INTRODUCTION

• Low tunnels are temporary, low-profile structures (usually 2 to 4 feet tall) that cover single single crop rows or beds. The frame is simple – often flexible PVC, or pushed directly into the soil. Tunnel film polyethylene (100-150 \mu). UV Stabilized: Prevents the plastic from shattering under sunlight. Infrared (IR) / Thermal: Traps long-wave heat radiation at night, keeping the interior significantly warmer. It Protects crops from adverse weather and Enables off- season cultivation.

OBJECTIVE

To create a controlled environment for plants by maintaining the temperature between 25- 27°C maintaining humidity above 60 to75% monitoring environmental conditions by manual data logging

METHODOLOGY

80% Shade-net is used for the outer covering: This is to restrict the amount of solar energy entering the polyhouse Cooling pads are used for temperature reduction and also for increasing humidity by evaporative cooling.  exhaust fan is  used to accelerate evaporative cooling Water circulation to keep pads wet

A digital humidity Temperature meter is used for temperature and humidity monitoring

understanding previous project by nachiket that how a polyhouse works 

Project planning

Originally the was to build the project with dimensions of 6 ft length, 4 ft height and width of 3 ft 

However, after consulting with Arun Dixit Sir, the tunnel dimensions were set to a height of 2.5 feet and a length of 6 feet, featuring a rectangular flat head; a flat head was chosen because a dome-shaped tunnel would have resulted in higher aerodynamic drag.

MATERIAL SELECTION 

Second week of july 

I have selected the pvc pipe material with elbow and T joint to construct the frame for tunnel, because of that frame will be lightweight and flexible compare to a metal frame 

COOLING PAD INFORMATION 

Area of the cooling pad will be decided by smaller rectangular in frame which will be opposite to fan section 

Length of pad= 3 ft 

width of pad =2.5 ft 

Total area of pad required= 3×2.5 ft =7.5 square ft 

COOLING FAN 

Volume Calculation: l×b×h

6×3×2.5=45 cubic ft 

Air Changes Per Hour (ACH): Greenhouses require 1 to 2 complete air changes per minute to control heat and humidity

Fan Sizing: volume ÷ minutes per exchange

For 1 air exchange per minute: 45 CFM (ideal for peak summer)

For 1 exchange every 2-3 minutes: 15 to 25 CFM

Temperature can goes very high here in pabal so I will use 50 CFM to 150 CFM fan for the tunnel 

STARTED MATERIAL CUTTING FOR TUNNEL 

Carefully assembled  final frame  for the project 

pit for root zone

• It is essential to dig a pit for the root zone; if we dig the pit without lining it with polyethylene, the irrigation water will simply percolate into the ground. Therefore, lining the pit with polyethylene helps conserve water and prevents it from seeping away.

SEEDBED PREPARATION 

For seedbed preparation, the key step was to mix fertilizer into the soil—which had been dug out of the pit and then backfilled—to make it suitable for optimal plant growth; so, I mixed in organic fertilizer and tilled the soil using a hand cultivator.

PLANTATION 

I chose Napier grass for planting, as it is excellent for animal feed; so, I found some Napier grass plants and cut their stems. Then, I planted the stems into the soil at an angle and finally watered them a little.

Fourth week of july 

DATA LOGGER INSTALLATION 

1. A data logger is a device that provides continuous information on temperature and humidity. So, I installed a data logger in this tunnel, and it kept providing me with data on the temperature and humidity.
2. With this tunnel prototype, the main thing we need to observe is whether it protects the plants from damage caused by high temperatures. Since plants can get damaged in excessive heat, maintaining a temperature inside that is lower than the outside temperature during the day—especially around noon would be better for their growth.

WATER CHANNEL 

During heavy rainfall, water can accumulate around the tunnel and seep inside, potentially damaging the plants; therefore, I constructed a water channel around the tunnel so that any excess rainwater would be diverted to the other side.

INCREASE IN TEMPERATURE 

Using a data logger, I observed that during the day when there is sunlight the temperature inside the tunnel rises significantly, exceeding the outside ambient temperature by 7 to 8 degrees Celsius. I discussed this with Mr. Arun Dixit, who explained that warm, moist air rises because it is lighter than carbon dioxide; conversely, carbon dioxide is heavier and tends to settle at the bottom. Therefore, an exhaust vent was needed to expel this warm, moist air, and an intake was required to bring in fresh air (containing carbon dioxide), with the intake opening positioned near the bottom

DIMENSIONS AND LOCATION ON INTAKE ,EXAUST HOLES 

For your small polyhouse with dimensions:

Length (L) = 6 ft = 1.829 m

Width (W) = 3.5 ft = 1.067 m

Height (H) = 3 ft = 0.914 m

1. Floor Area

A = L ×W

A = 1.829 ×1.067 = 1.95 m^2

2. Volume

V = L × W × H

V = 1.829 × 1.067 × 0.914 = 1.78 m^3

3. Total Ventilation Area

For natural ventilation, use 20% of the floor area.

A = 0.20 × 1.95 = 0.39 {m}^2

0.39{m}^2 = 3900{cm}^2

4. Divide into Intake and Exhaust

Intake (60%)

  3900 × 0.60 = 2340{cm}^2

Two intake vents:

  2340 ÷div 2 = 1170 {cm}^2  each

Practical size: 30 cm × 40 cm = 1200 cm² each.

Exhaust (40%)

  3900 ×0.40 = 1560 {cm}^2

One roof vent: 40 cm × 40 cm = 1600 cm².

Final Vent Design

1.  2 Intake vents: 30 cm × 20 cm each, positioned 10–15 cm above the ground on opposite long sides.

2.  1 Exhaust vent: 40 cm × 30 cm, at the highest point of the roof.

This vent arrangement is appropriate for  6 ft × 3.5 ft × 3 ft polyhouse and should provide effective natural ventilation while maintaining good airflow.