Devices: Sun Fridge

World Health Organization (WHO) studies show that many vaccines shipped to treat preventable diseases in the developing world spoil before caregivers have the chance to dispense them. The valuable medicine is most frequently ruined by exposure to high temperatures and rough conditions during transport.

That’s why alumnus Steve Lanzisera (Ph.D.’09 EECS), an expert on using network-embedded sensor and actuator systems to manage energy usage, is part of an effort to design a portable solar-powered refrigerator to safely deliver vaccines to the developing world. The scale of the medicine shortage problem is huge. The WHO estimates that up to 1.5 million children under the age of five die each year from vaccine-preventable diseases such as diphtheria, pertussis, tetanus and polio.

Sun fridge detail. Photo by Thomas Walden Levy

Problem

“We just haven’t had good technology for delivering vaccines with good temperature management,” says Lanzisera, who works in the environmental energy technologies division at Berkeley Lab, part of a team developing the vaccine refrigerator. “But this fridge design leverages the deep knowledge other people have of thermal design, as well as our years of work on making sensors smarter and bringing a useful Internet-of-Things application to the developing world.”

Vaccines are extraordinarily heat sensitive. Their safe temperature range may only extend from 2º to 8ºC (35º to 46ºF). If hotter or colder than that for even short periods of time, vaccines can become useless.

With grid electricity and batteries unavailable or unreliable in many regions where vaccines are needed, such as tropical South Asia or sub-Saharan Africa, the most common method for keeping vaccine vials cold is coolers stuffed with ice packs.

But inside these coolers, which lack any means to regulate temperature, the ice packs, often chilled to around -10ºC (14ºF), can freeze and destroy the vaccines. Meanwhile, daytime temperatures in these areas are routinely sweltering.

Solution                                                                                                                     

Lanzisera and the team designed a refrigerator that combines lightweight passive thermal design with smart energy/temperature management technology, all powered by photovoltaic cells able to generate up to 385 watts of electricity. Their refrigerator, also connectable to wall outlets or generators, can keep vaccines within their safe temperature range for days at a time, even without external power or sunlight to drive its solar cells.

The cubical refrigerator, about the size of a large cooler, swaddles dozens of vaccine vials inside each of four aluminum sleeves — with a total capacity of 18 liters (4.75 gallons) — spaced symmetrically around two central reservoirs filled with about 12 liters (3.17 gallons) of water. Thermo-electric technology, instead of the traditional, heavier vapor compression, is used to freeze the water and cool the vaccine.

The refrigerator is also packed with sensors to monitor and record temperature data about how well it’s keeping the vaccines tucked inside at the proper temperature. The refrigerator uses cell phone text messaging technology to periodically deliver temperature and GPS location data to vaccine-delivery managers and healthcare workers.

Result                                                                                                                        

The team filed a patent last fall. Starting this year, they will field-test prototypes in Africa. The sun fridge team members are also in late-stage talks with a large healthcare device manufacturer.

The target cost is less than $1,000, and the team hopes to get thousands of the refrigerators in use by governments and healthcare organizations, particularly for use in South Asia and sub-Saharan Africa.