Batteries: thermoelectric and photoelectric – Photoelectric – Panel or array
Reexamination Certificate
2002-03-13
2003-03-25
Diamond, Alan (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Panel or array
C136S256000, C136S291000, C428S426000, C428S441000, C296S215000, C296S216010, C257S433000
Reexamination Certificate
active
06538192
ABSTRACT:
This invention relates to glazing intended for automotive roofs comprising a part providing a desired interior luminous transmittance.
BACKGROUND OF THE INVENTION
Automotive manufacturers are developing models having increasing glazed surface areas. The dimensions of windscreens and rear screens are increasing particularly to improve aerodynamic profiles. In addition, glazings are becoming preponderant in the manufacture of sunroofs. Following this tendency, manufacturers wish to use glazings to provide the whole of, or at least a significant part of the roofs of vehicles.
The aim of this invention is to provide glazings for vehicle roofs, having at least one portion having a desired transparency, and at least another portion which must satisfy different requirements of transparency. A typical case of glazings satisfying this requirement is that of glazings provided with photovoltaic cells. The invention is described in relation to glazings adapted to comprise cells of this type. However, the invention may be applied to other sort of glazings in respect of which only a part must offer the indicated transparency.
On certain models, particularly top of the range models, automotive manufacturers propose photovoltaic cells whose function is to limit the drain on the batteries, particularly when the vehicle motor is not running. This is currently used for example to recharge the batteries or to power a ventilation system and thus limit heating of the vehicle when stopped. Other applications have already been envisaged all of which have in common the provision of a complementary energy source to reduce the use of energy generated by the vehicle motor.
For good efficiency, the cells may be arranged on a surface which is as large as possible, and underneath a shield which protects them from environmental elements: humidity, grease etc. The cells are thus placed behind a transparent screen, usually provided by a sheet of glass.
For convenience, the cells have generally been arranged at the roof in vehicles which have already been commercialised. The adaptation of photovoltaic cells on glass roof elements has been the subject of various previous propositions.
With respect to these types of commercialised vehicles incorporating this type of equipment, the photovoltaic cells have been arranged on a sheet of glass forming at least part of the roof, and on the face of the sheet which is not exposed to the exterior. The cells are adhered to the sheet of glass and protected and hidden from the inside of the vehicle by a facade.
One difficulty for the manufacture of these roofs comprising cells resides in the fact that in order to satisfy safety standards, particularly with respect to mechanical resistance, the glass sheet must have a certain thickness. The thicker the glass, the less the energy transmitted to the cells.
In known articles, a sheet of tempered glass at least 5 mm thick has typically been necessary. At these thicknesses, ordinary clear glass has an absorption which is not negligible. The energy transmittance (ET) measured in the Moon system is about 82% of the incident radiation.
These known articles lead to a non-optimised efficiency for the cells. It is desirable to find a construction which reduces the absorption to a minimum without compromising the mechanical properties.
In this context, it is possible to use so-called “extra clear” glasses whilst keeping the structure described above. Theses glasses which have the particularity of having an extremely low quantity of iron have relatively low levels of absorption. At thicknesses under 5 mm, as previously described, the ET can be of the order of 90%, thus giving a gain of the order of 8%. The disadvantage of this glasses is its cost. The cost is approximately 2.5 times that of ordinary clear glass. Even if the cost of the glass only contributes to part of the total cost of the roof, this difference is not insignificant for the manufacturers.
Furthermore, in known structures, the use of a sheet of glass having an energy transmittance as great as possible to increase the efficiency of the photovoltaic cells is directly contradictory to the requirements of motor vehicle manufacturers regarding the transmittance in the interior of the vehicle. For reasons of comfort, the energy transmittance should be as low as possible, should not be greater than 20%, and should preferably be less than 15%. The use of clear glass and particularly extra clear glass, can only be envisaged if only a part of the roof will receive the cells, the rest being adapted for the vision of the passengers.
In order to satisfy the contradictory requirements previously referred to, it is possible to deposit a thin coating using a traditional techniques to limit the transmittance. The coating must nevertheless be limited to part of the sheet which does not carry cells, which increases in the complexity of the operation. In addition, the coating is relatively fragile, irrespective of the technique to form it, and at the interior of the vehicle, it remains exposed to the risk of degradation, abrasion etc. Faults resulting from such degradation are extremely sensitive to the extent that the coating absorbs and/or reflects a significant part of the incident light. Faults in the coating thus appear as luminous points or lines on a surface which is significantly less luminous.
SUMMARY OF THE INVENTION
The invention provides glazings for vehicle roofs having a new structure which responds to the previously described requirements. The glazings according to invention comprise at least one transparent portion, and at least one portion which is not transparent, particularly due to the presence of photovoltaic cells or other functional elements. This solution offers a number of advantages which will be described in more detail.
The following description refers to a vehicle roof. This designation relates to the case where the whole of the roof is envisaged. It also relates to the case where only part of the roof is equipped in the way described. It can easily be understood that the “glass portion” may be limited for example to the part comprising the movable element of a sunroof. The case of the complete roof corresponds best when seeking to arrange the cells on as large an area as possible, without necessarily ignoring other aspects. In addition the tendency in automotive design, referred to above, is clearly towards an increase in the glazed surface area. Embodiments according to invention which follow this tendency favour a roof made entirely of glass. The description and the examples referred in a non-limiting way to a roof made entirely of glass.
The roof glazings according to the present invention provide at least one transparent portion and one portion which is not transparent due to the presence of non transparent functional elements. It comprises a first sheet of glass comprising the external surface, a second sheet of glass comprising at least part of the internal surface of the roof, and an intermediate sheet of one or more thermoplastic materials traditionally used for forming laminated glazings, the intermediate sheet extending at least over the portions of the sheets of glass which are face-to-face. The non transparent functional elements, for example photovoltaic cells, are arranged under the first sheet of glass.
In the following, for reasons of convenience, photovoltaic cells are referred to in terms of functional elements. This example is particularly representative. However, the elements may be of any other non-transparent type which cover a significant portion of the surface of the roof.
The combined characteristics of the elements superposed in the transparent portion of the glazings are such that the energy transmittance of this portion is not greater than 25%, and preferably remains less than 20%. In the transparent portion, the luminous transmittance is at most 25%, and is usually less than 30%.
When the functional elements are photovoltaic cells, the first sheet of glass is chosen such that its energy transmittance ET is at least 82% and is preferab
Baudin Pol
Coster Dominique
Guindon Christian
Legrand Denis
Masereel Alain
Diamond Alan
Glaverbel S.A.
Piper Rudnick LLP
Schneider Jerold I.
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