The aim is to optimise evacuated glazing in order to reduce heat transfer through windows below that available currently, while allowing high daylight transmittance. This is to be achieved by developing and implementing new methods of creating the edge seal so that the temperature required to create the bond is less than the upper thermal tolerances of soft low emittance coatings, while achieving an acceptable unit life. Frame design suitable for use with evacuated glazings will be developed. Modification of presently-existing transient finite-element and finite-volume thermophysical simulation computer codes will be undertaken and validated by means of an experimental program designed to provide a comprehensive data set. Additionally, the investigation of the use of materials as spacers whose refractive indices enable them to be less visually obtrusive will be considered and the fabrication and experimental testing of a suitable optimised evacuated glazing and frame window design.
Evacuated glazings are contiguously-sealed double glazing units with an evacuated gap, see three dimensional representation below. Midplane heat loss coefficients as low as 0.6W/m2/K can be achieved with suitable low emittance coatings.
Initial investigations will determine suitable low emittance coatings and the different methods and materials for the fabrication of the contiguous edge seal required. Small laboratory samples will be manufactured during this stage to appraise their durability - the main criterion by which the success of a material and its fabrication process will be judged. The successful systems will be scaled up for evaluation of their thermal and optical properties by means of bench-top hemispherical emissivity and transmittance instruments. This will be supplemented by outdoor testing in northern and southern latitudes of Europe and by a series of indoor tests using a solar simulator to measure the thermal transmittance and to design a generic family of suitable frames.
Expected Achievements and Exploitation
Small pre-prototype samples will be produced which will demonstrate the ability to use a low temperature, vacuum stable edge seal to manufacture the units, and that the thermal advantages out weigh any small incremental costs incurred. Detailed stress and thermal analyses will be presented as evidence of the success of this method of manufacture. A validated dynamic model for the optimisation of the frame design will also be developed, and a generic family of appropriate frames for evacuated window systems specified. Further testing of larger prototype samples as a means of convincing the conservative building industry, will be necessary before exploitation can be considered.
Funding SchemeCSC - Cost-sharing contracts
2600 AA Delft
L40 5UF Ormskirk