In order to reduce the temperature of an object or chamber, heat must be removed faster than it is generated. There are two primary attributes that a designer needs to determine to specify a Thermoelectric Cooler assembly for an application. The first parameter is calculating the required cooling capacity. This is achieved by estimating the total heat load of the system. This consists of calculating the active heat load (Qa), passive heat load (Qp), and for outdoor applications, the radiant heat load (Qr). The active heat load consists of the load from objects to be cooled, powered electronic devices, and dehumidification of air. Heat from active devices can simply be measured by input power to the device. When the object being cooled is at a lower temperature than the ambient environment, heat from the ambient environment will naturally be drawn to the cold source in order to reach equilibrium in the surrounding environment. This is known as passive heat load. It is critical to minimize this parameter as thermal shorts in the system level design will require the Thermoelectric Cooler Assemblies to pump more thermal energy. As a result, the Thermoelectric Cooler Assembly will be less efficient. Therefore, insulating the chamber walls or objects to be cooled will maximize the efficiency of the Thermoelectric Cooler Assembly. For outdoor applications, the radiant (solar) heat load must also be considered which is infrared heat generated from the sun. Solar shields are commonly used to reduce the affects of solar heat load. The second primary parameter is defining the temperature differential (ΔT = Ta – Tc). This is defined as the difference between the temperature in the ambient environment (Ta) and the desired control temperature of the application (Tc). Ta is generally chosen to be the worst case ambient temperature for a particular application.