Development and performance assessment of a solar-powered vaccine refrigeration system for off-grid rural health facilities

Abstract

Safe vaccine storage – vaccine efficacy depends on a safe cold chain. However, many rural and off-grid healthcare centres in Uganda suffer from frequent power crises, high cost of energy, as well as lack of proper cold chain equipment and infrastructure. Consequently, in order to keep safe storage conditions (between 2 and 8 °C) and to lessen dependence on electricity and the cost of cooling with low environmental impact, we developed a 50-litre solar refrigerator. This concept integrates 50 W of solar PV, a 100 Ah battery, grid back-up and a 50 W vapor compressor using R290 (propane). The use of R290 was chosen as part of the move to refrigerants which do not negatively impact climate change. R290 has a Global Warming Potential (GWP) of roughly 3 as opposed to1,430 for R134a. The system was tested in Busamuzi Health Centre II, Buvuma District. We recorded temperatures with an Arduino every 15 minutes. I also employed thermodynamic simulation, statistical analysis, and a Total Equivalent Warming Impact assessment. This device kept the internal temperature stable at an average 4.1C. The average value fluctuated between 3.8 and 4.4C most of the time. The Stability Reliability Index value is 96.8%, as, after achieving the target temperature, the value never fell outside 2- 8 °C. The steady-state COP was 5.80, much better than the target of 3.0 of the study. It used around 468 watt-hours per day. The statistics showed that the real performance was significantly different from the performance of our simulation (p < 0.05). Simulations also showed that refrigerants behave very differently. The system took 165 minutes to reach the desired storage temperature, which was above the target of 120 minutes. The results overall indicate that the combination of solar power, a 100 Ah battery, a grid power option, and R290 refrigeration is a good way to improve vaccine cold storage in rural areas, especially given the low environmental impact of the system. Recommend adjustingcompressors sizeand Insulation with some more test cases of hot conditions, safety, and certification for mass production.