Shade and sun drying are the most sustainable ways to preserve food for long duration. We, at our farm, utilize the power of the sun directly with this process. With minimum industrially produced goods such as meshed trays, glass and black paint, we have got a solar dehydrator made locally to shade dry flowers, herbs, leaves etc.
The principle behind the working of the dehydrator is simple. The solar collecter that you see is nothing but a channel for air to pass through. It is called a collector because in a way it collects rays of the sun. Because it is painted black, the surface heats up thereby heating the air above it beneath the glass. Hot air is lighter and so it rises in the channel moving upwards towards the produce stacked in trays inside the shelf.
Once it comes in contact with the moisture laden produce, the hot air, in order to reach an equilibrium with the air inside the shelves, collects moisture. This increases the weight of the hot air, thereby resulting in it moving downwards through the shelf. This exchange of moisture is what results in the drying of the produce. A channel is then provided for the dry air to escape outside. But the air inlet and the air outlet are covered by SS meshes to prevent any small mammals or reptiles to enter the cabinet.
The most important advantages of this kind of a dryer is that it needs no continuous energy source that needs to be operated and it protects the nutrition & colour of the produce from the harsh rays of the sun. It also ensures that the produce doesn’t get contaminated by dust or by rodents, squirrels and other animals.
The design of this particular dehydrator was taken from this website http://www.i4at.org/surv/solarchm.htm . In case any of you reading own a farm and shade dry produce often, then this is the design for you. There are possibilities to build a similar design for rooftop terraces in apartments. You can google sizes according to your design and get your local carpenter to make it for you.
The direction the solar collector should face is South in the Northern Hemisphere. Also, it should ideally be at 30 degrees with the ground for maximum capture of solar energy. We realized this a little late, after the carpenter had finished the job. He constructed it with the collector at 45 degrees. Anyways, we are in a place as tropical as it can get in India. So, sunlight is in abundance and this design consideration doesn’t seem to affect us much, given our low throughput. The produce would get dried even more quickly if the collector was flatter though.
The one herb that grows in our farm in abundance, in the wild is Vana Tulsi. Given that we practice the most eco-friendly form of orchard maintenance : no-tillage agriculture, tulsi grows without any manual interference or support. That is the herb that is shade dried in the largest volume in our solar dehydrator. We are selling 100 gms of Dried and Crushed Tulsi Tea @ Rs. 240, including postal charges. Please visit www.Vivasayees.Life to order from our online store. 🙂
It can be used by infusing in boiled water and had as Tulsi Tea. It can be added to your regular teas to give a beautiful earthy flavour. Tulsi is a herb that has been used by local doctors for ages to provide relief to cold, cough, fever. It also helps in controlling blood sugar levels.
4 Comments Add yours
Hello! I’m Harini, a post retirement learner-farmer. Just stumbled on your fascinating blog while looking for a solar dehydrator. Can this design be used to dry things in the sun as well as for shade drying? What changes would have to be made?
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Hi Harini. Sudhakar here. How are you doing? This design is exclusively for shade drying. You will have to have a separate set up for solar drying. An alternative would be to use these mesh trays, get same size glass trays made as a cover and use them for solar drying. However, that wouldn’t be the best design. As hot humid air would be heavy and would need an escape route. There are solar dryer designs available which you could use.
Hello Sudhakar, and thanks for your response. I’ll look for the solar dryer designs. Actually I was looking at some ready manufactured models but all of them have polycarbonate sheets as a cover, and refuse to sell it without that. One has to spend so much energy just avoiding plastic!
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Grass is risky to transport. Best to get it custom made by your local carpenter. 🙂