Access to refrigeration is key to a number of the UN’s Sustainable Development Goals. Refrigeration contributes to health and nutrition, provides economic opportunities for farmers and businesses and reduces the burden on women.
However, it remains scarce in many parts of the developing world. As many as 2 billion people on the planet don’t have access to reliable refrigeration. Communities without access to the power grid or with unreliable electricity oftentimes don’t have refrigeration in their homes, businesses and health care facilities.
Engineers Without Borders USA (EWB-USA) addressed this problem through their ambitious Chill Challenge.
The challenge awarded $300,000 in grants to projects with real-word impacts. But the broad, international undertaking was first born out of a simple friendship.
A Friendship with Purpose
Engineers Andrew Dowdy and Larry Bentley met at an EWB-USA conference in 2014 and quickly became friends. They both have extensive experience working in refugee camps and medical clinics across the globe and lamented the absence of essential off-grid refrigeration units.
“They tend to be very expensive and basically only occur when there was a donor who cared enough and wanted to plop down about $2,500 to get a refrigeration unit that needed solar panels,” said Larry. “Basically, you don’t see refrigeration in the developing world once you get past the power line.”
Andrew said the pair began brainstorming ways to solve refrigeration challenges around the world.
“My expertise is writing about fixing problems,” said Andrew. “Larry’s expertise is actually fixing things.”
Their skills and personalities complemented each other, and they decided that EWB-USA should issue an energy-related challenge that would invite teams to propose solutions to a particular problem.
The stars seemed to align when the XPRIZE Foundation invited innovators to design a challenge as opposed to designing an actual solution. With hundreds of thousands of dollars on the line, Larry and Andrew created the Chill Challenge — a call for engineers to design solutions for off-grid refrigeration.
They submitted their challenge idea in three of the five different XPRIZE categories: ‘Lifting Farmers Out of Poverty,’ ‘Feeding the Next Billion’ and ‘Off-Grid Energy for the Developing World.’
As they advanced to the final round of the XPRIZE, Larry and Andrew pitched their idea at the Visioneering Summit in Los Angeles, CA. Andrew said it was a glitzy event with world-renowned executives and innovators.
Larry said, “Andrew and I were the grandparents of the crew. The youngest participant was 16.”
But they were unfazed, and their academic rigor and scientifically-grounded pitch drew the attention of the Open Philanthropy Project, who committed $500,000 to EWB-USA to establish the Chill Challenge. Larry and Andrew were also awarded the XPRIZE for the category ‘Off-Grid Energy for the Developing World.’
A Challenge Without Limits
Once EWB-USA had the funds to support the challenge, it was time to solicit proposals.
The objective of the Chill Challenge was to develop affordable, energy-efficient refrigerators and ice makers to off-grid communities in developing countries.
The challenge focused on affordability. Refrigeration systems could be more cost-effective by using energy sources typically available in off-grid communities.
It also aimed to include refrigeration systems that could benefit entire communities instead of households. A larger (150-250 liter) fridge or a community-sized (100-1000 kg/day) ice maker would be suitable for commercial applications, like a shop or bar.
The Chill Challenge didn’t limit the projects to vapor compression refrigeration. It was open to all cooling technologies, including thermally-driven processes. The full design parameters are featured here.
The solicitation attracted 43 proposals from 36 teams representing universities, companies, NGOs and individuals. Sixteen of the teams were based in the U.S. Other proposals came from teams in Cameroon, Ethiopia, France, Germany, Nigeria, South Korea, Switzerland, Uganda and the UK.
The ideas were creative and resourceful. One team proposed the use of draft animals as a source of power. The EWB-USA panel narrowed the 43 proposals down to a shortlist of 14. They then awarded grants to seven final teams. The grants range from $30,000-50,000 and represent a good mix of refrigeration technologies, including vapor compression, thermal sorption and sky radiant cooling.
“It was really difficult to select only a handful of proposals for grants,” said Andrew.
Technologies Represented In The Challenge
Vapor Compression:
Vapor compression refrigeration, powered by solar PV panels, is the most widespread off-grid refrigeration technology in use today. However, it is difficult to meet the Chill Challenge affordability targets using this technology.
The two vapor compression proposals that received grants were for ice makers, which offer more advantages for the cost. Ice makers also address “dark day” challenges by storing ice, rather than using battery storage.
