Design Brief

To design low maintenance and low energy using Refrigerator for keeping Vegetables fresh in Vigyan Ashram.

Introduction

In India our major form of occupation the environment supports are Agriculture. Growing plants and having them harvested is one thing but having them preserved for future use is also a major problem faced by farmers and vegetable dealers.

In some dry areas where humidity is less the vegetables lose their weight and in some places where the humidity is high not having good air circulation leads to fungal growth. So we need a storage unit for having vegetables fresh. We knew there are already available refrigerators in the market. But a refrigerator needs a lot of power or electricity. Lack of continuous electricity is one of the major issue.

So at least for the rural areas of India we need storage systems which works on low power compared to refrigerator and maintenance cost of storing is less compared to Cold Storage . So in Vigyan Ashram, since a long time they have been conducting research on the vegetable storage units based on completely conventional principle known as” Evaporative cooling”.

Evaporative Cooling

Since a long time we have been observing this phenomenon in nature and this is tone of the major reason for formation of life on this planet. Even in living organisms this happens to let the organisms body cool. Even in human body you might have seen the formation of sweat, the water in our skin cells when exposed to sunlight they let the natural evaporation happen in cells and let the water vapor flow out of the body and let the body cool down.

Evaporative cooling is a physical phenomenon in which evaporation of a liquid, typically into surrounding air, cools an object or a liquid in contact with it. When considering water evaporating into air, the wet-bulb temperature, as compared to the air’s dry-bulb temperature, is a measure of the potential for evaporative cooling. Evaporation of water produces a considerable cooling effect and the faster the evaporation the greater is the cooling. When the temperatures are the same, no net evaporation of water in air occurs, thus there is no cooling effect. The principle of working of this system is ‘when a particular space is conditioned and maintained at a temperature lower than the ambient temperature surrounding the space, there should be release of some moisture from outside the body’. This maintains low temperature and elevated humidity in the space compared to the surrounding. This evaporative cool chamber fulfills all these requirements and is helpful to small farmers in rural areas (Dadhich et al. 2008).

Evaporative coolers or Desert Coolers

Coolers based on the evaporative cooling phenomenon are also known as evaporative coolers. Evaporative coolers provide cool air by forcing hot dry air over a wet pad. The water in the pad evaporates, removing heat from the air while adding moisture. When water evaporates it draws energy from its surroundings which produces a considerable cooling effect. Evaporative cooling occurs when air, that is not too humid, passes over a wet surface; the faster the rate of evaporation the greater the cooling. The efficiency of an evaporative cooler depends on the humidity of the surrounding air. Very dry air can absorb a lot of moisture so greater cooling occurs. In the extreme case of air that is totally saturated with water, no evaporation can take place and no cooling occurs. The evaporative cooled storage structures work on the principle of adiabatic cooling caused by evaporation of water, made to drip over the bricks or cooler pads. Generally, an evaporative cooler is made of a porous material that is fed with water. Hot dry air is drawn over the material. The water evaporates into the air raising its humidity and at the same time reducing the temperature of the air.

Factors that affect while using Evaporative Cooling are Temperature, Relative humidity, Air movement and Surface Area.

Existing Cooling units for storing vegetables in Practice

In all these concepts the good air circulation is one lacking thing which causes fungal growth in between the vegetable.

Proof of concept for preserving Vegetable

This one worked well the readings were also quiet good this was done by Vigyan ashram student named Komal but there’s a direct interaction of air from top of this chamber and even having these jute bags inside the storage unit is not hygienic.

Challenges faced while making Concept

1. Maintenance of temperature
2. Maintenance of humidity
3. Maintenance of good air circulation
4. Good Interaction and
5. Good Manufacturing capacity.

