Innovative application of solar energy for sustainable cocoa drying

The department of Nariño in Colombia is recognized as one of the regions where the highest quality cocoa is produced. Cocoa production is largely in charge of farming families of African origin with very limited resources. An innovative application of solar energy has been designed through Social Solver to improve the sustainability of cocoa production in the community.

Since 2018, the NGO Ayuda en Acción is working to reinforce the cocoa value chain in these communities. However, the profitability of the small cocoa plots of these families is still low, which leads to loss of competitiveness in the local and external markets.

The participating communities show high rates of Unsatisfied Basic Needs, lack of opportunities for young people, poor health and education systems, among others.

Cocoa is produced by fermentation, drying and packaging for transport. The monthly production of fresh cocoa is 45,700 kg, which becomes 25,135 kg after fermentation.

Once fermented, the cocoa is dried by keeping it in greenhouses to reduce the humidity of the beans from 55% to 10%, or by taking it to a drying oven, which uses propane gas to reduce its humidity down to 7.5%.

Propane gas is expensive, difficult to obtain in this area of Colombia and not always available. In addition it has a negative impact on the environment. As a result, the cocoa cannot be dried properly and the product quality is not optimal.

A challenge was launched at Social Solver website to find a sustainable and effective cocoa drying system. The objective was to reach humidity levels below 7%, the quality required for export, using renewable energies or biofuels available in the area.

More than 30 participants from different countries participated in the challenge: Spain, Iran, Venezuela, Australia, France, Argentina, Switzerland, Indonesia, Portugal or Serbia. Finally, 14 solutions were received. 

Some of the proposed solutions were commercially available while others were being used in a few countries, e.g. to generate energy from agricultural waste.

The winner of this challenge is a solution from the French engineer Olivier Loidi. That solution is a completely new and innovative application of solar energy for drying cocoa beans. Consequently it requires building a prototype and testing in the field.

Olivier's solution consists of a solar collector dryer. It uses a technology based on high-performance flat-plate solar collectors, similar to those used to heat water or oil in processes. The system is made in 3 layers:

• A double glass (replaced by plastic to make it lighter and cheaper) where the sun hits. Being double has good insulating properties.
• A double grid to introduce a layer of cocoa beans.
• A double crystal equal to the first, to collect the radiation that bounces on the floor of white stones or similar.

Solar collector design by Olivier Loidi.

Between each layer there is a space of about 2cm where the air circulates through small holes made at the base and at the top.

This way, the cocoa beans are heated directly, instead of heating water or oil and then heating the air to dry the beans. Higher temperature and faster drying will be achieved, making the system viable even on cloudy days, due to the efficiency of the panel and the high radiation available in the area.

Olivier Loidi lives in France and works in process engineering at his own company O.L Mineo. He has always liked science and engineering. He has participated in other Ennomotive engineering challenges and won some of them. Passionate about renewable energy and environmental awareness, he also wrote an article for ennomotive’s blog about the future of solar energy.

We also want to highlight another solution proposed by Adeesh Autar, which proposes to  improve the existing greenhouses. The approach is to control temperature, humidity, light and air quality electronically, with a simple Arduino UNO device.

A similar system was already being prototyped by an Ayuda en Acción volunteer that is in the region. The system sends messages to the farmer’s mobile to open or close the greenhouse windows at the right time. However, the results used with greenhouses point to a limit of 9.5% humidity in the drying process.

They are planning to improve the system with motorized hatches (similar to Air Conditioning). Maybe a small dehumidifier will be needed to reach the 7.5% target or just a decrease in the air inside the greenhouse.