Can sun rays reflected by a mirror to a solar panel generate electricity?
K. RAMAMOORTHY
Chennai
The sunrays emanating from sun’s outer surface due to nuclear fusion take about 8 minutes to reach earth’s atmospheric region. They consist of ultraviolet, visible and infrared radiations ranging from 100nm (nanometre) to 100,000 nm. The visible rays ranging from 250nm to 800nm (violet to red) reach the earth’s spherical surface effectively. This range contains 45 per cent of the total solar radiation energy reaching the planet’s ground surface. This visible sunlight generates photovoltaic (PV) current on hitting a solar panel.
The reflective mirror changes the direction of the falling sunlight, not its quality when the reflectivity of the mirror is 100 per cent. But this does not happen in reality. The reflectivity of the mirrors ranges from 40 per cent to 95 per cent. With a mirror of good reflectivity (95 per cent) the intensity of the reflected sunlight will not be affected much. The reflected sunlight can generate PV current almost as effectively as the incident rays.
In the countries located far away from equator (Norway, Sweden etc.) the intensity (power) of sun light will be low (100-300w/m). Here larger sized plane mirror reflects the sun light on to the PV panels. An array of mirrors focuses the low intensity sunlight on panels to boost PV current generation. A big concave mirror also enhances the power of solar rays at the focus.
DR. C.E. SOORIMOORTHI
Solar Energy Consultant
Madurai, Tamil Nadu
This week’s questions
Why do black holes have high gravity?
Thommen Shaji, Kottayam, Kerala
In humans, the lens forms an ‘inverted’ real image of the object on the retina. Then how are we able to perceive it ‘upright’?
Pravin Nichit, Pune, Maharashtra
What is the working principle of a space telescope?
Balaji Akiri, Hyderabad
Why and how do oceans absorb carbondioxide?
Anu, Lucknow
Why are gold ornaments packed in dark rose coloured paper while selling?
Appu Jayaram, Mananthavady, Kerala
