56
TECHNICAL
The science of solar geysers for
domestic use
By Erich Seeger, Senior Manager at SABS Laboratory Services, Pr. Sci. Nat.
The concept of solar collection is not new at all – there are
records of solar collection dated back to before the 1900s, where
one of the first solar water heaters found was a tank painted
black and mounted on a roof.
Basically, white light is all the colours in the
visible spectrum. The closer a body is to white,
the more light energy it reflects, while a black
object effectively absorbs all the energy from
the light as heat. Visible light forms a very
small part of the electromagnetic spectrum,
with wavelengths of 400nm to 700nm. On each
side of the spectrum we find ultraviolet (short
wavelengths) and infrared (longer wavelengths),
both invisible to the human eye. We feel infrared
as heat.
The full electromagnetic spectrum extends from gamma-
rays (very short wavelengths) to radio waves (very long
waves) which has other useful purposes. Sunlight covers
the entire electromagnetic spectrum which makes it a
very valuable source of energy. A black object absorbs
this energy which is transformed in heat. We can then
transfer this heat to another body such as water.
1
www.plumbingafrica.co.za
@plumbingonline
@plumbingonline
@PlumbingAfricaOnline
November 2019 Volume 25 I Number 9