by Steve McCarney and Joanie Robertson, PATH
Many health facilities in remote areas operate without grid electricity, have unreliable electricity, or find that using electricity is too costly. In these settings, solar energy is a promising solution for powering the storage and transportation needs of vaccines and heat-sensitive drugs at controlled temperatures. Project Optimize has been collaborating with public and private partners on several solar technologies tailored to local electrical power conditions: unavailable or unreliable power, intermittent power, and reliable power.
When electricity is available less than four to eight hours on average per day, it becomes very difficult to rely on electric refrigerators for vaccine storage. While kerosene- or gas-fueled absorption refrigerators are one option, they are difficult to maintain at proper temperatures, require significant maintenance, are not energy efficient, contribute to global warming, and the fuel is often diverted to other uses.
An alternative option that has been in use for over 30 years is solar-powered vaccine refrigerators. Until recently, the refrigerators available in this class were essentially first-generation design, using photovoltaic (solar) modules that recharge a high quality, industrial battery system to store solar energy for use during night and poor solar weather conditions. While successful solar refrigeration projects of over ten years have been reported, many have suffered from battery system failures. If battery replacement is not anticipated or funding is unavailable, then the entire vaccine refrigeration system fails. Optimize has been encouraging companies to improve the reliability and life of solar-powered vaccine refrigeration.
Lifetime battery refrigerators in Vietnam
A “lifetime battery” is a battery that can outlast the 10- to 20-year lifetime of the refrigerator or the 20+ year lifetime of the solar module. New battery technologies (e.g., lithium) developed for the growing electric and hybrid vehicle market appear promising in solar refrigeration applications. This innovation decreases battery maintenance and disposal burden for health centers while hopefully eliminating battery replacement entirely. Vietnam is currently piloting the use of lifetime batteries in refrigerators at two government health centers on Cat Ba and Cat Hai. This PATH Health Innovations Portfolio project is principally funded by the Bill & Melinda Gates Foundation with support from Optimize and collaboration with Hai Phong Medical University.
Solar direct-drive vaccine refrigerators in Vietnam and Senegal
The next generation of solar refrigerators will solve the problems of the external battery by doing away with it all together, connecting solar panels directly to the compressor driving the refrigeration cycle. In 2010, the first solar direct-drive vaccine refrigerator was prequalified by WHO, meeting a new set of Performance, Quality and Safety (PQS) standards for solar direct-drive refrigerators. Instead of storing electrical energy in a battery, these direct-drive refrigerators use cool storage (i.e., an “ice battery”) hidden in the refrigerator cabinet to maintain vaccine temperatures between the required +2º to +8ºC. At night or during prolonged cloudy, rainy weather, the well-insulated cool storage maintains acceptable temperatures for many days.
Senegal and Vietnam are conducting demonstration projects of solar direct-drive battery-free refrigerators in health facilities. Field demonstration of 15 WHO PQS prequalified solar refrigerators is taking place at health posts in Senegal’s Podor and Pete districts. In Vietnam, a solar direct-drive refrigerator is being tested at a health center in Thanh Phu district (Ben Tre province) in the south of Vietnam and the Thanh Ba district (Phu Tho province) in the north.
With intermittent power conditions, electricity shortages result in frequent interruptions and sudden re-establishments of power. In places where grid electricity is not reliable, diesel backup generators are needed to ensure an energy supply to refrigerators. However, generators are costly to operate, difficult to maintain and repair, create air and noise pollution, and the fuel supply is subject to disruptions and may be diverted for other uses.
Hybrid solar and electric refrigeration in Senegal
Senegal benefits from excellent solar radiation, but solar energy is not exploited because of the high initial equipment costs. Meanwhile, grid electrical power outages are common in Senegal. Fortunately, solar power system costs are decreasing, making a solar and electric grid hybrid system an attractive alternative where diesel-fueled back-up generators traditionally have been used.
The Senegal Department of Preventive Medicine is working with project Optimize to explore ways to improve reliability, acceptability, and efficiency of solar energy in powering the cold chain at regional and peripheral levels. The team is installing a hybrid solar and grid electric power system at the Regional Supply Pharmacy in St. Louis. In addition, new ice-lined refrigerators have become WHO PQS prequalified, demonstrating over ten days of sustained vaccine temperature control without any power, even in the hot climate of Senegal. Grid power will be used for these super long-life ice-lined refrigerators while solar electricity backs up other critical loads like freezers, lights, and computers.
Locations with reliable energy are often dependent on jet fuels, diesel vehicles, and electric refrigeration for vaccine distribution and storage. Some countries, like Tunisia, are using limited sea transport for vaccines shipped from Europe, which is an energy-saving solution because boats are more efficient and pollute less than air freight. However, there are several additional opportunities for energy efficiency in the transportation and storage of vaccines and heat-sensitive drugs even in places with reliable power.
Toward net-zero energy in Tunisia
The Tunisian Ministry of Health is working with project Optimize to demonstrate the benefits of a “net-zero energy” supply chain. Over the course of a year, four health facilities are being designed to produce as much on-site renewable energy (e.g., wind or solar) as is consumed by on-site cold chain storage and transport. Rather than operating diesel-fueled vehicles, the team is introducing electric vehicles that can be powered by solar energy collected on site.
In addition, energy-intensive equipment such as refrigerators, computers, and lights are being made more efficient through low- or no-cost management decisions. In some cases, the contents of two refrigerators can be consolidated into one, cutting energy use roughly in half. Older, less efficient refrigerators and desktop computers can be replaced with new, higher efficiency refrigerators and laptops.
The Tunisia team (as well as the Senegal team) has started using light emitting diode (LED) lights in place of traditional incandescent lights. This reduces energy without sacrificing lighting levels and ultimately cuts operating costs. And because LED lights run cool, this reduces unwanted heat from less efficient lights, decreasing the need for cooling energy. LED lights also last up to 25 times longer than incandescents and are mercury free which minimizes pollution. Through measures like these, the anticipated benefits of the net-zero supply chain include reductions in electricity costs, fuel costs, maintenance, and environmental impacts.
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