Field testing of an innovative solar powered milk cooling solution for the higher efficiency of the dairy subsector in Tunisia

Project background

The region of Sidi Bouzid, in central Tunisia, is responsible for approximately one sixth of the national milk production in Tunisia. The majority of its milk is produced by small and medium sized dairy farms with ten to twenty cows and a daily milk output below 200l. Their milk is currently being produced on farm and transported to milk collection facilities without any form of cooling. In this situation, bacterial growth during on farm short-term storage and transportation represents a significant problem for the dairy sector.

Under the given climatic conditions, milk can exceed the maximum bacterial count prescribed by Tunisian food safety laws after about two to five hours. During the hottest periods of the year, the lack of quality is the most common reason of refusing milk at collection centers. Furthermore, due to low production volumes, evening milk collection is not available year round, thus causing additional on-farm losses.

 Project component aim and approach

The project supports the field assessment of a solar-powered milk cooling solution, designed to meet the refrigeration needs of small and medium-sized dairy farmers in Sidi Bouzid, Tunisia. The ice-based cooling solution was developed specifically to overcome the challenges during short-term on-farm storage of milk and transportation to collection centers.

 Planned activities

• Installing 10 small-scale milk cooling systems, with a capacity of 60l per day each, at 6 dairy farms with production volumes ranging from 60l to 180l per day
• Monitoring technological performance under field conditions, specifically by measuring achieved milk quality improvements
• Analyzing business opportunities and technology promotion strategies, as quality-price-premiums and cooperative models, to give access to higher milk quality and productivity to the regional dairy industry
• Assessing social acceptance and social impact in terms of gender and labor organization

Promoted cooling technology and energy supply

The milk cooling solution developed by the University of Hohenheim is based on a commercially available DC Refrigerator, with a modified control unit to make it works as a smart solar freezer by adjusting its working-operation to the availability of solar energy. The freezer has a volume of 166l and is capable of producing approx. 8-13 kg ice per day. One system includes 25 reusable ice tins of 2 kg capacity and two 30l isolated milk cans( prototypes) with removable ice  compartment. To cool down 30l of milk from 36°C to 15°C in one of the supplied milk cans, the systems needs 6kg of ice and approx. 80 minutes.

The smart solar freezer is powered by 600Wp solar PV modules. Due to the application of a 120 Ah battery and thermal energy storage (ice), the system is able to run autonomously for up to 7 days even during periods of low solar radiation and high ambient temperatures.

Progress of the project

The project is currently shipping  10 solar milk cooling systems to Sidi Bouzid while national partners have carried out surveys to numerous farms in the region and selected 6 farms for the field assessment that will start in April 2016.