Cooled by the Sun

How can the light and heat of the sun be used to cool the air?

This isn’t a trick question. It’s what FedEx Ground® is doing at its sorting facility in sunny Davenport, Florida, with the help of an innovative technology. The solar thermal air conditioning system cools the areas where packages are sorted and loaded onto trailers, dropping the temperature inside the trailers by as much as 20 degrees Fahrenheit on average—a big difference in comfort for package handlers on hot summer days. So far, 19 of the site’s 100 loading and unloading doors have been equipped with the state-of-the-art system to maximize comfort.

How does it work?

Large truck trailers that carry non-perishable items are typically not insulated. When a trailer is being loaded or unloaded in the sun at a distribution center, the inside can get uncomfortably hot.

The FedEx Ground maintenance team in Davenport came up with a design to feed conditioned air into trailers parked at the load doors, using air cooled with the help of the sun. Solar thermal panels mounted on the roof take sunlight and use it to heat the compressed fluid inside the air conditioning units installed above the load doors. This cuts down on the work the air conditioning compressors have to do and reduces their electricity needs. The conditioned air then feeds into fans that blow the cool, comfortable air into trailers parked at the load doors. 

“This solar thermal air conditioning system is innovative and sustainable,” says Greg Hudak, Sustainability Advisor at FedEx Ground, “but the biggest benefit is occupant comfort. Package handlers work in all kinds of weather, and it’s been a challenge trying to keep the trailers cool in hot climates.” Greg adds that other FedEx Ground sites continue to explore innovative methods to sustainably improve comfort for employees.

How is this different from solar electricity?

Photovoltaic panels—what we commonly think of as solar panels—collect the sun’s energy to create an electrical current. This electricity can power lights and equipment or charge an electric vehicle. FedEx Ground currently uses photovoltaic energy to power buildings at 16 sites.

Solar thermal technology is somewhat different. Like photovoltaic, it uses the sun’s energy, but rather than converting solar energy to electricity, it uses the sunlight to create heat. In the case of the system installed in Davenport, the sun heats the refrigerant used in the air conditioners, greatly reducing the amount of electricity needed for this task. Solar thermal technology is also more efficient and affordable than photovoltaic and offers promise for cooling other FedEx facilities in the future.

How much energy does it save?

The Davenport system has been installed for less than a year, but savings estimates are promising. The solar thermal air conditioning system is expected to reduce the workload on air conditioner compressors by almost 40%. In turn, this will reduce energy demand by 33%, or about 16,090 kilowatt hours, and avoid 11.4 metric tons of CO2e emissions per year. That’s equivalent to avoiding the annual emissions from 28,229 miles driven by an average passenger vehicle. In addition to the energy and emissions savings, the system also extends the life of air conditioning equipment.

“Our team members work as efficiently as they can,” says Alan Nichols, Facility Maintenance Manager at FedEx Ground, “but we know it can get hot inside those trailers on summer days. This system keeps everyone comfortable and safe without using much electricity. It’s a solution we can all feel good about.”