Walk-in hemi-cylindrical enclosure
- Approx. 12.5 × 8 × 7 ft
- Galvanized structural framing
- Transparent polycarbonate cladding
- Modular construction concept
ENGINEERING • AGRICULTURAL DRYING SYSTEMS
Greenhouse drying systems, from design to field use.
This section brings together my work on agricultural drying systems, from designing and locally fabricating a greenhouse dryer prototype to installing larger dryers at project sites and working with smaller conduction-based drying systems for more compact applications.
01 • FLAGSHIP CASE STUDY • PRODUCT DEVELOPMENT
Making the Dryer Here
Design and fabrication of a 100 ft² solar greenhouse dryer prototype
Aastha Engineering Solutions Pvt. Ltd. • National Innovation Center • 2020
FOCUSAffordable local manufacturing
ROLEDesign + Sourcing + Prototype Fabrication
DESIGN TOOLAutoCAD
WHY THIS PROJECT EXISTED
The problem was not whether a greenhouse dryer could work in Nepal. It was whether a farmer could afford one.
Greenhouse dryers of this type were being sourced from India, but the cost made them difficult to justify for many of the farmers they were intended to serve. I wanted to see whether the same basic idea could be translated into something that could be manufactured in Nepal.
The goal was not to make the system cheaper by removing useful functions. It was to understand the product properly, redesign it around local fabrication, source as much as possible within Nepal, and reduce dependence on a complete imported unit.
I was not trying to redesign solar drying.
I was trying to redesign how we obtained the dryer.01 • UNDERSTAND THE PRODUCT
Start with a working idea. Make it buildable here.
I began by studying the existing Indian system as a technical reference. I broke it down into the parts that made it work: the curved enclosure, structural members, transparent cladding, tray arrangement, fastening system, circulation fans, exhaust, access points, controls, and supporting hardware.
From there, I used AutoCAD to develop the geometry and arrangement for a locally manufacturable version rather than treating the imported dryer as one indivisible product.
PROTOTYPE FOOTPRINT100 ft²
DIMENSIONS12.5 × 8 × 7 ft
TRAY SYSTEM24 trays
DESIGN RANGE45–55°C
FIRST BUILD≈ 4 days
02 • LOCALIZATION
Designing around what Nepal could actually supply.
Once the design was defined, I prepared a material breakdown and searched different suppliers to understand what could realistically be sourced in Nepal. Procurement was not something that happened after engineering. Material availability became one of the design constraints.
In the first stage, both the specialized polycarbonate sheet and the food-grade HDPE trays had to be sourced from abroad. Later, we identified a suitable local source for the trays, reducing the imported portion of the system further. The specialized polycarbonate sheet remained the principal component that still needed external sourcing.
01
Imported reference
Study the system and materials
02
Break it down
Structure, trays, fans, cladding, controls
03
Source locally
Search Nepalese suppliers component by component
04
Reduce imports
Localize additional components over time
03 • FROM CAD TO FABRICATION
National Innovation CenterA drawing still had to survive the workshop.
The National Innovation Center supported the idea of building useful technology in Nepal and making it more accessible to farmers. I communicated the concept and its purpose to Mahabir Pun, and the Center supported fabrication of the first prototype.
I stayed physically involved during fabrication rather than handing over the drawings and waiting for the finished structure. The fabrication team was a major part of translating the design into a real system.
DESIGN VALIDATION
Very little had to change once fabrication started.
One of the most useful validations of the AutoCAD work came during fabrication: the prototype largely followed the original drawings without requiring major redesign.
The first 100 ft² prototype took roughly four days to manufacture. Being present through fabrication allowed me to see directly how dimensions, bends, joints, access, tray supports, cladding and fan positions translated from a drawing into a physical product.
04 • HOW IT WORKS
The physics was simple. Making it practical was the real task.
SUNLIGHT
→
POLYCARBONATE ENCLOSURE
→
SOLAR HEAT GAIN
→
CIRCULATED WARM AIR
→
PRODUCT TRAYS
→
HUMID AIR EXHAUST
Solar-assisted forced circulation
- 24 V DC fan system
- 2 internal circulation fans
- 1 exhaust fan
- Specified 45–55°C drying range
Food-grade tray arrangement
- 24 HDPE trays
- 765 × 330 × 70 mm tray size
- Nominal ~100 kg/day configuration
- Designed for agricultural produce and herbs
05 • WORKING PROTOTYPE
The first build was a working dryer.
We tested the completed dryer after fabrication rather than treating construction itself as the finish line. The system operated successfully and validated the basic structure, airflow and drying concept.
The original prototype remains at the National Innovation Center and, to my knowledge, is still functioning there.
What mattered to me was not that greenhouse drying itself was new. We had taken a system that previously arrived as an imported product and proved that it could instead begin with a drawing, a material list and local fabrication in Nepal.
06 • FROM PROTOTYPE TO SCALE
Once the 100 ft² unit worked, the next question was how far the same design could scale.
The first dryer established the basic tunnel geometry, tray arrangement and airflow concept. Increasing capacity did not require starting again from zero. The same design language could be extended by increasing structural length, tray capacity, airflow provisions and the corresponding material quantities.
