Rebound developing nontoxic refrigeration
And that’s the premise behind new technology being developed by Boulder-based Rebound Technology LLC.
First, the closed-loop system freezes water at night when electricity rates are lower for many commercial customers. During the day, that ice is melted and mixed with a salt, causing a chemical reaction that creates a minus 31 degrees Fahrenheit refrigerant that is used to keep the freezers freezing cold. At the back end of the cycle, the brine is separated using waste heat from the supermarket, such as from nonfreezing refrigerators, so that the salt can be stored while the water is refrozen.
Because of the corrosive nature of the salt, Davis said Rebound is testing different additives to reduce that characteristic of the brine. But, rather than piping the brine to the freezers, he said the brine could also be used to chill another secondary liquid like glycol that would then be circulated to the freezers.
Davis and Muren – the company’s chief technology officer and the one who created the patent-pending technology – say the system is about 45 percent more energy efficient than conventional systems used in stores now. The other 20 percent of cost-savings comes from the load shifting, or purchasing power from the electric grid during low-demand hours and essentially storing it in the ice.
As smart-grid technology progresses, Muren said IcePoint could even be tailored to receive signals from the grid to cycle on and off on demand.
“It becomes like a community battery because it’s pulling power when the utility needs a load reduction,” Muren said.
Muren said the early stage of development leaves some ambiguity in what the system will someday cost. But he said that for a typical supermarket the target would be to make the capital cost $200,000 or less. However, the important point, he said, is that the payback period due to operating cost-savings is just three years.
“At the end of the day, everybody cares about return on investment,” Muren said. “It’s more about the payback.”
Davis and Muren met while working together at Abengoa Solar in Lakewood, Muren on thermal energy storage research and Kevin managing research and development projects. Muren left Abengoa in late 2011 and began developing the IcePoint technology in early 2012, with Davis joining him in May of that year.
For about the first 18 months, the company operated on $55,000, with Muren building the initial lab-scale prototype in his garage. About $15,000 of that came out of Muren’s and Davis’ pockets. The other $40,000 came from participating in an entrepreneur program sponsored by the Chilean government in which Davis spent seven months in the South American country participating in workshops and other events to help teach locals there what it’s like to be an entrepreneur and turn an idea into a viable business.
Rebound recently hired its first employee, chief engineer Luke Erickson, to support Muren. Davis, meanwhile, is living and conducting business in California because Rebound envisions that state to be an initial target market due to its progressive energy and environmental policies and incentives.
The grant from the NSF gave the company a much-needed boost, but it wasn’t Rebound’s first. In October, the company received a $1.4 million award from the United States Agency for International Development to build a low-cost solar-cooled refrigeration system for developing countries called SunChill that will help farmers reduce spoilage after harvest.
The SunChill technology is still in its infancy, existing only on Muren’s computer. But over the next two and a half years, Rebound will work on developing that system, further building its relationship with the CSU Energy Institute through prototyping and testing there.
The final year of that award cycle will be spent in Mozambique, building a prototype out of local materials and testing it in the field. Partners on the SunChill project also include TechnoServe, a nonprofit organization focused on business development in developing nations, and Mozambique Organicos, a research farm that will be the primary demonstration site.
The IcePoint technology, though further along, still has plenty of development ahead. The initial NSF award is to demonstrate proof of concept with the prototype. A phase 2 award would allow Rebound to validate a larger demonstration unit.
“We’re hoping that we meet the milestones and convince the NSF to award us a phase 2 … to really start developing the technology,” Davis said.
If IcePoint makes it to market, Davis said he anticipates that the technology would be licensed out or purchased by a larger refrigeration company due to the nature of the industry. But he said he does anticipate that the majority of the system would be manufactured in the United States.
“One of the beauties of this system is it is mostly off-the-shelf parts,” Davis said.
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