Passive electromagnetic cooling is achieved using a first enclosed chamber having an antenna array surface, and a second chamber comprising open space external to the first enclosed chamber, wherein the open space comprises the sky. An interface is defined between the first chamber and the second chamber, wherein the antenna array surface is positioned with respect to the first chamber to thermally insulate between the interior of the first chamber and the open space of the second chamber. The antenna array surface is configured to direct beams from the interior of the first chamber towards the zenith of the sky. Solar irradiation in the optical spectrum range is reflected in the pyramidal dielectric surfaces or the ground plane in the dielectric rod array antenna.

A multi-stage sodium heat engine is provided to convert thermal energy to electrical energy, the multi-stage sodium heat engine including at least a first stage, a second stage, and an electrical circuit operatively connecting the first stage and the second stage with an electrical load. One or more methods of powering an electrical load using a multi-stage sodium heat engine are also described.

The present invention relates to a cooling device that cools a working fluid using a thermoelectric element which not only can increase cooling efficiency and reduce electricity consumption by minimizing the volume of the heat exchange block through which a working fluid flows while ensuring a length of the flow path therein long to the maximum extent, but also can further increase cooling efficiency by sandwiching a gasket between the heat exchange block and the heat dissipation block to fix the heat exchange block and the heat dissipation block without heat transfer.

A system for cooling drilling fluid on a drilling rig includes a heat exchanger and a solid-state chiller including at least one of a magnetocaloric chiller, an electrocaloric chiller, and an elastocaloric chiller. A first pump is configured to circulate drilling fluid through the heat exchanger and a second pump is configured to circulate a coolant through the solid-state chiller and the heat exchanger. The solid-state chiller is configured to cool the coolant circulating therethrough and thereby cool drilling fluid circulating through the heat exchanger.