The 250 ft² configuration shown here was developed after the working prototype as a larger design variant, while retaining the same core greenhouse-drying concept.
WHAT THIS PROJECT REQUIRED
Problem framing
Affordability for the intended users
Reference study
Understand an existing imported system
CAD development
Translate concept into manufacturable geometry
Supplier research
Source locally and reduce imports
Fabrication collaboration
Work directly with the Innovation Center team
Prototype validation
Build, test and retain a functioning system
We were not trying to reinvent solar drying.
We were trying to change where the dryer had to come from.
NEXT • FIELD INSTALLATION
250 ft² dryer at Sanga ↓
02 • FIELD INSTALLATION • SCALE-UP
Taking the Greenhouse Dryer Beyond the Prototype
Complete installation of a 250 ft² solar greenhouse dryer
Sanga, Nepal • Aastha Engineering Solutions Pvt. Ltd.
SYSTEM250 ft² walk-in greenhouse dryer
ROLEMechanical Engineer
WORKComplete on-site installation
The first 100 ft² dryer proved we could make it here. Sanga was where the larger system had to be assembled, completed and put to work in the field.
FROM 100 FT² TO 250 FT²
A larger dryer meant more than extending the frame.
The 250 ft² installation retained the curved greenhouse geometry of the prototype while expanding the enclosed drying area and internal product capacity.
I worked through the complete installation: structural assembly, longitudinal supports, polycarbonate enclosure, entrance, tray racks, circulation and exhaust fans, control components, final adjustments, testing and preparation for operation.
DRYING AREA250 ft²
TYPEWalk-in
ENCLOSUREPolycarbonate
AIRFLOWFan-assisted
ROLEFull installation
MY ROLE
Structure to operationI installed the system, not just the equipment list.
My responsibility covered the complete field installation. I worked through the structural setup, fixing of the enclosure, installation of internal tray supports, fan and ventilation arrangement, control components, final adjustments and testing.
The work ended only when the different parts were functioning together as one usable drying system.
The prototype taught me how the dryer could be built.
Sanga taught me what it took to install the larger system completely in the field.
NEXT • COMMUNITY APPLICATION
Manakamana Mahila Krishi Samuha ↓
03 • COMMUNITY APPLICATION • SOLAR CONDUCTION DRYER
Taking Solar Drying to the User
Three Solar Conduction Dryers for ginger processing
Manakamana Mahila Krishi Samuha • Nuwakot, Nepal • 2021
UNITS3 dryers
APPLICATIONGinger drying
FORMATCompact modular SCD
A compact dryer mattered here because the technology had to fit the scale at which the group actually processed its product.
COMMUNITY USE
The useful question was not how large a dryer we could build, but what size the users could actually use.
The Solar Conduction Dryer offered a smaller alternative to a walk-in greenhouse system. The modular units could be placed close to the users, loaded directly and operated without constructing a permanent drying chamber.
At Manakamana Mahila Krishi Samuha, the dryers were used alongside ginger preparation and value-addition activities. The photographs show the complete chain from product preparation to loading and drying at the group level.
UNITS3
MODULE SIZE≈ 2 × 2 m
DRYING AREA4 m² / unit
TRAYS4 / unit
NOMINAL LOAD≈20–25 kg
WHY THIS SYSTEM FIT
Same drying problem. Different scale.
The greenhouse dryer creates a larger walk-in drying chamber. The Solar Conduction Dryer reduces the system to a compact modular unit that can be deployed much closer to an individual user or small group. The engineering choice depends on the quantity, site and way the product is actually handled.
NEXT • MUNICIPAL DEPLOYMENT
Seven dryers in Modi Rural Municipality ↓
04 • MUNICIPAL DEPLOYMENT • SOLAR CONDUCTION DRYER
Seven Dryers Across One Rural Municipality
Delivery, installation and field setup of Solar Conduction Dryers
Modi Rural Municipality • Parbat, Nepal • April 2021
UNITS7 dryers
ROLEMechanical Engineer
WORKDelivery + installation + setup
One dryer is a piece of equipment. Seven become a deployment problem.
FIELD DEPLOYMENT
The product had to arrive as a working system, not as a box of parts.
In April 2021, seven Solar Conduction Dryers were supplied for use within Modi Rural Municipality.
I personally brought the products to the site and set them up. My role covered delivery, on-site installation and physical setup so the units were properly assembled and ready for use in the field.
UNITS7
DATEApr 2021
MODULE≈ 4 m²
TRAYS4 / unit
WORKDeliver + install
WHY THIS PROJECT WAS DIFFERENT
Scaling did not mean making the machine bigger.
The value of the compact system was its ability to reach more users without requiring a permanent greenhouse structure at every location. With several units being deployed, consistency in transport, assembly, positioning and setup became part of the engineering task.
The project moved the same drying technology from a single-group application into a broader municipal setting.
Engineering is not finished when a product leaves the workshop.
For this project, it finished when the dryer reached the user, was set up and was ready to work.
AGRICULTURAL DRYING SYSTEMS
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