Compact laser-based sensors for sUAS and their applications to natural gas leaks!

!Mark A. Zondlo!

Department of Civil and Environmental Engineering!Princeton University"

Anthony O’Brien, Kevin Ross, Josh DiGangi"Dept. of Civil and Environmental Engineering, Princeton University!

William Harrison, Brian Nathan, Dave Schaefer, David J. Lary"William B. Hanson Center for Space Sciences, Univ. Texas at Dallas!

! Mid-Atlantic Symposium on Aerospace, Unmanned Systems and Rotorcraft !

Villanova University, April 10, 2014!

!

their applications to natural gas leaks

Department of Civil and Environmental Engineering

!"#$%&'%()$

Mid-Atlantic Symposium on Aerospace, Unmanned Systems and Rotorcraft

Lary

What advantages do sUAS provide?"•" profiling of lower boundary layer (0-1000 m)!

–" tree canopies (10s m)!–" local emissions (leaking well, emissions – 10-100 m)!–" marine boundary layer!–" emissions from surface to atmosphere!

•" near complex terrain (safety)!

•" near-field emissions from highly-! localized sources!

•" where nimble movements needed!–" e.g. trees, buildings, roads, etc.!

!"#$%&''()#&*+,-%,+.%'+--)/(0%1).$%02)-*,3%40-0&4#$%),54&-.4"#."40%%6!7869:;%9<=>?@%6A::%&,B%6:!:%C><D-@%EAF%G<=@%6!7%G<H@%6:!:%G(+/&(%I&1J@%0.#K%

emissions from surface to atmosphere

e.g. trees, buildings, roads, etc.

Why laser-based sensors for environmental sensing?"

Performance"high sensitivity!fast response (<< 1Hz)!high selectivity!multispecies detection ! !

! !!

Physical specifications low power (~ 1-10s W) low mass (~ 1-5 kg) compact size rugged

Only large UAVs (e.g. NASA Global Hawk, SIERRA) fly existing laser-based sensors

To fully utilize UAV capabilities, need low power, light weight, compact sensors for smaller, cheaper, easier-to-deploy UAVs and UAV fleets

(existing sensors consume 100s W power, 10s of kg, bulky)

! !

Laser-based hygrometer on the NSF G-V aircraft"

!L:;L?M%

•" NSF Gulfstream-V, typical flight duration ~ 8-9 hours, ~ 15 km altitude!

29 cm!

Parameter ! ! !Specifications!Dew point range ! !-110°C to +30°C!Sensitivity (SNR=1) !0.05 ppmv!Frequency ! ! !25 Hz !Accuracy ! ! !! 5%!Precision ! ! !! 3%!!Power ! ! !5 W!Weight ! ! !5 kg!Size ! ! ! !25 cm " 16 cm " 5 cm!Operation ! ! !unattended!!• Open-path, laser-based design critical for cloud-scale questions!

• Over 1000 flight hours, from the surface to stratosphere, Arctic to tropics to Antarctic!

(Zondlo et al., JGR-Atmos., 2010)!

Principles of detection: Beer-Lambert law"NO#P%%%%%%%%%%%%%Q%%02'%O<$O#PP%N+O#P%

where: ! I(#) is light intensity after absorption!! !Io(#) is incident light intensity!! !$(#) is absorbance!

N+%N%

%%%%%%%%%%%%%%%%%$O#P%Q%!OLP%3O#@L@CP%6%l !

where: !S(T) is the linestrength!! !g(#,T,P) is the normalized Voigt lineshape function!! !N is the absolute concentration!! !l is the pathlength!

%%Q%R+(0#"(&4%#4+--<-0#*+,%

NH3

*($

*$

S5%-)3,

&(%O&

4/K%"

,).-P%

Key innovations: Vertical cavity surface emitting lasers Quantum cascade lasers Interband cascade lasers Open-path spectroscopy (no pumps!) Multiharmonic in-line stability system %

VCSEL sensors on electric, robotic aircraft"•" • Test flights on electric TREX Align helicopter, on balsa wood plane!•" • Successfully flew three sensors (CH4, CO2, H2O)!•" • 1.0-2.2 kg incl. batteries and all data acquisition/laser control electronics!

9IT%-0,-+4%

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Specifica1ons   Plane    Payload  

 9  kg  

Dura5on  at  Payload   20  min.  Horizontal  Range   50  km  (line-­‐of-­‐sight)  Ver5cal  Range   0–5  km  Airspeed   20-­‐30  m·∙s−1  Opera5on   Remote-­‐controlled  Data   Serial  ports  

Flights at DISH, TX"

VCSEL  CH4  sensor  

-­‐  Custom  (Balsa  wood)  body  frame  -­‐  Dual    5500  mAh  LiPo  ba^ery  -­‐    much  higher  drag  on  plane  than  heli  

0.0003  

0.00035  

0.0004  

0.00045  

0.0005  

0.00055  

0.0006  

0.00065  

0.0007  

0.00075  

2f-­‐m

ag.  (a.u.)  

VCSEL  detuning  

DISH  >  20  ppmv  

H2O  

CH4  

-­‐0.0002  

-­‐0.00015  

-­‐0.0001  

-­‐0.00005  

0  

0.00005  

0.0001  

0.00015  

0.0002  

VCSEL  detuning  

Background  ~  1.9  ppmv  

H2O   CH4  

2f-­‐m

ag.  (a.u.)  

scan both water vapor and methane lines

simultaneously!

