A black vehicle requires 26.2% more energy to cool on a sunny summer day than the same baseline vehicle painted white.
National Renewable Energy. Laboratory
Thermal storage systems provide cooling when the engine is off through the use of cold energy storage. They capture cooling while the truck is in motion that can be used to cool the sleeper when the truck is parked. They work by using thermal energy stored in a frozen graphite/water matrix. An electric refrigeration compressor freezes the water in the storage unit when the truck is running. Then, when the engine is off and cooling is required, a pump circulates coolant through a storage core and then through a heat exchanger in the cab. Fans in the heat exchanger draw in warm bunk air where it gives up its heat to the chilled mixture and then cooled air is blown back into the sleeper.
Unlike other idle-reduction systems, thermal storage systems do not require batteries to operate.
Thermal storage systems do not consume fuel or generate emissions
The systems are quiet, preventing sleep disruption
The systems require no additional maintenance
These systems are limited in their functionality and can only provide cab cooling. They cannot provide heating or AC electrical power.
These systems do not keep the truck engine coolant warm so they cannot help with cold starts.
Unlike diesel APUs, thermal storage systems provide cooling for only a limited amount of time.
In order to provide charging for the cold storage unit, a large alternator is needed. This large alternator places an additional load on the engine.
There are already a wide variety of payback calculators for any given type of idle-reduction system. In an effort to meet the industry’s need for more information, we have also developed a high-level payback equation to aid fleets in choosing the right combination of technologies.