
15 December, 2017 Antonello Cherubini 102
Picture from: AWEC 2017, Freiburg, book of abstracts
Kitemill
Ground-gen drone with takeoff motors
15 December, 2017 Antonello Cherubini 103
Pictures from: AWEC 2017, Freiburg, book of abstracts
Twingtec
Ground-gen drone with takeoff motors
15 December, 2017 Antonello Cherubini 104
Biplanes
Pictures from: Antonello Cherubini, Andrea Papini, Rocco Vertechy, Marco Fontana, “Airborne Wind Energy Systems,
a review of the technologies”, Renewable and sustainable energy reviews, 2015 51, 1461-1476
Ground-gen drone with takeoff motors
15 December, 2017 Antonello Cherubini 105
Biplanes
Pictures from:
Wikipedia biplane, Adrian Pingstone
Florian Bauer, AWEC 2017, Freiburg, book of abstracts
15 December, 2017 Antonello Cherubini 106
Joby Energy
Pictures from: Joby Energy, http://www.jobyenergy.com/tech/visit
• Fly-gen biplane
• VTOL
15 December, 2017 Antonello Cherubini 107
Skypull
Pictures from: skypull.com
AWEC 2017, Freiburg, book of abstracts
https://www.startups.ch/it/blog/skypull-la-startup-ticinese-dellenergia-eolica-ad-alta-quota/
• Ground-gen biplane
• Onboard motors for takeoff
• Low aspect ratio
15 December, 2017 Antonello Cherubini 108
Flygen drone
Pictures from: Antonello Cherubini, Andrea Papini, Rocco Vertechy, Marco Fontana, “Airborne Wind Energy Systems,
a review of the technologies”, Renewable and sustainable energy reviews, 2015 51, 1461-1476
Ground-gen drone with takeoff motors
15 December, 2017 Antonello Cherubini 109
Flygen drone - Makani
Picture from: http://berc.berkeley.edu/berc-visits-makani-power/
• Onboard turbines
• High voltage tether
15 December, 2017 Antonello Cherubini 110
Makani Wing 7
[1] Makani’s Response to the Federal Aviation Authority -
Docket No.: FAA-2011-1279; Notice No. 11-07
http://www.energykitesystems.net/FAA/FAAfromMakani.pdf
Picture from: https://www.thedailybeast.com/whos-next-the-
mysterious-blind-item-king-who-exposed-weinstein-spacey-
and-lauer-before-the-media
Wing 7 Specs [1]
Rated power: 20 KW
Full rated power wind speed: 10 m/s
Operational altitude range: 40 m - 110m
Circling radius: 40 m
Wing
Wing mass: 60 kg
Wing spar: carbon fiber
Wing skin: carbon fiber
Generation system: 4 brushless DC motors
Tether
Mass: 16 kg
Length: 144 m
Conductor: copper
Structure: UHMWPE (Dyneema)
Voltage: 1.1 kV
15 December, 2017 Antonello Cherubini 111
Makani Wing 7
Video from: Makani Power Website.
http://www.google.com/makani/solution/
15 December, 2017 Antonello Cherubini 112
Makani M600
[1] Makani’s Response to the Federal Aviation Authority -
Docket No.: FAA-2011-1279; Notice No. 11-07
http://www.energykitesystems.net/FAA/FAAfromMakani.pdf
Picture from: http://www.businessinsider.com/google-x-
wants-to-revolutionize-wind-energy-with-makani-power-2015-
8?IR=T
M600 Specs
Rated power: 600 kW
Full rated power wind speed: 9m/s
Operational altitude range: 140m - 310m
Circling radius: 135 m
Wing
Wing spar: carbon fiber
Wing skin: e-glass
Wing mass: 1050 kg
Generation system: 8 brushless DC motors
Tether
Mass: 250 kg
Length: 440m
Conductor: aluminum
Structure: pultruded carbon fiber
Voltage: 8 kV
15 December, 2017 Antonello Cherubini 113
Makani M600
Picture from: AWEC 2017, Freiburg, book of abstracts
15 December, 2017 Antonello Cherubini 114
Makani M600
Picture from: AWEC 2017, Freiburg, book of abstracts
15 December, 2017 Antonello Cherubini 115
Makani M600
Video cut from: https://www.youtube.com/watch?v=CKFlMDUHtLg
15 December, 2017 Antonello Cherubini 116
Makani M600
Pictures from: http://berc.berkeley.edu/berc-visits-makani-power/
• Critical aerodynamics of 2-way rotor
• Thick profile
15 December, 2017 Antonello Cherubini 117
Makani M600 - 28m wingspan
Pictures from:
Response to the Federal Aviation Authority - Docket No.: FAA-2011-1279; Notice No. 11-07
http://www.energykitesystems.net/FAA/FAAfromMakani.pdf
Makani website 2015
Current version
• Symmetric wingspan
• Non-symmetric bridle length
Alternative option
• Non-symmetric wingspan
15 December, 2017 Antonello Cherubini 118
Makani M5 - 65m wingspan
[1] Makani’s Response to the Federal Aviation Authority -
Docket No.: FAA-2011-1279; Notice No. 11-07
http://www.energykitesystems.net/FAA/FAAfromMakani.pdf
Picture from: [1]
M5 Specs
Rated power: 5 MW
Full rated power wind speed: 9 m/s
Operational altitude range: 350m - 650 m
Circling radius: 265 m
Wing
Wing mass: 9,900 kg
Wing spar: carbon fiber
Wing skin: e-glass
Generation system: 8 brushless DC motors
Tether
Length: 1060 m
