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Radiative Coolers for Rooftops and Cars

Stanford University
ARPA-E Award: 
Stanford, CA
Project Term: 
02/20/2013 to 03/19/2018
Project Status: 
Technical Categories: 
Critical Need: 
New and more efficient cooling methods are needed to reduce building energy consumption and environmental impact. Residential and commercial buildings currently account for nearly 75% of the nation's electricity use, the vast majority of which comes from coal-fired power plants that produce harmful carbon dioxide (CO2) emissions. The demand for air conditioning in homes and buildings is increasing each year, so new and substantially more efficient cooling methods are needed to reduce energy consumption and environmental impact going forward.
Project Innovation + Advantages: 
Stanford University is developing a device for the rooftops of buildings and cars that will reflect sunlight and emit heat, enabling passive cooling, even when the sun is shining. This device requires no electricity or fuel and would reduce the need for air conditioning, leading to energy and cost savings. Stanford's technology relies on recently developed state-of-the-art concepts and techniques to tailor the absorption and emission of light and heat in nanostructured materials. This project could enable buildings, cars, and electronics to cool without using electric power.
Potential Impact: 
If successful, Stanford's radiative coolers would improve the energy efficiency of buildings and vehicles, save consumers money, and reduce peak-power demand.
Reducing building cooling loads reduces pressure on the electrical grid, improving its stability.
Better building efficiency and cooling devices would limit electricity consumption and reduce CO2 emissions.
Improvements in heating and cooling efficiency could save homeowners and businesses thousands of dollars on their utility bills.
Innovation Update: 
(As of May 2016)
Stanford University has developed and demonstrated a prototype panel of novel cooling material that radiates heat away from structures and sends it directly into space. The team is now scaling its technology to cool water for use in conventional air conditioners and for direct use in the chilled water loops of office buildings, shopping centers, and warehouses. The team is also exploring other commercial applications for its technology, including standalone systems or as a complementary component to larger cooling systems. 
The team’s principal technical success is the development of a multi-layered coating capable of reflecting nearly all the sunlight across the solar spectrum and emitting energy in the mid-infrared frequency range. Stanford’s technology incorporates nanostructured materials that tailor the reflection, absorption, and emission of light and heat. Stanford’s successful demonstration has led several separately funded groups to propose similar approaches to passive, radiative cooling for thermoelectric power plants, including projects that are part of ARPA-E’s Advanced Research In Dry-cooling (ARID) program.
For a detailed assessment of the Stanford team's project and impact, please click here.

ARPA-E Program Director: 
Dr. Christopher Atkinson
Project Contact: 
Dr. Shanhui Fan
Release Date: