Solar Dryers exist in many different designs. After testing various models Solare Brücke e.V. has mostly worked with the solar tunnel dryer developed at the University of Hohenheim. Originally these dryers are 20m long. Heike Hoedt adapted them to a size of 2m x 1m for the use in private gardens and for the starting phase of solar drying projects (evaluation of the technology).
The biggest project with those small tunnel dryers that we accompanied so far (together with ABS e.V.) has been a project in Afghanistan. In a center of competence in Kabul several hundred of the dryers have been built.
Smaller projects took place in India and on Dominica.


Project Example: Solar Drying in Afghanistan

Afghanistan has a distinct cultur of drying agricultural products. In most areas the climate is very dry and therefore ideal for drying. Almost everything is dried out in the open: fresh cheese, meat, all kinds of vegetables and fruits, lots of raisins, tomato paste, herbs and spices. Even honeydew melons can be dried to a deliciouse sweet.
Farmers are used to dry parts of their crop to sell it in dried form on the market. A lot of drying is for own needs and subsistance. People who live in town and can not grow anything still have the habit to buy vegetable in peak season cheaply and dry it for their requirement during winter.
In India the Afghan traders from the olden days are still well know for their dried fruits.

Nowadays the quality requirements on the international markets are very high.
But also for the local markets in Afghanistan it is recomendable froma hygenic point of view not to dry food in the open. Solar radiation is very intense due to the altitude and the number of sunshine days per year is very high.

The NGO ABS e.V. started 2004 with experiments on solar drying. 2005 the first small solar tunnel dryer was build togeher with Heike Hoedt. Through the Solar Food Processing initiative sponsored by ISES (International Solar Energy Socity) it was possible to do many tests and to develop a trainingprogram and manual that includes many locally important aspects of solar drying.

Meanwhile a center of competence for solar drying has been established by ABS e.V. In Kabul. Solar tunnel dryers are manufactured in two sizes: 2m² for projects and farmer who wish to test the technology and 9m² as an entry into commercial solar drying. The dryers are also sold to NGOs, always with a 2 day training workshop on solar drying for the users.
Next to the production facilities there is an exhibition and test ground with a room for preparation of fresh food items and packaging of dried goods. Interested people can get information and consultation.
In 2009 over 50 of the 2m² solar tunnel dryers were sold. In 2010 it was already over 200.

Packaging and Labeling is an essential part of commercial solar drying.


samples: Okra, white onion, tomatoes, aubergines, chilli, apricots,red onions



visitors from the provinces receive information


Projectreport 2008 for Dowload (English and German)




The following booklet by Heike Hoedt contains construction manuals for small solar tunnel dryers and lots of useful information on solar drying.


FaLang translation system by Faboba