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Autore: M. Cucumo, A. De Rosa

Collana: FM - 2004 Sorrento - Third International Symposium - Energy and Environment

Note:
Presso il Laboratorio di Energetica dell’Edificio dell’Università della Calabria, da alcuni anni, si stanno effettuando delle misure sperimentali per stimare l’entità del raffrescamento passivo radiativo prodotto da rivestimenti selettivi depositati su superfici esposte alla volta celeste. In una prima fase è stata condotta un’indagine sperimentale su un intonaco innovativo e, in una seconda fase, un’indagine di approfondimento sui rivestimenti a base di biossido di titanio e di esafluoruro alluminato di sodio per tener conto dell’effetto dell’inclinazione e dell’orientamento della superficie. I dati sperimentali raccolti hanno permesso di effettuare delle valutazioni energetiche, sia in condizioni di clima invernale che estivo, con diverse situazioni meteoclimatiche: da condizioni di cielo perfettamente sereno a quelle di cielo coperto e con pioggia.


At the Building Energy Laboratory of the University of Calabria, for some years, experimental measurements have been carried out to estimate the entity of the passive radiative cooling produced by selective coverings placed over surfaces exposed to the sky. In an initial phase an experiment was effected on an innovative plaster based on IVB cement and Cryolite (Sodium Aluminium Fluoride) and, in a second phase, an examination of coverings (paints) based on Titanium Dioxide and on Cryolite to take into account the effect of the inclination and the orientation of the surface. The experimental data gathered allowed energy evaluations to be made, both in winter and summer climatic conditions, with different meteoclimatic situations: ranging from a perfectly clear sky to a cloudy sky and a sky with rain. The energy performances of the plaster proved to be modest inasmuch as, owing to problems of mechanical strength, it was possible to use only 10% Cryolite. The passive saving fraction obtained was about 10% for the hottest months experimented.
The selective properties of the two paints instead proved to be very evident and dependent on the lying position of the surface.
The passive saving fraction, for surfaces coated with Cryolite-based paints, for just the summer months was 48% at horizontal exposure and 20% for exposure at 30° SOUTH. The PSF value proved to be even more contained for vertical surfaces because of the reduction of the radiation angle factor between the surface and the sky.
The selectivity characteristics of the Cryolite revealed themselves completely comparable to those of the Titanium Dioxide, but with a notably lower expenditure.