Clean Energy

Zero energy solution for cold storage is amazing. Wanna Try?

I don’t have a refrigerator at my flat, so I came across a problem of fruits and vegetables deterioration sooner during summer. I couldn’t buy more fruits to store for more days. The vegetables like tomatoes deteriorated and flies were attracted to it which made my kitchen so unhygienic.  So, I thought of a simply proven technology at my home which might help to keep vegetables and fruits fresh for days.
This was not the first time I was making it. I loved this technology at my school project too. My intense interest in zero energy technology drove me again to learn more about it, build, test and analyze the performance. So, here’s what I want to summarize the “zero energy cold storage” technology.
“Zero energy Cold Storage Technology”
Zero energy cold storage works on passive cooling principle which means no use of any forced pump or compressor for cooling. It is totally a natural process where system is designed such that the system maintains the temperature below ambient temperature without use of any kind of energy, particularly fossil fuels. This technology can be a boon to store agricultural products cool and fresh in rural areas which has no access to grid energy. It helps enterprise being sustainable by increasing longevity life where as decreasing damage of agro products till the access of market. It also helps to maintain nutritive value of fruits and vegetables good.
Zero energy cold storage can be built with “Evaporative Cooling” principle. It can be classified in two types
1.      Pot in Pot Refrigeration for household utility
2.      Community cold Store
Evaporative cooling
 The science behind evaporative cooling system is “During evaporation it gains heat energy from the system so the temperature of system goes down “. Or simply to understand “Evaporation causes cooling”.
For example from our day to day life, water in a clay pot is cooler than the water in the plastic bucket because clay pot has small pores and water evaporates with the air flow through that pores. The same principle can be applied to build a “Pot in Pot Refrigerator” or a “Community Cold Store”. The rate of cooling depends on rate of airflow in outer surface of refrigeration.
Evaporative cooling  is effective to keep agro products at 8ºC to 12 ºC , which means relative rate of deterioration  of products are  maintained at 3 and potential shelf life is 15 to 20 days i.e. gaining 5 times longer life.
Pot in Pot Refrigeration
It is a simple technology which can be built in a local level with the use of two clay pot, one inside another where fine sand is filled in between two pots. The fresh fruits and vegetables are kept inside the inner pot and the water is sprinkled on sand timely to cause evaporation.
This technology is useful in small scale where load is between 6 to 10 Kgs.
Community Cold store
Community zero energy cold store can be build with two brick walls, with the gap of 10 – 12 centimeter in between the walls which can be filled with the fine sand. The size of room can be designed on basis of volume of load. The fresh fruits and vegetables are kept inside the store in a porous crate. Here, water is drenched or sprinkle timely in the outer surface of the wall and in between the walls.
v  Lay the floor of cold storage cabinet with the bricks.
v  Erect the brick walls with the gap of 10 to 12 cm in between the walls.
v  Sprinkle the cabinet with the water.
v  Fill the gap between the walls with the fine sand.
v  Drench the sand portion and outer surface of wall with the water. The water should be drenched in sand and outer surface of wall twice a day.
v  Store the agro products in plastic crate with enough air flowing pores/ holes.
v  Cover the cabinet with  well insulated roof or lid.
Improvements in evaporative cooling system


Use of solar powered fan, preferably computer processor fan( in Pot in Pot refrigeration) and 6 inch dc fan (in community cold store)  in outer surface of  four walls  can help increase the air flow so that to speed up the evaporation rate. Higher the evaporative rate higher the cooling rate.

Prakash Acharya is an entrepreneur from Nepal, passionately working to substitute fossil fuels with clean energy technologies. He co-founds Mukti Energy, a solar energy company providing a one-stop solution in the sector. He is also a big believer in change so he advocates and works for creating impact in society. His topics of interest spans from sustainability, zero energy, poverty reduction, sociology to smart city. He graduated from Institute of Engineering, Thapathali Campus on Industrial engineering. He is also a former assistant lecturer in IOE, Thapathali . Prakash is a fellow for Social Entrepreneurship Outreach Program 2014, Social Entrepreneurship Forum Sweden.

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