Chill Challenge: Affordable, Off-Grid Refrigeration

“Our mission is to lift people out of poverty and reliable, affordable and sustainable refrigeration is a huge step in the right direction. Successful solutions to our Refrigeration Challenge will be a game changer for millions of people. We are extremely proud to launch our Challenge, catalyze innovative solutions and bring affordable refrigeration to improve the lives of those far removed from the grid.”
Cathy Leslie, EWB-USA Chief Executive Officer

The Problem

Refrigeration is a key to economic and social development; it is critical for health and nutrition, and can reduce food waste, provide economic opportunities for farmers and businesses, and reduce the burden on women. However, there may be as many 2 billion people worldwide without access to reliable refrigeration. While economic growth may bring refrigeration to a large portion of this population, refrigeration will be a particularly difficult challenge for the hundreds of millions of people who will acquire electricity via “mini-grids” or “solar home systems.” These distributed power systems increasingly have been used to provide power for lighting, cell-phone charging and TV for households far from the electricity grid. However, refrigeration requires a quantum leap in power and investment, and with current technology may remain out of the reach of most off-grid households for the foreseeable future.

The Challenge

To address this refrigeration “gap,” Engineers Without Borders – USA is launching the Chill Challenge, which has been funded by a generous grant from the Open Philanthropy Project. EWB-USA is also proud to have ASHRAE as a Chill Challenge partner, contributing to our expert panel of technical reviewers and providing outreach for the Challenge. 

The objective of the challenge is the development of refrigerators and icemakers that are significantly more affordable for off-grid communities than currently available units. EWB-USA intends to award grants of $25,000-$50,000 to as many as 10 teams to build and test prototypes. The competition will be open to all interested parties, and open to all refrigeration technologies.

Key Objectives:

  • Development of a 150-250 liter refrigerator that can chill 20 liters of water/day from 35ºC to 3ºC, and cost less than $12/month to own and operate, or
  • Development of an icemaker that can produce 100-1000 kg. of ice/day at a cost of $0.03/kg or less.

Both units must achieve these targets while operating on off-grid energy sources, and be otherwise suitable for use in remote developing communities. Detailed design parameters can be found here. This initiative is intended to be the first phase of bringing affordable, off-grid refrigeration solutions to developing countries. If viable prototypes are demonstrated, EWB-USA hopes to secure additional funding to support further development and marketing activities. We encourage anyone interested to sign up for updates and more information.

Response to Our Call

EWB-USA received 43 proposals from 36 teams from universities, companies or NGO’s, and individuals. Sixteen were U.S.-based, and 20 were located overseas, including teams from Cameroon, Ethiopia, France, Germany, Nigeria, South Korea, Switzerland, Uganda and the UK.Fourteen of the best proposals were shortlisted, and final grant winners were selected by a distinguished panel of reviewers, including EWB-USA volunteers and international refrigeration experts. The following teams will be awarded grants ranging from $30,000 to $50,000 to develop their innovative concepts:

Meet the Teams

Meet the teams and learn more about their proposed solutions.


Arup, London, UK
Arup’s Passive Cooling Box:   Arup’s Advanced Digital Engineering team will test a passive refrigeration system that uses, as a cold source, passive cooling materials that emit heat as infrared radiation through the “atmospheric transmission window” into space. Phase change materials will provide cold storage..


Imperial College London, Clean Energy Processes (CEP) Laboratory, South Kensington, UK
Affordable Decentralized Off-Grid Icemaking: The CEP team in collaboration with Solar Polar will design and demonstrate a solar-driven diffusion absorption refrigeration (DAR) icemaker based on new working-fluid pairs and innovative designs aimed at increasing system performance, affordability and lifetime..


New Leaf Dynamic Technologies, New Delhi, India
Ice Maker Powered by Farm Waste: The company will use its “GreenChillTM” adsorption technology to build a 1000 kg/day ice-maker powered by biomass in the form of husk, straw, wood, or biogas.  Solar PV will provide electricity to power auxiliary equipment.


Purdue University: Ray W. Herrick Laboratories, West Lafayette, Indiana
Cold Storage Battery for Domestic Refrigeration: This project will evaluate the use of heat from clay or brick cook stoves to drive an intermittent sorption “cold storage battery,”  which requires no electricity to operate.
Combined Heating and Cooling for Agricultural Applications: This project will examine the potential for a simultaneous heating and cooling vapor compression system in which evaporator capacity is used to create ice and condenser heat to dry crops. The system will be powered entirely from solar PV.


Solar Cooling Engineering, Hohenheim, Germany
Solar Ice Maker Using Key Components and Engineering: This team will use solar powered SelfChill® cooling units for its ice-maker to produce 100-120 kg ice per day. The concept is fully scalable and will allow a local assembly and the integration of locally available materials. The ice-maker can be powered without electrical batteries.


Xergy, Inc., Harrington Delaware
Off-the-Grid Refrigerator Utilizing Solid-State Refrigerants: Xergy will build an intermittent adsorption refrigerator using hydrogen and metal hydride as the working pair.  Hot water provided by solar thermal collectors will drive the process.


Meet the Grantee Review Panel

Our grantee review panel is one-of-a-kind! Learn more about their diverse backgrounds and experiences.