- Solar Cooling Engineering will build an ice maker using five of its SelfChill® cooling units powered by solar PV. These are DC direct drive vapor compression units using R-600a (isobutane) as a refrigerant with low global warming potential (GWP). A key to affordability is to combine these units with locally produced refrigeration cabinets to provide flexible, lower-cost refrigeration options. The unit will use a smartphone connection for monitoring and will be enabled for pay-go financing.
- Purdue University proposed to offset the cost of an ice maker by using a combined heating and cooling vapor compression system to make ice and to dry crops. The unit will make 100-150 kg of ice per day, using R-290 (propane) as a low GWP refrigerant and solar PV as an energy source. The research will evaluate food drying and storage practices, including their prices and seasonality. Potential applications of the technology will then focus on locations that produce food items that command high value and/or are available throughout the year.
Solar Thermal Sorption:
Solar refrigeration, using sorption processes, has been investigated for many years, but commercial success has been elusive. A big challenge is that the coefficient of performance (COP) for thermal sorption systems is well below that of vapor compression systems.
The low COP’s of thermal systems, combined with the falling cost of solar PV panels has favored vapor compression systems for off-grid applications. However, the costs of evacuated-tube solar collectors have also fallen rapidly. Furthermore, thermal systems may be able to address “dark-day” contingencies by storing hot water.
- Imperial College London proposed to use hot water from solar collectors to drive a diffusion absorption refrigeration (DAR) process. The basic process, used for decades in propane and kerosene refrigerators, has proved to be simple and reliable with no moving parts. But COPs, using ammonia and water as the working pair, are typically 0.2 or less. The team expects to significantly improve performance by using alternative working fluid pairs and optimized unit design.
- Xergy Corporation will build an adsorption refrigerator driven by solar thermal energy. It uses hydrogen and metal hydrides as the working pair. The unit will employ an advanced heat exchanger design, which the company believes will result in an efficiency of 70%. If successful, the team believes the refrigerator would provide a simple, easy to maintain solution for remote off-grid communities.
Biomass Thermal Sorption:
On paper, sorption systems using biomass should be quite affordable. Biomass, in the form of fuel wood or charcoal, is widely available for cooking in off-grid communities, and is an extraordinarily cheap source of thermal energy. This should make it affordable even for processes with relatively low COPs.
- Purdue University proposed to test a “Cold Storage Battery” driven by heat from a cook stove. This is essentially an intermittent adsorption refrigeration system – a heat source will generate the refrigerant, which can be discharged at a later time to provide cooling on demand. While the unit will be designed to be used alongside cook stoves, other thermal sources could be used.
- New Leaf Dynamic Technologies will use its GreenCHILLTM technology to build a 1000 kg/day ice-maker that can be powered by any number of biomass sources. This is an adsorption system, using R-717 (ammonia), that the company has already deployed in more than 25 locations in India. The system will need an estimated 105 kg of wood equivalent biomass per day to produce 1000 kg of ice and will use electrical power, provided by solar PV, to run auxiliary equipment.
Sky Radiant Cooling:
“Night sky radiation” is a well-known phenomenon that was used by ancient Persians to produce ice. It was also tested in “roof-pond” houses in the 1970s for residential cooling. In recent years, researchers have developed surfaces that enhance this effect by radiating heat at infrared wavelengths that can pass through the atmospheric window into space. At the same time, the surfaces are highly reflective of sunlight which allows them to maintain temperatures below ambient while exposed to full sun.
- Arup Engineering proposed to build a completely passive cooling box using this phenomenon for cooling and using phase change materials for cold storage. If successful, this could lead to the development of a refrigerator that operates without electricity or refrigerant, a simple and inexpensive cooling solution for many communities in the developing world.
Next Steps for the Teams
The teams now will focus on the development and testing of these prototypes. If the prototypes prove viable, EWB-USA intends to solicit additional funding to further support the projects.
Cathy Leslie, EWB-USA’s chief executive officer said, “Successful solutions to our Chill Challenge will be a game-changer for millions of people and we are extremely proud to be catalyzing new ideas and inspiring out of the box thinking on this vital development tool.”
As the ‘grandfathers’ of the challenge, Andrew and Larry hope to see the prototypes being put to use as they work on EWB-USA projects around the world.
“My goal before I kick off is seeing one or two of these things in a bush clinic or at a little store on the side of a dirt road somewhere,” said Larry. “Affordable refrigeration in off-grid communities will be more than a cool drink. It will, in a small way, change the world because of wider benefits such as improved nutrition and education,”