Design and development of solar dehydrator for fruits and vegetables
Processing of fresh vegetables and fruits is carried out to preserve for a longer period of time. Dried products have ease of transportation and storage hence they can be easily exported to other parts of countries and even to international markets. Dehydration adds worth to fresh vegetables and fru
2025-06-28 16:26:19 - Adil Khan
Design and development of solar dehydrator for fruits and vegetables
Project Area of Specialization Mechanical EngineeringProject SummaryProcessing of fresh vegetables and fruits is carried out to preserve for a longer period of time. Dried products have ease of transportation and storage hence they can be easily exported to other parts of countries and even to international markets. Dehydration adds worth to fresh vegetables and fruits by eliminating water by presenting them to high temperatures to diminish their weight and increment time the span of usability. Extending the worldwide market of dried vegetables offers an attractive chance for private investors. It additionally opens a window for the farmers of Punjab to sell their surplus produce to local and international markets that get wasted due to harsh weather conditions. A solar dehydrator is used to dry foods, like fruits and vegetables, so that they can be stored for long periods of time. Running on solar power makes these food dryers efficient and inexpensive. Adding chemicals and preservatives affect the quality of food while the product obtained from dehydrators are better in terms of nutrients, hygiene, and taste.
In an active solar dehydrator, the air is heated by the solar radiation received by the solar collector. The heated air is forced to circulate inside the drying chamber with a blower. The heated air absorbs moisture from the sliced fruits and vegetables spread over the perforated trays. The temperature inside the chamber is maintained from 45 to 50 degrees Celsius. The temperature is regulated using a feedback control system. The feedback system senses the temperature inside the drying chamber and varies the speed of the blower accordingly. The moisture level inside the drying chamber is regulated and when the equilibrium moisture stage is achieved, automatically the bell ring indicated that the product is dried. The design is based on the geographical location which is Islamabad. In Islamabad, during the month of June, we get maximum solar irradiance of 886 Watt per square meter. In December, the solar irradiance is found to be 572 Watt per square meter. From calculations, we get the result that almost 300 Watts is required to dry one kilogram of any fruit and vegetable sample within a time period of 2 hours. With zero-emission, the solar dehydrator is environmentally friendly.
The dehydration process will be carried out using solar power. The process will be supported by auxiliary systems for removing any residual moisture during the days when adequate sunlight may not be available due to unfavorable weather conditions.
Project ObjectivesIn Pakistan, 70% of the population lives in villages and they have related to agriculture most of the villages are away from grid stations so we will target the cottage industry related to agriculture. We will assure them that our product will be beneficial for them and it will be one time cost. We will connect with the industries related to agriculture like the ketchup industry or corn industry. We will convince them if their farmers use our product then they will receive the high-quality dried product. We can also sell it to the local market of villages. We can also export dehydrator units to international markets for better profit. Dehydrated vegetables and fruits are produced and traded in large quantities around the world. International trade of dehydrated horticultural products has been increasing over the years. Expanding the international market of dried vegetables offers an attractive opportunity for private investors. It also opens a window for the vegetable and fruit farmers of Punjab to sell their surplus products in local as well as international markets that are available in large quantities during peak production seasons and usually get wasted. Our design of solar dehydrator will be inexpensive.
The cost of a solar dehydrator of 20 kg capacity ranges from about RS 30,000 to RS 50,000. Industrial-scale systems may cost between RS 400,000 and RS 1 million. While conventional dehydrator of capacity 20kg cost RS 100,000 to 150,000.
Project Implementation MethodIn an active solar dehydrator, the air is heated by the solar radiation received by the solar collector. The heated air is forced to circulate inside the drying chamber with a blower. The heated air absorbs moisture from the sliced fruits and vegetables spread over the perforated trays. The temperature inside the chamber is maintained from 45 to 50 degrees Celsius. The temperature is regulated using a feedback control system. The feedback system senses the temperature inside the drying chamber and varies the speed of the blower accordingly. The moisture level inside the drying chamber is regulated and when the equilibrium moisture stage is achieved, automatically the bell ring indicated that the product is dried. The design is based on the geographical location which is Islamabad. In Islamabad, during the month of June, we get maximum solar irradiance of 886 Watt per square meter. In December, the solar irradiance is found to be 572 Watt per square meter. From calculations, we get the result that almost 300 Watts is required to dry one kilogram of any fruit and vegetable sample within a time period of 2 hours.
