A vegetable dryer
Combines solar and electrical energies
Designed for professional farmers
Scalable and autonomous
This project is dedicated to farmers needing drying solutions for their vegetables, aromatic or medicinal plants, fruits or other kinds of products. The drying process allows farmers spreading their outcome beyond the harvest season and therefore to secure a stable revenue over the year.
We concur with the idea that open source and DIY farming tools support technical independence, which is a critical issue for farmers. Therefore, dryer we want to develop here is aimed to be open source, to be produced indifferently in DIY or industrial production settings, and to be easily repaired. we are committed to provide technical solutions with sufficient documentation securing the four freedoms of open source:
Freedom to study: the right to access enough information to understand how the piece of hardware (referred herein as the product) works and to retrace the logic behind its design;
Freedom to modify: the right to edit the product definition documents and to tweak or develop the product further for any purpose;
Freedom to make: the right to use the product definition documents to manufacture the piece of hardware;
Freedom to distribute: the right to share or sell the product definition documents as well as the physical products fabricated according to these documents.
The documentation shared in this repository is licensed under a GNU GPL v3 license. Designs are licensed under a CERN Open Hardware Licence V1.2.
Every bit of help is more than welcomed. If you want to support the project, promote it or concretely participate in the development, have a look at our Contribution guide!
Drying is one of the most efficient food conservation methods. It helps keeping a great share of nutriment, reduces the weight and the volume of food products and enables long warehousing duration. It is a physicochemical reaction, whose aim is to extract water out of something. Professional alimentary applications requires dealing with conflicting constraints of high processing speed and keeping control on the reaction in order to conserve valuable nutriments.
That technic begins with the beginning of the agriculture, around 12 000 B. C. by inhabitants of the modern Middle East and Asia region. In beginning drying was realize by evaporation (air drying, sun drying ...). With time and technical evolution, there's actually a lot of different technic to dry food, from very low tech solution to high tech solution (we exclude freezing drying, because it's a very different process).
In drying, there is no “one-size-fits-all”-solution. Each farmer may need a very specific solution fitting their specific requirements regarding size and temperature range for example. The objective of the project is therefore to develop a scalable and modular dryer which can be adapted to each specific situation. Doing so, we want also to provide documentation about drying which can be easily accessible to farmers.
A dryer is composed of:
a drying room, whose aim is to host the food products to be dried and to put their surface in contact with a dry and heated airflow. The role of the air flow is to capture the water contained in the food products while getting in contact with their surface. In order to maximise the contact surface, a good solution is to use trays helping to distribute the products and let the airflow circulating around them. Trays are generally made of food-safe screens and frameworks. For drying aromatic and medicinal plants, there are generally two ways to distribute products on the trays: the “thin layer”-way with only one layer of product on each tray, and the “thick layer”-way with around 10 to 15 centimetres of products on each tray.
a heating system, which can either be solar (direct or indirect), electrical or fuelled by biomass or combustion.
an air flow drying system, which can be either based on air exchange, condensation or absorption.
a convection system to convey the dry air flow through the drying room. The choice of the convection system depends on the product to be dried, the expected drying time and the thickness of the food's layer. It can be either natural or forced.
optionally a thermal inertia system, helping dryers whose heating system can't operate all day long (like solar systems) to stock energy.
Basic dryers tend to combine functions such as drying and heating into one component and to use wind to create ventilation. More advanced solutions use one component for each function.
We intend to use low tech and low energy consumption solutions whenever it is possible. The current development focuses on a solar solution with electrical assistance and regulation which enable professional users to process food products regardless of the daytime (that is, even when there is no sunlight).