Preliminary results: DISH,TX "

8&9:0'&$;,,<=>$

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C40b)+"-(]%R0&-"40B%><S?%''Rb%9IT%B+1,1),B%+5%#+R'40--+4%-.&*+,%&.%&)4d0(B%600B0B%$)3$04%40-+("*+,%&,B%"'1),B8B+1,1),B%e)3$.-%.+%B04)b0%e"20-%C40b)+"-(]%R0&-"40B%><S?% %B+1,1),B%+5%#+R'40--+4%-.&*+,%&.%&)4d0(B%

What are the CH4 leak rates?"Leak rate !Area ! ! ! ! ! ! ! !Study!3-9% ! !industry-reported components ! !Howarth et al., 2011!3-7% ! !Denver-Julesberg basin! ! ! !Pétron et al., 2012!6-12% ! !Uinta (Utah) basin ! ! ! ! !Karion et al., 2013!0.3-0.5% !190 sites nationally ! ! ! ! !Allen et al., 2013!0.4-0.6% !national estimate ! ! ! ! !EPA 2011 national inventory!!!Brandt et al., 2014 è large values unlikely representative but must be larger than EPA!!Clearly, large discrepancies still exist: significant need to improve measurements!!

Experimental: UTD remote control aircraft / Princeton CH4"

Aircraft: Payload Master 100!!Payload mass: 5 kg!!Aircraft size: 2 m wingtip-to-wingtip!!Typical flight duration: 15 min.!!Flight speed: 20 m s-1"

!Ceiling: 400’ AGL!!Restrictions: Line-of-sight,!! !permission of landowner!

!Payload:!

! !Parameter !Precision !Accuracy !Freq. !Make/model!! !CH4 !! !! !0.1 ppmv !1% ! !10 Hz !Princeton!! !wind spd.! !0.1 knot !1 knot !10 Hz !New Mnt. Innovations NM150!! !wind dir. ! !1º ! !1.5º ! !10 Hz !New Mnt. Innovations NM150!! !pressure ! ! ! !1.5% !10 Hz !New Mnt. Innovations NM150!! !air temp. ! !0.1ºC !1.5ºC !10 Hz !New Mnt. Innovations NM150!! !position ! ! ! ! ! !1 Hz! !Garmin/Trimble!!!!Plane flies relatively fast at ~ 20 m s-1!!!

What are CH4 plume sizes and magnitudes from well pads?!What are the spatial and temporal characteristics of plumes?!What are the emissions of CH4 from these sources?!!!!!!!!!!!!!! focus on Ponder Compressor station in Dish, TX!

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Scientific Objectives"

Preparing for Takeoff"

Searching the sky for CH4"

Safe landing and storage"

!• intercompared with LICOR before every flight!!• 1σ noise ~ 0.05 ppmv!!• LICOR calibrated with NOAA GMD standard prior/after campaign!!• for large plumes, this level of precision and accuracy is sufficient (not looking at small changes above background!)!!• accuracy ~ 3%, some spatial

!differences between sensors!

Intercomparison with LICOR"

Operations summary"Oct. 14-16: rain prevented check flights!Oct. 17: engineering check flight!Oct. 18, 21: broke front landing gear!Oct. 19-21: further CH4 sensor modifications!!!

%%

Example: Flight 23"

Flight 23 CH4 vertical profile: two elevated plumes"

Flight 23: timeseries of multiple plumes"

most plumes 1-2 s in duration (30 m width) – need for fast measurements!

10 Hz measurements of two plumes"

•  very small!

Another very fine plume with ~ few m resolution"

9"

8"

7"

6"

5"

4"

3"

2"

CH4"(pp

mv)"

Calculating flux across surface perpendicular to wind"

G4)B%.+%-"45&#0%B+1,1),B%+5%-+"4#0%%1$040%%f9g)h%)-%9IT%&.%0&#$%34)B'+),.%f9g/%)-%.$0%R0&,%/&#J34+",B%i)h%)-%.$0%'04'0,B)#"(&4%1),B%-'00B%%34)BB0B%.+%c%Z%2%=?%R%34)B%40-+("*+,%%%%W&]-%0.%&(K%fS??Yg%%%%%

)hf9g

Flight 23: lofted and surface plume"

Total  Flux  =  15.31  g/s  

Plume  Flux    =  3.41  g/s  

   

   

Plume  Flux    =  2.62  g/s  

Very  narrow,  lojed  and  surface  plumes  observed  downwind  of  compressor  sta*on  Emissions  consistent  with  detailed  leak  flange/stack  emissions  inside  sta*on  (8  g  CH4  s-­‐1)  Future  flights  require  autopilot  for  more  systema*c  sampling  

sUAS-based CH4 environmental sensing outlook"• 1.65 µm laser-based sUAS CH4 sensor shows excellent in-flight performance!

! !<3% accuracy!! !2 ppbv precision in-flight!! !2-15 W power, 2-3 kg mass!! !fast response (10 Hz)!

!• fast response critical to capture fine-scale,!

!near-field plumes (10-20 m width)!!• mean emission=18 g ± 7.4 g CH4 s-1 at Ponder!

!!!• lofted plumes point to difficulties of mobile,!

!drive-by approaches to estimates!!• laser-based sensors for s-UAS have wide!

!applicability in natural gas leak detection and environmental sensing! ongoing: 1.65 µm!3.27 µm laser, 100X more sensitive (smaller, lighter)!