Mass: 3660 kg
Structure: pultruded carbon fiber
Conductor: aluminum
Voltage: 8 kV
15 December, 2017 Antonello Cherubini 119
Lifting balloon
Pictures from: Antonello Cherubini, Andrea Papini, Rocco Vertechy, Marco Fontana, “Airborne Wind Energy Systems,
a review of the technologies”, Renewable and sustainable energy reviews, 2015 51, 1461-1476
Ground-gen drone with takeoff motors
15 December, 2017 Antonello Cherubini 120
Altaeros Energy
Picture from: http://www.altaerosenergies.com
Airborne Wind Energy book 2013, U. Ahrens, M. Diehl, R. Schmehl Eds. Chris Vermillion, Ben Glass, Adam Rein,
«Lighter-Than-Air Wind Energy Systems» Chapter 30
30°
• Conventional wind turbine lifted by a balloon
• Blowdown angle is a criticality, typical values around 30 degrees
• The turbine shell must generate lift (either aerostatic or aerodynamic)
• Very famous, it was mentioned in an interview about AWE with Bill Gates
15 December, 2017 Antonello Cherubini 121
Flying copters
Pictures from: Antonello Cherubini, Andrea Papini, Rocco Vertechy, Marco Fontana, “Airborne Wind Energy Systems,
a review of the technologies”, Renewable and sustainable energy reviews, 2015 51, 1461-1476
Ground-gen drone with takeoff motors
15 December, 2017 Antonello Cherubini 122
Self lifting multi-rotors
Pictures from: http://www.skywindpower.com; AWEC 2015, TU Delft, book of abstracts
Sky wind
power
Bryan
Roberts
15 December, 2017 Antonello Cherubini 123
Rotokites
Picture from: Moritz Diehl, AWEC 2017, Freiburg, book of abstracts
15 December, 2017 Antonello Cherubini 124
Rotokites
Picture from: Gianni Vergnano
Cierva rotor
15 December, 2017 Antonello Cherubini 125
Moving ground station
Picture from: https://angel.co/nts-gmbh-nature-technology-systems/jobs
x-wind - NTS Energy
15 December, 2017 Antonello Cherubini 126
Other concepts
Picture from: Kitegen; Tigner Benjamin, Patent: US8066225
Multi-tether planeTigner 2008
CarouselIppolito, 2004
Torsional multicable
transmissionRod Read 2017
15 December, 2017 Antonello Cherubini 127
Simple kite vs Crosswind kite
Crosswind kite Simple kite
Powerful 2 orders of magnitudeless powerful for example in GG configuration[1]
Large swept area Tiny swept area
XM..L. Loyd, “Crosswind Kite Power” 1980
15 December, 2017 Antonello Cherubini 128
Magnus effect balloon
Omnidea, Magenn
Picture from: AWEC 2015, TU Delft, book of abstracts
• Equivalent to Loyd’s
“simple kite” mode
• Simple kite is about 100
times less powerful than
crosswind flight mode
15 December, 2017 Antonello Cherubini 129
Helium vs Hydrogen vs Hot air
Picture from: https://en.wikipedia.org/wiki/Zeppelin#/media/File:Hindenburg_burning.jpg
Airborne Wind Energy book 2013, U. Ahrens, M. Diehl, R. Schmehl Eds. Chris Vermillion, Ben
Glass, Adam Rein, «Lighter-Than-Air Wind Energy Systems» Chapter 30
• He: inert, expensive, hard to contain
• H: 70-80% cheaper, 8% more lift, low ignition energy, anti-static fabric
• Hot air: requires power, provides less lift
15 December, 2017 Antonello Cherubini 130
Rotational takeoff systems
Picture from: Moritz Diehl, AWEC 2017, Freiburg, book of abstracts
15 December, 2017 Antonello Cherubini 131
Rotational takeoff systems
Picture from: Moritz Diehl, AWEC 2017, Freiburg, book of abstracts
15 December, 2017 Antonello Cherubini 132
Tether drag
Warning! Cable drag
15 December, 2017 Antonello Cherubini 133
Higher availability, even at low altitudes
Pictures from: Makani Power website 2016
15 December, 2017 Antonello Cherubini 134
Higher availability, even at low altitudes
Pictures from: Makani Power website 2016
Which piece of
information is
missing in this map?
Multiple drone AWES
15 December, 2017 Antonello Cherubini 136
A dual drone system is better than a single drone
Picture from: antonellocherubini.com, blog about wind drones
15 December, 2017 Antonello Cherubini 137
Multiple drone system working principle
Pictures from: Antonello Cherubini, Marco Fontana, An Assessment of a Megawatt Scale Wind Energy Drone Generator at Jet
Stream Altitude, 2016
Take off (1) Take off (2) Production
The dual drone system exploits the intrinsic stability of u-control flight, thus allowing to foresee an easier and more
robust control system for take off, production and landing. Notice that automatic take off and control is a major
problem in many companies involved in wind drones.
15 December, 2017 Antonello Cherubini 138
Multiple drone system - work in progress
Video from https://www.youtube.com/watch?v=PaeCZ72ghRQ&t=2s