Abstract: The invention relates to a fluid power accumulator in which the fluid undergoes a state change as the system is pressurized to store energy. A state change can be a phase change, a chemical reaction, or a combination of these. Generally the state change results from the interaction of a compressible fluid contained in the accumulator with another substance, which can be a fluid or a solid. Preferably, the state change includes the physical adsorption of a fluid by a solid adsorbant. The invention can improve the energy storage density of a fluid power accumulator, allow a given energy storage density to be achieved at a lower maximum pressure, facilitate heat transfer and storage within an accumulator, and/or improve accumulator efficiency by storing energy in a form other than thermal energy, such as in the form of chemical energy.

Abstract: The invention relates to systems for removing NOx from exhaust. In one aspect of the invention, after adsorption, an NOx adsorber is isolated from the main exhaust flow and desorption induced by raising the temperature. The desorbed NOx is combined with a reductant and reduced over a catalyst. Preferably, the reductant is syn gas produced in an on-board reformer. The catalyst need never be exposed to the main exhaust flow, which is particularly advantageous for catalysts sensitive to water, oxygen, or sulfur. In another aspect of the invention, a recirculating flow is induced through an NOx adsorber during a regeneration cycle. Recirculation can induce greater desorption at a given temperature, provide a source of heat for the adsorber, and allow a higher conversion rate with a fixed amount of catalyst. A further aspect of the invention relates to a vehicle-mounted adsorbers with provisions for heating.