For PEat's Sake
Project undertaken in course year 2022-23 with the Stanford Precourt Institute for Energy
Embedded Files
Project Goal
Project Goal
Design an automated standing flux chamber for collection of data on concentrations of carbon dioxide and methane gases emitted from the water surface of peatland environments.
Project Motivation
Project Motivation
The current lack of suitable instrumentation requires the development of a low-cost, easily deployable sensing device for greenhouse gas (GHG) emissions.
An automated floating flux chamber would enable the large-scale collection of GHG emissions data to better understand Earth's changing climate and inform actions for environmental sustainability.
Background
Background
The rise in greenhouse gas (GHG) emissions is correlated with the rise in global temperatures, worsening gllobal disasters like wildfires, groughts, and storms and ultimately threatening life. The current methods of collecting GHG emissions data are expensive, non-portable, or not suitable for large-scale production.
Peatlands
cover 2.84% of earth's surface
Sequester more carbon than any other terrestrial ecosystem (>25%)
Drained peatlands emit at least 2 billion tonnes of carbon per year
Peatlands are a type of wetland ecosystem that contain deep accumulations of decomposed organic material, or peat.
High Priority Requirements
High Priority Requirements
System must be water-tight and minimize the amount of leaking to 3% over a duration of 5 minutes
After collecting gases, the chamber must reset to ambient GHG concentrations within 5% of steady state values within 5 minutes
System should operate in flooding conditions of 0.3 meters.
Ethical Considerations
Ethical Considerations
Environmental Impact
Displacement of peatland inhabitants form reflooding
Negative effect on conservation motivations
Solution
Solution
Designed and built Peatricia: a stationary modular flux chamber composed of 5 major components: 1) a bottom collar for mounting into the ground, 2) mid-section to accommodate different depths of water, 3) top housing which carries 4) the sensor system and desiccant, and 5) the ventilation door. Water sealing flanges are between the collar and mid-section, and between the mid-section and top-section, to ensure no water or gas leakage.
Working system
Working system
System mounted into the ground, with a mid-section sized to achieve the 0.3m floodwater requirement. Note the flanges between sections.
Sequence to build Peatricia
Sequence to build Peatricia
Starting with the collar being placed in the ground, connect and scure flanges for the center pipe section. Connect top section subassembly that includes the sensors and lid via flanges.
Leakage testing
Leakage testing
Testing the leak rate of the flange, by using a closed top-section and pressurizing the system to 10 psi and observe the decay over time. Results showed a top of 1 psi over 5 minutes, which equates to <1% loss of gas in this time.
Humidity testing
Humidity testing
The device includes a desiccant with the sensor pcb to maintain humidity levels. We ran testing to determine how much desiccant would be needed. We tested up to 30g of desiccant, and test results suggest it will saturate after 44 days and need to be replaced. Given that researchers intend to leave Peatricia in the field for longer periods than 44 days, further evaluation is required
Water sensor testing
Water sensor testing
Results show the water sensor has a linear output across its entire length, and is accurate to measurements made by hand.
Door mechanism
Door mechanism
System design for ventilation door at the top of Peatricia.
Door prototype
Door prototype
Underside of door assembly, showing servo motor, 2-bar linkage
Vent test setup
Vent test setup
When tested for leakage, the door did not seal adequately to the gasket and leaked. Opportunity to improve!
Other testing conducted
Other testing conducted
Temperature testing
Humidity Testing
Ventilation test to observe CO2 decay
Student team
Student team
Future Work
Future Work
Refine system for ventilation - both minimizing leak at door, and ensuring appropriate air exchange so CO2 vents
Humidity Control
Locatability - since units is in the field for extended periods of time, look at ways to find it, such as by color, low-power transmitter
Portability
Ease of insertion into the ground
Materials for scaled manufacturing
Field Testing
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