Here at Three Pools we needed a way to dry the abundance of leaves and flowers we’ve been harvesting to keep their flavour and nutrition for later in the year, to share with guests and to post to friends of the farm. So we decided to harness the suns energy and build a passive solar dehydrator.
To make it we looked around for ideas online and contacted some other smallholders. We got back some links and a book reference Practical Self Sufficiency by Strawbridges. Our french friends were planning to build one too and shared this video. A zoom meeting later and some help with translation we felt we understood the environmental principles of a solar dehydrator and got thrifty sourcing the materials from the farm & local area.
We constructed the heat generator and dehydration cabinet so they can be moved and connect with a flexible pipe. The materials we reclaimed and repurposed to provide insulation, weatherproofing, shelves, heat storage and collection were raw wool, roofing membrane, off cuts of beech, slate and free glass from facebook marketplace. Not everything could be foraged and we decided to invest in a fresh sheet of OSB, and some food-grade mesh for the trays.
To effectively capture the suns energy the heat generator rests at different angles at different times of the year. The angle is calculated based on our latitude in the same way as solar panels. We have ended up putting it at 20 degrees for peak summer, and we expect around 60 degrees for the low sun of the winter, we are curious what weather conditions it will work in.
Different plants and their parts require different temperatures to dry to keep the best of the nutrients within the plant matter. Electric dehydrators generally go to 40c as their lowest setting. Following research, many plants need less than 40c as a drying temperature and darkness, which is why our solar dehydrator is so fantastic!
It took a whole team of us to make this dehydrator over the last week and we learned a lot. We’re happy to share what we learned so if you would like to build one get in touch. We will be keeping a diary of the results.
Photos by: Daisy Saul