CAPACITY ENERGY STORAGE AT CRYOGENIC TEMPERATURES

A BASIC RESEARCH PROGRAM IS PROPOSED TO STUDY CAPACITIVE ENERGY STORAGE AT 77 K BASED ON CADMIUM-LEAD NIOBATE CERAMICS FOR TWO REASONS: (1) THE DIELECTRIC CONSTANT IS UNUSUALLY LARGE AT THESE TEMPERATURES (\8000); AND (2) THE FERROELECTRIC TRANSITION CAN BE COMPOSITIONALLY ADJUSTED BELOW 77 K. TWO ADVANTAGES ACCRUE: (1) THE STORED ENERGY DENSITY AT 77 K IS MAXIMIZED; AND (2) ON DISCHARGE (I.E., E O) THE DIELECTRIC COOLS BY ADIABATIC DEPOLARIZATION, THUS PARTIALLY COMPENSATING HEATING EFFECTS. ADDITIONALLY, AT CRYOGENIC TEMPERATURES DIELECTRIC BREAKDOWN STRENGTHS INCREASE AND METAL RESISTIVITIES DECREASE. A ROUGH ESTIMATE SUGGESTS THAT ENERGY DENSITIES -25 J/CM3 (-4 J/G) MIGHT BE ACHIEVED. THE RESEARCH PLAN CALLS FOR DIELECTRIC, ELECTROCALORIC, AND DIELECTRIC-BREAKDOWN STUDIES AT LIQUID NITROGEN TEMPERATURES ON PROTOTYPE, MULTILAYER, CERAMIC CAPACITORS. EXPERIMENTAL DATA WILL BE ANALYZED USING GIBBS AND HELMHOLTZ THERMODYNAMIC FUNCTIONS.