Tech Watch: New refrigerator type aids vaccine cold chains

From the newsletter

Supply challenges already hinder vaccine delivery in Africa, but cold chain issues, specifically maintaining temperatures between 2°C and 8°C, further exacerbate access gaps and hinder vaccination efforts. Solar Direct Drive (SDD) refrigerators, which differ from traditional solar vaccine refrigerators that store energy in batteries, have proven beneficial for many African nations.

• The SDD refrigerator is powered directly by photovoltaic (PV) solar panels, eliminating the need for batteries. When sunlight is available, the system freezes water or another phase change material within an internal cold storage bank.merging

• Our quarterly survey of health tech in Africa includes 3D telemedicine vans bringing expert care to remote areas and PROMPTS, an AI-powered SMS service offering maternal health support to millions of Kenyan women.

More details

• The SDD (Solar Direct Drive) refrigerator utilises a frozen reserve to maintain the required internal temperature, typically between 2°C and 8°C, during nights or cloudy periods. The absence of a battery system reduces maintenance needs and enhances reliability, particularly in remote areas.

• SDD refrigerators feature a charge controller that regulates energy transfer from photovoltaic (PV) panels to the compressor. As sunlight powers the compressor, the refrigerant cycles through the evaporator and condenser to provide cooling. Simultaneously, a thermal storage medium, usually water, freezes within an insulated compartment.

• When sunlight diminishes, the stored thermal energy gradually melts, maintaining internal cooling through latent heat absorption. This passive thermal energy storage ensures consistent temperatures for up to four days without sunlight.

• To ensure proper vaccine preservation, SDD units are equipped with thermostats and temperature monitoring devices, such as Vaccine Vial Monitors (VVMs). These indicators signal when vaccines may have been exposed to temperature deviations, ensuring only potent doses are administered.

• SDDs are WHO PQS-certified and designed to operate efficiently in high-ambient temperature regions like Northern Nigeria, where conventional refrigeration is challenged by frequent power outages.

• In 1999, former NASA engineer David Bergeron licensed solar cooling technology and founded SunDanzer. By the early 2000s, SunDanzer developed the PV Direct-Drive refrigerator, which employs solar-powered vapour compression and phase change materials to store cold without batteries.

• In 2009, global health non-profit PATH funded SunDanzer to ensure compliance with WHO vaccine storage standards. Following technical upgrades, including air circulation fans and thermal optimisation, the fridge received WHO prequalification in 2011. Today, organisations such as the United Nations Children's Fund and the Global Alliance for Vaccines and Immunisation deploy SDD fridges in off-grid health clinics globally.

• While SDD refrigerators are efficient and less expensive compared to battery-powered systems, they require a significant upfront investment compared to other refrigeration technologies. This cost can pose a barrier for some health facilities, particularly in resource-constrained areas, with installation costs starting at around $4,000.

• 3D Telemedicine (3DTM) is a healthcare technology that employs Microsoft Holoportation communication technology to deliver a 360-degree, real-time, immersive virtual consultation experience. It was developed through collaboration between Microsoft, the Canniesburn Plastic Surgery Unit, and Korle Bu Teaching Hospital (KBTH) in Ghana.

• The technology uses specialised cameras to capture 3D models of patients, allowing healthcare providers to interact with them remotely as if they were in the same room. This capability enhances pre-operative and post-operative care, as well as communication for complex medical procedures.

• The PROmoting Mothers in Pregnancy and Postpartum Through SMS (PROMPTS) project, a collaboration between Jacaranda Health, the Kenyan government, and The Rockefeller Foundation, has reached over three million women across 23 counties in Kenya.

• The service provides maternal healthcare information via SMS. With an AI-powered system managing daily inquiries, 70% of the 10,000 to 12,000 daily questions are answered automatically within minutes. The service's cost-effectiveness is notable, with a lifetime cost of just $0.74 per mother.

Our take

• In Sub-Saharan Africa, inadequate energy access in hospitals and clinics has historically impeded healthcare quality. The challenges associated with maintaining the vaccine cold chain further underscore the urgent need for dependable power sources.

• While data on this issue is still scarce, multiple multi-country studies consistently indicate a substantial energy gap within the health sector, which negatively impacts the provision of essential services to millions in the region.