Passive solar radiant system, SIRASOL. Physical-mathematical modeling and sensitivity analysis

MERCADO V.; ESTEVES A.; FILIPPIN C.; FLORES LARSEN S.

SOLAR ENERGY

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2013 vol. 96 p. 10 - 20

0038-092X

When using passive solar heating systems, it is necessary to have available an Equator-facing facade on which to install them. Rooms without such a facade are not the best option for conventional passive solar heating systems. SIRASOL is a passive solar radiant systemthat captures solar energy and it is installed in the building roof, which not necessarily must have an Equator-facing orientation. Solar energy heats up a metal sheet named the radiant panel, which transfers heat by long-wave radiation to the room below it. Thispaper presents the physical model of the system and it shows the results of the sensitivity analysis. The mathematical model is used to analyze the radiant panel temperature,the radiant mean temperature, the operative temperature, and the panel surface area. Results of the sensitivity study showed that when solar radiation rises (from 200 to 800 W), the panel temperature increases from 36 C to 92 C. Variations in outside and inside air temperature have a negligible impact on the panel temperature. Thus, the use of SIRASOL is possible in locations with clear skies. Moreover, from panel temperature values we calculated mean radiant temperature and thereby the room?s operative temperature, which is proportional to the radiant panel area. When this area is 50% of the room?s floor area, operative temperature grows 3.1 C higher than inside air temperature for solar radiation levels around 500 W/m2. The analysis shows that a thermal asymmetry appears only when SIRASOL's surface area to floor area ratio is higher than 32%.