Introduction
When I joined Vigyan Ashram, I got the opportunity to work on an active polyhouse cooling optimization project.
A polyhouse is supposed to create a controlled environment for plant growth by regulating temperature, humidity, and airflow. But here, even with multiple exhaust fans running, the inside temperature was rising to 44–46°C during peak afternoon hours.
That raised a simple but important question:
Why was the cooling system not performing as expected?
That question became the starting point of my work.
Objective
The main objective of this project was to understand why the fan-pad cooling system was underperforming and optimize the airflow inside the polyhouse.
The key goals were:
• Study airflow patterns inside the polyhouse
• Identify leakage points
• Analyze thermal behavior during solar loading
• Improve air distribution
• Validate cooling performance through experiments
Initial Research
Before making any modifications, I first focused on understanding the basic science behind the system.
I studied:
• Greenhouse effect inside enclosed structures
• Heat transfer through poly film
• Thermal buoyancy and air density changes
• Evaporative cooling principles
• Fan-pad cooling mechanics
• Air leakage and short-circuiting in ventilation systems
I also discussed these concepts with Arun Sir and Anand Sir while comparing observations with theory.
One thing became clear very early:
Airflow is not only about fan capacity. It is about pressure distribution and path control.
That changed the way I started looking at the whole polyhouse.
Work Done Till Now
Phase 1: Understanding Airflow
My first task was conducting smoke tests.
Smoke helped visualize how air was actually moving.
What I observed:
• Airflow was highly non-uniform
• Some regions had stagnant air
• Near the center, smoke was rising vertically instead of moving horizontally toward fans
This was my first real clue.
Later, Arun Sir explained this as thermal buoyancy: cool air entering gets heated, becomes lighter, and rises.
To verify this, we repeated smoke tests in the evening.
Interestingly:
• Afternoon smoke rose upward
• Evening smoke moved mostly horizontally
This confirmed the effect of solar heating.
That was my first practical lesson in thermodynamics.
Phase 2: Quantifying Airflow
After visual observations, I started measuring air velocity at multiple points using an anemometer.
I measured:
• Near exhaust fans
• Near cooling pads
• Center zone
• Leakage points
Results showed:
• Strong airflow near fans
• Almost negligible airflow in center
• Low airflow near pads
• Major leakage through poly-film gaps and gate opening
This meant air was bypassing the intended path.
Instead of:
Pad → Crop Zone → Fans
Air was taking shortcuts.
That explained poor cooling.
Phase 3: Leakage Identification and Fixing
After locating leakages, we started sealing:
• Poly-film gaps
• Structural corner openings
• Side leakages
After repairs, airflow measurements showed:
• Side leakages reduced significantly
• Fan-side velocities improved
• But gate leakage became dominant
This was important.
Fixing one leakage exposed the next major weakness.
That’s how real systems behave.
Phase 4: Thermal Logging Experiments
This phase gave the strongest insights.
I logged temperature and humidity continuously under different conditions.
Case 1: Fans ON, Pads OFF
Result:
Temperature still reached ~44–45°C.
This showed:
Fans alone cannot counter peak solar load.
Case 2: Fans ON, Pads ON
Result:
Temperature dropped by ~5–6°C within 20 minutes.
Humidity increased sharply.
This confirmed evaporative cooling was functional.
Case 3: Wet Soil + Fans ON
This was an interesting experiment.
I drenched the soil early morning.
Observation:
Temperature rise slowed by ~1–3°C.
This showed soil moisture contributes to latent cooling and reduces sensible heat emission.
This was an unexpected but valuable finding.
Phase 5: Gate Leakage Analysis
One important question came up:
How much air was entering through the gate?
I calculated:
Measured gate leakage = ~93 CFM
But this was only local.
Sir pointed out:
Actual leakage could be much larger due to distributed openings.
This taught me an important engineering lesson:
Small local leaks can have large system-level effects.
Even if volumetrically small, they disturb pressure paths.
To fix this, we modified the gate to open outward.
This structural change was completed on 20th June.
Challenges
This project was full of challenges.
Technical:
• Unpredictable airflow patterns
• Difficult thermal behavior
• Data logger malfunction
• Power cuts during experiments
Practical:
• Heavy equipment movement
• Structural repairs
• Continuous monitoring in extreme heat
Scientific:
• Matching theory with real observations
• Separating fan effect from solar effect
• Understanding thermodynamic behavior
Learnings
This project taught me much more than I expected.
I learned:
• How to observe before acting
• Importance of experimental validation
• Airflow measurement techniques
• Thermal analysis of enclosed systems
• Leakage impact on ventilation systems
• Practical evaporative cooling behavior
• Importance of questioning assumptions
The biggest lesson:
Engineering is rarely linear. Every fix reveals the next problem.
Current Status
As of now:
Completed:
- Smoke flow studies
- Airflow mapping
- Leakage identification
- Leakage sealing
- Thermal logging experiments
- Gate modification
- Comparative fan-only and fan-pad studies
Ongoing:
• Post-gate modification validation
• Airflow redistribution testing
• Further cooling optimization
Next Steps
Moving ahead, the plan is:
• Repeat airflow mapping after gate modification
• Compare center airflow before and after structural changes
• Perform new smoke tests
• Test improved pad-to-fan air path
• Study long-duration cooling stability
• Further optimize internal air circulation
Conclusion
What started as a simple temperature observation turned into a deep exploration of airflow, thermodynamics, and system optimization.
This project taught me how a real engineering system behaves: messy, interconnected, and full of hidden variables.
Every observation raised new questions.
Every experiment changed my understanding.
And every small modification helped reveal how important airflow control really is in a polyhouse.
This project is still ongoing.
But now, I no longer see a polyhouse as just a farming structure.
I see it as a living thermodynamic system.
