Validation Test Protocol: Single-Cell SAT Module

Purpose: Validate core ITB-100 thermal storage concept before building full system

Scale: 1/50th of full design
Cost: ~$180 in materials
Time: 3 days build + 4 weeks testing
Goal: Answer critical questions about SAT chemistry, nucleation, and thermal performance

🎯 What This Test Will Tell You

Critical Questions

✅ Phase Change Chemistry:

Does SAT with stabilizers cycle reliably 50+ times?
What’s the real supercooling duration? (24 hours? 48 hours?)
Does phase separation occur after repeated cycling?
Any unexpected crystallization behavior?

✅ Nucleation System:

Does 1.5V silver electrode trigger work reliably?
What’s the success rate? (Target: >95%)
How long does nucleation take after trigger? (Should be <5 minutes)
Any auto-nucleation events (unwanted crystallization)?

✅ Thermal Performance:

What’s the measured UA value (thermal conductance)?
Does power output match the model predictions?
How uniform is the temperature in the SAT?
What’s the charge/discharge efficiency?

✅ Mechanical Durability:

Does the HDPE pouch survive 50 thermal cycles?
Any aluminum corrosion or thermal epoxy degradation?
Does the system hold pressure over time?

🔧 Bill of Materials

Item	Specification	Quantity	Unit Cost	Total	Source
Phase Change Material
Sodium acetate trihydrate	CH₃COONa·3H₂O, 99%+	4.5 kg	$8/kg	$36	Chemical supplier
Sodium polymethacrylate	Na-PMAA, MW 15,000	30 g	$2/g	$6	Polymer supplier
Disodium hydrogen phosphate	Na₂HPO₄, anhydrous	91 g	$0.20/g	$18	Chemical supplier
Heat Exchanger
Aluminum plate	6061-T6, 300×400×2mm	1 pc	$15	$15	Metal supplier
SS tubing	316L, 1/2” OD, 0.035” wall	0.5 m	$4/m	$2	McMaster-Carr
Thermal epoxy	Arctic Silver or equivalent	50 g	$12	$12	Electronics supplier
Pouch & Sealing
HDPE sheet	0.5mm thick	350×450mm	$5	$5	Plastic supplier
Impulse sealer	Heat sealer for HDPE	1 pc	$25	$25	Amazon
Nucleation System
Silver wire	99.9%, 1mm diameter	0.2 m	$2/m	$1	Jewelry supply
DC power supply	0-5V adjustable	1 pc	$15	$15	Amazon
Instrumentation
K-type thermocouples	±0.5°C accuracy	5 pc	$3	$15	Amazon
Arduino Uno	For data logging	1 pc	$25	$25	Arduino store
SD card shield	For logging	1 pc	$10	$10	Amazon
SD card	8GB minimum	1 pc	$8	$8	Amazon
Heating/Cooling
Hot plate	With temperature control	1 pc	$40	Use existing
Ice bath container	Large enough for module	1 pc	$0	Use existing
Circulating pump	Small aquarium pump	1 pc	$15	$15	Pet store
Miscellaneous
Silicone tubing	1/2” ID for water flow	2 m	$2/m	$4	Hardware store
Insulation	Foam board scraps	–	$0	Use existing
TOTAL				~$180

🏗️ Construction Steps

Step 1: Prepare SAT Mixture (2 hours)

Safety first: Wear gloves and eye protection. Work in ventilated area.

