Isobar an Ammonia-water filled backpack chiller

Published by Nick Barrowclough on

Isobar vaccine delivery system
ISOBAR logo Ammonia-water filled backpack chiller

The Isobar is a concept designed by William Broadway and won the James Dyson Award for its innovation. The backpack is a lightweight, vaccine delivery system that uses an ammonia-water refrigeration technology. it is capable of keeping vaccines cool for up to 6 days, much longer than traditional vaccine chiller and delivery systems. This could make it an effective method of transporting vaccines to rural areas where health services and electricity are lacking.

In Africa for example, there are often issues with vaccine programs failing to meet international standards for temperature-safe vaccine distribution. path.org found that many countries do not comply with safe vaccine transportation practices. This causes vaccines to loose their efficacy resulting in inoculations that do not protect the patient.

Millions of deaths can be prevented through the proper use of safe cold chain equipment.

Polio vaccines in transit

AVC 44 mobile vaccine boxes are the most widely used vaccine boxes in the world. They are cheap to produce and provide an insulated environment to store temperature-sensitive vaccines.  However, when you look closely into their effectiveness as a tool for safe vaccine carriage they have many failings in last mile delivery to rural areas.

AVC 44 mobile vaccine box

The best performing boxes on the market only provides 2-8°C temperature stability for 7.48 hrs at ambient temperatures of 43°C. it also requires 10 hours preparation to condition the box and cold packs.

As is typical in rural areas there are many challenges in getting to your destination, rainstorms, landslides, broken down vehicles. Is this box enough to protect $3,500 worth of vaccines?

How does Isobar work?

“It has two chambers and they have two sets of chemicals [ammonia and water] in the bottom. When you heat it, the chemicals separate and when you want the cooling effect, you flip the device over. When those two chemicals recombine, they give a really strong cooling effect,” explains William Broadway.

The Isobar heats a mixture of ammonia and water in a lower pressure vessel. The ammonia vaporises and separates from the water into an upper chamber where it is trapped by a valve. It remains trapped until the cooling effect is needed.

Isobar exploded view Ammonia-water filled backpack chiller

The process is controlled using an automated valve that monitors the internal temperature of the insulated vaccine backpack and recharged using either an internal electric heating element or propane burner. It can be sustainably recharged in an hour using a 900W heating element for day-to-day use with the propane burner allowing emergency recharging for up to 30-days.

The device is simple to use and can be worn as a backpack, making it easy to take to remote locations.

For more details visit http://isobar.org.uk


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