How Accurate Weather Data Can Strengthen Logistics

by Steve McCarney, PATH Chihuahua, Mexico, just south of the US border, is so predictably sunny, one hardly needs to consult a newspaper to predict the weather. Chances are it will be sunny and dry. A few hours south, in Mexico City, the weather is more temperate and cloud cover more frequent during the year. Until now, if both cities followed World Health Organization Performance, Quality, and Safety (PQS) standards procedure, they would need a solar refrigerator capable of lasting five days without sunshine. In fact, lacking data to support a different policy, WHO has reluctantly maintained a global policy stating that all solar refrigerators, anywhere in the world, must be capable of providing five days of solar autonomy. As a result, a health center in Chihuahua would have more battery space than it needs, and a health center in Mexico City would never have enough. To remedy the situation, PATH's HealthTech program, funded by the United States Agency for International Development, has developed a tool to estimate the days of solar autonomy required in a specific location using local, historical weather data. PATH did this by selecting locations with 5 to 30 years of daily solar radiation data and charting the data to see periods of bad weather. Considering data over a 20 to 30 year period reveals how well a location supports solar energy collection. This in turn determines the size of the battery needed to maintain power at that location during periods of low sunlight. In areas with no solar radiation data, the tool provides a best guess, based on regional data and local data. Optimize is working with PATH and WHO to incorporate this battery requirement estimation tool into the WHO PQS standards for solar power systems. Accompanied by new standards for solar-powered, ice-lined fridges with no battery and refrigerators with longer-lasting batteries, this tool can not only predict accurate solar needs, but also identify a product to meet those needs.