In this project the design of the blower speed control system using PWM technique based on the drying chamber temperature. A temperature sensor PT-100 has been used to measure the temperature of the room and the speed of the blower is varied according to the chamber temperature using PWM technique. The Arduino accepts inputs from the temperature sensor, PT-100, then the controller will give the action to maintain the required blower speed. The duty cycle is varied from 0 to 100 to control the blower speed depending upon the chamber temperature, which is displayed on Liquid Crystal Display.
Benefits of the ProjectSolar dryers are more economical compared to dryers that run on conventional means such as electricity. The drying process is completed in the most hygienic and eco-friendly way. Solar drying systems have low operation and maintenance costs. Solar dehydrators last longer. A solar dehydrator can last 20-25 years with minimum maintenance. As dehydrated products have ease of transportation so they have a good export opportunity to international markets such as Saudi Arabia, UAE, and central Asian states. For diabetics, dried fruit prepared without adding sugar is a healthy choice instead of desserts. The farmers can earn good revenue even from a surplus product that gets wasted due to harsh weather conditions. This revenue will lead to the financial stability of local farmers and even the economy of Pakistan.
It also improves the bargaining position of farmers. Sometimes farmers sell their products at very low prices during the harvest season because they cannot store or preserve their surplus products.
Technical Details of Final DeliverableThe final deliverable will be an active solar dehydrator for fruits and vegetables. The sliced fruits and vegetables are placed over the trays inside the drying chamber. The temperature inside the chamber is maintained from 45 to 50 degrees Celsius by the control feedback system. When the air is blown over the wetted surface (sliced fruits and vegetables) the heat and mass transfer occurs. The slices absorb energy and the moisture is evaporated. The moisture is absorbed by the unsaturated air. Then the moisture from the air is absorbed by desiccants. The heated unsaturated air is recirculated inside the drying chamber. The dried product is obtained in almost two hours. While the conventional dryers almost require up to 6 to 8 hours. The designed dehydrator has a capacity of 2 kg. The energy requirements for desired capacity can be calculated by multiplying energy requirements per kilogram of a sample. The energy requirements can be compensated by the size of the solar collector.
Final Deliverable of the Project HW/SW integrated systemCore Industry AgricultureOther IndustriesCore Technology Clean TechOther TechnologiesSustainable Development Goals Affordable and Clean EnergyRequired Resources| Item Name | Type | No. of Units | Per Unit Cost (in Rs) | Total (in Rs) |
|---|---|---|---|---|
| Total in (Rs) | 78350 | |||
| Solar panel | Equipment | 1 | 12000 | 12000 |
| Solar collector Glass | Equipment | 1 | 5000 | 5000 |
| Temperature sensors | Equipment | 6 | 900 | 5400 |
| Aurdino | Equipment | 1 | 2500 | 2500 |
| Ply-wood sheet | Equipment | 1 | 5000 | 5000 |
| Net wire | Equipment | 1 | 600 | 600 |
| Partal Wood | Equipment | 4 | 1000 | 4000 |
| Moisture sensor | Equipment | 2 | 2500 | 5000 |
| LCD | Equipment | 1 | 2000 | 2000 |
| Blower 12V | Equipment | 1 | 4500 | 4500 |
| Small fans | Equipment | 4 | 800 | 3200 |
| Wires | Equipment | 1 | 2500 | 2500 |
| H bridge | Equipment | 1 | 1000 | 1000 |
| Variable resistors | Equipment | 5 | 250 | 1250 |
| Transistor | Equipment | 6 | 250 | 1500 |
| Aluminum sheet | Equipment | 1 | 5000 | 5000 |
| Plastic strips | Equipment | 5 | 100 | 500 |
| Nails and adhesives | Equipment | 1 | 1500 | 1500 |
| Wheels | Equipment | 6 | 150 | 900 |
| Other | Equipment | 1 | 5000 | 5000 |
| Report printing | Miscellaneous | 1 | 10000 | 10000 |