Download Implementation of an Energy Harvesting System for

Implementation of an Energy Harvesting System for
Powering Thermal Gliders for Long Duration Ocean
Research
Clinton D. Haldeman III, Oscar Schofield
Center for Ocean Observing Leadership
Rutgers, The State University of New Jersey
New Brunswick, NJ 08901
Douglas C. Webb
Teledyne Webb Research Corporation
North Falmouth, MA 02556
Thomas I. Valdez, Jack A. Jones
Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109
I. Background – Slocum Thermal glider to Slocum-TREC
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Building on success of previous
ONR funded project that resulted
in 2 thermally propelled gliders
Joint project; NASA’s JPL &
TWRC integrate SOLO-TREC
(Sounding Oceanographic
Lagrangrian Observer, 2009) and
Slocum glider. Rutgers – year 2,
operational expertise.
Testing – 15 miles offshore (trim,
ballast, etc.)
Thomas I. Valdez – Power
Subsystem Analyst
ROCKET SCIENCE!!!
Autonomous Platforms –
buoyancy driven
APEX Floats – 4 year
life
Seaglider – up to 10
months duration
Slocum electric glider – ~1 year w/ extended energy bay
Spray Glider - ~6
months duration
Slocum Thermal glider
Slocum electric glider – single engine;
stepping stone to the thermal
Projected endurance – 4 years or more
Uses Phase Change Material (PCM) to
drive oil used for buoyancy control.
Duration is limited to ability of primary
battery to power “hotel load”
II. Slocum-TREC – design difference
Solo-TREC
Slocum-TREC
2 thermal engines, so more oil available. PCM uses aluminum metal foam
to enhance thermal conductivity - thermal response by factor of 50.
What can we do with that extra oil?
Slocum-TREC Energy Storage
Functional System Schematic
P
Control
Electronics
HP
SW0
BV
+
SW3
Hydraulic
Motor
AXI-
Rectifier
SW2
Charge Discharge
Battery Battery
Power Out
(14.4 to 12.5V) (14.4 to 12.5V)
Nominal: 13.2 V Nominal: 13.2 V
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LP
Motor
Driver
Speed
Control
Electronic
SW4
Load
SW1
Back-up
Primary
Control
Nominal: 12 V
Power
DAQ Sense
Hydrauli
c
Switch
Pressure
2 battery packs; 1 being charged, 1 being discharged (used)
Ball Valve
Current
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7
Electronics Delivery: Electronics Integration
Control Electronics
Batteries
Slocum Controller (TWR)
Energy Storage System
Control Electronics (JPL)
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Energy Harvesting Specifics
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Typical generation cycle – 40-45 seconds
Generates 1.8 Wh/Dive, stores 1.7 Wh/Dive; delivers 70 Wh every 80
generation cycles
Battery voltage – 13.2-13.4 V, an optimal operating range for a variety of
scientific sensors
Energy can be delivered at power levels as high as 800 W, opening the
door to a wide array of other sensors where power levels are a concern
Voltage levels correspond to 40-75% state-of-charge (SOC) - optimized to
maximize battery cycle life, allowing 10+ years of operation!
90 generation cycles * ~4
hours/dive = ~15 days,
Voltages steady
III. Testing – Tropical Waters
• Goals – Endurance Tests
– A) Hawaii
• 2 Slocum-TREC gliders deployed (Lewis and Clark)
• Lewis never resurfaced (possible large animal interaction?)
• Clark – suffered issue w/ trim mechanism; recovered after 45 days
– ½ of planned initial endurance test
– B) St. Thomas, USVI
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Clark repaired; redeployed Jan 2015
Oil volume issue; necessitated recovery
Recovered after 27 days; adjustments made
Redeployed for another 68 days; accumulator leak
Total of 95 days; but non-consecutive
• Results – What did we learn?
– A) Energy harvesting/generation/storage system worked
incredibly well. Shunting energy, so increased CTD resolution
while remnants of Hurricane Danny and then Tropical Storm
Erika passed by. Energy budget issue is solved; perhaps
bringing biofouling to the forefront
– B) Differing ballast & flight mechanics/nuances, such as twist
– C) Latitudinal range of operation – still TBD. Or, how much
energy can we generate? Electric pump?
– D) Environmental interaction – how to pilot this glider. Buoyancy
drive vs. power generation, etc.
– E) Water Mass Layering / CTD issues
…summed up in 7 lines of text on a website…
Area of Rapid Intensification (RI)
Increase of sustained winds of at least 30 kts in a 24 hour period
What We Know…
• High intensity storms destructive; loss of life and property, cause
economic damage…
• …National Centers for Environmental Prediction (NCEP) mission
statement includes delivering climate products protecting life,
property, and economic well-being.
• Real-Time Ocean Forecasting System (RTOFS) to input into
hurricane and climate forecast systems
• It’s a data issue…or the lack thereof
What Can We Do?
• Working on pushing all Rutgers glider data to Global
Telecommunications System (GTS) for model ingestion
• Provide continual high resolution data needed for assimilation to
correct errors in model
Subtropical underwater (SUW) significantly deeper than shown in RTOFS
What Can We Do?
• Working on pushing all Rutgers glider data to Global
Telecommunications System (GTS) for model ingestion
• Continual high resolution data needed for assimilation, else errors in
model occur
What Have We Done?
• Lagrangian drifters, but only yield a profile every 10 days
• Buoys, but don’t provide profiles
When zoomed in to surface of
temperature profiles, cooling
visible as storm passes
Strengths of Slocum-TREC become apparent
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Continual data collection, with a cost that diminishes over lifetime of glider; Iridium
satellite communications become primary expense
Providing high resolution data in sparsely sampled areas can correct errors in
models, leading to better track and intensity forecasts. Examples include Hurricane
Irene in NJ, where glider data resulted in a reduced intensity forecast due to bottom
boundary layer mixing and surface layer cooling
Summary
• Slocum-TREC – “next generation” of ocean gliders
• Harvesting thermal energy from the ocean has solved the issue of a
limited power budget – now on to the next
• A few minor mechanical issues need addressed, but piloting will still
contain a learning curve. Nuances particular to the thermal design
and latitudinal limits may pose challenges
• Providing continual data over an extremely long duration can
increase the accuracy of models, ultimately resulting in the
preservation of life and property.
• As Henry Stommel suggests, we need a fleet of “about 1,000.”