Designing a solar-powered refrigerator to store vaccines
In 2008, WHO estimated that 1.5 million deaths among children under 5 years were due to vaccine-preventable diseases. Immunization systems in low-resource areas are unsustainable due to a lack of electricity, unreliable transportation, and gaps in the vaccine supply chain. The Solar Fridge is an inexpensive, portable, and low-maintenance adsorption refrigerator for vaccine storage that ensures the safety and viability of vaccines in low-resource communities. Between 2008 and 2012, this project transitioned between different departments and teams. Although the general focus of vaccine sustainability has persisted, the user needs and target population were either lost or not found. Therefore, the project has recently focused efforts on the reevaluation of its needs assessment approach. In doing so, the team has compiled a list of approximately 50 potential partnerships based in Asia and Africa for evaluation. A Pugh chart was developed to evaluate each community in the following categories: travel safety & feasibility (1), capacity to host (2), and goal alignment (3). A rubric was also created for each category to outline criteria that are most suited towards the project. This process has helped Solar Fridge in re-establishing a need, allowing for future progress towards improving vaccine sustainability.
Vaccines prevent disease and save lives every year. However, vaccines are extremely sensitive to temperature and must be kept within a range of 2-8 degrees Celsius. In rural areas with extremely warm climates and unreliable electricity, keeping vaccines at their optimal temperature is a challenge. According to the World Health Organization, vaccines prevent more than 2.5 million child deaths a year, yet nearly 24 million children under one year of age are not being vaccinated. There is a need for an alternative way of refrigerating vaccines to help these rural regions.
Adsorption refrigerators use thermal energy to keep the contents of the refrigerator at a desired temperature. At night, the pressure and temperature in the refrigerant system decrease, and the heat from the cold chamber evaporates the liquid refrigerant. The adsorbent material in the solar collector then adsorbs this vaporized refrigerant. During the day, the heat is absorbed by a silica gel, causing the pressure and temperature of the refrigerant in the adsorbent material to increase. The refrigerant is then released as a vapor, which then travels in a condenser, releasing heat to the environment before it condenses back into a liquid. The refrigerant returns back to the evaporator, and the cycle can begin again.
The solar fridge team has been designing and building a prototype of an adsorption solar refrigerator that could easily be built on site. Our design uses a solar collector and cold chamberinsulated with polyurethane. At this point, we are running evaporation tests and continuing to work on the prototype.