A dairy processing plant in Atwater, Calif., commissioned 250 tons of subfreezing refrigeration.

The refrigeration produces 33°F propylene glycol for the plant chilling loop. A Thermosorber from Energy Concepts Co. LLC., Annapolis, Md., operates automatically and unattended and is equipped with remote monitoring. The refrigerant (ammonia) has zero ozone depletion and zero global warming potential, and both jacket heat and exhaust heat are converted to subfreezing refrigeration.

As for the plant, it is powered by engine waste heat. The engine is powered by renewable methane from manure in an anaerobic digester. In addition, the waste heat from the refrigeration plant supplies useful heat to the dairy.

According to Energy Concepts Co., similar systems can be powered by biomass-fired boilers or solar thermal collectors to achieve comparable results. A financial incentive from the California Energy Commission helped implement this project.