Solar AiR Marks for the Food Industry

Crop Drying Shutterstock

Let’s talk about the benefits of using solar heating to reduce the carbon footprint in the processing of food products. This is something that is gaining traction in both the agricultural community and with end-use consumers who ascribe a premium to such products.

Solar air heating systems are used in different configurations around the world to produce heated air that can be used for ventilation heating or process heat applications. This specific use – solar process drying – has expanded in the agricultural community as it provides a carbon reduction solution that also helps to produce high quality food products.

Many of the world’s food products need to be dried to remove moisture as part of the production process. For example; coffee beans, tea, cocoa, nuts, fruit, rice, spices, and corn all require drying to transform the raw goods into the final product. It can also be extremely carbon intensive when using mechanical drying methods that rely on propane, oil or wood.  In more traditional drying operations, it is common for produce to be passively air-dried in the sun, which lengthens the processing time and can lead to uneven  moisture levels in the final product.

Solar air heating produces a double-benefit in terms of improving both the process of drying and the final product. The solar technologies can work with a traditional mechanical dryer and heat large volumes of incoming air up to 55°C  (100°F) above ambient. This makes it ideally suited for types of crop drying  applications.  The solar heating system may provide all of the heat during a sunny day or act as a pre-heat during cloudy conditions. Typically solar air heating systems operate as a pre-heat to traditional mechanical operations where they can be easily incorporated into trough, tunnel or conveyor dryers.

In both cases, solar crop drying  reduces the dependency on traditional fuels and creates the following benefits:

  • 1) Reduced operating costs;
  • 2) Lower reliance on fuels that need to be transported to remote sites;
  • 3) Reducing deforestation by lowering the quantity of trees that are harvested for fuel;
  • 4) Lower humidity in the incoming air (because it is heated before entering the building or drying chamber) which means that the air has been preconditioned to absorb more moisture;
  • 5) Reducing carbon emissions, and
  • 6) Producing a high quality finished product that is eco-friendly and was processed using “clean & green” energy.


SolarWall® heating  helps agricultural producers promote their products as being “solar-dried” with the Solar AiR logos. This allows companies that produce solar dried fruit, coffee, tea, nuts, herbs, and other food products to proudly display their commitment to sustainability and carbon reduction on their product packaging and in their promotional material.  It will also provide consumers with a choice to favor those foods and products that are dried and processed using solar heating.

Examples in Food Industry

Carriere & Sons; Walnut Drying California

Carriere & Sons owns and operates hundreds of acres of walnut trees, in addition to their walnut drying facility. They are also in partnership with Borges of California, which is owned by Borges of Spain. Borges is the world’s leading walnut operator and has forty-eight companies in its group devoted to the production and marketing of oils, dried fruits and nuts. Walnuts are dried at a relatively low temperature with a minimum temperature of 110°F (43°C) leaving the dryer. This low temperature requirement is ideally suited for the use of solar air heating technology.

A normal drying season consists of two months of drying from September 1st to October 31st. The walnuts are dried from 35% moisture content to 10% moisture content.

The SolarWall solar heater was installed on the roof of a drying building at Carriere. The 3,200 ft2 (300 m2) solar system spans the entire roof area and will displace around 308 million BTU of natural gas for the two month drying season. The system heats approximately 25,000 cfm of air, which is then ducted into the 70,000 cfm blower.

Coopeldos Coffee Drying; Costa Rica

The coffee drying cooperative Coopeldos R.L., located in the province of Guanacaste in Costa Rica, installed a solar drying system on the entire roof of their building. Coopeldos, an ISO 9000 and ISO 14000 registered company, was the perfect candidate to demonstrate state-of-the-art solar air heating crop drying technology, since maintaining the ISO 14000 designation necessitates meeting certain energy conservation standards.

A 860 m2 (9,250 ft2) black solar air heating system was installed on the roof at the Coopeldos facility. The warmed air that is collected from the system is used for two purposes:  It heats the vertical pre-drying silo, which dries the coffee beans from 60% moisture content, to 35%.  It also heats the guardiolas, which are the rotating drums that carry out the final drying stage. Here, the beans are further dried to a 12% moisture content. Following this second drying stage, the beans are packaged in bags.

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