Abstract: A control method is provided for a cryogenic refrigeration system having an evaporator-heater coil, an electronically controlled valve for regulating the amount of cryogen to the coil, and a vapor motor driven by the cryogen that is coupled to both an alternator for recharging a battery, and a fan for generating a discharge air flow through the coil and into a conditioned space. The shaft rpms of the vapor motor is determined by a rectified output of the alternator, and the electronically controlled valve is incremented or decremented so that the shaft rpms stay above a preselected amount sufficient to both to recharge the battery of the system, and to circulate sufficient air in the conditioned space to avoid undesirable temperature non-uniformities therein. The pressure of the cryogen in the system is further continuously measured, and the electronically controlled valve is incremented or decremented in order to maintain a sufficient pressure to maintain the cryogen in a gaseous state.

Abstract: A control system is provided for a cryogenic refrigeration system having an evaporator-heater coil, an electronically controlled valve for regulating the amount of cryogenic gas to the coil, and a vapor motor powered by the cryogenic gas that drives both an alternator for recharging the system battery, and a fan for generating an air flow through the coil and into a conditioned space. The control system includes a temperature sensor for generating an electrical signal indicative of the temperature of the conditioned space, and a microprocessor that is electrically connected to the temperature sensor, the alternator, and the electronically controlled valve for modulating the flow of cryogenic gas through the evaporator-heater coil in said vapor motor to achieve a selected set point temperature in the conditioned space, and to maintain a sufficient alternator current to effectively recharge the system battery.