Calculate masses:

SAT (pure):           4,370 g  (97.1%)
Na-PMAA (stabilizer):    30 g  ( 0.67%)
Na₂HPO₄ (stabilizer):    91 g  ( 2.02%)
────────────────────────────────
Total:                4,491 g  (100%)

Mixing procedure:
- Heat distilled water to 60°C in a large beaker
- Slowly add SAT crystals, stirring until dissolved
- Add Na-PMAA powder, stir for 10 minutes until fully dissolved
- Add Na₂HPO₄, stir for 10 minutes
- Continue heating and stirring for 30 minutes to ensure homogeneity
- Visually inspect: Should be clear liquid (no cloudiness)
Cool to room temperature (naturally, don’t rush)

Step 2: Fabricate Heat Exchanger Plate (3 hours)

Mark tubing path on aluminum plate:

Serpentine pattern: 8 passes across 300mm width
Spacing: 40mm between passes
Entry/exit on same side

Machine shallow groove (optional, improves contact):
- 10mm wide, 1mm deep along tubing path
- Can use router or milling machine
- Alternative: Use thermal epoxy without groove
Bend stainless tubing:
- Create 180° bends at ends (use tube bender)
- Test-fit on plate before bonding
- Leave 50mm straight sections at inlet/outlet
Bond tubing to plate:
- Clean both surfaces with isopropyl alcohol
- Apply thermal epoxy to groove (or plate surface)
- Press tubing firmly into epoxy
- Use clamps or weights to maintain contact
- Cure per epoxy instructions (typically 24 hours)

Step 3: Fabricate Pouch (1 hour)

Cut HDPE sheet: 350×450mm rectangle
Create pouch:
- Fold in half (175×450mm when folded)
- Heat-seal three sides using impulse sealer
- Leave one short side open for filling
- Test seal by filling with water first!
Install nucleation electrodes:
- Insert two silver wires through sealed edge
- Position 50mm apart in center of pouch
- Seal around wires with additional HDPE patch
- Connect wires to power supply (outside of pouch)

Step 4: Assemble Module (30 minutes)

Fill pouch with SAT mixture:
- Use funnel to pour prepared SAT solution
- Fill to 90% capacity (allow for expansion)
- Squeeze out air bubbles gently
- Heat-seal final edge quickly (SAT must stay liquid)
Bond pouch to heat exchanger:
- Apply thin layer of thermal epoxy to plate
- Press pouch firmly against plate
- Ensure good contact over entire surface
- Allow to cure (24 hours)
Insulate sides:
- Wrap exposed pouch edges with foam board
- Leave heat exchanger side exposed
- Goal: Force heat transfer through plate only

Step 5: Install Instrumentation (2 hours)

Attach thermocouples:
- TC1: Aluminum plate surface (center)
- TC2: SAT bulk temperature (insert through sealed edge)
- TC3: Water inlet temperature
- TC4: Water outlet temperature
- TC5: Ambient temperature

Connect to Arduino:

// Simple Arduino code for 5-channel thermocouple logging
#include <SD.h>
   
void setup() {
  Serial.begin(9600);
  SD.begin(chipSelect);
}
   
void loop() {
  // Read all 5 thermocouples
  float T1 = readTC(A0);  // Plate
  float T2 = readTC(A1);  // SAT
  float T3 = readTC(A2);  // Inlet
  float T4 = readTC(A3);  // Outlet
  float T5 = readTC(A4);  // Ambient
     
  // Log to SD card with timestamp
  logData(millis(), T1, T2, T3, T4, T5);
     
  delay(60000);  // Sample every 60 seconds
}

Test data logging:
- Verify all sensors reading correctly
- Check SD card writes
- Calibrate if needed (ice water = 0°C, boiling water = 100°C)

🧪 Testing Protocol (4 Weeks)

Week 1: Baseline Characterization

Goal: Establish initial performance before cycling

DSC Measurement (if available):
- Take 10mg sample of SAT mixture
- Measure latent heat of fusion
- Target: 264 kJ/kg
- Document: Take photo of DSC curve
Initial Melt-Freeze Cycle:
- Heat to 65°C (clear liquid)
- Cool to 25°C (trigger nucleation)
- Measure: Time to complete crystallization
- Expected: <10 minutes once triggered
UA Value Measurement:
- Circulate 40°C water through tubing (constant flow)
- Wait for steady-state (inlet = outlet temperature)
- Measure SAT temperature vs. water temperature
- Calculate: UA = Q / (T_water - T_SAT)
- Expected: ~2.2 W/K for single cell
Document Initial State:
- Photos of pouch (any bubbles? clarity?)
- Dimensions (any swelling?)
- Visual SAT appearance (color, clarity)

