To keep circuits and equipment cool inside enclosures, engineers at TECA Corp., Chicago, designed and built three new solid-state thermoelectric coolers, the AHP-2250,-3250, and -4200. (There’s also a larger AHP-6200 being readied for market.) They all use Peltier devices which act as solid-state heat pumps for active cooling.
Peltier devices put dissimilar semiconducting materials in contact with each other. As dc current flows across them, one surface absorbs while the other emits it. Compared to traditional air-conditioning units, Peltier modules have no moving parts and use no working fluids. The devices also intrude relatively little inside the enclosure, leaving more room for circuits and components, and the they work for indoor or outdoor enclosures.
To reduce running costs, the units rely on passive heat exchangers until inside temperatures rise above 25°C. The AHP-3250, for example, uses 83% less energy in passive mode than it does when active cooling kicks in.
The coolers have efficiencies ranging from 0.81 to 0.95.
For enclosures that can be exposed to hot and cold temperatures, the Peltier devices can be wired to cool and heat. In these units, the thermoelectric devices run with polarity reversed, letting them move heat from outside the enclosure to the inside when conditions warrant.
The AHP-2250 provides 2,060 btu∕hr (605 W) of cooling, while the AHP-3250 offers 2,600 btu∕hr (765 W), and the AHP-4250 generates 2325 btu∕hr. When configured to provide interior heating, the AHP-2250 generates 3,750 btu∕hr of heat capacity, the AHP-3250 provides 5,320 btu∕hr, and the AHP-4250 puts out 2455 btu∕hr. EE&T