Fundamentals of Airborne Wind Energy Systems · 2018-04-25 · Airborne Wind Energy book 2013, U....

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

http://www.antonellocherubini.com/

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?


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:


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


Effects of energy availability: +250% productivity in agriculture

Graphical representation by Marcello Corongiu


Effects of energy availability: urbanization



Effects of energy availability: transport



Effects of energy availability: welfare (late 19th century)


Health

care

Free

time

Pensions

Social

mobility


Effects of energy availability: population growth

Picture from Wikipedia https://en.wikipedia.org/wiki/World_population#/media/File:Population_curve.svg


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


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


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


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/


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


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


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)


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


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


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


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


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


So what?

OK!!! Let’s be optimistic! Someone will create the

technological system to make us all happy, what next?


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


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)


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)


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


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.)


Offshore would be nice but it’s even more expensive

Will it happen?

High altitude wind energy


Wind Power Density

𝑊𝑃𝐷 =1

2𝜌 𝑉3

[ W/ m 2]


High altitude winds, way more power, everywhere


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



Picture from: Antonello Cherubini, “Advances in Airborne Wind Energy and Wind Drones”, PhD Thesis, Sant’Anna University of

Pisa, 2017


High altitude winds, higher availability

Pictures from: Ragusa Salvatore Marco. Valutazioni energetiche dell'eolico d'alta quota: Kitegen. Politecnico di Torino, Bachelor

Thesis, 2007.


Please be elegant

Picture from a company website, company not stated on purpose

Do not use average

Use percentile instead


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


High altitude winds, smooth?

Picture from: antonellocherubini.com AWE Blog

Where is AWE?


Some investors in wind drones

Graphical representation by Daidalos Capital.


Where is AWE?

Picture from: http://www.starnetllc.net/valley-of-death/

AWESales

start


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


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


Where is AWE?


Pisa, 2017


Where is AWE?

Picture from: Prof. Roland Schmehl

How does it work?


Crosswind flight

Example: Leading Edge Inflatable (LEI) kite

Picture in public domain.

Wind window (wind going inward)


Crosswind flight


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/


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.


Single wind drone - fly-gen

Fly-gen continuous operation


Single wind drone - flygen

Video from: Makani Power Website.

http://www.google.com/makani/solution/

Constant

cable length


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


Math time

Theoretical optimal power output, Loyd 1980

Hypotheses:

- Steady state flight

- E > 10

- Power zone flight

WPDAerodynamic

parameters

Wing area


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


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


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


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


AWES

Pictures from: Antonello Cherubini, Andrea Papini, Rocco Vertechy, Marco Fontana, “Airborne Wind Energy Systems,


Ground-gen drone with takeoff motors


Sailplane





Ampyx Power

Picture from: AWEC 2017, Freiburg, book of abstracts

• Ground-gen

• Sailplane as kite

• Onboard control and batteries


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


Ampyx Power – landing without tether

Video from: https://www.youtube.com/watch?v=oP8t4zHFxD0&t=2099s Ampyx Power 50 minutes fully automatic flight


Ampyx Power



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

https://en.wikipedia.org/wiki/Deuterium

https://en.wikipedia.org/wiki/Helium-3

https://en.wikipedia.org/wiki/Fusion_reactor

https://en.wikipedia.org/wiki/Fusion_power

https://en.wikipedia.org/wiki/Energy_density#cite_note-nrl2016-2

https://en.wikipedia.org/wiki/Uranium

https://en.wikipedia.org/wiki/Breeder_reactor

https://en.wikipedia.org/wiki/Nuclear_power

https://en.wikipedia.org/wiki/Energy_density#cite_note-whatisnuclear-3

https://en.wikipedia.org/wiki/Compressed_hydrogen

https://en.wikipedia.org/wiki/Chemical_energy#Chemical_energy

https://en.wikipedia.org/wiki/Methane

https://en.wikipedia.org/wiki/Natural_gas

https://en.wikipedia.org/wiki/Chemical_energy#Chemical_energy

https://en.wikipedia.org/wiki/Diesel_fuel

https://en.wikipedia.org/wiki/Gasoline




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

https://en.wikipedia.org/wiki/Gasoline

https://en.wikipedia.org/wiki/Coal

https://en.wikipedia.org/wiki/Bituminous_coal

https://en.wikipedia.org/wiki/Methanol_fuel

https://en.wikipedia.org/wiki/Carbohydrate

https://en.wikipedia.org/wiki/Lithium_battery

https://en.wikipedia.org/wiki/Electrochemical_cell

https://en.wikipedia.org/wiki/Lithium-ion_battery

https://en.wikipedia.org/wiki/Energy_density#cite_note-7

https://en.wikipedia.org/wiki/Energy_density#cite_note-8

https://en.wikipedia.org/wiki/Flywheel_energy_storage

https://en.wikipedia.org/wiki/Alkaline_battery

https://en.wikipedia.org/wiki/Energy_density#cite_note-:8-9

https://en.wikipedia.org/wiki/Lead-acid_battery

https://en.wikipedia.org/wiki/Supercapacitor

https://en.wikipedia.org/wiki/Electric_double-layer_capacitor

https://en.wikipedia.org/wiki/Electrostatics









• Modern batteries have a density 50-100 times lower than

petrol


• 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


Platform takeoff (with propeller)