Questioner, The results and their Conclusive Points

Questioner to Vegetable vendors

• How much of vegetables do you usually have to store in vegetable market?
• How good will be the sales and when will they be highest and lowest?
• How much of vegetables usually go waste from total?
• What kind of vegetables do usually get wasted fast? What are the reasons?
• Do you know any method to lessen the wastage? If you know are you using it?
• If we provide a system which can lower the wastage rate do you prefer using it?

Vegetable Vendor

Questioner to Vegetable vendors (Home to Home)

• How much of vegetables do you usually have to carry on cart?
• How often do you have to stop while selling vegetables?
• What is weight of the complete system you pull/push?
• How good will be the sales and when will they be highest and lowest?
• How many hours do you usually roam around to sell vegetables?
• How much of vegetables usually go waste from total?
• What kind of vegetables do usually get wasted fast?
• Do you know any method to lessen the wastage? If you know are you using it?
• If we provide a system which can lower the wastage rate do you prefer using it?

Questioner to Buyer

• Which service do they usually prefer while buying vegetables Market or Home to home service? What are the reasons?
• If you are selecting the vegetables from market what features makes you to buy them.
• What kind of vegetables do you usually buy in large quantities in market.
• What kind of vegetables do you prefer buying from home to home delivery service.
• Do you keep large amounts of vegetables open or in some system where they can be preserved?

Results got from Vegetable vendor

• Weight = 300kg (approx)
• If markets new stock comes on Monday then it will be the highest selling day and the sales decreases as the days proceeds, lowest will be on weeks end.
• Around 15% – 18% is wasted in a day in a day.
• Maintenance of Green leafy vegetables are the greatest problem and even the vegetables which have high water content is difficult to maintain.
• They are using nearby vegetable storing cold storage units.
• If it has low maintenance cost and good units for vegetable storage then they will use it, and it’s capacity should be at least 500kg and around 3 times normal refrigerator’s volume.

Results got from Vegetable vendor (Home to Home)

• Weight = 100kg- 130kg(approx)
• He stops while selling the vegetables, he stops nearly 20-30 times in a lane.
• It is around 160 kg load.
• The sales are highest around 9am and it lessens by 4pm. They start working by 7am.
• He roams around 6hours minimum at the start of his business but now he roams around 4 hours around selected locations where his business runs well.
• Around 10% of vegetables go waste.
• Tomatoes and green leafy vegetables go waste fast.

Results got from Buyers

• House wives prefer buying from venders (home to home) as they can’t go every day for fresh vegetables. But those who go to jobs usually buy from vegetable markets as good pricing and a lot of varieties at their good freshness are available.
• Mostly they touch the vegetables with their own hands, most of the vegetables freshness and their age can be estimated by touching.
• Tomatoes and potatoes are bought in a bunch.
• Most people prefer buying green leafy vegetables from home to home delivery vegetable venders.
• Most of the things like tomatoes and green leafy vegetables are kept in fridge and there is no need for potatoes.

Points to remember while making a low energy using vegetable refrigerator(Stationary)

• Less human intervention should be done.
• The design should be ergonomic and it should be precise and simple.
• The Space it requires in house should be compact.
• Large amount of water storage unit should be present so that it can work for longer periods.
• If it is a never stopping power usage system it should use less energy or electrical energy.
• It should never have any sharp edges and it should not be too slippery surface.
• Better if we can provide low center of gravity position in design so that the design can be stable.
• The Power units and the control unit along with all mechanical working systems should be covered.

Points to remember while making a vegetable refrigerator for Vender (Home to Home)

• Already more human intervention is present with the storage unit so the cooling unit should not be present in the chamber where we keep the vegetables.
• The mechanical, electrical and control units should not visible and they should be covered or better sealed.
• The chamber where the vegetables are stored should be transparent.
• The placement of water tank and capacity of water tank should be kept in mind.
• Less usage of human’s muscular energy should be there while using this system.
• The relative humidity and temperature along with air circulation should be kept in mind.
• Energy consumption should be kept in mind, it is perfect if its zero.
• Universal setup for all seasons and good replacing tech and parts should be used.