Hybrid solar drying system for herbs cuts costs

In 2014 five Portuguese herb producers joined forces to form the organic herb farm ‘Under the Sun’, which made them the biggest Portuguese exporter of aromatic and medicinal plants. To save energy costs in the herb drying process, one of the farmers started a cooperation with a local engineer. This led to the creation of an innovative solar drying system.

“With our 34 ha of land we are the largest exporter of herbs in Portugal. We cultivate different types of herbs, like lemongrass, peppermint, thyme and French tarragon,” says Gonçalo Costa Martins. Gonçalo is one of the five herb producers involved in Under the Sun and also founder of the company that developed the new solar drying system.

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“We wanted to have a dryer that would lead to high quality, consistent and reliable results, so that we could produce good quality dried herbs,” says Gonçalo Costa Martins. – Photos: EIP – AGRI Service Point

Challenges

“We all graduated in different fields; I am a landscape architect for instance. Due to the deep economic crisis in Portugal, we decided to join forces and start a farm in aromatic and medicinal plants. This worked out well. However, we need to deal with several challenges. These include competition from producers asking lower prices for their herbs, but also from countries with lower wages, like Eastern-Europe and Northern Africa.”

High energy costs

“In the beginning we had a problem drying our plants. The energy costs for drying were quite high. I started thinking about less costly ways to do this, so that it wouldn’t influence the prices of our herbs. That’s how the idea for the solar dryer that we have called Black Block came about.”

Hybrid solar drying system

“The idea is a hybrid solar drying system that uses both solar and electrical energy. The drying is done in recycled containers, painted black, insulated with a new wall and covered by polycarbonate sheets. This turns the containers into drying chambers. Our hybrid containers use an auxiliary energy source and they can reduce energy costs by up to 70%. In addition, we also have containers that fully rely on solar energy.”

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The drying is done in recycled containers, painted black, insulated with a new wall and covered by polycarbonate sheets.

Sensors collect data on temperature and humidity

Several sensors in the containers collect data on temperature and humidity. This data is analysed in real time by an automatic programme that controls all the equipment. Therefore, the drying environment parameters can be stabilised at optimal levels. This leads to a high quality drying process with a maximum saving of energy costs. The system can be accessed locally or remotely from a computer, tablet or smartphone.

By and for farmers

“The system was created by farmers and for farmers. We, as partners of Under the Sun, wanted to have a dryer that would lead to high quality, consistent and reliable results, so that we could produce good quality dried herbs. Eventually we managed to optimally finetune this system, so that we could continue it as a business in addition to Under the Sun. It’s amazing that we could offer the agricultural market an innovative drying solution.”

“Surprisingly, we won EDP (Energias de Portugal) Innovation Award, which helped us a lot to continue with this project. So, what initially started as a solution to save energy costs in Under the Sun, turned out to be a new successful business,” Gonçalo concludes.