Many health facilities in low- and middle-income countries lack access to reliable mains electricity, making the refrigeration of vaccines at appropriate temperatures challenging. A common solution is to use solar direct drive refrigerators. The solar arrays that power solar direct drive refrigerators often produce more energy than the refrigerator requires, and this underutilized energy could be used to power a range of electric devices to improve the service offerings and conditions in the health facility.

Potential uses include powering lights, fans, cellular phones, and medical devices such as fetal Doppler heart rate monitors and otoscopes. We tested two energy harvest control (EHC) systems that could send the underutilized power to other devices while prioritizing the power requirements of the vaccine refrigerator. Testing was conducted at health facilities in Senegal.

Monitoring of the power diverted by the EHCs to both dump loads and user–selected devices demonstrated that useful amounts of electricity could be harvested. Monitoring of the refrigerator vaccine compartment temperature showed that temperatures remained within the appropriate range during energy harvesting. Informal and structured interviews with health facility staff indicated acceptance of the EHC, appreciation of the additional power provided, perceived improvements in care, and better community/client perceptions of the health facility.

These results show that EHCs used with solar direct drive vaccine refrigerators can provide a useful source of additional electricity to health facilities without compromising the primary function of the vaccine refrigerator.