Week 2-3: Accelerated Cycling (50 Cycles)

Goal: 50 charge/discharge cycles in 14 days

Daily procedure (3-4 cycles/day):

CYCLE SEQUENCE (repeats every 6 hours):

Hour 0:00 - CHARGE PHASE (Heating)
  - Set hot plate to 65°C
  - Monitor SAT temperature rise
  - Target: Complete melting (SAT = 60-65°C)
  - Log: Time to full melt, temperature profile
  
Hour 0:30 - SUPERCOOL PHASE (Cooling)
  - Transfer to ice bath (or turn off heat)
  - Cool to 25°C
  - Monitor: Does auto-nucleation occur? (it shouldn't)
  - Log: Supercooling duration

Hour 1:00 - NUCLEATION TRIGGER
  - Apply 1.5V DC across silver electrodes for 10 seconds
  - Observe: Temperature should spike to 58°C within 5 minutes
  - Log: Success/failure, time to crystallization
  
Hour 1:10 - DISCHARGE PHASE (Heat Extraction)
  - Circulate 40°C water through heat exchanger
  - Flow rate: ~0.1 L/min
  - Monitor outlet temperature vs. time
  - Continue until SAT = 40°C
  - Calculate: Energy delivered = ṁ × cp × ∫(T_out - T_in)dt
  
Hour 3:00 - REST PHASE
  - Allow system to equilibrate
  - Check for leaks, damage
  - Verify data logged correctly
  
Hour 6:00 - REPEAT

Every 10 cycles:

Take detailed photos
Measure pouch dimensions
Re-measure UA value
Visual inspection for degradation

Week 4: Final Characterization

Goal: Compare performance after 50 cycles to baseline

Final DSC Measurement:
- Take new 10mg sample
- Compare latent heat: Should be >90% of initial
- Document any change in melting temperature
Final UA Measurement:
- Repeat steady-state test
- Compare to Week 1 value
- Acceptable: <10% degradation
Destructive Inspection:
- Cut open pouch (carefully!)
- Examine SAT visually: Any phase separation? Solid layers?
- Inspect aluminum: Any corrosion?
- Inspect thermal epoxy: Still bonded?
Final Report:
- Summarize all data in spreadsheet
- Create plots: Temperature profiles, power output over cycles
- Document success rate: X/50 nucleation triggers successful
- Note any anomalies or unexpected behavior

📊 Data Analysis

Key Metrics to Calculate

Nucleation Success Rate:

Success Rate = (Successful triggers / Total attempts) × 100%
Target: ≥95%

Capacity Retention:

Capacity = (Energy cycle 50 / Energy cycle 1) × 100%
Target: >90%

UA Value Stability:

UA Degradation = (UA_initial - UA_final) / UA_initial × 100%
Target: <10%

Average Discharge Power:

Power = ṁ × cp × (T_out_avg - T_in_avg)
Expected: 30-40 W for single cell

Round-Trip Efficiency:

Efficiency = (Energy out / Energy in) × 100%
Target: >85%

Plots to Generate

Using your data, create these plots:

Temperature vs. Time (Cycle 1 vs. Cycle 50):
- Shows any degradation in thermal performance
- Should overlay closely if no degradation
Power Output vs. Cycle Number:
- Shows capacity fade over time
- Should be relatively flat
Nucleation Response (Temperature Spike):
- Shows how quickly crystallization starts
- Should be <5 minutes consistently
UA Value Over Time:
- Shows thermal interface degradation
- Should be stable within 10%

✅ Success Criteria (Go/No-Go Decision)

Use this rubric to decide if full system is worth building:

