Active thermal insulation system including evacuated structures and a vacuum sustaining unit

Not Applicable

Not Applicable

1. Field of the Invention

This invention relates to thermal insulation systems, more particularly to such systems including evacuated structures, and yet more particularly to the use of such systems to allow heat retention within solar heat collectors.

double glazed vacuum structures, and, more particularly, to such structures having a means for providing and maintaining a vacuum between spaced-apart glass sheets for thermally insulating solar heat collectors.

2. Summary of the Background Information

A solar heat collector typically includes a heat receiving structure through which a fluid, such as water, is circulated to be heated by solar radiation. The heat receiving structure comprises elements such as piping, tubing, a reservoir tank, and a thermally conductive structure to absorb heat from radiant energy and to transmit the heat to the fluid. Preferably, a transparent cover is placed over the heat receiving structure, allowing the passage of radiant energy, so that the vessel is heated by sunlight, while minimizing the conduction of heat, allowing the heat receiving structure to rise to a relatively high temperature without substantial heat losses to the atmosphere around the solar heat collector. The effectiveness of the thermal insulation in preventing heat loss to the atmosphere has a significant effect on the overall efficiency of the solar heat collector, particularly when the solar heat collector is operated in a cold climate.

One method that has been applied to provide thermal insulation while allowing the transmission of radiant energy is the use of a pair of glass plates that are spaced apart to form an intervening air space. A single plate of glass has an insulation value of R1, with this value being increased to R2 when a second plate is installed to provide a separate air space. Evacuating the air within the space between the glass plates can provide substantially higher insulation values of R30 to R50, at the cost of a need to provide air tight seals around the edges of the glass plates and of a need to provide a structure that can withstand a pressure of about 15 psi acting on each of the plates. However, the use of structures including evacuated spaces for thermal insulation has been the brittleness and relatively low strength of the glass materials generally used and by a lack of reliability of such structures in large thermally insulating systems because small leaks result in a loss of vacuum.

The patent literature includes a number of descriptions of structures for reducing the transfer of heat through the use of spaced-apart glass plates on opposite sides of an evacuated space. For example, U.S. Pat. No. 2,216,332 describes a window including a pair of spaced-apart glass plates and a pipe extending within the wall from the space between the glass plates. The pipe extends to a valve that can be opened to withdraw air form the space between the plates or to return air to this space. A supporting structure, composed of slotted, interlocking vertical and horizontal spacers dividing the space between the plates into a number of smaller rectangular spaces, extends between the plates to help resist the atmospheric pressure acting on the plates when air is removed from this space.

U.S. Pat. No. 3,990,201 describes a An evacuated dual pane window structure is provided for reducing heat loss through the window structure. The window structure comprises a pair of closely spaced panes of glass having a spacing of less than 0.25 inch with a spacer means positioned between and uniformly spaced in the area between the panes, and sealing means such as an 0-ring positioned around the perimeter and between the panes of glass. A vacuum=pump may be provided for evacuating the area between the panes of glass for reducing thermal losses through the window structure. Reflective coatings may ;′ be provided on the inside surfaces of the glass. A plurality of windows of the above structure may be connected by manifold piping to a single vacuum pump, which is actuated by a thermostat when a preset temperature differential exists between the outside and the inside of the building where the windows are used.

U.S. Pat. No. 4,184,480 describes a conventional flat plate solar heat collector provided with a contoured vacuum insulation window supported solely about its peripheral edge portions. The window is a composite formed from a pair of minimum thickness complementarily contoured glass sheets, which with the exception of their peripheral portions which are sealed together, are spaced apart from one another so as to provide an evacuated chamber therebetween and thus insulate one sheet from the other. The window formed by the nested or complementary contoured glass sheets is contoured in both its longitudinal and lateral directions, such that in its longitudinal direction the window is composed of a plurality of sinusoidal corrugations whereas in its lateral direction the peaks of such corrugations are contoured in the form of paraboloids so as to provide maximum uniform tensile strength to the window such that it may withstand the forces generated thereon by the atmosphere. However, the size of the insulated glass member is limited by the forces, principally caused by the air pressure acting on the two glass sections, and possibly additionally by manufacturing and transportation difficulties associated with handling and forming large pieces of glass. What is needed is a method for a way to provide a thermally insulating cover over a larger and taller solar heat collector.

