High Temperature Direct Solar Thermal Conversion

摘要

Technical challenges of efficiently and cost-effectively deriving energy from the sun are addressed using a manifold and an array of evacuated tubes in fluid connection, in a butterfly or other planar arrangement. Tube and manifold fluid guides are plumbed for coaxial flow and/or parallel flow, and thermally protected by sleeves, stainless steel piping, and/or vacuum. Tubes are provided with a selective low emissivity coating and/or internal mirror to reduce thermal loss. The solar absorption surface of evacuated tubes may be five square meters or more, with only low-quality concentration optics, or no concentration optics used. The tubes array tracks the sun with a two-axis motion platform. Fluid operating temperatures range from 150 to 300 degrees centigrade, depending on the sunlight exposure, working fluid, and supplemental heat source if any. Fluid may circulate heat between the manifold and heat engine, cogeneration facility, and/or other module.

主权项

1. A system comprising:
multiple evacuated tubes, each evacuated tube containing a sunlight absorption surface and a tube fluid guide, the tube fluid guide having a tube fluid supply and a tube fluid return; a manifold containing a manifold fluid supply and a manifold fluid return, the manifold fluid supply connected to the tube fluid supplies and the manifold fluid return connected to the tube fluid returns; water without antifreeze as a working fluid within the manifold and fluid guides, and wherein the working fluid is unfrozen over a 16 hour period with an ambient temperature below 0 degrees centigrade and no sunlight reaching the absorber (e.g., during the night), and the system contains a periodic circulation of a warming fluid in thermal connection with the working fluid, and that thermal connection has a negligible impact on overall system thermal efficiency; and wherein the system is further characterized in at least one of the following ways: (a) each fluid guide is a direct flow coaxial flow fluid guide having a fluid return pipe coaxially inside a fluid supply pipe, and the fluid return pipe is stainless steel or another material having a thermal conductivity lower than a copper pipe of the same size and configuration; (b) each fluid guide is a direct flow coaxial flow fluid guide having a fluid return pipe coaxially inside a fluid supply pipe, and the fluid return pipe is thermally insulated (e.g., by a sleeve) from the interior of the fluid supply pipe; (c) each fluid guide is a direct flow coaxial flow fluid guide having a fluid return pipe coaxially inside a fluid supply pipe, a supply fitting is located at a junction of the manifold fluid supply and the tube fluid supply, a return fitting is located at a junction of the manifold fluid return and the tube fluid return, and the return fitting is contained within a fluid supply; or (d) at least a portion of the manifold fluid return and/or associated plumbing is contained within an evacuated manifold chamber.