SolarChill harnesses the sun's energy to freeze an ice compartment that maintains the desired temperature, even at night.
The nuts and bolts of compressor technology can take on a humanitarian form. Consider the efforts to use state-of-the-art refrigeration expertise to deal with the issue of immunization.

Nearly 30 million children around the world have no access to immunization, according to the World Health Organization (WHO). The medical crisis is due in part to the difficulties of transporting vaccines to remote areas.

“In developing countries in the countryside and villages, there is no electricity at all,” said a spokesperson for the United Nations Children Fund (UNICEF). “Electricity is essential to maintain the cold chain. Otherwise, by the time the vaccine reaches the child, it is like water.”

Solar energy is helping the organization deal with the problem. In 1999, an international collaboration between industry, humanitarian, and environmental concerns was formed that eventually gave rise to SolarChill, a solar-powered refrigeration cabinet. Among those involved in the project were Danfoss, GTz/Proklima, Vestfrost, Danish Technical Institute (DTI), United Nations Environmental Programme, UNICEF, WHO, and Greenpeace.

Direct-current Danfoss BD compressors.

Harnesses Energy

The refrigerator runs on a direct current Danfoss BD compressor. It harnesses the sun’s energy to freeze an ice compartment in order to maintain the desired temperature, even at night. According to Danfoss, the unit does not require a battery and its price is about two-thirds the cost of other solar technology.

“The compressor from Danfoss is quite advanced and can run at variable speeds to control the cooling capacity,” said Per Henrik Pedersen, project manager for SolarChill at DTI. “We can adapt the cooling capacity to match the sun’s power.”

Danfoss has introduced a series of compressors with an electronic module enabling them to be powered directly from solar panels, with or without batteries.

Designated types BD35F and BD50F, the models use the 101N0300 electronic module.

They can be set up to operate over a continuous voltage range of 9.6 to 31.5 V. A programming option that is included will adapt the compressor for the voltage range of different solar power modules. According to the company, the compressors are designed to complement the current development efforts of OEMs in the field of solar refrigeration.

Type BD35F has a range of capacities from 92 Btu (at 25 W) to 137 Btu (at 45 W). Its capacity depends upon speed, which is controlled by the compressor’s electronics. The BD50F version ranges from 120 Btu (at 35 W) to 201 Btu (at 59 W).

A cabinet with a BD compressor was displayed at the Johannesburg UN Summit in September 2002. During the summit, the unit met UNESCO’s requirements for five days’ storage powered only by solar panel. Solar BD compressors can be connected to a photovoltaic panel without the use of batteries or any additional electronics, according to the company.

The units measure 8.7 by 5.1 by 4.4 inches. Danfoss said the product could also be used for beverage and ice cream stands, in remote bottle coolers, and for food preservation in stores during power outages.

For more information, visit

Publication date: 04/07/2003