Metric	Target	Acceptable	FAIL
Nucleation success	100% (50/50)	≥95% (48/50)	<90%
Capacity retention	>95%	>85%	<80%
UA stability	<5% change	<10% change	>15%
Pouch integrity	Perfect	Minor bulging	Any leaks
Power output accuracy	±10% vs model	±20% vs model	>30% off
Auto-nucleation events	0	≤2	>5

Decision Matrix:

✅ All “Target” or “Acceptable” → Full system is LOW RISK, proceed with confidence

⚠️ Mix of “Acceptable” and one “Fail” → MEDIUM RISK, consider design modifications before building full system

❌ Multiple “Fail” criteria → HIGH RISK, do not build full system without addressing issues

📝 Reporting Your Results

What to share with the community:

Summary Report (GitHub Issue):

Title: "Single-cell validation test results - [GitHub username]"
   
Content:
- Test dates and duration
- Key findings (3-5 bullet points)
- Success criteria table (filled in)
- Link to detailed data
- Photos of module before/after
- Lessons learned

Data Files (GitHub PR to /data/):

/data/validation/[your-username]/
├── README.md           # Test conditions
├── cycle-001.csv       # All 50 cycle files
├── ...
├── cycle-050.csv
├── dsc-initial.pdf     # If available
├── dsc-final.pdf
└── photos/             # Visual documentation

Plots and Analysis:
- Generate the 4 key plots listed above
- Include in your report
- Share high-res versions

Even if your test fails, please report it! Negative results are just as valuable as positive ones. The community learns either way.

🚨 Safety Reminders

⚠️ Chemical Handling:

SAT is low-toxicity but wear gloves
Na-PMAA and Na₂HPO₄ are irritants - avoid skin contact
Work in ventilated area
Have eyewash station nearby

⚠️ Thermal Hazards:

Hot plate can cause burns (65°C)
Molten SAT at 60°C will burn skin
Use tongs/gloves when handling heated components

⚠️ Electrical:

1.5V DC is safe, but avoid short circuits
Keep water away from power supply
Use GFCI outlet if near water

⚠️ Pressure:

Pouch may swell during heating
Do not overfill (90% max)
Ensure seals are strong before heating

❓ FAQ

Q: Can I use a different PCM instead of SAT?
A: Yes, but you’ll need different stabilizers and nucleation method. SAT is chosen for its 58°C phase change temp (ideal for heating) and proven chemistry.

Q: What if my nucleation success rate is <95%?
A: Try increasing voltage (up to 3V), increasing electrode surface area, or improving electrode contact with SAT. If still failing, may need different electrode material (copper, zinc).

Q: My UA value is lower than expected. Why?
A: Likely thermal interface issue. Check: (1) Thermal epoxy bond quality, (2) Air gaps between plate and pouch, (3) SAT mixture homogeneity.

Q: Can I speed up the testing (more cycles/day)?
A: Yes, but ensure complete melting and crystallization each cycle. Rushing can lead to incomplete phase change and skewed results.

Q: Should I cycle continuously or take breaks?
A: Continuous cycling is fine. The 3-hour rest in the protocol is for data checking, not required for SAT chemistry.

Q: What if SAT auto-nucleates (crystallizes without trigger)?
A: This indicates insufficient stabilizer or contamination. Try: (1) Remix with fresh chemicals, (2) Increase Na-PMAA concentration slightly, (3) Ensure pouch is clean.

🎯 Next Steps After Validation

If your test succeeds (≥90% on all metrics):

Share your results publicly (GitHub, YouTube, blog post)
Consider building full system with confidence
Help others by answering questions
Contribute improvements to the design

If your test fails:

Share your results (equally important!)
Identify root cause (chemistry? thermal? mechanical?)
Propose solutions for community to test
Don’t build full system until issues resolved

Either way, you’ve contributed valuable data to the project!

📞 Questions?

Technical questions: Open a GitHub Issue with label validation-test
Report results: Open a GitHub Issue with label build-report
General discussion: Use GitHub Discussions

Good luck with your testing! 🔬

Document version: 1.0
Last updated: October 30, 2025