No abstract

Interest in the power potential of tidal streams is growing worldwide. While the latest assessment for Canadian coastlines estimates a resource of approximately 42 GW, these results are based on the average kinetic energy flux through the channel. It has been shown, however, that this method cannot be used to obtain the maximum extractable power for electricity generation. This work presents an updated theory for the extractable power from a tidal stream in a channel linking a bay to the open ocean. The maximum average extractable power from a channel linking a bay to the open ocean may be estimated, within approximately 15 per cent, as 0.22ρ gaQ0, where a is the amplitude of the dominant tidal constituent in the open ocean and Q0 is the maximum volumetric flowrate in the undisturbed state.

An investigation of active magnetic regenerators ͑AMRs͒ has been performed near room temperature using helium as a heat transfer fluid and a magnetic field of 2 T. To evaluate the impact of the operating conditions, the performance of two reciprocating 90 g gadolinium packed bed regenerators was mapped as a function of the fluid flux and cycle frequency. In addition, two multilayer regenerators of similar mass and dimensions, composed of a layer of gadolinium and a layer of a gadolinium-terbium alloy, were tested and compared to the performance of the Gd-only regenerators. The multilayer regenerators produced a larger temperature span and cooling power compared to the single material regenerators of equivalent mass and geometry ͑temperature spans of about 20 and 16 K, respectively͒. Theses results validate the concept of a multilayer AMR, provide useful data for magnetic refrigerator design, and provide better understanding of active magnetic refrigeration.

No abstract

No abstract