Refrigerated warehouses preserve perishable food with energy-intensive refrigeration. Biomass is a ubiquitous by product of producing food. For one refrigerated warehouse owner in the Philippines, the circle of sustainability was closed when the equipment to provide refrigeration for food preservation was replaced with a biomass-powered absorption chiller.

Energy Concepts Co. LLC, Annapolis, Md., developed the biomass-powered Thermochiller for the refrigerated warehouses. In the Philippines, rice husks are burned to provide heat to an ammonia absorption refrigeration unit. At full load, (12 lb/min (300 kg/hr) of rice husks are burned to make 110 psig (8.5 bar) steam. The steam powers the Thermochiller, which produces 80 tons (280 kW) of refrigeration at -22°F (-30°C).

At the first location in Mamplasan, the cold is transferred from the Thermochiller to the storerooms by pumped ethylene glycol (50 percent solution in water). At a second location, pumped 20 percent aqua ammonia will be used, which is appreciably more energy efficient, primarily due to much lower viscosity. Ultimately, it is planned to use pumped saturated carbon dioxide (CO2), which also saves both pumping power and capital, says Energy Concepts Co.

The biomass-powered Thermochiller has reduced the electric demand by 85 percent, according to the companies. In addition, the sustainability is achieved due to the ammonia-water working pair, which has zero ozone-depletion potential and zero global-warming potential.

The reduced electric demand of the biomass-powered Thermochiller is especially important in developing economies where electricity is in chronic short supply, yet the demand for refrigerated storage is growing rapidly.