Refrigeration and air conditioning in buildings accounts for an enormous amount of U.S. primary energy consumption (>8.5 quads). Most existing air conditioners, heat pumps, and refrigerators achieve cooling through mechanical vapor compression cycles which: i) contribute to electric utility peak loads, generally met using inefficient and polluting fossil-fuelled combustion turbines, ii) reduce grid reliability, iii) use refrigerants that are strong greenhouse gases and iv) cannot be made more efficient cost effectively. A number of alternative technologies that have the promise of alleviating these problems are in various stages of development, but none can cost effectively compete with the status quo. Ergenics proposes to develop and commercialize a two-stage refrigeration system that uses low grade heat (