A team of researchers from the University of Valencia (UV) has proven that 34% of ultraviolet radiation filters through under beach umbrellas. According to what is published in the journal Photochemistry and Photobiology, umbrellas intercept the full direct flow that comes from the Sun, but not the diffused radiation that penetrates through from the sides.
"We have proven that irradiance (radiation incidence per unit of surface area) that reaches the ground covered by an umbrella is 34% of the total", Jos Antonio Martnez-Lozano, co-author of the study and coordinator of the Research Group of Solar Radiation in UV, highlights to SINC.
To carry out the Project, which was published recently in the journal Photochemistry and Photobiology, the team positioned an ultraviolet ray sensor on the base of a canvas umbrella painted blue and white, with a radius of 80cm and height of 1.5 metres.
"The umbrella intercepts the direct radiation that comes from the Sun, but part of the diffused radiation, which makes up approximately 60% of the total, reaches the sensor from the sky not covered by the umbrella", explains Martnez-Lozano.
The results show that canvas has a very high capacity for absorbing radiation, "with only 5% transmissivity", but this does not prevent diffused ultraviolet radiation from penetrating through on the sides.
In addition, the team has developed a geometric model to obstruct the sky to calculate the irradiance that is received on the different horizontal and vertical planes under the umbrella. In the case of horizontal irradiance, the values that the model provides coincide with those registered experimentally with only a relative error of 3%.
In this way, and using various configurations of sky, ground and umbrella, the researchers have been able to simulate the real situation of people, who do not always remain lying down under sunshades, as they often tend to rise, sit or
FECYT - Spanish Foundation for Science and Technology