13 research outputs found
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Electricity generation and storage for residences using Li/I/sub 2/ electrochemical engines to augment photovoltaics
Electrochemical engines use electrochemical cell reactions and a temperature gradient to convert heat directly to electric power. Such engines can both generate electricity and store electric energy. Application of such engines as used with solar photovoltaic conversion is discussed. Specifically, it is shown that such engines could both store electric energy generated in daytime for nighttime use, and generate electric power from gas or other fossil heat in bad weather. If the photovoltaics remain expensive, the electrochemical engines themselves could be used to generate electric power from focused solar collection
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Night storage and backup generation with electrochemical engines
Li/I/sub 2/ electrochemical engines both store and generate electric power. These dual capabilities complement solar photovoltaic generation in critical areas: Photovoltaics need backup storage at least for nights and, if possible, for two or three days' needs. Such storage must be relatively cheap and compact--aqueous batteries would have trouble filling these requirements. Likewise, photovoltaics need backup generation based on combustion of fossil fuels for periods of bad weather--solar residences or communities will probably have to supply their own backup generation because central generating stations cannot be expected to keep large amounts of equipment on standby for solar users. Li/I/sub 2/ engine designs are described which could be developed to fill these needs of solar users, i.e., storing electricity generated by photovoltaics and generating additional electricity from fossil fuels as needed. Calculations based on laboratory performance indicate that the devices could be simple to manufacture, economically competitive, and efficient both in storage and generation. These engines also could directly use solar energy from focused and tracking solar collectors, or they could indirectly use solar energy through the combustion of biomass materials
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Kinetic and equilibrium measurements of coal drying
The retention, attachment, and release of water (sorption, adsorption, and desorption) in Fruitland subbituminous coal are shown to be very complex phenomena. The vapor pressure and thermodynamic activity of water in the coal at about 315 K vary sharply with composition. Removal of 60% of the water initially present reduces the vapor pressure by about 60%. The total moisture content of saturated coal also varies with temperature. A 10 K rise in temperature reduces the sorbed water by about 8%. There is strong hysteresis in the sorption behavior; water which is desorbed by reducing the vapor pressure over a coal sample is not fully replaced by adsorption when the vapor pressure is returned to its original level. These measurements of desorption and adsorption reflect stable and metastable equilibria. Kinetic measurements are reported for approach to a new equilibrium if the vapor pressure over the coal is reduced. The kinetic measurements reflect the shape of the pores while equilibrium vapor pressures reflect how tightly the water is bound in the pores. Both types of measurement show changes in behavior at the same compositions. Implications of these results for UCG are discussed