Sustainable cooling solutions: Designing a zero-energy chamber with local materials in Eritrea

Tomatoes are one of the most widely consumed vegetables globally, yet they are also among the most perishable agricultural products, resulting in significant losses. In Eritrea, a low-income country, tomatoes hold great importance as a vital vegetable crop. To prolong the shelf life of tomatoes and other vegetables, controlled storage conditions, including temperature and humidity management, are essential. However, many small-scale farmers in Eritrea cannot afford expensive storage equipment for their harvested crops. This research aims to address this challenge by exploring the use of a zero-energy cooling chamber to extend the shelf life of raw tomatoes. The cooling achieved by this chamber also results in getting high relative humidity of the air in the cooling chamber from which the evaporation takes place relative to ambient air. A four side rectangular storage with total 0.175 cubic meter capacity, made of bricks; fine bed river sand, jute pad, PVC pipe having 16mm nominal diameter and it is reshaped in to square shape the edges connected by elbow connector placed at the upper center of cavity for keeping wet the sand with dimension of 78 x 78cm, a water tank with capacity of 20 litres connected to perforated PVC pipe for supplying water to the system. Results of the transient performance tests revealed that the zero energy cooling chamber storage temperature varied from ambient temperature by 17-20 oC. The environmental temperature at the period of test ranged over 25-32 oC. After construction of the structure, two stages (red and green mature) of sanmarzano variety tomato were tested. Data at 1, 5, 8,11,23,28 days was recorded and evaluated for firmness, color, general observation, and weight loss. As a result, those stored outside the chamber in ambient environment was in poor state and stayed only for 8 days in case of red tomatoes and 11 days in case of green mature tomato respectively, whereas tomato stored inside ZECC remained fresh at 23 and 28 days red ripe and green mature respectively.