Other patents describe methods for sealing the interface between glass plates and structural framing members and for providing channels for the evacuation of air between the glass plates to form thermally insulating structures. For example, U.S. Pat. No. 6,383,580 describes a vacuum insulating glass (IG) unit and method-of making the same. An edge-mounted pump-out structure is provided, including a pre-positionable insert capable of receiving a pump-out tube therein. Following formation of the edge-mounted pump-out structure and its positioning on the unit, an edge seal is formed for hermetically sealing off the low pressure space located between the substrates.

U.S. Pat. No. 6,506,272 describes a A vacuum insulating glass (IG) unit. In certain embodiments, the internal cavity is evacuated (i.e., pumped out) via a pump-out aperture. A cover with one or more sealing element(s) may be provided over the pump-out aperture so that during the pump-out process air flows out of the internal cavity and through space(s) between adjacent sealing elements or sealing element portions. Following evacuation or pumping out, the sealing element(s) is/are heated and the sealing member may be pressed downwardly toward the substrate. This causes the heat-softened sealing element(s) to expand horizontally and merge with one another so as to form a hermetic seal around the pump-out aperture and between the sealing member and the substrate.

U.S. Pat. No. 5,902,652 describes a method for providing pillars to space apart thermally insulating glass panels that are spaced apart, a method for providing an improved edge seal around the glass panels, and a method for providing an improved pump-out tube for use during construction of the panels.

Various difficulties and shortcomings of prior-art thermally insulating systems including evacuated spaces are overcome through the use of the present invention. A dome-shaped central space within a thermally insulating system is provided for holding the heat-receiving portion of a solar heating system. The mechanical weakness of glass panels extending adjacent evacuated spaces is overcome by curving the panels and, optionally, additionally by providing a panel with an impact-resistant film coating and by composing a panel of a ceramic glass material. In applications where transparency is not needed, a strong and resilient material, such as a metal, is used in place of the glass. The reliable, long-term use of large thermally insulating systems is achieved through the use of vacuum sustaining units to make the systems tolerable of small leaks.

In accordance with a first aspect of the invention, a thermally insulating system including a thermally insulating structure and a vacuum sustaining unit is provided, with the thermally insulating structure including an internal space. The vacuum sustaining unit includes a first input tube connected to the internal space, a pressure sensor sensing a pressure within the internal space, and a vacuum pump evacuating air from the internal space in response to a signal from the pressure sensor indicating that a pressure within the internal space has risen above a predetermined level.

In accordance with a first embodiment of the invention, the thermally insulating structure includes a floor structure and a dome-shaped structure, extending upward from the from the floor structure. The dome-shaped structure includes an internal surface forming a central space extending from the internal surface to the floor structure, and an external surface. Preferably, the heat-receiving portion of solar heating system is disposed within the central space. The internal space extends within the dome-shaped structure, separate from the central space and between the internal and external surfaces. The dome-shaped structure transmits solar radiation from outside the dome-shaped structure to the central space within the dome-shaped structure.

Preferably, the floor structure includes a flat inner plate, a flat outer plate, a frame, and a second input tube. The flat inner plate and the flat outer plate are each composed of a strong and resistant material. The frame holds the flat inner and outer plates in a spaced-apart relationship, forming an inner space extending within the frame and between the flat inner and outer plates. The second input tube connects the inner space within the floor structure with the vacuum sustaining unit.

In accordance with a first version of the first embodiment, the dome-shaped structure comprises an inner transparent dome, and outer transparent dome, a gasket, and at least one bracket. The inner transparent dome includes the inner surface, a first lower surface, and a lower flange extending outwardly around the first lower surface. The outer transparent dome includes the external surface, a second lower surface, and an upper flange extending outwardly around the second lower surface.