Video courtesy of Pasquale Adobbato, Pisa, 2017


Platform takeoff (with propeller and tether)

Picture from: Prof. Lorenzo Fagiano, AWEC 2017, Freiburg, book of abstracts


Video from: Prof. Lorenzo Fagiano, https://www.youtube.com/watch?v=UPiTiHPXciE

Platform takeoff (with propeller and tether)


LEI kites





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


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


TU Delft 100 kW



Kite Power Systems


• Ground-gen

• Ram air kite

• Airborne control pod

• 5 M£ recent investment

• Little information available


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


Ram air kites





Skysails

Picture from: Skysails

http://www.skysails.info/english/media/

150 m2

• Ground-gen

• Ram air kite

• Airborne control pod


Skysails

Video from: Skysails: MS "BBC SkySails"

http://www.skysails.info/english/media/footage/


Skysails



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)


Cable shape - math time


Cable shape – polynomial curvature

Picture from: http://www.kitepowersystems.com/markets/onshore-kite-power/


Cable shape – polynomial curvature

Picture from: Makani Website


Cable shape – math time


Angle of attack control - math time


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°


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


Swept rigid wing





Swept rigid wing

Picture from: AWEC 2017, Freiburg, https://www.tudelft.nl/en/2017/lr/awec-conference-tailwind-for-airborne-wind-energy/

Enerkite


Rotary takeoff system

Picture from: Enerkite https://www.youtube.com/watch?v=6cb9Pxf9Xro

Enerkite


Semirigid kite





Semirigid kite

Picture from: http://kitegen.com/2014/08/29/la-prima-power-wing/


Semirigid kite

Picture from: Kitegen on indiegogo



Kitemill



Pictures from: AWEC 2017, Freiburg, book of abstracts

Twingtec



Biplanes





Biplanes

Pictures from:

Wikipedia biplane, Adrian Pingstone

Florian Bauer, AWEC 2017, Freiburg, book of abstracts


Joby Energy

Pictures from: Joby Energy, http://www.jobyenergy.com/tech/visit

• Fly-gen biplane

• VTOL


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


Flygen drone





Flygen drone - Makani

Picture from: http://berc.berkeley.edu/berc-visits-makani-power/

• Onboard turbines

• High voltage tether


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


Makani Wing 7

Video from: Makani Power Website.

http://www.google.com/makani/solution/


Makani M600




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


Wing


Wing skin: e-glass

Wing mass: 1050 kg


Tether

Mass: 250 kg

Length: 440m

Conductor: aluminum

Structure: pultruded carbon fiber

Voltage: 8 kV


Makani M600



Makani M600

Video cut from: https://www.youtube.com/watch?v=CKFlMDUHtLg


Makani M600

Pictures from: http://berc.berkeley.edu/berc-visits-makani-power/

• Critical aerodynamics of 2-way rotor

• Thick profile


Makani M600 - 28m wingspan

Pictures from:

Response to the Federal Aviation Authority - Docket No.: FAA-2011-1279; Notice No. 11-07


Makani website 2015

Current version

• Symmetric wingspan

• Non-symmetric bridle length

Alternative option

• Non-symmetric wingspan


Makani M5 - 65m wingspan




Picture from: [1]

M5 Specs

Rated power: 5 MW

Full rated power wind speed: 9 m/s

Operational altitude range: 350m - 650 m


Wing

Wing mass: 9,900 kg


Wing skin: e-glass


Tether

Length: 1060 m

Mass: 3660 kg

Structure: pultruded carbon fiber

Conductor: aluminum

Voltage: 8 kV


Lifting balloon





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


Flying copters





Self lifting multi-rotors

Pictures from: http://www.skywindpower.com; AWEC 2015, TU Delft, book of abstracts

Sky wind

power

Bryan

Roberts


Rotokites

Picture from: Moritz Diehl, AWEC 2017, Freiburg, book of abstracts


Rotokites

Picture from: Gianni Vergnano

Cierva rotor


Moving ground station

Picture from: https://angel.co/nts-gmbh-nature-technology-systems/jobs

x-wind - NTS Energy


Other concepts

Picture from: Kitegen; Tigner Benjamin, Patent: US8066225

Multi-tether planeTigner 2008

CarouselIppolito, 2004

Torsional multicable

transmissionRod Read 2017


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


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


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


Rotational takeoff systems



Tether drag

Warning! Cable drag


Higher availability, even at low altitudes

Pictures from: Makani Power website 2016


Higher availability, even at low altitudes

Pictures from: Makani Power website 2016

Which piece of

information is

missing in this map?

Multiple drone AWES


A dual drone system is better than a single drone

Picture from: antonellocherubini.com, blog about wind drones


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.


Multiple drone system - work in progress

Video from https://www.youtube.com/watch?v=PaeCZ72ghRQ&t=2s

Fundamentals of Airborne Wind Energy Systems · 2018-04-25 · Airborne Wind Energy book 2013, U....

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