Black surface is not the main requirement, the surface should be rough or nanostructured to trap the incident light.

For example, polished Si surfaces have about 40% reflectance in the 400-1000 nm regions even though Si is black, while SiN deposited on Si appears bluish but the reflectance is reduced to 10-20% in the 400-1000 nm regions.

Thank You, we are talking about direct solar light, not about the reflected one? If it have been lighting some other material, it might have been reflected back to the space? Am i correct?

But how the other "part", of the solar light, we to`t use, in solar power plants, is there any change to reflect it back to the space. The way like: making the roofs of the houses facing almost south - in north half sphere - out of aluminum (90 per-cent of reflection), or even of sheets of polished stainless steel. The roof - tiles absorbs about 90 per cent of the lights energy.

Thank You.

Ideal black body absorbs the incident solar radiation where it will be heated and reaches to steady state temperature by re-emission of electromagnetic radiation according to its temperature. Since the temperature is relatively low it emits normally at infrared radiation. As its temperature increases spectrum shifts to shorter wavelengths. We can cool this black body absorber by a working fluid and or convection. You do not need mirrors to reflect the radiation back into environment. The temperature rise of the absorber plays such role of reemission but not in the same electromagnetic spectrum.

In order to increase the frequency spectrum of the remitted EM waves one can concentrate the solar radiation impinge on the blackbody by using concentrating mirrors.

Best wishes

Dear Tiit Marrandi

I absolutely agree with Dr.Abdelhalim Zekry...

Regards

In some early experiments with dye sensitized cells, we noticed that some of the light was passing through the photosensitive layer and being lost. Putting a mirror or white reflective surface behind the cell to capture this light did make a difference - if you looked closely at the least significant digit on your multimeter. Modern cells absorb all their required light in one pass so such ineffective complications aren't necessary any more.

Dear, the infrared radiation penetrates a greenhouse gas worse but the radiation of any other frequency. So the effectiveness of using of mirrors ore mirror - likes, to reflect the direct sun light back is seems reasonable to test. Regards

Dear, my point is: We are turning more visible light into heat, whits might have been reflected back to the space. Visible light penetrates the atmosphere easily.

Visible light also carries energy away from earth, but after some reflections on bodies on earth, will be turn to heat of those bodies, and if those are heater then the others, the atmosphere, they emits IR. The problem is, that those bodies are too hot to live with.

Is it hopeless to get some effect, at least locally, by reflecting the visible light to space? Regards