Stock material or miscellaneous articles – Light transmissive sheets – with gas space therebetween and...
Reexamination Certificate
2000-11-20
2003-07-08
Loney, Donald J. (Department: 1772)
Stock material or miscellaneous articles
Light transmissive sheets, with gas space therebetween and...
C052S786100
Reexamination Certificate
active
06589613
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an insulating glass element for glazing a building with a high degree of utilization of the solar radiation energy, the element comprising a clear glass pane and a further glass pane arrangement which is arranged at a distance from the clear plane.
German laid-open specification 28 29 523 describes a window-pane solar collector which comprises a crystal mirror glass pane arranged on the outside and a thicker, interior glass pane which is arranged at a distance from the mirror pane and the interior pane is colored green. The crystal mirror glass pane bears a selective coating on its inside which allows only the short-wave light radiation from the outside to pass through but does not emit long-wave thermal radiation to the outside. The intention for this arrangement is for the solar energy which strikes the window-pane solar collector to be converted into useable heat and to be discharged directly to the interior of the room without any transmission and storage thermal losses, or for that energy to be fed to a service water heating system.
DE 41 25 834 C2 from the same applicant describes such an insulating glass element which exhibits different transmission properties for the passage of solar energy radiation, depending on the positioning in relation to the radiation source. Depending on the positioning of the absorption pane in relation to the radiation source, this insulating glass element can be used in summer as a solar protection element with a low transmission of radiation energy and in the winter as a solar collector element with a high solar transmission of radiation energy. This known insulating glass element has a thermal insulation value of approximately k=1.0 W/m
2
K and is mounted in a window frame such that it can be rotated through 180°, so that, as desired, the insulating glass pane can point with one or other of its surfaces toward the outside of a room. In this way, the costs for the air-conditioning of rooms equipped with such insulating glass panes can be reduced both in winter and in summer.
The absorption pane of the insulating glass element is pointed outward when in the summer position. It is designed to be selective with regard to the predominantly non-visible region of the solar radiation, and it absorbs the non-visible components of the solar energy spectrum and converts them into thermal energy, which is dissipated to the external atmosphere convectively and via radiation. The entire energy transmissivity in this position is only about g=0.35 at the aforementioned k value.
In the winter position, the clear glass pane, which is free of iron oxide or has a reduced proportion of iron oxide, faces the outside and the selective absorption pane faces the interior. The solar radiation penetrates the clear glass facing the outside and strikes the selectively absorptive glass pane without any noticeable absorption losses. This glass pane converts approximately 50% of the solar spectrum, predominantly in the non-visible region, into long-wave thermal radiation, which is then almost exclusively radiated out into the interior of the room. This is impeded by a coating (low-E coating) that reduces the emission of long-wave thermal radiation and faces the interspace between the panes, and a noble gas filling in the interspace between the panes.
The overall energy transmissivity for solar irradiation is virtually g=0.8 in the winter position at the same k-value of approximately k=1.0 W/m
2
K.
This concept may also be referred to as a solar diode and includes the mechanical reversal of the polarity of the radiation flow of the insulating glass element. It permits the thermal utilization of the irradiated solar energy potential in order to relieve the load on the heating balance in the winter months and the transitional months, and it prevents excessive solar irradiation in the summer months.
In spite of these known, advantageous effects of the insulating glass element corresponding to DE 41 25 834 C2, only the thermal insulation function, that is the thermal transmission coefficient of insulating glazing, is given any primary consideration and worth in conventional building technology in the case of glazed building outer surfaces, while the overall energy transmissivity, that is the solar utilization function of transparent glass areas, is neglected by comparison.
For large-area building glazing systems, that is for quasi-glazed structures, the glass industry has provided insulating glass elements with excellent properties with regard to the thermal insulation function, having k values of k=1 W/m
2
K for two-pane insulating glass elements and k values of k=0.7 or 0.5 W/m
2
K for three-pane insulating glass elements.
These values are achieved by using single-sided or two-sided coatings which impede the emission of long-wave, solar radiation, and by an additional noble gas filling of the interspaces between the panes. In this case, however, considerable reductions in the g value, that is the overall energy transmissivity, are tolerated. In the case of three-pane insulating glass, only values of g=0.48 and below are still achieved, which means that more than 50% of the solar radiation striking the outer pane is rejected, and that energy is therefore no longer available for heating the interior.
Despite the energy losses because of neglecting to optimize the g value to the benefit of a slightly improved k value, for this insulating glass concept, the glass industry emphasizes as an advantage the fact that it is suitable both for thermal protection in the winter and for solar protection in the summer. In this case, however, it is overlooked that an improvement of the k value by 0.3 or 0.5 W/m
2
K in the case of a three-pane insulating glazing system, as compared with a two-pane system with a k value of k=1 W/m
2
K, referring to the achievable energy gain, is virtually unimportant, in any case in the central European climate area, if it is offset against the loss of 20 to 30% in the solar irradiation rate. This is because, during the heating period in the winter and in the transitional months, this irradiation rate, even under diffuse solar irradiation, is on average 100 to 150 W/m
2
and, given direct irradiation, is 300 to 600 W/m
2
, which may advantageously be used in a compensating manner for room heating. In this case, however, it is necessary to take into account the fact that the solar irradiation rate in the winter and transitional months is subject to large fluctuations during the day and, under conditions of severe cloud cover, can decrease to very low values.
In connection with DE 41 25 834 C2, it is already known that thermal comfort is influenced critically by the temperature of the wall surfaces in the room. Even when there is an adequate air temperature in the room, the temperature of the wall surfaces in the room must not fall below that of the air in the room if comfort is not to suffer. Given temperature deviations at partial areas of the room, such as the unavoidable ones in the case of glazed window fronts, and in spite of given, optimal thermal insulation values, comfort will already be noticeably impaired. Balanced wall temperatures are also an essential precondition for a comfortable room climate in order to avoid convective air flows. If balanced temperature is provided, room temperatures of 18° C. are already felt to be adequately comfortable, so that lowering the room temperature from the conventionally necessary interior temperatures of 22° C. to 18° C. provides a considerable saving of about 25% in heating costs.
SUMMARY OF THE INVENTION
The invention has the object of improving the thermal comfort of interiors having large window areas by utilizing the solar irradiation rate in the winter and transitional months in a sustained manner and largely independently of the current weather.
To achieve this object in an insulating glass element of the type mentioned above, the invention proposes a glass pane arrangement which is predominantly a
Loney Donald J.
Ostrolenk Faber Gerb & Soffen, LLP
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