78. Potential of Adsorption Refrigeration System for Off-Grid Cooling Applications

Lack of cold-storage facilities for food products, vaccines, medicines and artificial insemination services is a serious problem in many developing countries. FAO estimated that 32% of food produced in the world was wasted in the year 2009 while the IEA reported that more than 20% of the world’s population lacked access to electricity in the year 2010. Among them 57% lived in rural areas in sub-Saharan Africa. Water-ammonia kerosene and gas-driven absorption systems have been used to store vaccines. However, they do not meet the minimum standards established by WHO on Performance, Quality and Safety for the required +2 °C to +8 °C temperatures. PV-powered cooling systems preserve vaccines more efficiently and in an environmental friendly manner. However, batteries are needed. Batteries live shorter than refrigerators, implying extra costs. Also, PV systems have low possibility of being manufactured in most developing countries. Adsorption refrigeration systems have shown great potential to meet cooling needs in off-grid locations. They can utilise low-temperature waste heat and renewable energy sources like solar thermal energy to providing cooling.

A single-bed water-cooled condenser adsorption refrigerator prototype, which utilises CaCl₂-ammonia pair has been developed and tested in the laboratory. Experiments have been conducted for desorption temperatures ranging between 75 °C and 100 °C and desorption time of 1–4 h using an electric tape heater. The effect of desorption temperature and desorption time on the cold chamber temperature have been analysed and discussed. At desorption temperatures of 85 °C and higher and desorption time greater than 1 h, the cold chamber of the prototype attained temperatures between 2 °C and 8 °C, which is a suitable range for storage of food products and vaccines. Temperatures below 0 °C, which are suitable for ice production, were obtained at desorption temperatures greater than 95 °C and desorption times of 2 h and higher. Desorption temperature lower than 85 °C can be used for air conditioning applications as they have attained cold chamber temperatures below 15 °C for desorption time greater than 1 h. The tested desorption temperatures are common temperatures, which can be attained by flat plate and evacuated tube solar collectors.